An overground track-walking scheme with a body-weight support system can provide task-oriented and repetitive training. Furthermore, it improves gait stability and endurance more effectively than the conventional treadmill walking method. However, it does not improve asymmetry and reduces gait speed. Accordingly, we developed a 4-DOF mobile manipulator in which the position of the handle is controlled to provide continuous somatosensory information (cutaneous & proprioception information), such as a fixed rail to the user’s hand during overground walking for gait enhancement (velocity, symmetry, and balance). The system consists of 3 omni wheel-based mobile robot for robust track following and a 1-DOF revolute joint-based manipulator for gait enhancement during track-based gait guidance. To demonstrate the feasibility of the system, we conducted a pilot experiment with one stroke patient on a 15 m track. The experimental results showed that the robot could guide the patient along the track and enhance symmetry and balance, especially in the curved section of the track. Furthermore, the preferred walking speed of the participant on the track improved. Therefore, the system demonstrated promising potential for providing quantitative, repetitive, and safe track-based overground gait rehabilitation training.

The cable-driven redundant manipulator (CDRM) has significant potential for applications in narrow and hazardous spaces. However, traditional CDRMs have limited stiffness and load capacity due to their cable routing method. To address these limitations, several scholars have proposed new mechanisms and control strategies. Nevertheless, the cable routing method has not changed, and CDRMs continue to suffer from their limitations. Recently, a nematode-inspired cable routing method was proposed; however, stiffness calculations, derivation of inverse kinematics, and validation of stiffness and load capacity were incomplete. In this paper, we calculate the analytic equivalent stiffness of the nematode-inspired cable routing method and compare it with other cable routing methods. Additionally, we derived and simulate the kinematics and an effective inverse kinematics algorithm. Finally, we validate the stiffness and load capacity using a developed prototype.

To effectively enhance the spatial sensation for an immersive user experience (UX) in virtual reality (VR), the locomotion interface (LI) is one of the most critical factors. To offer a room-scale LI suitable for use in typical office or home environments, it is imperative that the LI device enables a natural walking experience while occupying minimal space. To realize LI for all directions, an omnidirectional treadmill (ODT) can successfully achieve 2-dimensional holonomic motion (X and Y axes) and provide the most natural walking experience, such as walking on real ground. However, a problem arises due to the excessive system thickness caused by the torus structure of a large treadmill (X-axis) carrying several small treadmills (Y-axis), along with the installation of a complex power transmission mechanism inside the ODT. To reduce the thickness of its double-layer and complex structure, we propose an ODT with a novel transmission mechanism. The proposed ODT utilizes helical timing pulleys (HTPs) to generate Y-axis motion and helical gears (HGs) to synchronized-actuate the HTPs. As a result, the proposed ODT achieves a super-thin configuration and fast actuation performance. A pilot test of the proposed ODT was conducted to assess its maximum performance. The results indicate achievable speeds of 3.175 m/s and 4 m/s, along with an acceleration of 5 m/s2for both the X and Y axes, respectively.

Magnetic Particle Imaging (MPI) is an emerging tomographic modality that allows for precise three-dimensional (3D) mapping of magnetic nanoparticles (MNPs) concentration and distribution. Although significant progress has been made towards improving MPI since its introduction, scaling it up for human applications has proven challenging. High-quality images have been obtained in animal-scale MPI scanners with gradients up to 7 T/m/ , however, for MPI systems with bore diameters around 200 mm the gradients generated by electromagnets drop significantly to below 0.5 T/m/ . Given the current technological limitations in image reconstruction and the properties of available MNPs, these low gradients inherently impose limitations on improving MPI resolution for higher precision medical imaging. Utilizing superconductors stands out as a promising approach for developing a human-scale MPI system. In this study, we introduce, for the first time, a human-scale amplitude modulation (AM) MPI system with superconductor-based selection coils. The system achieves an unprecedented magnetic field gradient of up to 2.5 T/m/ within a 200 mm bore diameter, enabling large fields of view of mm3 at 2.5 T/m/ for 3D imaging. While obtained spatial resolution is in the order of previous animal-scale AM MPIs, incorporating superconductors for achieving such high gradients in a 200 mm bore diameter marks a major step toward clinical MPI.

