To promote rapid recovery and quality of life after a musculoskeletal disorder, rehabilitation exercises that are suitable for each individual's physical condition are important. In cases of disuse muscle atrophy of the quadriceps, inappropriate training can cause injury. Although resistance-training robotic systems have been developed and could adjust resistance load, a systematic detection method with appropriate force strength for automatic adjustment for each individual has not yet been established. In the current study, we developed an electromyogram (EMG) based method that determines the minimum effective resistance load for muscle growth. Using an integrated EMG (IEMG) model of incremental resistance load focused, we constructed a method to determine the minimum effective resistance load with logarithmic functions. The feasibility of our method was tested with a slow training protocol using a wire-driven leg extension training robot to measure the relationship between IEMG and resistance load by applying the incremental resistance load. The proposed model was found to be suitable for six young and four elderly subjects with different levels of muscle mass, and the load derived for each person was shown to induce effectively acute thigh circumference expansion, which is a factor leading to future muscle hypertrophy.

A fall on stairs can be a dangerous accident. An important indicator of falling risk is the foot clearance, which is the height of the foot when ascending stairs or the distance of the foot from the step when descending. We developed an augmented reality system with a holographic lens using a visual illusion to improve the foot clearance on stairs. The system draws a vertical striped pattern on the stair riser as the participant ascends the stairs to create the illusion that the steps are higher than the actual steps, and draws a horizontal striped pattern on the stair tread as the participant descends the stairs to create the illusion of narrower stairs. We experimentally evaluated the accuracy of the system and fitted a model to determine the appropriate stripe thickness. Finally, participants ascended and descended stairs before, during, and after using the augmented reality system. The foot clearance significantly improved, not only while the participants used the system but also after they used the system compared with before.

This article assessed how surgical robot parameters influenced operator viewpoint during a simulated surgical procedure. Surgical robots are useful tools in minimally invasive surgery. However, even with robots, suturing is difficult because the needle is sometimes obscured by tissue or manipulators and is thus not always visible during the procedure. This is especially true in pediatric surgery, where the surgical environment is smaller than in adult surgery. Hence, surgeons must carefully track the instruments and tissues to understand and predict their current and expected situations. In this article, we used gaze-tracking techniques to analyze the location and timing of the gaze of participants while they manipulated a virtual robotic surgical simulation system. To differentiate between the ideal and actual viewpoint trajectories, we conducted experiments with and without obstacles (i.e., simulated tissue and the manipulator arm). In the obstacle condition, we modulated the wrist length of the manipulator to bring it into view. In the no-obstacle condition, the participants mostly watched the suture needle tip. In the with-obstacle condition, the participants spent less time watching the instruments and more time watching the target point. The amount of time spent watching the target point increased as wrist length increased. Given this tradeoff relationship, we examined the proportion of time the participants spent looking at the instruments or target points by wrist length. We calculated the Pareto solutions and clarified the relationship between wrist length and the watching parts.

Adaptive assistance of gait training robots has been determined to improve gait performance through motion assistance. An important control role during walking is to avoid tripping by controlling minimum toe clearance (MTC), which is an indicator of tripping risk, to avoid its decrease among gait cycles. No conventional gait training robots can adjust assistance timing based on MTC. In this paper, we propose a system that applies force intermittently based on the MTC prediction algorithm to encourage people to avoid lowering the MTC. This prediction algorithm is based on a radial basis function network, the input data of which include the angles, angular velocities, and angular accelerations of the hip, knee, and ankle joints in the sagittal and coronal planes at toe-off. The cable-driven system that can switch between assistance and non-assistance modes applies force when the predicted MTC is lower than the mean value. Nine participants were asked to walk on a treadmill, and we tested the effect of the system. The MTC data before, during, and after the assistance phase were analyzed for 120 s. The results showed that the minimum and first quartile values of MTC could be increased after the assistance phase.

Movement/walking assistance devices have the great advantage of supporting quality of life for the elderly in an aging society. To strike a balance between efficiency of movement and employment of the elderly user's own body, we developed a smart mobility system called Tread-walk, which is controlled by the user walking on a treadmill and amplifies the user's walking speed. Since the user's walking speed is different from the speed at which the Tread-walk moves, users experience a mismatch between their visual optical flow and somatic sense. In this article, we validate the feasibility of an amplifying gain decision method that analyzes user brain activity. To control Tread-walk, the visual sense is integrated with somatosensation in the parietal area of the brain and controlled in the medial prefrontal cortex. Therefore, first, we measure the parietal area when the participants walk while looking at their virtual optical flow. Second, we measure the medical prefrontal cortex when the participants control Tread-walk 2. These experiments are carried out for a variety of speed amplifying gains. We find that the brain activates significantly at amplification gain K = 1.1-1.7 in the virtual optical flow experiment and K = 1.5-2.0 in the Tread-walk experiment; this brain activation represents the amplification gain at which the visual and somatosensory senses seem to receive similar input. In conclusion, the brain would activate the most significantly at the most appropriate amplification gain.

Continuous, easy-to-implement, accurate inference of intended joint angles is important for effectively controlling powered prosthetic devices that can improve the lives and capabilities of upper-limb amputees. Estimation of intended joint angles is difficult because conventional biosignals are not directly related to the intended angle motion. In previous work, we began to address this issue by confirming that both transra-dial amputees and intact subjects, the measured deformation of the muscle bulge on the skin surface change according to the intended wrist joint angle. This paper presents a continuous prosthesis wrist joint control method using this deformation signal. We here verify the effectiveness of the distribution of the muscle bulge for accurate and stable wrist joint angle control in real time. The wrist joint angles were calculated in real time from a muscle viscoelastic model using the previously determined algorithm. We compared the error between measured and estimated angles with a conventional method, the Voigt model, and the KelvinVoigt model. Experimental results obtained for three intact people over three trials of wrist movement tasks gave the accuracy and stability of 7.96±6.16°when using the Voigt model; this is a similar performance compared to related work using a surface electromyogram. A method for continuously controlling the wrist joint angle for a prosthesis using the distribution of the muscle bulge was thus successfully established.

We developed a four-arm four-crawler advanced disaster response robot called OCTOPUS. Disaster response robots are expected to be capable of both mobility, e.g., entering narrow spaces over very rough unstable ground, and workability, e.g., conducting complex debris-demolition work. However, conventional disaster response robots are specialized in either mobility or workability. Moreover, strategies to independently enhance the capability of crawlers for mobility and arms for workability will increase the robot size and weight. To balance environmental applicability with the mobility and workability, OCTOPUS is equipped with a mutual complementary strategy between its arms and crawlers. The four arms conduct complex tasks while ensuring stabilization when climbing steps. The four crawlers translate rough terrain while avoiding toppling over when conducting demolition work. OCTOPUS is hydraulic driven and teleoperated by two operators. To evaluate the performance of OCTOPUS, we conducted preliminary experiments involving climbing high steps and removing attached objects by using the four arms. The results showed that OCTOPUS completed the two tasks by adequately coordinating its four arms and four crawlers and improvement in operability needs.

