Remotely controlled hydraulically driven robots are expected to play an important role in extreme environments such as disaster sites, and force feedback is effective for improving the fidelity of the remote environment and the work efficiency. However, it is not reasonable to attach a force sensor directly to the end-point of a hydraulically driven robot. In a previous study, the authors showed that the impact forces, which are important information to improve the fidelity of the remote environment and work efficiency, can be estimated by using the information of acceleration of each link in addition to the cylinder pressures. In this paper, we investigated how many accelerometers and where those accelerometers should be attached on each link by using an index called GDOP (Geometric Dilution Of Precision) to improve the accuracy of impact force estimation. The experimental results show that although the estimation accuracy could not be improved significantly by rearranging the accelerometers, the effect of reducing the noise of the estimated load due to the sensor noise was confirmed.

In this paper, control methods to avoid the conflict of operators' commands in multi-user teleoperation system is considered. The proposed methods insert virtual nonlinear springs between the master arms and the end of wave transmission line of the multilateral controller. The nonlinear springs becomes softer when the input force from the operators are above a certain threshold and limit the input force. Experiments are conducted in order to compare the effectiveness of the methods. The experimental results show that the proposed two-step gain improves the operation performance.

In this paper, a virtual prototype system for control panels is presented by using an encountered-type haptic device. The system can render different switches arranged on a virtual control panel by a single haptic device. A motion planning algorithm for the encountered-type haptic device is proposed so that the device is properly encountered by the user at the switch locations while it avoids unintended collisions with the user elsewhere. To reduce the duty of the device motion, the weighting function in the algorithm is improved. Control panel surface coordinates are newly introduced in the motion planning so that unintended collisions of the device with the user are completely avoided in free space. The proposed motion planning algorithm with some improvements is verified by numerical simulations.

In a robotic cell, an assembly robot has to grasp various parts robustly even under some uncertainties in their initial poses. For this purpose, it is necessary to design robust grasping strategies for robotic hands. In this paper, we propose a method to derive an optimal robust grasping strategy from a given initial pose error region of a target object. Based on the pushing operation analysis, it is possible to simulate multi-fingered hand grasping and derive a permissible initial pose error region of a target object from which planned grasping is successful. Adopting an active search algorithm proposed by the authors, we can find the optimal grasping strategy efficiently. As an example, we derive the optimal grasping strategy for grasping a circular object by a three-fingered hand.

In this paper, a novel method to synthesize a desired trajectory and sensory feedback control laws for robots based on the statistical characteristics of direct teaching data by a human is proposed. This work was motivated by a poor performance of an origami-folding robot developed by the authors. Since the robot simply replayed a given trajectory without sensory feedback control, it often failed in folding due to the fluctuation of origami paper behaviors.

In this paper, we extend the concept of dynamic manipulability to evaluate the dynamic property of multifingered grasping systems consisting of a multifingered hand and a grasped object, and propose a measure of dynamic manipulability of multifingered grasping. Similar to the original dynamic manipulability, the proposed measure evaluates the mapping from a set of realizable joint torques to a set of resultant accelerations of the grasped object, which forms an ellipsoid under a constant internal force constraint. It is clearly shown that the internal forces not only affect the volume of the ellipsoid, but also the amount of offset of the ellipsoid, while the gravity forces simply induce an offset. A new measure, i.e., omnidirectionality, is introduced to add a penalty to the original manipulability measure, which simply evaluates the volume of the ellipsoid, depending on how much the ellipsoid is offset. Numerical examples by using a simple two-fingered robot hand are shown to demonstrate the effectiveness of the proposed measure.

This paper presents the updateable probabilistic evacuation modeling (UPEM) technique, which allows sensor observation data to be included in the problem of estimating the state of an evacuating crowd, as the data are obtained. Each individual is modeled as a Newtonian particle which interacts with obstacles, such as walls and other individuals. The UPEM technique estimates not only the general trend of the crowd as a whole, but also the specific states of each of the evacuees in the crowd. Furthermore, an approach to cooperative autonomous searching in crowded urban emergencies is developed using UPEM. A number of simulated searches in emergency evacuations highlight the efficacy of the technique in reducing the time required to detect targets and in increasing the level of safety for human evacuees.