Cable driven redundant manipulator (CDRM) can provide complex movements with high dexterity and singularity reduction. However, traditional CDRMs with universal joints have the disadvantages of requiring a high number of motors and having a narrow joint workspace. Furthermore, there is a limitation in terms of stiffness and payload. Recently, CDRMs composed of Quaternion joints have been developed to address these disadvantages. They require fewer motors and have larger joint workspace due to the Quaternion joints. Yet, their cable routing method is the same as the traditional CDRMs. In this paper, we propose a novel nematode-inspired cable routing method to achieve complex movements and stiffness increase. To achieve the stiffness increase of CDRM, the proposed cable routing method was inspired by the alternately arranged muscle structure of nematodes. Moreover, moving pulley structure was selected to amplify the stiffness and force of CDRM. An 8-DOF CDRM prototype composed of four Quaternion joints was developed to show the effectiveness of the cable routing method. Kinematics simulation was conducted and then, verified by trajectory through experiments. Finally, a joint stiffness simulation was conducted and verified with the developed prototype by stiffness experiments.

Post-stroke gait rehabilitation is necessary to aid social re-integration. An active knee orthosis (AKO) can aid gait training through the provision of bodyweight support and assistive knee torque. However, its use may cause instability and it does not ensure improved gait symmetry and speed. Use of a speed regulation device such as a robotic cane in conjunction with and AKO may overcome these limitations. Therefore, to combine the beneficial effects of an AKO and speed regulation, we have devised a gait assistance system (GAS) that combines our developed AKO with our Haptic cane (HC) to provide combined knee assistance and speed regulation. The system can provide constant speed regulation and proprioceptive input to improve gait speed, symmetry and balance, while providing assistive torque to improve knee range of motion. The system is evaluated through tests with nine healthy subjects who wore ankle weights on one leg to simulate hemiparesis. The results show that for majority of the outcome measures (gait and balance parameters), use of the GAS and HC generated significantly better results than use of only the AKO. However, for nearly all the measures there were no significant differences between GAS and HC. Thus, the results indicate that the HC and GAS may be used according to patient's condition, where more severe patients who require assistive torque may use the GAS and less severe patients may use only the HC.

For immersive interaction in a virtual reality (VR) environment, an omnidirectional treadmill (ODT) can support performance of various locomotive motions (curved walk, side walk, moving with shooting stance) in any direction. When a user performs lateral locomotive motions on an ODT, a control scheme to achieve immersive and safe interaction with the ODT should satisfy robustness in terms of position error of a user to keep a reference position of the ODT by accurately estimating intentional walking speed (IWS) of the user, and it should guarantee postural stability of the user during the control actions. Existing locomotion interface (LI) control focuses on the reference position tracking performance regarding the position of the user's center of mass (COM) in order to respond to forward locomotion that can move at high speed. However, in sideways walking, the movement of the lower extremities is different from that of forward walking, and when the conventional LI control was directly applied to sideways walking, it was observed that excessive acceleration commands caused postural instability. For appropriate interface of sideways walking, we propose an estimation scheme based on an accurate walking model including the movement of the ankle joint. The proposed observer estimates the acting torque generated by the force of both lower extremities through the position information of COM and ankle joint to more accurately predict the user's intentional walking speed (IWS). In the sideways walking experiment conducted using a 1-dimensional user-driven treadmill (UDT), the proposed method allowed more natural interface of the lateral-side locomotion with better postural stability compared to the conventional estimation method that uses only the COM position information.

In this paper, a novel, low-cost lower extremity gait rehabilitation device using a single actuator is presented. The proposed device is based on a single DOF 8-bar Jansen mechanism, which was recently introduced as an efficient walking mechanism for legged robots. The mechanism is synthesized to generate the ankle trajectory during human gait relative to the hip, in terms of both position and time. Two mechanisms, one for each lower limb, are applied reciprocally and mechanically synchronized to guarantee symmetric gait. A custom designed seat-type weight support system is also introduced. It supports weight of the user and mechanisms, and also provides the required interaction while maintaining mobility at the hip. To accommodate different users, several parameters of the mechanism are adjustable. Ease of donning-doffing action, weight-bearing and possibility of unhindered arm swing have been considered to provide an effective and user-friendly training environment. A prototype is manufactured, and a pilot study with a healthy subject is conducted to demonstrate feasibility of the concept. Due to ease of control, cost-effectiveness and high intrinsic safety, the proposed system potentially offers a possible method of gait training.