A novel joint angle estimation method is proposed using a new bio-signal for an amputee subject. We used the muscle bulge movement on the forearm skin surface as a new bio-signal for estimating the extent of motion in a previous study. We found that it is feasible to estimate the intended wrist joint angle using the distribution of the muscle bulge for intact subjects. Thus, in the present paper, we validate the feasibility of our method for an amputee. In applying our method to an amputee subject, we improved our distance sensor device so that it can accommodate the position of the muscle, which is variable for an amputee subject. In addition, we improved the algorithm that estimates the wrist joint angle using linear multiple regression for calculating the relationship between the intended wrist joint angle and the distribution of the muscle bulge. As a result, we found that the distribution of the muscle bulge changes for the amputee as for intact subjects. The movement of the position of the muscle bulge on the forearm skin corresponded to the extent of the intended wrist joint angle. According to the result of the estimation of the wrist joint angle, the root-mean-square error of the estimated angle with respect to the measured angle for the amputee was slightly larger than the error for intact subjects. Nevertheless, the root-mean-square error for the amputee was smaller than that when employing the previous method for intact subjects. Finally, it is feasible to use the muscle bulge movement on the forearm skin to estimate the intended wrist joint angle for the upper limb amputee.

This paper presents a visual feedback available robotic gait training system for motor recovery of hemiplegic stroke survivors. The system is composed of a treadmill consisting of two split belts, a pelvic support manipulator assisting patient's pelvic movement, and a visual interface feedbacking patient's gait phase. The split-belt treadmill allow patient to walk in different velocities between sound side and affected side legs, and detect patient's gait phase by current value of DC motor. The pelvic support manipulator provides three active actuations to assist patient's leg swinging during walk training. The virtual walking scenario gives visual feedback for patient while providing patient's gait phase calculated from motor current of the treadmill. One subject with simulated stroke participated in this study. Experiment results indicate gait phase of the virtual model can well track that of patient's walking, verify the feasibility of the proposed system to improve gait recovery during rehabilitation.

Elderly people are at risk of falling because of their low toe clearance. Gait training to improve toe clearance could be instrumental in avoiding tripping. We propose using a gait-training robot that applies torque during the pre-swing phase to achieve this goal. It is still possible to revert to their original trajectory after the training, however, depending on the magnitude of the applied torque. We investigated the relation between the magnitude of the applied torque and the change in toe clearance before and after application of torque. We developed a robot and carried out an experiment in which a motor pulls a string embedded on the robotic frame worn by the participants, thereby applying torque during the pre-swing phase. The experimental task included walking on a treadmill for 50 s. We applied torque to the knee during the pre-swing phase for 20 s. The phases before and after applying torque were 15-s normal walking phases with no interference from the robot. We compared toe clearance during the phases before and after applying torque. We found that the toe clearance increased after applying a torque of 8 Nm. We were thus able to verify the influence of torque on toe clearance.

The increase in care-receiver/caregiver ratio is becoming a social problem in Japan, one factor in which is the increase in the number of falls in the elderly. The purpose of this study is to develop a balance training ability system for fall prevention. To effectively improve balance ability while walking, dynamic training specialized for somatic sensation is useful. We developed a system that greatly improves balance ability by removing visual information of the outside world during gait training and by producing visual feedback of somatic sensation information, consisting of joint angle information about the whole body and foot pressure distribution information, that is, somatic sensation information used for gait. One technical problem with this system is the selection of display method at the time of visual feedback. Therefore, in this paper, we hypothesize that the training effect improves when a combination of foot pressure information and joint information is used. As specific presentation information, center of pressure (hereinafter called CoP) and ideal CoP traces derived from each joint angle were used. The ideal CoP trace is shown with a broken line connecting the heel, metatarsal and toe-tip part of the foot, and is updated every 10 walking cycles by changing the transverse coordinates of the metatarsal and toe-tip. To verify the abovementioned hypothesis, we created a machine equipped with the feedback system, and verified and tested it. To create the feedback system, the relationship between each joint angle in the body and ideal CoP traces were derived by a multiple regression analysis of the gait data (foot pressure distribution, joint angle) of young, physically unimpaired volunteers. In the verification experiment, we compared the training using the feedback system to that without in a visual sense cutoff state. The standard deviation a of right-and-left directions of the CoP traces was used as a performance index of balance ability. Increased a indicates reduced dynamic balance ability. We found that a increased by 0.61 times by feedback training, which was a significant decrease, and by 0.84 times after the visual sense interception training. A significant difference (p < 0.05) was seen between the effects of these two training types, suggesting that dynamic balance ability is improved by our feedback system. In future, we will verify the long-term training effects over several months or years, as well as the improvement in motivation over training.

Eye-tracking technology has been applied to surgical skill improvement and can observe differences in gaze data between the experienced and novice surgeon. Some eye trackers can even detect pupil diameter. We hypothesized that differences in technical proficiency among surgeons affect the extent of changes in pupil diameter, because the higher mental workload a laparoscopic task requires, the larger the person's pupil diameter dilates. In this study, we recorded the pupil diameters of pediatric surgeons while they performed a suturing task in a dry box environment. The more proficient surgeons exhibited a smaller distribution in pupil diameter than did the less proficient surgeons. Our data indicate that an individual's suturing proficiency is closely related to the degree of dispersion of pupil diameter.

Minimally invasive surgery (MIS) is commonly used in pediatric operations. This method greatly benefits patients because of the reduced surgical trauma. To perform such surgery smoothly, doctors must be highly skilled. To reduce operating difficulties, a great deal of research on surgical systems have been carried out. However, in some cases, smaller workspaces limit the application of MIS. For example, the workspace of infant congenital esophageal atresia (ICEA) surgery is only around 30×30×30 mm. Until now, most ICEA surgeries have been manually performed with traditional instruments. This paper presents a smart surgical robot (SSR) for ICEA surgery. The robot is composed of two slave arms, each consisting of a positioning manipulator and a surgical tool manipulator. The positioning manipulator uses a selective compliance assembly robot arm (SCARA) and a screw-pair mechanism to achieve translational movement in 3D space, and the surgical tool manipulator uses a “double screw drive + universal joint” structure to allow an omni directional bending motion. During surgery, the surgeon first creates the workspace manually to explore the target esophagus. The SSR system is then applied to perform operation. The configuration of the SSR means it can perform tissue manipulation under endoscopic view in a small workspace. Experimental results show that the endoscopic view permits the SSR system to be operated intuitively and accurately in the target workspace.

