An estimation method of end-point impedance based on bilateral control system

SUMMARY This paper proposes a method of decoupled bilateral control based on a modal space observer. In a conventional bilateral control system, the structures of master-slave systems are not considered. This paper shows that a force controller and a position controller in a bilateral control system interfere with each other when the structures of the master-slave systems are different. In order to solve this problem, a bilateral control system based on a hybrid matrix has been proposed. However, the computational process for calculating the hybrid matrix becomes complicated as the numbers of degrees of freedom in the master-slave systems increase. In the proposed method, a nominal equivalent mass matrix with respect to the modal space is used, and the interfering terms are estimated and compensated using a modal space observer. Therefore, a simple control structure is realized using the proposed method. The performance of the proposed method is compared to that of the conventional methods through simulations and experiments, and the validity of the proposed method is confirmed.

Recently, there are many researches of a system which has implemented a bilateral control system which can touch an environment in distant place. However, a singular configuration due to the inverse Jacobian matrix becomes the problem in a bilateral control with different configurations. In this paper, the problem of a singular configuration regarding the inverse Jacobian matrix is avoided by singularity-consistent method. In addition, an error observation method of a torque regarding the singularity-consistent method is proposed. And, the bilateral control system consists of a parallel link manipulator and a serial link manipulator. When the direct kinematics of the parallel link manipulator is derived, mode decoupling method is introduced. Finally, proposed method and sc method are applied to the bilateral control system with different configurations, its system is realized and the error of the torque due to singularity-consistent method is observed. The experimental results of the bilateral control with different configurations are shown.

Time delay in bilateral control system seriously deteriorates stability. Conventional acceleration based bilateral control method has stabilized position control. But, force control is not stabilized. This paper proposed a stability improved structure for bilateral control system. Position control and force control of proposed bilateral control system are stabilized. The validity of the proposed method is shown by numerical and experimental results.

Bilateral control system has been developed as a method to transmit tactile sense in order to be applied to handling radioactive material, operating unmanned underwater vehicles, space robotics, telesurgery, etc. Bilateral control system is able to transmit tactile sense to only one operator. To transmit tactile sense to multiple operators, multilateral control was expanded from bilateral control. However, tactile sense of environment which general multilateral control system transmits to an operator is significantly affected by other operators' motion. This paper proposes a novel control system which transmits environmental impedance to multiple operators. The proposed system uses master-slave system consisting of multiple master robots and a single slave robot. Both position and force information is transmitted bi-directionally between each master robot and a slave in the proposed system, whereas the information is transmitted among all robots in general multilateral control system. In addition, a method to estimate environmental impedance given by spring-damper model is proposed, since the proposed control system requires real-time estimation of environmental impedance. The validity of the proposed system is confirmed by simulation and experiment.

Position error between master and slave occurs in bilateral control system under time delay and it is undesirable for delicate works. To solve this problem, this paper proposes a compensation method of position error in bilateral control under time delay. Firstly, the cause of position error is expressed. After that, it is shown that 3-channel bilateral control system, which is the conventional method, compensates position error. However, 3-channel bilateral control system is known to be unstable in contact motion. In 3-channel bilateral control system, a compensation term is added in master. In contrast, in the proposed method, a compensation term is added in slave. Moreover, stable contact motion and compensation of position error are realized. The validity of the proposed method is verified through experiments.

Recently, network-based control systems attract a lot of attentions. One of the applications of such control systems is haptic transmission using a bilateral control system. In order to construct the bilateral control system over the time delayed-network, many researchers have proposed many methods and succeeded to improve the stability and performance of the system. By assuring the system’s passivity, some of conventional methods have succeeded to stabilize the system even when the communication blackout occurs. However, the passivity-based methods are conservative and deteriorate the performance. In this paper, the mode shifting method is proposed to deal with the communication blackout without considering the system’s passivity. In the proposed method, the bilateral controller is shifted to a local controller when the communication blackout occurs. By shifting to the local controller, the system is not destabilized by the blackout. Moreover, when the communication recovers, the bilateral controller is gradually restored to regulate the robot’s output power. Owing to the power regulation, the robots never damage environmental objects during and after the communication blackout. Therefore, the proposed method realizes stable and safe control even under the blackout. The validity of the proposed method is confirmed by simulations and a experiment.

In this paper, the method which eliminates the reactive operational force in bilateral control system under time delay is proposed. In bilateral control system under time delay, an operator feels large operational force. In addition to that, amplitude of response increases and it makes system unstable. In this paper, the proposed method eliminates this increasing. Therefore, operationality in free motion is improved. To solve this problem, reactive operational force is introduced which is calculated by using power factor in mechanical system. Power factor in mechanical system is derived from power factor in electrical system. Then, the concept of power factor is explained. In this research, only free motion is considered. Then, contact motion should be considered in future work. The performances of the previous method and the proposed method are evaluated through experiments.

