Bilateral Servo Control Of The 6-DOF Parallel Electro-hydraulic Tele-Manipulator With Force-feedback

The master slave robot teleoperation system can fulfill the complicated task which is unreachable or hazardous for human beings, it is a remote operated system which involves human's intelligent interference. The main technology is called telepresence, which demand the instant exchange of information between operator and the telerobot. The operator, who stays in the safe place, needs to perceive the magnitude of counterforce and other haptic informations to better control the telerobot to perform the task more precisely and accurately. So that the security of the operator is guaranteed and the work efficiency is improved. Force telepresence is the most crucial research in concerning with the telepresence. It uses the force feedback technology to realize telepresence. First the counterforce of the robot and the environment was detected by the force sensor. Then it was feedback to the operator through haptic master to let the operator feel as if he is operating the environment directly. So the task was performed with the force feeling presented. Hence the study of performance of the haptic devices, the control theory, the control architectures and the control strategies of the master and slave teleoperation sysytem is paying more and more attentions by many researchers. And it is of great significance in theory and practice to the improvement of the human machine information exchange.This Ph.D. dissertation developed under the project named"Force bilateral servo control technology of the teleoperational 6 -DOF hydraulic parallel manipulator (No.50475011)"supported by National Natural Science Foundation of China and"Study on new type force sense bilateral servo control of teleoperation construction robotic"supported by Excellence Youth Teacher State Program of Ministry of Education (2003). The first time in china a systematic study of a 6-DOF parallel hydraulic force feedback haptic device with bilateral servo control strategy is performed.The haptic device is the key to sense the environmental information, and to realize the teleoperation with force feedback. It plays the role of man-machine interface. Their performance will have a direct impact on the overall quality of the teleoperation system, the research of its structure and performance characteristics can let us get an in-depth study of its operation mechanism and operation properties in order to design manipulator under scientific standards and with a good performance, and to enhance the overall performance of teleoperation system. At present, the average force feedback controller is electrical equipment more often than not, its shortcomings are poor rigidity, the poor ability to provide sufficient force feeling,the complex structure of multiple DOFs haptic devices, the serial type are large in size. To make up for these shortcomings, using hydraulic parallel robot, with high-speed, high precision, high rigidity, and efforts, small and simple structure characteristics to develop the Stewart-6-DOF parallel hydraulic force feedback haptic device, to achieve the control of all six degrees of translation and rotation at the same time such, as well as to provide adequate force feedback to operator.Force feedback bilateral control architectures and control strategies are keys for the bilateral teleoperation system design. The teleoperation system's performance is different with different control strategies and control architectures. The studies of these strategies and architectures reveal the intrinsic relationship of the structural parameter of force feedback device, the remote robot and performance index. It provides the theoretical reference for choosing the control architectures and control strategies. At present, scholars all over the world have been using a wide range of the bilateral servo control strategies, the main shortcoming of the present methods of control is that the performance is not satisfactory, and there is the impact force in the course of the operation. To this end, through in-depth theoretical study, a new hydraulic force feedback control strategy to improve the 6-DOF parallel hydraulic manipulator performance is proposed.This article first take two-port network theory as a analysis foundation, mainly under two channel architecture, established four kind of two port network model of tele-operation control architecture, established five kind of two-port network model of the hydraulic pressure servo force feedback teleoperation control strategies. An in-depth study of the internal relations of the next three factors is made. First is the overall system's performance and stability, next is the existing control architectures and control strategies, the third is the structural parameters of the force feedback teleoperation control system's components. The ideal transparency condition is derived based on the anti hybrid parameter matrices. The influence of the control parameters'scaling between the passive stability condition and Llewelyn absolute stability condition is contrasted. It is analyzed also that the system's performance and stability are affected when the delay causes the system to be latent active. With the application of the anti hybrid parameter matrices ideal transparency condition and hybrid parameter matrices ideal transparency condition and Llewelyn absolute stability condition, the stability and performance of different existing control architectures and control strategies are analyzed. The advantages and disadvantages of various existing control strategies is evaluated, the internal qualitative or quantitative relationship of the component structural parameters of teleoperation system, the overall system performance and stability of the system is derived. It has laid a theoretical foundation for the two channel architecture teleoperation control system designNext based on the summary of the performance's advantages and disadvantages of the existing control strategies, proposed one kind of new control strategy, which broke through the traditional thought format of "slave robot always follow the master's movement", there is innovation in theory. Under the two channels architecture, established the two-port network model of the new hydraulic servo control strategy for force feedback teleoperation control system. With the application of the anti hybrid parameter matrices ideal transparency condition and Llewelyn absolute stability condition, the stability and performance of the new hydraulic servo control strategy is analyzed. the advantages and disadvantages of various existing control strategies and the new one is compared, the feasibility of the new control strategie, which applied in the Bilateral Servo Control system of the 6-DOF Parallel Electro-hydraulic