Trajectory Tracking And Stability Of Teleoperator With Time Delay And Force Feedback

A teleoperation system includes a master manipulator and a slave manipulator which are connected by network. When human operator holds the master device and moves, the control signals will be transmitted to the slave side through the communication channel and the slave device will follow the corresponding movement. With teleoperator, human operator interacts with the remote environment where human operator is difficult to access or is dangerous for human being. Teleoperator can extend human hands to the remote places. Therefore teleoperator has a very broad application prospect in the fields of industry, medical care, services, national defense, rescues in dangerous environment, space technology and daily life.There are still a lot of problems to be solved in the application of teleoperator. Time delay is inherited, and it leads to system instability. Stability, trajectory tracking, transparency of force feedback are important indices to teleoperator performances. There often exist contradictions in getting these performances. It is a difficult problem to improve trajectory tracking together with stability and transpaency for a teleoperator with time delay and force feedback. Many researchers focus their attentions on these problems. We focused on how to improve trajectory tracking and stability of the teleoperation system with constant time delay and force feedback without scarifying transparency.The transmission of wave variables can solve the instability problem from signals communication between master and slave manipulators. We established simulation models for wave-variable teleoperators with single degree of freedom and two degrees of freedom. We did the simulation experiments to discuss the relationship between wave impedance and system performance. We should select wave impedance according the expected system damping in actual application. We also did simulation experiments to discuss the influences of the force feedback gain and the force from human operator on system performance. According simulation experiment, the system stability deteriorates with increasing of the force feedback gain, and the system stability will be improved when the human operator uses more force to hold the master manipulator. The human operator is easy to fatigue and is difficult to complete dexterous movements when he uses great force to operate. Therefore it is necessary to design a force feedback algorithm to improve system stability.The wave variables transmission can ensure passivity of the communication subsystem with arbitrary time delay. On the other hand it introduces velocity distortion between master manipulator and slave one, which results in not good trajectory tracking performance. The thesis analyzes the reason why the distortion arises and designs a tracking compensator at slave side to get rid of the distortion. With the compensator the slave manipulator can perfectly tracking the trajectory the master one. The data needed by the compensator is from slave side, so no extra signal transmit ion is needed. Passivity of the teleoperator with tracking compensator can be maintained by tuning the appropriate low-pass filter. The simulation experiments and the actual experiments have shown the perfect velocity or trajectory tracking is achieved with the tracking compensator, and the force presented to the human operator at the master side is also close to the environment force. In the other word, trajectory tracking is improved without scarifying system transparency.The transmission of wave variables rather than power variables in time-delay teleoperation system ensures system passivity--rendering the entire system stable, however the delayed force feedback will still lead to the unanticipated motion of master, which makes the system difficult to control and unstable. The thesis proposed a force feedback algorithm at master side to depress the unanticipated and disturbing motion. The algorithm corrects the force feedback to the master side according the force feedback to the master side and the velocity of the master manipulator. It is easy to accomplish. It also would not affect the passivity of the whole teleoperation system. The simulation and actual experiments showed that the teleoperator with proposed force feedback algorithm is more stable and easier to control for human operator than the traditional one.