Incidence of cancer is growing worldwide according to statistics, what increments costs of national health systems and decreases quality of life of cancer patients. Percutaneous cancer treatments can reduce the physical burden of cancer patients due to its minimally invasiveness and allow to treat small size tumors. Robotic needle placement has been proposed to overcome the difficulties of manual needle placement, which has not enough accuracy. Until now, researchers have focused on developing deterministic models for pre or intra-operative control. In this paper, we propose a novel approach by extracting patterns in needle insertion force that can provide information about the current status of needle tissue interaction. In particular, we focus in estimating the non-linear local elastic modulus and friction status in real-time during needle insertion.

An essential tremor (ET) is a disorder that causes involuntary oscillations. ET patients face serious difficulties in performing such daily living activities as eating, drinking, and writing. We have been developing an exoskeleton to suppress tremors and support the eating movements of ET patients. The objective of this study is to propose a passive mechanism that prevents the appearance of the compensatory shoulder movement without using an actuator. The basic concept of this study is developing the mechanism to coordinate two DoF movement of elbow joint. Two DoF movement of elbow joint is constrained to passive one DoF by our wearable robot. The mechanism of our robot and constrain mechanism is optimally designed to reduce the compensatory movement during eating movement. To develop such mechanism, we first analysed the eating movement to derive the required specification of the mechanism. Then, we proposed a prototype based on the requirement. Finally, we evaluate the effect of the prototype to reduce the compensatory movement. It is confirmed that the proposed prototype had great effect on the reduction. As a future work, we will optimize the structure and the material of the mechanism to reduce the weight of the mechanism.

Remote operation is commonly used in modern robotic assisted surgery. A surgeon sits beside the console to operate an input device to control the slave robotic instrument performing tissue manipulation, while guided by visual feedback. Most people have high more dexterity on one hand than in the other. Humans prefer to use their more dexterous hand to do important tasks, such as holding a needle for suturing, while the other hand is used to assist. However, surgeons need to perform important task using both hands on a surgery. For example, they sometimes need use left hand to hold scalpels or needles for vital tissue intervention even if they are right-handed. This paper presents a novel smart surgical robotic system for surgical application. The robotic system is composed of two slave arms and two visual modules. Each slave arm consists of a 8 degree of freedom dexterous manipulator. Each visual module is composed of a 3 DOF manipulator and a flexible endoscope. The two slave arms and the two vision modules are closely located in a rectangular frame. Two phantom Omnis are used for tele-control of the two slave arms for tissue manipulation. The correspondence between the phantom Omnis and the slave arms could be swapped depending on the surgical requirement. Therefore, the user could always use the most dexterous hand for vital tasks. The two visual modules, located in the front and the back of the two slave arms respectively are used for visual feedback. Based on the different correspondence between the master and the slave arms, only one visual module will be selected to show its image in a monitor. As a result, the operator could always drive the slave arms for tissue manipulation with good eye-hand coordination. The preliminary experiment shows that the surgical robotic system is adequate.

This paper deals with the design process and the dynamic control simulation of a new type of 4-DOFs parallel mechanism that can be used as an endoscopic surgical manipulator. The proposed mechanism, 2-PUU_2-PUS, is designed based on the parallel virtual chain concept and screw theory. Based on the structure analysis of the 4-DOF parallel mechanism, the inverse position equation is studied using the inverse analysis theory of kinematics. The design and the stress analysis of the mechanism are investigated using SolidWorks software. The virtual prototype of the parallel mechanism is constructed, and the dynamic simulation is performed using ADAMS™ software. The system model utilizing PID and PI controllers has been built using MATLAB software. A more realistic simulation in accordance with a given bending angle and point to point control is implemented by the use of both ADAMS/MATLAB softwares. The simulation results showed that this control method has solved the coordinate control for the 4-DOF parallel manipulator so that each output is feedback to the four driving rods. From the results, the tracking performance is achieved. Other control techniques, such as intelligent ones, are recommended to improve the tracking performance and reduce the numerical truncation error.

Powered prosthetic hands are becoming increasingly functional through sensory feedback. However, when using electrical stimulation as sensory feedback for electromyographic (EMG) prosthetics, stimulation artifacts may cause EMG data noise. Electrical stimulation and EMG measurements are therefore performed using time-division methods in rehabilitation facilities. Under time-division methods, EMG levels cannot be acquired at the stimulation time. Highly functional prosthetic hands that can estimate grip force, however, use advanced signal processing and require detailed EMG information. EMG measuring cycle expansion may make grip force estimation unstable. We therefore developed a grip force estimation system using muscle stiffness and EMG as the estimation source signals. The estimation system consists of a muscle stiffness sensor, an EMG sensor and an estimation algorithm. We chose a tray holding task for the system evaluation. A weight is dropped on the tray and subjects are expected to control the tray's attitude. Grip force, EMG, and muscle stiffness are measured, and the measured and estimated grip forces are compared. The proposed algorithm estimates grip force with an error of just 18[N], which is 30% smaller than in EMG-only methods. The system response time is lower than human mechanical reaction time, validating the effectiveness of the proposed method.

Mechanical performance of a surgical robot can be evaluated and improved based on a working score; however, intuitive operability cannot be evaluated in this way. We propose a method that measures the user's brain activity for evaluating intuitive operability from the perspective of cognitive science. We hypothesized that hand-eye coordination, such as the slave configuration for the endoscope, has the greatest effect on intuitive operability, because it is the cause of physical differences between a human and a robot. The objective of this paper is to clarify the appropriate slave configuration for the endoscope to study hand-eye coordination using brain activity measurements. In the experiment, we used a brain imaging device, optical topography, to measure the users' brain activity while they controlled the hand-controller to position the tip of the virtual arm on the target. The experiment was carried out a number of times with the virtual arm position configured in a variety of ways. According to the results, some subjects showed peak performance with a specific slave configuration. We conclude that the slave configuration with the highest brain activity depends on the body image, which is a spatial symbol in the human brain from the perspective of cognitive science.

Robotic gait training has been introduced recently in rehabilitation, and the related researches have been conducted to propose more effective mechanism and control. To automate gait training, position control with reference trajectory has been adopted in many researches. However, there remain problems such as enhancing self-dominated gait or adapting to asymmetry or individual difference to apply robotic gait training to moderately affected hemiplegia patient. To solve this problem, we quantified the manual pelvic assistance (handling) provided by physical therapy, which can enhance patient's self dominated gait individually. In this paper, the physical model of handling was proposed based on the measurement and verified by multiple regression analysis.

