This paper proposes a motion-reproduction method based on an iterative learning control (ILC) for variable reproduction speed. The motion-copying system consists of a motion-saving phase and a motion-reproduction phase. The motion-saving phase extracts the position and force information of an operator by a bilateral control. In the motion-reproduction phase, human motion is reproduced by using the extracted motion data as command values. This paper proposes the modification method of the reproduction speed during the motion-reproduction phase. When the reproduction speed is variable, the reproduction accuracy decreases due to the position and force errors. To address this issue, this paper uses an ILC during the motion-reproduction phase. The ILC modifies the position and force commands based on the extracted motion data. This paper focuses on character writing motion with a brush pen by a robot. The validity of the proposed method was demonstrated by experimental results.

This paper proposes local path planning based on velocity obstacle (VO) considering the collision probability and kinematic constraint for a mobile robot. Several types of VO-based methods have been reported since VO is one of the practice path planning methods. In VO-based methods, the velocity pairs with collision probability are treated as VO. For collision avoidance, the velocity pair outside VO is selected as the velocity command. In other words, the velocities with even a little collision probability are treated as unselectable velocity pairs. Therefore, VO-based methods are conservative. In the proposed method, weight coefficients according to collision probability are set in VO. By using these weight coefficients, the velocity pairs inside VO are evaluated. In addition, only the feasible velocity pairs are selected by considering the kinematic constraint. If the collision probability is low, the mobile robot can select the velocity pair inside VO. The validity of the proposed method was confirmed by the simulation results.

This paper presents development of a 2DOF haptic feedback control stick for remote control of a two-parallel-wheeled rover. In bilateral control, when dynamics are quite different between a leader and follower devices, e.g., between a linear-slider type of control stick and a wheel with a comparatively large moment of inertia, a force reproduced on the control stick based on external forces applied to the rover’s wheel, is disturbed largely. Since the position control forces the control stick’s position and the rover’s angular velocity to be synchronized, the operator feels not only the reproduced force but also a force by this position control inevitably on the same time. We call this force a restoring force. The restoring force disturbs the operator to feel the reproduced force accurately. But the authors think the restoring force is meaningful for remote navigation of the rover as another haptic information. Thus, in this paper, we developed a 2-DOF haptic control stick, which transfers the reproduced force and the restoring force separately to a slider and a grip, and proposed a control method for achieving this purpose. The control stick was implemented and was performed successfully in verification experiments using the proposed control method. Experimental results were discussed comparing to the former 1-DOF control stick.

This research focuses on an adaptive control method for a pulling motion of a fibril. From the viewpoint of the biotechnology, analyses of a mechanical characteristic of a fibril are important. For the analyses, the pulling motion of the fibril is conducted by a piezoelectric actuator with a cantilever. The fibril is attached at the tip of the cantilever, and is pull by the piezoelectric actuator. By this pulling motion, it is possible to measure the mechatronic parameters of the fibril. During the pulling motion, the mechatronic parameters of fibril are changed due to the pulling force. Therefore, it is hard to conduct the pulling motion at the desired force command such as the constant force. From this view point, this paper proposes the adaptive control method based on the recursive least squares algorithm (RLS). These mechanical parameters are estimated in real-time by RLS. By using these estimated parameters, the position command to achieve the force command is calculated. In the simulation, the proposed method is implemented, and the pulling motion with the contact force is simulated. The validity of the proposed method is confirmed from the simulation results.

This paper proposes a tracking control method considering an obstacle avoidance by a reflective motion for a mobile robot. In the mobile robot, a laser range finder is utilized to recognize environmental information. The obstacle avoid motion is created by using environmental information and the virtual manipulators mounted on the mobile robot. In the conventional researches, the flexible obstacle avoidance method by using the kinematic relation between the virtual manipulators and environmental information was reported. This method has the advantage for the calculation cost and flexibility like reflective motion. However, the robot may not follow the desired trajectory after the obstacle avoidance, since this conventional method is based on the velocity control. In order to solve this problem, this paper proposes a combination method of the tracking control and the obstacle avoidance. Considering the velocity limits of the tracking control, it is possible to modify the priority of the trajectory tracking and the obstacle avoidance. The effectiveness of the proposed method was confirmed from the experimental results.

This paper proposes the position and attitude control method using a disturbance observer for an underwater vehicle. When the underwater vehicle such as a remotely operated vehicle (ROV) and an autonomous underwater vehicle (AUV) moves, the position and attitude control of the underwater vehicle is important. In this situation, the underwater vehicle is affected by disturbances such as ocean current and tidal current. These disturbances have the bad influence to the position and attitude control of the underwater vehicle. In addition, the dynamic model of the underwater vehicle has the modeling error, since this shape is not simple. This modeling error also degrades the tracking performance. This paper proposes the robust position and attitude control system against disturbances and the modeling error for the station keeping in the underwater vehicle. In order to compensate for disturbances, the disturbance observer is implemented as the proposed method. The advantages of the disturbance observer is high robustness against these disturbances. It is possible to compensate not only disturbances but also modeling error by using the disturbance observer. The validity of the proposed method was confirmed from the simulation results.