This paper discusses variable-scale bilateral control for micro teleoperation. A method is proposed to synthesize robust variable-scale controllers that guarantee system stability and realize robust performance in contact with any arbitrary, but passive, operator and environment. The proposed method is based on the formulation as a robust output feedback constant scaled H∞problem. A variable scaled teleoperation system appears as a polytopic linear parameter-varying (LPV) plant, with an affine relation on the scale factors. Gain-scheduling is used to derive robust stable time-variant H∞controllers for online variable scaling. Improved controller performance is obtained through the introduction of an affine and scheduled-parameter-dependent weighting. The controller synthesis problem is formulated as a set of linear matrix inequalities (LMI’s) augmented with a nonconvex rank condition. An efficient algorithm is constructed to synthesize a set of sub-optimal controllers over the parameter space. The validity of the proposed methods are confirmed experimentally.

This paper describes the design of a new telepresence vision system developed to realize a higher immersive feeling for telemanipulation tasks. A new measure of 'permissible visual errors' was defined. Making use of this new measure, a minimal vision system is designed, containing only the strictly necessary DOF's (degrees of freedom) while keeping the vision errors below an experimentally obtained set of permissible errors. The result is a 4DOF camera system, containing two rotational joints (pan-tilt) and two prismatic joints (horizontal plane.) An evaluation of the system was done through a telemanipulation task using a unified hand/arm teleoperation testbed. It was found that during use of the vision system almost all visual errors remained within the permissible errors. The proposed vision system design framework suggests to break away from simply (and often blindly) mimicking human appearance. Although we only dealt with the vision system design, the same concept could be used when designing any other part of a robot.

In order to search and rescue the victims in rubble effectively, a 3D map of the rubble is required. As a part of the national project of rescue robot system, we are investigating a method for constructing a 3D map of rubble by teleoperated mobile robots. In previous work, we have developed the second prototype of laser range finder for rubble measurement. The prototype laser range finder consists of a ring laser beam module and two omni-vision cameras. Also, the third prototype, which is more compact than the second one, is newly developed. Our range finder has the features that the omni-directional distance around the range finder can be measured at once and the omni-directional picture image can be captured at the same time. The measurement accuracy of the sensor depends on the adjustment of some parameters. Although we were adjusting the parameters manually so far, this adjustment requires much time and effort. However, it is difficult for manual adjustment to derive fine measurement accuracy. Then, we developed a calibration system which adjusts the parameters using a Genetic Algorithm. In this paper, the third prototype laser range finder and the calibration system are described. The calibration method of the parameters for the laser range finder is also described. The calibration system makes it possible to adjust the parameters easily. Results of calibration by using the constructed calibration system show the availability of the system.

For the purpose of realizing the functions of the human hand on a mechanical system, fundamental understanding of the human hand is necessary through intensive observations of manipulation tasks by humans. As an example of skilled manipulation tasks, we target origami folding.We first analyzed the difficulty of origami manipulation and observed how the human folds the origami. We then designed a robotic mechanism that can make an origami work, the Tadpole, in the same way as the human does based on the observation of the origami folding by the human. Although the appearance of the developed robotic hand is dissimilar to that of the human hand, the robot succeeded in performing the origami task, the Tadpole.

This paper deals with the haptic rendering of collisions between a human operator and rigid objects in a virtual environment. The focus being on high-velocity impacts on a rigid wall. After discussing the importance of velocity measurements in contrast to force measurements, a new haptic device is introduced. The new device is capable of applying directly an 'impulse' to the operator, similar to collisions occurring in the real world. Based on a Poisson-model of the rigid virtual object, the necessary change of momentum of the operator's hand is being estimated online. A momentum wheel, under velocity-control, is engaged through an electromagnetic toothed clutch, at the estimated instant of impact. The resulting immediate change in momentum is thought to be essential for giving interactions with rigid virtual objects a realistic feel. Rather than generating so-called 'impulsive forces' with big motors, this approach relies only on small motors and is thus intrinsically safer. Experiments are performed on a one-degree of freedom setup. Conclusions are drawn and future directions of this research are sketched

The purpose of this research is to develop an intuitive interface to control rescue robots. We propose a new image stabilization system for easy operation of rescue robots. A promising method to search victims in rubble, is the use of teleoperated rescue robots. In the rescue activities with such robots, operators remotely control the robots through images captured by cameras mounted on the robots. Since the orientation of the robots change intensively while they move in rubble, image stabilization is necessary so that the operators can search victims without suffering from fatigue nor motion sickness. However, the orientation changes of the rescue robots are so intensive that conventional methods may not be capable of stabilizing the camera images. In this paper, we propose a new image stabilization system which can cancel the camera motion due to the intensive changes of the robot’s orientation on an uneven terrain. After a preliminary experiment, a 3-DOF camera system was designed based on the newly proposed mechanism. To verify the performance of the camera system, we conducted three experiments. The result of the experiments confirmed that the proposed mechanism shows good performance in motion stabilization as well as good performance in tracking the commanded head motion. Finally, we verified that the camera system works properly even when it was mounted on a crawler running on an uneven terrain.