Recently, a large amount of stroke survivors are suffering from motor impairment. However, existed therapy interventions have limited effects to restore normal motor function. Thus, we proposed a novel control strategy for gait rehabilitation of hemiplegic patients. The whole system consists of a Functional Electrical Stimulation (FES) device and Treadmill-Walk system. FES contributes to improve the quality of the gait based on real-time adjustment of gait pattern. During gait, the electrical stimuli from separate output channels of an FES device are launched to stimulate two lower extremity muscles (Tibialis Anterior (TA) and Hamstrings). Stimulus launching procedure is based on identifying subject's gait state (stance and swing phases). According to the current variation of treadmill motor, gait phase and muscle activation of lower limbs can be determined during walking on Treadmill-Walk. Three able-bodied subjects simulated hemiplegic patients in the experiment. The results indicated that the proposed method is a safe, feasible and promising intervention.

We herein describe a needle insertion method involving tissue preloading for accurate breast tumor treatment. A mechanical preloading probe locates a tumor lesion from ultrasound imaging information and reduces lesion displacement during needle insertion by pressing the breast tissue. We validated the insertion accuracy of this method by numerical simulation and experiments both in vitro and in vivo. For further accuracy enhancement, we evaluated the geometry effect of the preloading probe on needle insertion accuracy by experiments in vitro. We compared the insertion accuracy between insertion with preloading using different probe diameters and normal needle insertion. In addition, we compared insertion accuracy at different tumor depths. The data indicated a tendency for adaptation of larger preloading probe diameters with deeper tumors. This suggests the potential for our method to enhance placement accuracy by real-time geometry regulation.

Surgical robots have undergone considerable improvement in recent years, but the intuitive operability, representing user inter-operability, has not been quantitatively evaluated. Thus, we propose a method for measuring brain activity to determine intuitive operability in order to design a robot with intuitive operability. The objective of this paper is to clarify the angle between the endoscope and the manipulator that facilitates users perceiving the manipulator as part of their body. In the experiments, while subjects controlled the hand controller to position the tip of the virtual slave manipulator on the target in the surgical simulator, we measured the brain activity through brain imaging devices. We carried out the experiment a number of times with the virtual slave manipulator configured in a variety of ways. The results show that activation of the brain is significant with the slave manipulator configured such that the angles are slanted with respect to the horizontal. We conclude that the body image affects hand-eye coordination, which is related to visual and somatic sense feedback.

Recently, increased attention has been focused on single port endoscopic surgery (SPS). We have developed a robotic system for SPS with two surgical manipulators: an endoscopic manipulator and a positioning manipulator that moves the endoscope. The robot can manipulate both the position and orientation of the endoscope to achieve the desirable endoscopic field of view. Two methods can be used to operate the endoscopic view: “control corresponding to position” mode and “control corresponding to velocity” mode. Although both are widely used for moving the visual field, the operability of each method has not been examined quantitatively. Thus, we compare the operability of the two methods for adjusting the endoscopic view, and present the results and suitable applications of each method. The results of the quantitative evaluation experiments show that the “control corresponding to position” mode is suitable for short-distance or precise adjustment of the endoscope, whereas the “control corresponding to velocity” mode is better suited to long-distance movement.

This paper describes the development of a dexterous endoscopic parallel manipulator for laparoscopic surgery using rigid mechanism. Endoscopic parallel manipulator is developed based on the concept of virtual chain and screw theory. The inverse and forward kinematics solutions are derived analytically and numerically respectively. Also the singularity analysis is investigated. The known problem of limited bending angles was solved in the proposed manipulator as it can reach ± 90° in any direction. The proposed manipulator consists of four legs; two legs are 2-PUU (each leg consists of one active prismatic joint and two passive hook joints); the other two legs are 2-PUS (each leg consists of one active prismatic join, one passive hook joint and one passive spherical joint). The virtual prototype of the parallel mechanism was constructed in ADAMS. The kinematics simulation of the virtual prototype was realized. Four linear motors are used to drive the mechanism. The intuitive simulations with the combination of MATLAB/Simulink and ADAMS show that the control performance of kinematics analysis is satisfactory.

In this paper, by means of a statistical method, we use sole pressure on each part, angle of joint, femoral and crural muscle activities to produce a new foot muscle activity model for use in the design of ankle-foot orthoses. We built a Bayesian network model[1] by examining the normal gait of a nondisabled subject. We measured the activity of the lower foot muscles using electromyography, joint angles and the pressure on different parts of the sole. From these data, we built three models, representing the stance phase, the control phase and the propulsive phase. The accuracy of these models was confirmed. The largest feature of this model is making every 10% level nodes of each measurement data. Normal Bayesian network can estimate only muscle active or not active. But this method can estimate activity level of muscle. From this feature this method has three advantages. First, our use of 10% increments in the levels of the measured factors enabled changes in these factors during gait to be reflected in the model. Second, variations in the influence of factors that differ between low and high muscle activity are represented. Third, it is easier to use than physical models; three-dimensional motion analysis is not required and the method is convenient for clinical use. In an evaluation of this model, we confirmed that this model can estimate all muscular activity level with an accuracy rate greater than 95%.

The use of minimally invasive procedures for breast tumor diagnosis and treatment, such as needle biopsy and radiofrequency ablation (RFA), is steadily increasing. Accurate needle insertion requires solving the problems of tissue deformation and target displacement. In this study, we developed a robotic needle insertion method to improve the precision of diagnostic biopsy and RFA treatment. The mechanical probe was designed to reduce tissue displacement by pressing the breast tissue before needle insertion: a technique that is known as preloading. We focused on the needle insertion phase and evaluated the insertion accuracy achieved. Using a numerical simulation model and an actual hog breast, we compared tissue preloaded needle insertion with normal needle insertion. The data obtained with both test systems showed that targeting errors were greatly reduced using preloading-based needle insertion, as compared with normal needle insertion. The procedure is expected to offer a safe and effective alternative to the traditional methods of needle insertion for breast tissue biopsy or RFA. Our study also revealed the relationship between insertion accuracy and preloading probe force.

Walking is a fundamental human ability necessary for everyday life. We have developed an omnidirectional walker (ODW) for walking support to those who have walking disabilities. It is necessary for the ODW to know which direction the user is intending to go during walking support. A novel interface is proposed for the ODW to recognize directional intention according to the user's forearm pressures which are measured by force sensors embedded in the armrest. The relationship between forearm pressures and directional intention was extracted as fuzzy rules and an algorithm is proposed for directional intention identification based on distance type fuzzy reasoning method. In this paper, we conduct walking support experiments with the proposed method. The results show that the algorithm is applicable to directional control in walking support.

We have been developing the new personal mobility aid, "Tread-Walk 1," which is controlled by the driver's walking pace and amplifies walking velocity. The Tread-Walk 1 not only assists mobility but also helps the elderly maintain their physical abilities. However, the turning movement of the Tread-Walk is likely to be unstable, because the Tread-Walk is controlled by walking. In this paper, we focus on the stable turning movement of the Tread-Walk 1. First, we simulate the centrifugal force applied to the driver, which was not considered in our previous report. Then, a new algorithm to realize stable turning movement is established by measuring the driver's standing position. Finally, the developed algorithm for the turning movement of the Tread-Walk 1 is evaluated by measuring the handle grasping time. With the new algorithm, the Tread-Walk 1 turned steadily and driver did not lose their balance.