Tele-Manipulators with Force-feedback, is proved to be fully valid. Analysis showed that the new control strategy can overcome the existing control strategies'shock and impact, it forms the theoretical foundation to improve the performance of the 6-DOF parallel Electro-hydraulic Tele-Manipulators'control system with Force-feedback. Once again the Bilateral Servo Control system of the 6-DOF Parallel Electro-hydraulic Tele-Manipulators with Force-feedback is designed. Elaborated the structural features and working principles of the system's components. The digital simulation is applied to tune the PID control parameters of the system. The hardware of the bilateral servo control system of the 6-DOF parallel electro-hydraulic tele-manipulators with force-feedback is designed. Prepared the control software, using multi-threaded and messages technology solved the customer procedures blocking problem, it overcome the process operation difficulty which usually blocked by the cycling procedure. It laid a good foundation for the teleoperation system performance test.Finally, a master-slave teleoperation system test bench is set up by using two 6-DOF Parallel Electro-hydraulic Tele-Manipulators with same structure. Under the no-load, the elastic load and the hard object contact circumstance, applied the various bilateral Servo control strategies, the experiment of the control performance and the force telepresence performance is carried out on the master-slave teleoperation system test bench. It verified that the control strategies design is right; the new strategy has some advantage over other existing control strategies. It provides the experimental basis for the application of the new control strategy and the improvement of the performance of tele-manipulator with force feedback.The following results are yielded:(1) In this paper, a new type of hydraulic force feedback control strategy in bilateral servo control tele-manipulates system is raised. It uses the operator's operating force, which is detected by master's force sensor, to multiply a certain coefficient, and then minus the resistant force of the slave, finally use the result as a control reference to control the slave's motion. And the motion of the slave detected by its motion sensor is reflected to the master side as a motion reference to control the master's motion. And the master will follow the slave's motion. One can feel the resistant force of the slave by apply force on the master when it does or doesn't move. The new strategy abandoned the current control strategies'control method of "the slave always follows the movement of the master". It introduced theoretically the important innovation to bilateral servo control system strategy design.(2) An ideal transparency condition was deduced in the form of an anti-hybrid matrix by taking the transparency as the performance index and using the two-port network model of the teleoperation system. A detailed study is directed to the control architectures and strategies of the master and slave robot teleoperation system based on the stability theory and the anti-hybrid matrix ideal transparency condition. The internal relationship between the entire system's stability, the transparency and the haptic devices'models and its controllers was studied in depth. The impact of the scaling and the communication time delay to the stability and performance is also analyzed. Based on the summarization of present control architectures and strategies, apply the new strategy, under the two channel architecture, the internal relationship between the entire system's stability, the transparency and the haptic devices'models add its controllers for the new control strategy was studied in depth. It proved that the new strategy has the advantage over the existing ones in eliminating the impact of the communication time delay to the stability and performance. the new force feedback control strategy further improved the performance of the tele-operation control system, and has laid a theoretical foundation for the in-depth study of the electro hydraulic servo tele-operation system.(3) This paper pioneered domestically to use a 6-DOF hydraulic parallel manipulator as the haptic device in the bilateral servo control system with force feedback, an isomorphic master-slave teleoperation system is adopted, the mapping of master-slave is simple and intuitionistic, and the problems can be discovered easily. In order to verify the performance of the electro-hydraulic servo 6-DOF force-feedback manipulator and the validity of the bilateral servo control strategies, test-bench is built up by two 6-DOF devices. The hardware and software of measure and control system of the master-slave teleoperation system are designed to constitute the force telepresence system. The experiment is achieved under the zero load, elasticity load and hard contact by using different bilateral servo strategies respectively, and results shown that the 6 -DOF force-feedback manipulator developed in this dissertation can provide large control stiffness, stable performance, rapid response. Displacement control and force-feedback precision as well as the feedback force range is relatively fine and can be adjusted to satisfy the requirements of the teleoperation robot. It is also verified that the new strategy has the advantage over the existing ones in eliminating or overcoming the shock and impact of the existing control strategies', when the slave is contact with hard environment. The new force feedback control strategy further improved the performance of the tele-operation control system, and has laid a theoretical foundation for the in-depth study of the electro hydraulic servo tele-operation system.Theoretical analysis and experimental study showed that: the 6-DOF Parallel Electro-hydraulic force feedback Tele-Manipulator proposed in this paper can effectively solve the problem of small force feedback stiffness and inconspicuous force feedback effect, which is prevailing in the existing electric driving force feedback devices. It obtains a more good force feedback effects. The track precision and force feedback accuracy of the new control strategy is superior to other control strategies, the tracking property is good. The new control strategy solved the problem of the impact of excessive feedback force of the current control strategies internationally existed at the same time. It has an important theoretical and practical significance in the effective improvement of the overall force Feedback performance of the teleoperated systems and widening its application fields.The 6-DOF parallel hydraulic force feedback manipulator bilateral servo control system can be used in resource exploration, disaster risk schedule, social services and the military, aerospace and other fields, its future has broad application prospects.