In this paper, we propose a simulation model of uneven terrains based on fractional Brownian motions (fBm) for evaluating traversatility of mobile robots. Using fBm model, one can generate various terrain models by changing only two parameters. We modeled two different terrains by using fBm and checked statistical traversability of a robot with different wheel sizes and body configurations in computer simulation. To validate the effectiveness of the fBm model, we conducted real experiments with a wheeled mobile robot. Probabilities that the robot can travel a certain distance well agreed with the simulation results.

Unlike conventional haptic devices, an encountered-type device is not held by a user all the time. Instead, the device stays at the location of a virtual object and waits for the user to encounter it. In this paper, we extend this concept to fingertip contacts and design an encountered-type haptic display for multiple fingertip contacts to simulate tasks of grasping an object with any shape and size. Before designing the device, we intensively observed human grasping behaviors. This observation was very helpful to determine the mechanism of the device. An encountered-type device for three-fingered grasping was actually prototyped based on our design. We then discuss a path planning algorithm for the designed device, once again based on the observation of human grasping behaviors. A rough sketch of the algorithm is proposed and a preliminary experimental result to support our idea is shown.

In order to search and rescue the victims in rubble effectively, a 3D map of the rubble is required. As a part of the national project of rescue robot system, we are investigating a method for constructing a 3D map of rubble by teleoperated mobile robots. In this paper, we developed a laser range finder for 3D map-building in rubble. The developed range finder consists of a ring laser beam module and an omnivision camera. Ring laser beam is generated by using a conical mirror and it is radiated toward interior wall of the rubble around a mobile robot that mounts the laser range finder. The omnivision camera with hyperbolic mirror can capture the reflected image of the ring laser on the rubble. Based on the triangulation principle, a cross section range data is obtained. Continuing this measurement as the mobile robot moves inside the rubble, a 3D map is obtained. We constructed a geometric model of the laser range finder for error analysis and obtained an optimal dimension of the laser range finder. Based on this analysis, we actually prototyped a range finder. Experimental results show that the actual measurement errors are well matched to the theoretical values. Using the prototyped laser range finder, a 3D map of rubble was actually built with reasonable accuracy.

In this research, we focused on the degrees-of-freedom for robot foot mechanism. To realize the functions of human locomotion on biped robots, we should know the fundamental aspects of human foot mechanisms through intensive observations of human locomotion. We proposed a novel mechanical shoe with 2-DOF toe parts, which move independently and are able to constrain human foot in various ways. Wearing the mechanical shoes, three subjects were measured on their walking speed, toe joint angles, and center of pressure. They were walking in straight, zigzag and slalom courses. Through these observations, we show that a biped robot with the proposed toe mechanism could potentially walk faster than conventional ones.

A bilateral teleoperation experiment with Engineering Test Satellite 7 (ETS-VII) was conducted on November 22, 1999. Round-trip time for communication between the National Space Development Agency of Japan ground station and the ETS-VII was approximately seven seconds. We constructed a bilateral teleoperator that is stable, even under such a long time delay. Several experiments, such as slope-tracing task and peg-in-hole task, were carried out. Task performance was compared between the bilateral mode and the unilateral mode with force telemetry data visually displayed on a screen. All tasks were possible by bilateral control without any visual information. Experimental results showed that kinesthetic force feedback to the operator is helpful even under such a long time delay, and improves the performance of the task.

In this paper, we focus on a problem of how to confirm a feasible condition of applied force to a multi-legged robot on rough terrain. The problem often appeals as a subject of walking stability criterion for a legged robot. ZMP (zero moment point) is one of the well-known criteria. It shows the condition as footprints of a legged robot, but it cannot be defined on the rough terrain. Therefore, we suggest a new criterion FSW (feasible solution of wrench), which gives the feasible condition even on the rough terrain from the viewpoint of "wrench"-a special representation of force screw. And we present two short examples of FSW for a biped robot, how to analyse the validity of ZMP on stairs and how to design a force trajectory on rough terrain.