We describe a palpation-based needle insertion method for diagnostic biopsy and radiofrequency ablation treatment of a breast tumor. The mechanical palpation probe locates cancerous tissue from ultrasound imaging information and reduces tissue displacement during needle insertion by pressing the breast tissue. We examined the insertion accuracy of this method and compared palpation-based needle insertion with normal needle insertion both in vitro and in vivo. Palpation-based needle insertion had a smaller error, suggesting that this procedure is a safe, effective alternative to traditional methods of breast needle insertion.

The clinical target of this study is intratracheal balloon occlusion from minimally invasive fetal surgery for Congenital Diaphragmatic Hernia (CDH). The target for the surgery is prenatal temporary tracheal occlusion which enlarges the fetal lungs, and this procedure is promising for severe cases. A balloon is supposed to be inserted for tracheal occlusion using the manipulator. We propose a novel robotic manipulator for intrauterine fetal surgery for tracheal occlusion. In this study, a prototype of the robotic manipulator using a wire-driven mechanism has been developed. The manipulator is thin in structure and has multiple degrees of freedom to avoid damage to the fragile cells of the fetus. Specifically, we describe our development of the 3-unit robotic manipulator with ball joint-shaped arthroses and shaft diameter of 2.4 mm. The mechanism of the robotic manipulator was designed for providing the bending motion and controlling the contact force at its tip by the tension of the driven wires. Results of the experiment suggested that the contact force was controlled to under 0.04 N to insert the manipulator through the mouth of the fetus into the trachea without causing damage to the fetal tissues or changing the fetal attitude in the uterus.

It is often difficult for orthopedic surgeons to avoid LCL injury during ACL reconstruction. In this paper, we developed a steerable drill for ACL reconstruction to avoid LCL injury in the process of making a bone tunnel. There are two special requirements for the steerable drill mechanism. One is having sufficient flexibility to bend and avoid LCL while cutting the bone. The other is rigidity to avoid the buckle at the base of the drill when external force is exerted on the drill tip. These two requirements cannot be met simultaneously by using the previous material with uniform stiffness throughout its length. We therefore adopted a spring sheath with stiffness that varied between the top and base of the drill. This spring sheath has high stiffness at the base and low stiffness at the top. We performed the experiment to evaluate the effectiveness of the drill with uniform and non-uniform stiffness by comparing each result. Consequently, it was confirmed that the drill with non-uniform stiffness achieved 6 times the bending deformation and with 30% lower force as preventing the buckling compared to the drill with uniform stiffness. Subsequently, we presented a discussion concerning the reason for the experimental result, based on a physical long column model which simulated the steerable drill. In addition, at the end of this paper, a newly-developed control method to make the arbitrary trajectory of the bone tunnel using a steerable drill with non-uniform stiffness was described.

Essential Tremor (ET) refers to involuntary movements of a part of the body. ET patients have serious difficulties in performing daily living activities. We have been developing a myoelectric controlled exoskeletal robot to suppress tremor. However, the EMG signal of ET patients contains not only signals from voluntary movements but also noise from involuntary tremors. Then, we have developed a signal processing method to suppress tremor noise present in the surface EMG signal. The proposed filter is based on the hypothesis that tremor noise could be approximate to powered sine wave. In this paper, we have integrated tremor canceling filter and neural network (NN) to recognize the tremor patient's movement. According to the result, it was confirmed that the proposal filter increased accuracy of recognition, especially stable phase on elbow flexed position as “OFF”.

Gait phase based body weight support can be an effective method for patients who possess different ability in each leg and who require different unloading forces between the affected and unaffected sides. To realize this concept, we proposed a gait phase estimation method from pelvic motion focusing on the feature of its quasi-periodic movement at constant walking speeds. In this study, we analyzed the relationship between the heel contact point and the turning point of pelvic motion when using body weight support system at different amount of body weight support. The results indicate that the turning points of rotation movement can be useful to estimate gait phase because the values are similar between walking with different amounts of body weight support and have less variety.

The clinical target of this study is intratracheal balloon occlusion from minimally invasive fetal surgery for Congenital Diaphragmatic Hernia (CDH). The target for the surgery is a prenatal temporary tracheal occlusion, which enlarges the fetal lungs, and is a promising procedure for severe cases. A balloon is supposed to be inserted for tracheal occlusion using the manipulator. We propose a novel robotic manipulator for intrauterine fetal surgery for tracheal occlusion. In this study, the 3-unit robotic manipulator with ball joint-shaped arthroses and a shaft diameter of 2.4 mm using a wire-driven mechanism has been developed to approach the fetal trachea without the risk of damage to fetal tissue. The robotic manipulator has a thin structure and 7 degrees of freedom to avoid damage to the fragile fetal cells. However, the positioning control of the robotic manipulator is very difficult. In this paper, the mechanism of the robotic manipulator positioning control was confirmed by measuring the motion of each unit through the experiment. Additionally, a simulation was developed to estimate the mechanism of the robotic manipulator positioning control, and an approach method was considered. The results of the evaluation experiment suggested that the robotic manipulator could approach the fetal trachea through the mouth, and that the contact force was controlled to under 0.05 [N].

An EMG controlled intelligent orthosis was developed to support the rollover movement of cancer bone metastasis patients. In this paper, the validation of the developed signal processing algorithm to recognize the rollover was focused. Firstly, the ElectroMechanicalDelay of the internal oblique muscle was measured as the about 65 (msec). Secondly, it was confirmed that the rollover movement was recognized about 65 (msec) before the movement started. Therefore, the developed Micro Macro Neural Network (MMNN) recognized the rollover movement using the EMG signal as quick as possible. Finally, the robustness of the developed MMNN was discussed by conducting the experiment to discriminate between the rollover and turning out. We proposed and developed the original algorithm in which the logical XOR operation was added to the MMNN, because the MMNN which learned the characteristics of the only rollover recognized the turning out movement as the rollover movement perfectly. When the proposed algorithm that combined the MMNN and XOR operator was used, the rollover and turning out movements were discriminated 83%.

A movable body weight support (BWS) system for overground walking has limitations with respect to power and space for actuators. To solve this problem, a novel method by which to estimate the gait cycle from pelvic movement and feed forward control for leg-dependent force control are proposed. Based on an experiment on gait cycle estimation, a method of estimating heel contact timing from pelvic rotation is proposed. In addition, based on an experiment on leg-dependent force control, the developed feed forward control method is evaluated based on the vertical floor reaction force.