The control problem in self-adjustable treadmills is to keep the position of the user at a reference position. The position error is the key obstacle in facilitating the abrupt stopping on self-adjustable treadmills. Another difficulty in this application is the oscillatory response of the closed-loop system. The conventional control methods utilize a high-gain observer to estimate the user velocity and exploit this information beside feedback signals to decrease the position error. Utilizing the high-gain observer, however, applies anomalous force (AF) to the user, leading to an unnatural feeling, and does not guarantee an oscillation-free response for the output. This paper aims to alleviate these problems by proposing a supervisory control scheme. First, a RISE controller is utilized for walking/running stage to compensate for slowly varying uncertainties in the system model without applying a large AF. Then, a positive-output controller is exploited for the stopping stage to guarantee the convergence of the position error without oscillation. Using the estimated intentional velocity and acceleration, a supervisory system is designed to switch between the controllers. Experimental results show the superiority of the proposed approach over the existing methods.

To achieve immersive and natural navigation in a virtual environment through human locomotion, it is necessary to generate a 2-dimensional infinite ground for omnidirectional walking. However, the existing omnidirectional treadmills are heavy, complex and exhibit low acceleration due to power transmission inefficiency. In this paper, we present a novel fast-omnidirectional treadmill (F-ODT) with a new power transmission mechanism called the Geared Omni-pulley. This mechanism ensures higher power transmission efficiency for driving the belts of the multiple transversal treadmills for independent Y-axis motion. Due to the improved power transmission performance combined with a simpler and relatively light-weight structure, the proposed 2D treadmill can generate a maximum speed of 3m/sec with an acceleration of 3m/sec2. Based on the improved performance, the F-ODT system can be used as a locomotion interface platform in various virtual reality environments such as training of soldiers, gaming/educational experiences and gait rehabilitation.

The magnetic nanoparticles (MNPs) have been emerging as effective drug carriers. The electromagnetic actuated systems can steer the MNPs in vascular network for targeted drug delivery (TDD) systems. However, the real-time monitoring of MNPs remained as an open challenge which limits the application of these systems. In this paper, for the first time a 2D real-time imaging scheme has been developed for the MNPs guidance system. The proposed 2D navigation system based on magnetic particle imaging can allow real-time monitoring of MNPs and provides promising potentials for simultaneous monitoring and steering. In the experiments, MNPs of 45 to 65 nm diameter and 5 nm core (Iron) could be successfully monitored in real-time (update rate of 2 Hz) in 2D. The proposed 2D monitoring system can provide dynamic tracking of MNPs in targeted drug delivery and makes a MPI-based navigation system more feasible.

Among most existing gait rehabilitation robots, it is difficult to find adequate devices for gait rehabilitation of chronic stroke patients who can already stand and move but still need to rehabilitate the affected lower limb through simple, compact, and easy-to use devices. This paper presents a novel haptic based gait rehabilitation system (HGRS) which has the potential to provide over-ground gait training regimens for post-stroke ambulatory subjects. It consists of a portable cane for kinesthetic sensing and a wearable vibrotactor array for tactile biofeedback. Contact of user with the handle provides light grip force, it serves the purpose of balance assurance and increased muscle activity through light touch concept and vibrotactors contribute in enhancing the gait modification through afferent signal of vibration. Walking trials conducted with stroke patients indicate increased muscle activation and balance, and improved temporal symmetry with use of HGRS. HGRS is capable of assisting physical therapists in training individuals with stroke suffering from gait abnormalities. In addition, it is easy to use and low-cost which makes it reachable to a vast domain of subjects suffering from gait abnormalities.

Targeted drug delivery by using magnetic nanoparticles (MNPs) is an efficient technique to deliver drug molecules towards specific tissues in a human body. The MNPs' 1D guidance system is a combined electromagnetic actuation (EMA) and monitoring system, which can provide an accurate control scheme with nanoparticle's localization for more precise targeting of the drug delivery. The localization of the MNPs is done by magnetic particle imaging (MPI) with low amplitude excitation field. In this paper, we have developed a novel coil topology for 1D MNPs feedback control, by alternate supply of different currents to coils set in time sequence, the coil set alternates functions between MPI and EMA. Motion of MNPs is controlled by a gradient of the magnetic field in EMA period, the distribution of MNPs is reconstructed in MPI period and provides feedback to the EMA. The guidance system will provide navigation and tracking interleaved for targeted drug delivery of MNPs in compact and efficient ways. The 1D MNPs guidance system has 2Hz of EMA and MPI hybrid frequency, allowing a position control of MNPs with 90nm diameter.