In this paper, mathematical models for the management of biological resources based on a given predator-prey relationship are proposed, and two types of control strategies, unilateral and bilateral control with impulsive state feedback, are studied. The existence of the order-1 homoclinic orbit, order-1 periodic solution, and bifurcation of homoclinic of the unilateral control system are obtained, and the attraction region of this system is also discussed. Besides, sufficient conditions for the existence and stability of the order-1 and order-2 periodic solutions of the bilateral control system are also gained. A series of numerical simulations including bifurcation diagrams of periodic solution are performed, which not only verify the theoretical results we get but also reveal some peculiar dynamical phenomena, such as the appearance of high-order periodic solutions and existence of parameter intervals with drastic order change of periodic solution. By comparing the two management strategies, our study encourages bilateral control rather than unilateral control for the risk of predator extinction.

This paper proposes a controller for bilateral control system with communication delay. The bilateral control system consists of two master robots and two slave robots. A human operator handles two master robots, and two slave robots grasp and manipulate a task object cooperatively. The grasping force and manipulation force are fed back to the operator. The gain of master's controller is adaptively determined in terms of the stiffness of a contact object. Since conventional adaptive controllers are designed on robot coordinate system, the force and position information used for controller are based on robots, grasping force and manipulation force interfere with each other. The proposed adaptive controller is designed on task coordinate system, the force and position information used for controller are based on a task object, to reduce this interference. The validity of the proposed controller is verified via an experiment of a bilateral control using four liner motors.

Passivity theory is a very useful tool for the stability analysis of bilateral teleoperation with communication delay. Many researchers use passivity-based stabilization method such as those based on scattering theory or wave variables. However, passivity-based stabilization is too conservative for the design of a high-performance teleoperation system. The term “high-performance” implies that people who operate this system can experience a highly accurate reaction force from environments. In this study, we analyze the L2-stability of some bilateral control systems with time-varying communication delay by using the small-gain theorem. The small-gain theorem is known to be a stability condition for multi-input multi-output feedback systems. Additionally, a novel control structure for the bilateral control system with communication delay is proposed. The bilateral control system with the proposed structure satisfies the L2-stability condition of the small-gain theorem. The experimental results show the utility of the proposed control structure.

The paper proposes a method to reduce an operational force in a bilateral control system that realizes simultaneity property under communication delay. A bilateral control that realizes simultaneity property is previously proposed, which is achieved by delaying the own force information. It focused on the fact that the force information is the pure information that actuates the motor, therefore, timing of the force information input is corrected. However, the control system requires large force when operator tries to operate the system. In this paper, the problem is solved by utilizing the delayed position information of the own system. The proposed control system is designed to mix present and buffered position information to reduce the operational force. The delayed information can easily affect the stability problem, therefore, phase compensator and the velocity feedback is used. The validity of the proposed method is confirmed by experiments.

Haptic sense is indispensable for skillful operation in a telerobotic system. Bilateral control attracts considerable interest because it transfers the haptic sense to a remote place. Although it is simply composed of two manipulators, its design is complicated. This study proposes an idea that provides a new framework on design of a bilateral control system. The idea is to design the bilateral control system based on a “function”, a minimum component of a system role. It enables simple and explicit design for various tasks. The features of the proposed method provide a way to design an adjustable system, Experimental results show the validity of the proposed method.

Aiming to the problem of big impact feedback force and bad position tracking of parallel force feedback bilateral hydraulic servo control system, a novel force feedback bilateral servo system is presented, which regards the difference between the masterpsilas manipulative force and the slavepsilas resistance as command signal, simultaneity, the difference between the slavepsilas displacement and the masterpsilas displacement is fed back for driving movement of the master. In order to control master-slave displacement follows and feel ldquoforce senserdquo by joy stick, in view of the novel force feedback bilateral servo control system, it was proposed that one kind of RBF neural network tuning PD on-line from study, adaptive control strategy, through optimizing two parameters of PD by RBF neural network, which can approach willfully the continuous function characteristic using the RBF neural network by the free precision. Simulation experimental results show that this control algorithm of novel force sense bilateral servo system is practical and feasible, and let the operator feel ldquothe force senserdquo well from feedback, thus improves the human and the environment interaction characteristic and enhances the working efficiency. Moreover, this control arithmetic has taken on control briefness, constringency rate rapidness, real-time well, strong robustness, self-adapted and the rapidity.

Finishing processes such as deburring are performed on a wide variety of products in various quantities by workers on a piece-by-piece basis. Accordingly, the accuracy of the product depends on the worker’s skill. The aim of this research is to develop a finish machining support system. The machining is supported by using a haptic device and controlled by a bilateral control system. Here, we propose a original bilateral controller which have the gain components on the line used to transfer the force signal between master and slave robot. These gains change the binding force between master and slave robot to change the construct of the system. The effectiveness of this system is shown in simulations using haptic device and virtual model of slave robot.

Recently, human activity support systems by remote control of robots have been developed. Bilateral control is an effective control system of teleoperation because it can transmit the information of position and force. However, it is difficult to design multi-degree-of-freedom wearing robots that have used in previous studies. It can be solved by using functional electrical stimulation (FES) in the teleoperation system. On the other hand, there are only few studies of human-machine bilateral control systems using FES and they are not sufficient because the control systems have not been compared. This paper considers bilateral control systems using FES through comparative analysis.