In the navigation of the visually impaired, an external input such as force or sound is required about the direction of travel to reach a particular target position. We develop a new haptic interface called “Force Blinker 2” to navigate the visually impaired. In Force Blinker 2, rotating weights and repulsive magnets are used to reduce the force generated to the direction opposite the traveling direction, which caused false recognition in the previous system, “Force Blinker 1.” In Force Blinker 2, the rotational radius of the weight varies depending on the velocity of the rotational weight. Ten visually impaired subjects evaluated Force Blinker 2 by comparing it with Force Blinker 1, a fixed radius type interface. The directions presented by Force Blinker 2 were correctly recognized at a rate of approximately 85%, which is approximately a 10% improvement over the rate by Force Blinker 1.

In this paper we present a new robotic palpation method to perform quantitative measurement of the material parameters of human tissues, for use in medical applications. The proposed method is achieved by the use of a system that integrates a robotic component and a numerical simulation component. The robotic component is used to measure the contact force and displacement at each point on the human body contacted by a robotic probe. The numerical simulation component identifies the material parameters using the proposed method, where two data sources are used, namely, (1) the measured data from the robotic part, and (2) simulated deformation data obtained by the finite element method. In order to validate the proposed system, we report initial results from several phantom tissue experiments, which demonstrate the ability of the system to quantitatively determine the elastic moduli of tissues. We also discuss several potential challenges in the future of the proposed system.

We reported a novel impedance control method based on a fractional calculation inspired by the viscoelastic properties of biomaterials such as muscle. This fractional impedance controller was found to realize superior impact absorption for the purpose of flexible contact for assistive and rehabilitation robots. This paper presents a preliminary evaluation of this concept using simulations and experiments. The numerical analysis results demonstrate that a fractional impedance controller has superior impact absorption performance than a conventional controller for contact with the elastic objects, especially for high stiffness objects and high velocity movement. The numerical analysis also reveals that using a fractional controller improved the robustness with respect to the robot dynamics. Moreover, the experimental results demonstrate that the fractional controller effectively suppresses the force between a person and a robot.

Needle insertion treatments require accurate placement of the needle tip into the target cancer. However, it is difficult to insert the needle accurately because of cancer displacement caused by organ deformation. Therefore, a path planning using numerical simulation to analyze the deformation of the organ is important for accurate needle insertion. The problem in developing a planning method is that puncture conditions, such as the force applied to the needle, is difficult to be decided deterministically, because the experimental data of puncture conditions have variations. Therefore, the purpose of this research was to develop a novel planning method to decide the robust paths of straight needle insertion for various puncture points. The basic idea of this planning method is to consider the puncture condition probabilistic and to evaluate the expected value of needle placement accuracy. First, a probability-based puncture condition was introduced, and then the expected value of needle placement accuracy was defined. Next, the optimization method was developed to search the insertion path in a way that minimizes the expected values of needle placement accuracy. Then, a numerical simulation and evaluation of the planning method was conducted, using a liver-shaped 2D model. Furthermore, an in-vitro experiment was carried out to measure needle placement accuracy from the optimized path. Experimental results show that the planning method realizes needle insertion with a mean accuracy of 1.5 mm.

Many motion support robots of the elderly and disable were studies all over the world. We have developed the rollover support system, which is one of the ADL. Our ultimate goal is to develop an effective rollover support system for patients with cancer bone metastasis. The core of this system is a pneumatic rubber muscle that is operated by EMG signals from the trunk muscle. A Time Delay Neural Network (TDNN) is the traditional method for recognizing EMG signals. However, response delay and false recognition are the problem of the traditional neural network. We previously proposed a new neural network, called the Micro-Macro Neural Network (MMNN), to recognize the rollover movement earlier and with more accuracy than is possible with TDNN. MMNN is composed of a Micro Part, which detects rapid changes in the strength of the EMG signal, and a Macro Part, which detects the tendency of the EMG signal to continually increase or decrease. However, the methodology to determine the structure of the MMNN was not established. In this paper, the optimal structure of the MMNN is determined. A comparison of each of the 360 sets of test times of MMNN versus TDNN was done. These results showed that recognition using MMNN is 40 (msec) (S.D. 49) faster than recognition using TDNN. Additionally, the number of false recognitions using MMNN is one-third of that using TDNN. By comparing the output using only the Micro part and Macro part in MMNN, it was found that the combination of quick response of the Micro part and stable recognition of the Macro part are advantages of MMNN. In the future, we plan to test the effectiveness of the total system in clinical tests with cancer patients in terminal care.

It is often difficult for visually impaired persons to walk outside to his or her destination. In this paper, we develop a cane with a built-in haptic interface for use by visually impaired persons. The cane is paired with IC tags buried underground (e.g., under street pavement). The haptic interface is controlled with a position and velocity control system that accurately indicates four directions (forward, backwards, right and left). After evaluating the vibration in the haptic interface, we determined the optimal vibration frequencies indicating a specific direction were combinations of 5 (Hz) and 1 (Hz). Furthermore, the optimal repetition of vibrations was determined to be two times. By using these conditions, the four directions were recognized more than 95% of the time. It was also confirmed that the visually impaired person recognized the presented direction even when an IC tag was buried underground. In the future, a mechanism will be developed that will allow visually impaired persons to recognize directions more accurately even if they swing the cane in a controlled manner. In addition, we will integrate a route decision system into the cane equipped with the haptic interface.

We describe a control method, for a surgical robot, which prevents the overload at fragile tissues. In particular, we focused on the control parameter setting method to ensure the robustness of the performance relative to the variation of the organ stiffness parameter. Firstly, we present Position/ Limited Stress control to achieving both precise positioning and prevention of overload. FEM based organ model was used to estimate the stress in this control method. Secondly, we describe the control parameter setting method. The control parameter was set to realize sufficient performance within the range of stiffness variation. Finally, we carried out a numerical simulation and an in vitro experiment. The simulation result suggests that our control method and parameter setting method helps prevent stress overload, not depending on the stiffness of organ model. The in vitro experimental result suggests that our method helps prevent stress overload of the in vitro-liver, the stiffness parameter of which is unknown.

We describe here a palpation-based needle insertion method for diagnostic biopsy and treatment of breast cancer. The mechanical palpation probe locates cancerous tissue from force information and reduces tissue displacement during needle insertion. We compared palpation-based needle insertion to normal needle insertion by numerical simulation of a breast tissue model and by experiments in vitro. The data showed palpation-based needle insertion had a smaller error in both tests. Our findings suggest the procedure is a safe, effective alternative to traditional methods of breast tissue biopsy.