This research aims to develop a novel gait assistive device with enhanced gait stability and training efficiency for stroke patients. The proposed assistive device for mobility aid is composed of a motored wheel and a cane for providing only a light grip force, which prevent a patient using excessive support force of an upper limb like a conventional cane and motivate the patient to use more actively a paralyzed limb due to the reduced weight support. In addition, the proposed device can provide the user with intuitive and safe interaction during walking by integrating an F/T sensor and a tilt sensor at the cane, and a switch sensor at the hand grip. Also, admittance control has been implemented for a patient, it intuitively changes cane speed by measuring interaction forces at the hand grip. A hemi-paretic stroke patient participated in the walking experiments as a pilot study to verify effectiveness of the proposed system. The results showed that the patient could improve walking speed and muscle activation during experiments with a constant speed mode of the haptic cane. Moreover, in the admittance control mode of the haptic cane, the patient could keep higher preferred walking speed and higher gait stability regardless of magnitude of resistance forces. The proposed gait assistive device with cheap, compact and easy-to-use characteristics can provide efficient gait training modes to chronic stroke patients.

Magnetic drug targeting is an approach to guide and concentrate magnetic nanoparticles (MNPs) into the diseased target organ after being injected into blood vessels. Although many works for drug targeting have been conducted, there are few studies on delivering the nanoparticles to the target region. Drug delivery performance has not been addressed sufficiently or fully. In this paper, we investigate the effect of dominant factors to MNPs delivery performance. Then, an optimized field function scheme with a pulsed magnetic actuation is proposed to significantly improve the MNPs guidance performance. With a specific condition of blood vessel size, particle size, and applied magnetic field, the optimized parameters of the field function are selected through extensive simulation studies. We find out that the optimal negative and positive time for the magnetic pulsed field mainly depends on the exit time for particles to reach the bifurcation and the critical time as the maximum time for them to reach the vessels wall, respectively. With the chosen parameters, we show that ratios of correctly guided particles in a Y-channel are reached to 100%. In addition, to minimize the power consumption, a modified field function (MFF) scheme is introduced. The MFF includes a no-power time, called zero-time, between the positive and negative time. It is shown that with the proposed MFF, the energy consumption and the heating problem of the actuator system can be significantly reduced. Therefore, the proposed guidance scheme for MNPs can overcome the sticking issue and maximize the guidance performance as well as reducing the power consumption. It should be noted that the MFF can be easily implement by programmable DC power supplies connected to electromagnetic coils.

Virtual reality (VR) now a day is progressively being used in our manufacturing environments. In production or maintenance processes, the most important VR application can be assembly areas as the efficiency of a production or maintenance scheme primarily depends on the assembly and disassembly (A/D) sequence, number of gripper changes and the path used in an A/D process. In this paper, a novel optimum assembly algorithm with ant colony algorithm is proposed to solve the maintenance assembly process for 3D objects and complex environments, and to find both optimal sequence and 3D path planning. Sequentially, the assembly sequence was optimized by a traditional ant colony optimization algorithm and then, the 3D path planning with the optimized sequence information was optimized by combining an ant colony algorithm enhanced by potential field concepts. Simulation results showed that proposed algorithm has faster convergence rate towards the optimal solution when compared with existing algorithms based on genetics and traditional ant colony approach.

In virtual MAD environment the most significant phase is the A/D process (Assembly / Disassembly). The effectiveness of the maintenance scheme depends on the A/D sequence, number of gripper changes and the path used in an A/D procedure. However, in a constrained 3D environment simulating realistic models, path planning of the parts becomes more complex because of the factors like complex geometry computations, obstacles, orientation and initial/final position of the part. In this case the path planning of the parts becomes an important factor affecting the overall efficiency of the maintenance process. Therefore, to address this problem an intelligent assembly planner is developed with a combined approach based on potential field method and genetic optimization process for MAD path planning. Furthermore, haptic-assisted feature is implemented for user support for realistic 3D MAD path planning simulations.

This paper describes an enhanced haptic assembly simulation system, in which an optimal assembly algorithm is used to allow haptic interactions and traditional assembly sequence problems. The optimal assembly algorithm provides optimal paths for haptic guidance as well as an assembly sequence of the parts to be assembled. The performance of the given assembly schemes were simulated and analyzed using a haptic assembly system. Experimental results showed that the haptic-path sequence-guidance (HSG) mode gave the best performance improvement in terms of accumulated assembly time (28.56%) and travel distance (15.64%) compared to the unguided mode, while the sequence-guidance (SG) mode alone increased performance by 16.91% for assembly time and 11.66% for travel distance. The experimental results were analyzed by the sub-tasks of gripper selection, inter-part movement, and part assembly which showed the effectiveness of the optimal assembly algorithm.