In order to search and rescue the victims in rubble effectively, a 3-D map of the rubble is required. As a part of the national project of rescue robot system, we are investigating a method for constructing a 3-D map of rubble by teleoperated mobile robots. We are also planning to build an intuitive user interface for teleoperating robots and navigating in a virtualized rubble model using the obtained 3-D model. In this paper, some preliminary research results are introduced. We did some design studies of laser range finders that can be mounted on a mobile robot and can get the range data of the rubble around the robot. Then, we formulated a 3D SLAM (Simultaneous Localization and Map Building) algorithm and conducted some simulation studies. Lastly, we proposed a novel motion canceling camera system and confirmed its validity by experiment.

In this paper, we propose a method for image overlay on the front glass of a vehicle to navigate a driver to a desired destination. By overlaying the navigation information on the front glass, the driver need not gaze at the console panel. Therefore, accidents caused by gazing at console panel could be reduced. To overlay the image accurately on the target object through the front glass, both the vehicle's position/orientation and the driver's position/information are estimated by vision-based tracking and measuring angular velocities of the vehicle's wheels. Experimental results show the validity of the proposed method.

To replace human activities by humanoid robots in hazardous environment, they should perform various motions, not only simply walking by their two legs but also passing through a narrow way, climbing a ladder and even getting in a operating machine. In such cases, humanoid robots are contacting/grasping the surrounding environment through their hands as well as their legs. In this paper, we propose a method to evaluate the postures of humanoid robots when their limbs (arms and legs) are constrained to the surrounding environment. From a given posture, a quantitative measure is calculated considering various aspects, such as joint torque limit, joint motion range, and the robustness from falling down and slipping down. Only static posture is evaluated, assuming stationary postures or quasi-static motions. Numerical examples show the validity of the proposed evaluation method. Based on the proposed evaluation, an example of optimizing a motion sequence is also shown.

A bilateral teleoperation experiment with ETS-VII was conducted on November 22, 1999. Round-trip time for communication between the NASDA ground station and ETS-VII was approximately six seconds. We constructed a bilateral teleoperator that is stable even under such a long time delay. Several experiments, such as slope tracing task and peg-in-hole task, were carried out. Experimental results showed that kinesthetic force feedback to the operator is helpful even under such long time delay and improves the performance of the task.

A path-planning algorithm for encountered-type haptic devices that render multiple virtual objects in 3D space is proposed. To render multiple virtual objects with a single haptic device, the following two behaviors must be realized: (i) the device should move to the target object location in advance of the user's hand so that the user can encounter it; (ii) otherwise, the device should keep away from the user's hand, avoiding an unexpected collision. To realize such a consistent encounter, the user's hand motion must be tracked. The proposed algorithm determines the device location based on the minimum distance problem between a point (the user's hand) and a convex polyhedron constructed from the reference points of multiple objects. An automobile virtual control panel was constructed using an encountered-type haptic device in which the proposed path-planning algorithm was implemented. The validity of the proposed algorithm was confirmed and the required performances, such as the device speed and the accuracy of hand tracking were evaluated.

In previous work, we (1999) have proposed a control scheme based on wave variables. Unlike other methods, the proposed method could minimize the performance degradation due to the fluctuation of time delay. With this method however the system may potentially generate infinite energy in some special situations and the system stability could not be ensured rigorously. In this paper, we modify the method by introducing an energy input/output balance monitoring mechanism, which limits the energy that the system can generate. We conducted some simulation studies with a one DOF system. Simulation results show the validity of the proposed scheme.

A unified hand/arm master-slave system was developed to conduct more dexterous tasks by teleoperation. Both the master and the slave consist of a two-fingered hand and a 3-DOF planer manipulator. The system is also aimed at investigating the bottleneck of autonomous robotic manipulation systems. To evaluate the performance of individual teleoperation systems all over the world in equal condition, we propose toy block assembling (LEGO) as the benchmark test for teleoperation systems. Using our hand/arm master-slave system, we announce the measured completion time for assembling some block structures, expecting other research group to try the same task in the future.

Proposes a method for accurate image overlay on head-mounted displays (HMDs) using vision and accelerometers. The proposed method is suitable for video see-through HMDs in augmented reality applications but is not limited to them. Acceleration information is used for predicting the head motion to compensate the end-to-end system delay and to make the vision-based tracking robust. Experimental results showed that the proposed method can reduce the alignment errors within 6 pixels on average and 11 pixels at the maximum, even is the user moves his/her head quickly (with 10 m/s/sup 2/ and 49 rad/s/sup 2/ at the maximum). The viewing range was enlarged by placing additional landmarks in the environment.