To develop a gait rehabilitation robot for hemiplegic patients, quantitative evaluations of patient ability is needed. Patient's walk phase, which includes time balance of stance and swing legs, is one of the most useful indexes. However, conventional methods measuring walk phase require laborious preparations. In this paper, a novel algorithm estimating walk phase on a treadmill by observing DC motor current is proposed. In comparison of this algorithm and conventional methods, it was verified that the proposed algorithm had as the same accuracy as foot switch. Moreover, the proposed algorithm could estimate stance phase in 0.2 (s) errors between measurements of force plate mostly (4 out of 5 healthy subjects). However, result from the 5th subject showed that the proposed algorithm had erroneously identified stance phase as swing phase when little body weight loaded on leg. This characteristic is often observed in hemiplegic gait. Therefore, the proposed algorithm might need improvement of motor current threshold. However, this algorithm had capable of estimating the time of loading body weight on leg, and thus could be useful as a quantitative evaluation tool.

A mechanism using a pneumatic artificial rubber muscle (PARM) to restrict trunk twisting range of motion was proposed and an intelligent corset was developed to support the rollover movement of cancer bone metastasis patients. In this research, the specifications of the intelligent corset were deteminated so that it could perform in the same way as a traditional hard corset. Furthermore, based on the permitted trunk twist angle derived from interviews with hospital nurses, systems were evaluated for detecting the intention of rollover, using a neural network to recognize rollover, and using a PARM to restrict trunk range of motion (ROM). Through experimentation, the effectiveness of the intelligent corset was confirmed in ULPT and LLPT rollover movements. However, in 11% of the LLFT rollover trials, the twisting angle was higher than the permitted angle. Additionally, it was found that the intelligent corset solved the problem of the hard corset that patients feel pressure because of the constant restriction. In future, the intelligent corset will be evaluated in the clinical test.

Needle insertion treatments require accurate placement of the needle tip into the target cancer. However, it is difficult to insert the needle into the cancer because of cancer displacement due to the organ deformation. Then, a path planning using numerical simulation to analyze the deformation of the organ and the timing of puncture is important for the accurate needle insertion. In this study, we have explained the modeling of conditions where the puncture occurs. Firstly, this paper shows needle insertion experiments for the hog liver in order to measure the needle force and displacement where the puncture occurs. According to the experimental results, significant variations in puncture force were observed. Accordingly, we proposed a novel condition of the force causing a puncture considering probability distribution. We summarized variations of the puncture force in the experimental data and represented conditions where a puncture occurs with probability distribution models where the force is random variable. In addition, the boundary conditions and liver shapes are considered by analyzing the stress status near the needle. Then, we derived the conditions of the puncture with probability distribution models where the stress is random variable.

The development of assistive technologies, especially mobility devices, has an important impact on the daily activities and social participation of elderly people. The authors have developed a new mobility aid, ldquoTread-Walkrdquo, which extends mobility activities, maintains body function and maintains natural walking appearance. In the current research, we designed and developed a more natural operation system based on human walking movements. The new system concept is to use separate treadmill belts to measure the acceleration/deceleration force of each leg and use it as the input signal to change the direction of the system. This new device, ldquoTread-Walk 2rdquo, permits the user to walk naturally while a servo motor amplifies his normal walking speed. Its main components are a treadmill with two belts, two middle driving wheels, and four omni-directional casters. Sensors in the treadmill detect forward and backward reaction forces that are applied to the surfaces of the belts during walking. These forces for each leg are recognized as signal of the userpsilas intention to change direction and are used to turn the vehicle. These sensors also control the rotational speed of the driving wheel motors. Preliminary evaluations indicate that this turning system is both safe and effective for use by elderly people.

Currently, over seven million people die of cancer each year; some of whom suffer from pain caused by bone metastasis. In their final stages of life, the pain is such that they cannot even roll over, one of the activities of daily life. With this in mind, in this research, we aim to develop equipment for patients with cancer bone metastasis to support roll-overs in terminal care. Specifically, the EMG signal, which is the input signal of the equipment, is discussed in this paper. The activities of four muscles affecting trunk movement were monitored during the process of rolling over. Following an EMG experiment with four subjects, the internal abdominal oblique (IO) muscle was seen to be active in the early stages of roll-over motion, although IO muscle was relatively prevalent in previous works. If we support roll-over at this point, the patient feels no pain, because the timing is detected before the strongest burden movement, which involves buoying the trunk and rotating the pelvis. Hence, the EMG signal of the IO muscle is suitable for the input of the signal to support roll-overs.

A bending laser manipulator of 2.4 mm in diameter has been developed for intrauterine fetal surgery. This manipulator deflects a laser fiber in any direction thorough 90 degrees. The results of a positioning test and in vitro/in vivo tests are reported. Meanwhile, creep tests for fetal rat tissue of 16 to 20 days in gestation were performed to evaluate fetal tissue fragility. Unique features of fetal rat tissue compared to other soft organs are discussed and a viscoelastic model of the fetal rat tissue was proposed. The result of the modeling will be used not only for fabricating fetal tissue phantom but also for the force control of robotic application for fetal surgery.

Organs have many vulnerable tissues such as blood vessels and nerves which must never be damaged. This paper shows a control method which prevents the overload of vulnerable tissues. Firstly, the force control method, which prevents overload, is shown. Secondly, a FEM-based stress observer using the organ model is described. Finally, a control method incorporating the first and second steps, and which prevents overload at vulnerable tissue, is shown. Based on the experimental result of positional and stress data; it is shown that the stress at vulnerable tissues didn't widely exceed limit stress, in the event that a target position potentially resulting in damage to vulnerable tissue was ordered.

Hip joint surgeries are commonplace in our aging society. Robotic hip joint surgery is performed to cut bone precisely and is expected to be performed as minimally invasive treatment. Minimally invasive hip joint surgery needs operating space between muscle tissues and the bone around hip joint. In this paper a prototype of an articulated muscle-retracting robot for minimally invasive RAO (rotational acetabular osteotomy and one of the hip joint surgeries) is described. The muscle-retracting robot's role is to create an operating space between muscles and the surface of the bone for the other robot, whose role is to cut bone. The mechanical structure is very thin to follow a narrow path and tough enough to scrape and retract muscles around a hip joint. The prototype is designed based on the required specification from the previous experiments data. The prototype has 9 DOF, in which 3 DOF arms are capable of controlling the tip position and the force between muscle tissues and the surface of the bone. Evaluation of the prototype was done by using a compliant control as scraping method of muscle tissues from surface of the bone. The capability is revealed as a scraping length on a phantom of 140 mm around human hip joint model and on the living tissues of 27 mm in the crest of the ilium by magnitude of maximum force of 25 N. The scraped living tissues were a narrow part around the hip joint. We shall continue to research it and establish a stable control method to scrape tissues.