In a virtual environment, a virtual maintenance process can be used to simulate real-world maintenance, and the efficiency of the simulation depends mainly on the assembly/disassembly task sequence. During the simulation, the path planning of mechanical parts becomes an important factor since it affects the overall efficiency of the maintenance system in terms of saving energy and time. Therefore, planners must consider the path-planning factors under constraints such as obstacles and the initial/final positions of the parts, as well as the assembly sequence, for example, the number of gripper exchanges and direction changes. We propose a novel optimal assembly algorithm that considers the assembly sequence of mechanical parts and the path-planning factors for a virtual maintenance simulation system. The genetic algorithm is used to determine the optimal parts sequence to minimize the numbers of gripper exchanges and direction changes, as well as find a repulsive force radius using the potential field method to generate the shortest optimal distance for each part during the assembly operation. By applying the proposed algorithm to a virtual maintenance system, users can be haptically guided to the optimized assembly solution during mechanical parts assembly operations.

An objective of this research is to optimize the designing parameters of a 6-DOF parallel manipulator required the large workspace for the sophisticated and complicated work on the basis of mechanism's compactness. The method uses a genetic algorithm with respect to the maximization of tranlational/rotational workspaces and isotropy of mechanism to obtain the optimal linkage parameters. It is studied for fifteen cases which are divided by combination of translational and rotational workspaces corresponding to the range of translational motion and tilt angle of the end-effector. To decide the best model in the total optimized cases, compactness of mechanism, translational workspace, rotational workspace on the boundary of translational workspace, and global conditioning index (GCI) as kinematic performances, and then kinematic performances of best model are verified by comparing to those of the preexisting model

This paper presents a novel reconfigurable ankle rehabilitation robot to cover various rehabilitation exercise modes. The designed robot can allow desired ankle and foot motions including toe and heel raising as well as traditional ankle rotations since the mechanism can generate relative rotation between the fore and rear platforms as well as pitch and roll motions. In addition, the robotic device can be reconfigured from a range of motion (ROM)/strengthening exercise device to a balance/proprioception exercise device by simply incorporating additional plate. Further, the action of the device is two folded in the sense that while a patient’s foot is fastened firmly to the ROM/strengthening device for task specific training, s/he can also stand on the balance/proproception device. The suggested ankle rehabilitation robot is expected to substitute not only the traditional therapy in various exercise modes but also supply the advanced functional exercises.

This paper presents walking control of a novel omni-directional locomotion interface with a dual-planar parallel robot. The suggested interface can generate infinite floor on planar surfaces, allowing user's upright and turning walking motions. To provide continuous walking in a confined area, a walking control algorithm is suggested for planar surfaces. For continuous walking, each independent platform of the locomotion interface will follow a human foot during the swing phase, while the platforms will move back during single stance phase. For accurate foot tracking control, magnetic trackers are attached on each shoe with careful calibration and transition phases between the swing and the stance phases are detected by using switch system, which is composed of light steel plate, spring, and micro switch. For double limb support, two platforms will manipulate neutral positions to compensate the offset errors generated by velocity change. This algorithm can satisfy natural walking conditions for any directions of planar surfaces. From experimental results, a subject can walk naturally for upright motions without significant limitations, while limitations of maximum yaw angle of 20/spl deg/ are applied to each platform to prevent the collisions of two platforms during turning motions. By using the suggested interface, it is anticipated that a user can interact with virtual normal pathways by real walking including upright and turning motions.

Presents the control and evaluation of a haptic device with a 6-DOF parallel mechanism for interfacing with virtual reality. This haptic device has low inertia, high bandwidth, and high output force capability mainly because of base-fixed motors. In addition, it has large orientation workspace due to RRR type spherical joints. A control method is presented with gravity compensation and with force feedback by a F/T sensor to compensate for the effects of unmodeled dynamics such as friction and inertia. Also, dynamic performance has been evaluated for force characteristics such as maximum applicable force, static-friction force, minimum controllable force, and force bandwidth by experiments. Virtual wall simulation with the developed haptic device has been demonstrated.