The motion of the operator's fingers has been tracked by a real-time tracking vision system to provide a user interface to a machine tool. The desired cutter position is determined from the finger position and the machine tool path is controlled to follow. The system provides an environment where a machining center can be controlled remotely without any special apparatus, such as a master manipulator. Thus, the user interface described in this paper is one of the crucial technologies for "technology transfer with real feeling". Experimental results show the effectiveness and the performance of the developed system.

Soft fingertips can easily achieve high friction contacts but their frictional moment around the contact normals makes manipulation control difficult. We propose a control scheme to manipulate an object by a multifingered hand with soft fingertips. The proposed scheme cancels the frictional moment according to the direction of the relative rotation between the fingertip and the object. Whatever the fingertip contact type is, accurate pose measurement is very important for the object manipulation. We also propose a systematic method to estimate the object pose with a complementary use of camera images and finger joint information. The proposed control scheme and the pose estimation method were combined and implemented in an experimental system. Results of the experiment show the effectiveness of the proposed pose estimation method and the overall control system for manipulating an object by a soft-fingered hand.

We propose a method for accurate image overlay on head-mounted displays (HMDs) using vision and accelerometers. The proposed method is suitable for video see-through HMDs in, augmented reality applications but not limited to them. Acceleration information is used for predicting the head motion to compensate the end-to-end system delay and to make the vision-based tracking robust. Experimental results showed that the proposed method can reduce the alignment errors within 6 pixels on average and 11 pixels at the maximum, even if the user moves his/her head quickly (with 10 [m/s/sup 2/] and 49 [rad/s/sup 2/] at the maximum).

Several approaches based on wave variables have already been proposed for bilateral teleoperation control under time-varying delay. However, these approaches are too conservative for keeping the system passivity or for estimating the amount of virtually constant time delay. These conservative approaches result in too much degradation of maneuverability from the constant time delay situations. We propose a novel control scheme that is also based on wave variables, but minimizes the performance degradation due to the fluctuation of the communication time delay. The proposed method is simple and easy to implement. We conducted some simulation studies with a one DOF system. Simulation results show the validity of the proposed scheme.

In this paper, two kinds of the degree of freedom in constraint state (CSDOF) are defined for motion of an object in contact with an immobile environment, and then their application to planning of assembly tasks is discussed. The CSDOF of the first kind is defined as the number of independent directions in which the object can move, keeping the current constraint state. The CSDOF of the second kind is defined as the number of independent directions in which the object can move bilaterally when it is allowed to break the current constraint conditions and to go away from the current constraint state. We discuss the difficulty of state transition by considering the two kinds of CSDOF as well as the degree of constraint in constraint state (CS-DOC) and give a criterion function for state transitions. Based on this criterion function, we propose an algorithm for planning the optimal procedure for assembly tasks. Some numerical examples are given to show the validity of the proposed approach.

We have been working on developing a visual/haptic interface for virtual environments. The authors have previously (1996) proposed a WYSIWYF (What You See Is What You Feel) concept which ensures a correct visual/haptic registration so that what the user can see via a visual interface is consistent with what he/she can feel through a haptic interface. The key components of the WYSIWYF display are (i) vision-based tracking, (ii) video keying, and (iii) physically-based simulation. The first prototype has been built and the proposed concept was demonstrated. It turned out, however, that the original system had a bottleneck in the vision tracking component and the performance was not satisfactory (slow frame rate and large latency). To solve the problem of our first prototype, we have implemented a fast tracker which can track more than 100 markers in video-rate. In this paper, new experimental results are shown followed by the improvements of the vision-based tracking component.

In this paper, we first define the ideal response of micro-teleoperation. Then, we discuss the robust stability of bilateral control systems based on the structured singular value of scattering matrix. Finally, we propose a new control scheme which can realize the ideal response. It is shown that the proposed control scheme satisfies the robust stability condition. A prototype of 1DOF teleoperation system with a mini manipulator was developed. The validity of the proposed control scheme is confirmed by experiments and compared to the conventional control schemes, such as the symmetric position type and force reflecting type.>

In this paper, the analysis and design of master-slave teleoperation systems are discussed. The goal of this paper is to build a superior master-slave system that can provide good maneuverability. We first analyze a one degree-of-freedom system including operator and object dynamics. Second, some ideal responses of master-slave systems are defined and a quantitative index of maneuverability is given, based on the concept of ideal responses. Third, we propose new control schemes of master-slave manipulators that provide the ideal kinesthetic coupling such that the operator can maneuver the system as though he/she were directly manipulating the remote object himself/herself. The proposed control scheme requires accurate dynamic models of the master and slave arms, but neither parameters of the remote object nor the operator dynamics is necessary. Last, the proposed control scheme is introduced to a prototype master-slave system and the experimental results show the validity of the proposed scheme.

