Bilateral control considering singularity based on observation of torque error

This paper presents analysis on kinematics and statics of redundant serial link manipulator and redundant parallel link manipulator with passive joints. Passive joint is a joint that the joint torque depends on the joint angle. Redundant manipulator is a manipulator that has actuated joints more than dimension of the task space. We study the theme not to be defined well the fundamental theory of the manipulator with passive joints. First, we study the redundant serial link manipulator with passive joints. We propose a solution method of kinematics and statics and a control method in a limited condition. Moreover, we can show a better performance of the serial link manipulator with additional passive joint, so-called semi-active joint, if we can control the equilibrium positions of passive joints by using numerical example. Secondary, we study the redundant parallel link manipulator with passive joints. We proposed a solution method of kinematics and statics. We can show the performance in each parallel link manipulator mode with semi-active joints by using numerical example.

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, 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.

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.

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.

ABSTRACTThis paper aims at developing an estimation method of end-point impedance. Human operators are constantly changing their end-point impedance for adapting to the surrounded environment and executing some complicated tasks, and it is highly meaningful to investigate these variations for the further understanding of human motion. Most of the conventional researches, however, have considered non-contact-point impedance or tasks that is only holding the vibrated sticks due to the experimental constraints. This paper proposes the estimation method of end-point impedance by using bilateral control system. The extra signal is added to the force controller for the impedance estimation. In addition, the effect of the bilateral controller is estimated and removed from the impedance estimation process for securing the applicability of moving tasks. The proposed method was validated through simulations and an experiment. The experimental result showed that the end-point stiffness can be estimated properly even if the operator robot was moving and changed its end-point impedance.

In this paper, approaches for the solution of parallel manipulators forward kinematics have been addressed. Current research on this topic has been analyzed to determine the status and unresolved issues of the research field. Articles on parallel manipulators forward kinematics were reviewed, and numerous approaches for resolving forward kinematics in particular have been identified and published, which may assist researchers in selecting the most appropriate technique for solving the problem in this domain. Researchers have also attempted to apply these methods to a variety of other parallel manipulator-related problems, such as inverse kinematics and dynamics. In robotics, serial manipulators were invented before parallel manipulators. Hence, methodologies for solving forward kinematics were first developed for serial manipulators and many methods are ineffective for parallel manipulators. In this paper, all identified methods can be used for solving forward kinematics of parallel and serial manipulators.

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.

Robotic manipulators inevitably encounter singular configurations in the process of movement, which seriously affects their performance. Therefore, the identification of singular configurations is extremely important. However, serial manipulators that do not meet the Pieper criterion cannot obtain singular configurations through analytical methods. A joint angle parameterization method, used to obtain singular configurations, is here creatively proposed. First, an analytical method based on the Jacobian determinant and the proposed method were utilized to obtain their respective singular configurations of the Stanford manipulator. The singular configurations obtained through the two methods were consistent, which suggests that the proposed method can obtain singular configurations correctly. Then, the proposed method was applied to a seven-degree-of-freedom (7-DOF) serial manipulator and a planar 5R parallel manipulator. Finally, the correctness of the singular configurations of the 7-DOF serial manipulator was verified through the shape of the end-effector velocity ellipsoid, the value of the determinant, the value of the condition number, and the value of the manipulability measure. The correctness of singular configurations of the planar 5R parallel manipulator was verified through the value of the determinant, the value of the condition number, and the value of the manipulability measure.

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.

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.

This research presents Pure Condition approach, which has used in analyzing simultaneously the singularity configuration and the rigidity of mechanism. The study cases analysis is implemented on variable joints orientation of 6R (Revolute) Serial Manipulators (SMs) and variable actuated joints position of 3-PRS (Prismatic-Revolute-Spherical) Parallel Manipulators (PMs) using Grassmann-Cayley Algebra (GCA). In this work we require in Projective Space both Twist System (TS) and Global Wrench System (GWS) respectively for serial and parallel manipulators which represent the Jacobian Matrix (J) in symbolic approach to Plücker coordinate vector of lines and unify framework on static and kinematics respectively. This paper, works, is designed to determine geometrically at symbolic level the vanished points of inverse form of this Jacobian Matrix (J) which called superbracket in GCA. The investigation vary to those reported early by introducing GCA approach on the singularity of serial robot, variable joints orientation and actuated positions on robot manipulators (RMs) to analyze rigidity frame work and singularity configuration which involve simultaneously Pure Condition. And the results also revealed a single singularity condition which contains all particulars cases and three general cases such as the shoulder, elbow and wrist singularity for SMs while double, single and undermined singularities respectively for 3-PRS, 3-PRS and 3-PRS PMs which contain all generals and particulars cases.

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.