This paper shows the viscoelastic and nonlinear organ deformation model for organ model-based control of needle insertion, in which the deformation of an organ is calculated intraoperatively and the needle is manipulated with organ deformation taken into consideration. An organ model including such detailed material characteristics is important to achieve the control method in question. Firstly, the material properties of the liver are modeled from the measured data and its viscoelastic characteristics are represented by differential equations, including the term of the fractional derivative. Nonlinearity in terms of the fractional derivative was measured, and modeled using the quadratic function of strain. Next, a solution of an FE model using such material properties is shown. We use sampling time scaling property as the solution for the viscoelastic system. The solution for a nonlinear system using the Modified Newton-Raphson method is also shown. Finally, the organ deformation, assuming the needle is inserted, is simulated using an organ model and the overall deformation and distribution of the strain is computed in these simulations.

We propose a new surgical robotic system for intrauterine fetal surgery in an Open MRI. The target disease of the fetal surgery is spina bifida or myelomeningocele that is incomplete closure in the spinal column and one of the common fetal diseases. In the proposed surgical process, the abdominal wall and uterine wall would not widely be opened but rather surgical instruments inserted through the small holes in both walls to perform minimally invasive surgery. In this paper, a prototype of the micro manipulator of diameter is 2.4mm and bending radius 2.45 mm is presented. The diameter and bending radius of this manipulator is one of the smallest ever developed among surgical robots to the best of the knowledge of the investigating authors. The mechanism of the manipulator includes two ball joints and is driven using four wires able to bend through 90 degrees in any direction. The features of the mechanism include a small diameter, small bending radius, ease of fabrication, high rigidity and applicability for other surgical applications. Although the manipulator is not yet MRI compatible, the feature of the prototype demonstrated the feasibility of robotic intrauterine fetal surgery.

Medical procedures such as RFA and cryosurgery require the insertion of a needle into the target area within the body. Needle insertion is difficult because it can easily result in organs being deformed and displaced. This research aims to produce an intelligent robot for needle insertion, incorporating the following three techniques, A: visual feedback B: organ-model base control C: force control. This research uses a robot model and a liver for the target object to evaluate organ-model base control. For the purpose of organ-model base control, three experiments were conducted to evaluate the physical properties of the liver for robot control. A dynamic viscoelastic test was then carried out to show the dynamic properties of the liver in the form of a differential equation. The nonlinearity of the liver was supported by the creep test while an axial needle insertion test was also carried out to model the force and the extent of deformation experienced during needle insertion. In addition, an intelligent needle insertion robot was developed for the purpose of the experimentation concerning intelligent control of the needle. The experimental result displayed the margin error between the needle tip and target marker when the needle reaches the target position was around 1[mm] and a result led to positive findings.

Minimally invasive surgery has recently become a key word in medical engineering. In this operation, to introduce surgical instruments, spatulas which push tissues aside and retain the approach path to the affected area as well as workspace for the insertion of such instruments are necessary. Therefore, a new type of hydraulically-driven flexible manipulator for neurosurgery has been developed. With an attached balloon and using only physiological saline for the drive system, safety of the brain tissue, especially in terms of pressure, is assured as is the simplicity of the mechanism. In addition, this provides the advantage of MRI compatibility. From the results of several evaluations, this manipulator has been proved effective as a new type of medical device.

This paper proposes the planning and navigation of a surgical robot to perform safe and effective operations using finite element analysis results based on physical models of the brain. The physical brain models were proposed based on the results of physical property tests. Finite element analyses of virtual tension tests were carried out under the same conditions as the actual tension tests, and the results of the analysis coincided with those of the test. The finite element analyses of robotic brain surgery were carried out using a two-dimensional structure, which consisted of the proposed physical models. Assuming two types of robot models are used (the brain spatula and capsule type robot respectively), stress distribution in the brain, caused by each robot model, was simulated in the analyses. The preoperative planning was considered based on the analysis results, and the safe velocity of the robot’s movement was estimated from the same. The results of this research showed that organ modeling was necessary for preoperative planning in order to implement safe surgery.

A prototype master-slave system consisting of two MR-compatible manipulators with interchangeable surgical tools was designed, implemented, and evaluated. The manipulators are designed so as to fit into vertical-magnetic-field open-configuration MR imagers. They are also designed so that the surgical tool mounted at the tip of their arm is interchangeable. The MR compatibility of the manipulator including a surgical tool was evaluated by moving it close to a phantom in the field of view of an open-configuration MR imager. No noticeable deformation, but deterioration in the signal-to-noise ratio of approximately 10 percent, was observed in the MR images. Consulted clinicians then evaluated the manipulability of the master-slave system by maneuvering a pair of slave manipulators through an operation input device consisting of a pair of master manipulators. After several minutes of trial and error, they could perform each primitive motion for suturing tasks on training material mimicking human tissue.

Medical procedures such as RFA and cryosurgery require inserting a needle into the target location inside the body. Needle insertion is difficult because it is easy for organs to be deformed and displaced. Modeling the target object is essential in analyzing and developing a control system. Thus, a precise model is required to develop an intelligent robot that is able to insert the needle into the target area. This research uses a robot model and a liver for the target object. Four experiments were conducted to show the physical properties of the liver for robot control. A dynamic viscoelastic test was carried out to show the dynamic properties of the liver as a differential equation. The nonlinearity of the liver was supported by the creep test. In addition, the liver model was validated using a constant strain rate test. A needle insertion test was also carried out to validate the model.

To extend applicable area of minimally invasive neurosurgery, multi-DOF brain retract manipulator is developed. By inserting this manipulator deeper into the brain as an conductor and then other micromanipulator afterwards, it will be possible to realize new minimally invasive neurosurgery. The brain retract manipulator system is controlled by new safety method with brain retraction pressure monitoring system, Tendon-driven unit which controls lock or free status of each joint of multi-joint spatula, Passive-hybrid control system that assure the system a suitable safety. In evaluation test with a hog, insertion of the multi-joint spatula as deep as the cerebral base was realized, and the possibility of securing the space between the temporal lobe and the cerebral base is verified.

It is necessary to develop machinery that will help the aged support themselves, and the ambulatory capability is most important for the aged. We therefore started developing the Walk Training System for use in walk rehabilitation. To provide walk rehabilitation that can be adapted to trainees who have unequal leg abilities due to strokes, we designed a treadmill that has two endless belts driven by servo motors, one for each leg. By adjusting the belt settings individually, the trainee can do walk rehabilitation without braces. Field tests with people suffering from heavy hemiplegia confirmed that this system is useful in improving the ability of stroke victims to control their posture.

Japan's growing elderly population is becoming a serious problem. In addition, the ratio of elderly people who are bedridden is higher than in western countries. A range of facilities have been developed to help old people with excretion, bathing and sleeping. However, improvements can be made in all areas by improving this mobility. As a first step in this direction, we have developed a walking rehabilitation system for elderly people, with sponsorship from the Ministry of Health and Welfare.>