The authors discuss how to manipulate an object in contact with the fixed environment with robot-fingers to perform a planned assembly operation successfully. First, the region of possible fingertip force to balance the reaction force from the environment (quasi-static analysis) is explicitly represented to ensure that the moving object is manipulated correctly. Next, by considering the assembly operation in quasi-dynamic way (i.e., assuming that the velocity of the motion is small enough to be neglected but its acceleration is not negligible), the region of feasible fingertip forces to operate the object is described. According to the region of possible finger forces, the corresponding feasible range of the fingertip positions on the object surface can be obtained. And the difference between the fingertip position obtained by the quasi-dynamic analysis and the fingertip position obtained by the quasi-static analysis is shown. Lastly, the validity of this quasi-dynamic method is verified by serval experiments., All discussions are on the assumptions that objects are polyhedra and their notions are planar and frictionless, and its velocity is small enough.

In this paper, a quasi-static object manipulation by an articulated three-fingered robot hand with slip motion of grasping is discussed. This kind of manipulation achieves more dexterous manipulation by robot hands. The equilibrium relations of fingertip forces for grasping an object are solved in three dimensions. It is assumed that a slip happens when the fingertip forces go beyond the bound of the cone of maximum static friction. Possible directions of slip within a grasp are determined from the analysis. The fingertip force which achieves a desired slip motion is determined uniquely. Finally the set of fingertip forces is obtained, and the planning method of slip motion is discussed.

Efficient computational algorithms for the trajectory control of multiarm free-flying space robots are presented. The motion of the aircraft itself during manipulation is considered in order to obtain an accurate trajectory control. The generalized Jacobian of multiarm free-flying space robots is obtained efficiently by regarding the total multilink system as a composite system consisting of two links with a joint. The algorithm can be easily extended to any tree-structured multiarm robot with rotational as well as prismatic joints except for closed-loop structures. An efficient computational algorithm for the resolved acceleration control of the multiarm free-flying robots is also presented. The computational complexities are evaluated and compared to those of fixed-base manipulators. It is shown that the computational complexity for the generalized Jacobian is five times greater than that for fixed-base manipulators whereas the resolved acceleration control requires twice the computation for fixed-base manipulators.>

The analysis and design of master-slave teleoperation system are discussed in order to build a superior master-slave system that can provide good maneuverability. The authors first analyze one degree-of-freedom systems considering operator and object dynamics. Secondly, they define some ideal responses of master-slave system, and a quantitative performance index is given based on the concept of the ideal responses in order to evaluate the maneuverability of the system. Thirdly, they propose new control schemes of master-slave manipulators which can provide the ideal object realities so that the operator can feel the object through the system ass though he were manipulating it himself. Lastly, the proposed control scheme is examined by a prototype master-slave system, and its validity is confirmed experimentally.>

Deals with robust control of robot manipulators in the case where joint torque sensors are available. First, the authors derive a dynamic equation of the manipulator with joint torque sensors that explicitly expresses the total nonlinear multivariable structure. This dynamic equation makes it possible to construct the control system of the manipulator with joint torque sensors using the same method as in the conventional case without the sensors. Second, based on this dynamic equation, they propose a robust trajectory control scheme which achieves the specified tracking accuracy in the presence of the modeling errors including the modeling errors of actuator systems. In the proposed method, the joint torque sensor information is fully exploited to compensate the uncertainty of link and load parameters. Furthermore, an illustrative simulation result is given to show the effectiveness of the proposed control method.>

For autonomous assembly operations by a robot, it is required to build a planning function that can generate a series of operations to reach a goal state. This paper describes an automatic planning algorithm that synthesizes the assembly operation strategies. By minimizing a criterion function based on the difficulty of state transitions the method can find an optimal path in a contact state network. The degree of constraint is proposed by regarding the assembly task as a process of changing the constraint state of the object. State transition difficulty is discussed by considering the variation of the degree of constraint and the shape information from the geometric models of objects. Then, a criterion function for state transitions is defined based on the state transition difficulty. Lastly, an algorithm which plans an optimal state transition path from an initial state to a goal state is proposed. Some examples are given to show the validity of this algorithm.>