This paper proposes the improvement method of operability in a bilateral control by using visual information. The bilateral control system consists of a master system which is manipulated by the operator and a slave system which contacts remove environment. Considering the actual use of the bilateral control, the operator manipulates the master system while watching the visual information from the slave side. In this situation, there is the time delay of visual information. This time delay has the bad influence of the operability. In order to improve the operability, the synchronization method of visual and tactile information is described. The virtual model, which consists of the virtual slave model and the virtual object model, is proposed to compensate this time delay. This virtual model is overlaid on the visual image from the slave side. As a result, the operator grasps the motion of the slave system and the object without time delay. The validity of the proposed system was confirmed from the experimental results.

This paper describes a remote control system with a virtual force feedback in a mobile robot. In the mobile robot, a laser range finder is utilized to recognize environmental information. By using this environmental information and the specification of the mobile robot, the safety velocity area (SVA) is calculated in real-time. On the other hand, an operator generates the velocity commands for the mobile robot in real time. By using the relation between SVA and the velocity commands, the virtual force is generated. If the velocity commands are out of SVA, the operator can feel the virtual force. In the previous research, the virtual force is generated based on the only velocity differences. Therefore, the chattering of virtual force commands may occur. In order to solve this problem, this paper proposes the virtual force generation method with hysteresis. Therefore, the operability of the remote control system is increased. From experimental results, the validity of the proposed method was confirmed.

This paper proposes a synchronization method of visual and tactile information by using a virtual slave model in a bilateral control. Considering an actual remote-operated system, an operator operates a master system while watching visual information that is sent from a slave side. However, transmission of position, force, and visual information has communication delay. This is because the slave system on the image moves later than the actual slave system. This communication delay gives a bad effect on operability in the bilateral control. Therefore, the synchronization method of visual and tactile information is important. From this viewpoint, visual and tactile information in bilateral control is synchronized by using the virtual slave model. This virtual slave model is overlaid on the image from the slave side. The operator operates the master system while watching the virtual slave model overlaid on the image. As a result, the operability is improved, since the virtual slave model helps the communication delay of visual information. The effectiveness of the proposed system was confirmed form the experimental results.

This paper proposes an implementation method of a workspace observer (WOB) considering a fluctuation of an equivalent mass matrix. WOB is one of useful methods to achieve robust control systems. The stability and transient response of WOB is influenced from a modeling error of a nominal plant model. For a high performance of WOB, a precise modeling of a nominal plant model should be used. From this viewpoint, this paper modifies a nominal plant model in real time due to an estimation of an equivalent mass matrix. Here, a nominal plant model includes off-diagonal elements. An equivalent mass matrix is fluctuated due to a manipulator motion. This fluctuation is influenced to a control performance of WOB. Therefore, this fluctuation is compensated in this paper. In addition, a decoupling in an acceleration dimension is actualized, even if a nominal plant model includes off-diagonal elements. The validity of the proposed method was confirmed by simulation results.

In order to assist human beings, the reproduction methods of the recorded human motions have been researched. On these systems, the human motions are recorded as the haptic data (i.e., position, velocity, and force data) by using bilateral control. However, these conventional methods show poor adaptability to the difference in the environmental location during the reproduced phase. In order to compensate this spatial difference, the spatial data processing of the recorded human motions was utilized. On the other hand, the reproduction method of the recorded human motions with time scaling is proposed to compensate this spatial problem in this paper. In other words, the proposed method applies time scaling to compensate the spatial difference. For the realization of the proposed reproduction method with time scaling, the recorded velocity and force data are utilized. By using the proposed method, the physical meaning is clear compared with conventional methods, since power on the certain moment of the reordered task is reproduced. This paper focuses on the point-to-point motion, which includes the force motion and the position motion, as one of typical tasks in the industry field. The validity of the proposed method was confirmed by the experimental results.

This paper proposes a system and its control method to boost part of the battery voltage for electric vehicle. This system consists of the powertrain of electric vehicles and a bi-directional isolated DC-DC converter called dual active bridge (DAB). The powertrain of electric vehicles in the market has the problem that its performance degrades due to fluctuations in battery voltage. In order to solve this problem, a DC-DC converter is often inserted serially between the battery and the inverter. However, in this solution, the conduction loss of the DC-DC converter always occurs. In this paper, as a solution to the above problems, a voltage boosting system using DAB converter is shown.

This paper proposes driving range extension by series chopper power train for Electric Vehicles (EV for abbreviation). The proposed method was experimentally verified and compared with the previous publication [1]. Further measurement on motor test bench, to compare this drive with the conventional power train, showed a 2.1 % improvement.

This paper describes real-time gait planning for pushing motion of humanoid robots. This method deals with an object whose mass is not known. In order that a humanoid robot pushes an unknown object in both single support phase and double support phase, real-time gait planning for pushing the unknown object is proposed. Real-time gait planning consists of zero moment point (ZMP) modification and cycle time modification. ZMP modification is the method that modifies the influence of reaction force to ZMP. By cycle time modification, the period in double support phase is modified to avoid a robot tipping over. These modifications are calculated from reaction force on arms in every cycle. With these methods, trajectory planning for pushing an unknown object in both single support phase and double support phase is calculated. Even if parameters of an object and friction coefficient on the floor vary, the robot keeps on walking while pushing an object. The effectiveness of the proposed method is confirmed by a simulation and an experiment.