Research On Bilateral Control Of Teleoperation Space Robot

With the development of space exploration, space robot will play more and more important function. Teleoperation is an important control method of the space robot. Replacing the astronaut with teleoperate space robot to work in out space can avoid the risk of astronaut working in out space, and also can enhance the economy of space exploration. The teleoperation has three ways: predictive control, teleprogramming, bilateral control. Because bilateral control can be applied in non-structure, unknown environment, it becomes research hot in recent years. After years of development, bilateral control with force feedback and delay has made some progress, but still faces many problems. Based on previous research, this paper studies following issues: the performance indicators of bilateral system and their measurement methods; the bilateral control method based absolute stability theory; the method improving the performance of bilateral system; the method structuring two freedom bilateral system and controlling this system; the method simulating the movement of teleoperate space robot using ground physical simulation system. The following are the detail introduction of these aspects.The basic requirements of bilateral control with force feedback include three aspects: the system is stable; the operator feels the force that the slave acts on envionment; the movement of slave tracks the movement of master. The performance indicators of system should capable to measure these aspects. In previous studies, the main performance indicators of bilateral system with force feedback are stability and transparency. They can measure the stability and the capacity that the operator feels the force between the slave and envionment separately, but can't measure the capacity that the slave tracks the master. Because of this, this paper presents a new performance indicator to measure the capacity that the slave tracks the master: tracking. To quantitative measure the transparency and tracking of bilateral system, this paper defines quantitative measurement function of them separately.The bilateral control method based passivity can guarantee delay-independent stability, so the robustness of stability is very strong. Because the stability and transparency are conflicted, the transparency of this system is bad. To enhance the transparency of bilateral system, this paper introduces absolute stability theory as stability criteria. I prove that the passivity is sufficient but non-essential condition of absolute stability, namely, passivity is more conservative than absolute stability to system stability, so bilateral system based absolute stability have better transparency than the system based passivity. In addition, because the stability of bilateral system based absolute stability is delay-dependent, the robustness of stability is weaker and the transparency is better. Based on these analyses, this paper introduces double PD method of bilateral control, which based on absolute stability theory. Then, I analysis its stability, transparency, tracking and certificate the analysis result by experiment. To enhance the performance of double PD method, from Anderson's virtual force concept, I present a new bilateral control method: virtual force feedback control method, which feedback the control force of slave to master. Then, I analysis its stability, transparency, tracking and certificate the analysis result by experiment.The performances of double PD control method and virtual force feedback control method are not adaptive to slave environment. The performances of these systems get worse when slave's environment change. I present two methods to improve the adaptive of the system: 1, Regulate control parameter on-line. Firstly, this method measures environment resistance by parameter recognizes. Then, regulate control parameter according to the environment resistance and the result of transparency or tracking analysis. The control parameter is adaptive to environment always, so the system always has good transparency or tracking. The performance of this method is adaptive to slave's environment manually. 2, The method of measuring the force between the slave and environment by force sensor and feedbacking it to the master, and then reacting on operator directly. In this method, the force sensor is directly applied in bilateral system for the first time. Because that the measured force include the informance of environment resistance, the performance of this method is adaptive to slave's environment automatically. In addition, this method can avoid the conflicted between transparency and tracking.To experimentally research previous control method, this paper builds a two freedom bilateral control system. Its master is a drive-redundant parallel-mechanism, and slave is PUMA562 manipulator. According to the forward kinematics and inverse kinematics of the drive-redundant parallel-mechanism, a method quickly calculate jacobian matrix and force-mapping matrix is present. Using this system, I completed successfully the operation of tracking unknown curve with the time-delay of 6 seconds.When the slave of teleoperate system is a free-floating space robot, the control of system faces new problem. There exist kinematics and dynamics coupling between the base and manipulator arm of the free-floating space robot. The movement of the manipulator arm will induce reaction movement of the base. So the kinematics and dynamics models, the control method of free-floating space robot is very different to those of on-earth robot. To verification the model and control method of space robot, this paper present the movement equivalence principle between on-earth robot and space robot, and build a physics simulation system on earth to analogue the movement of teleoperate space robot. The kinematics model of free-floating space robot use generalized jacobian matrix method, which is derived from the principle of momentum conservation. The movement of simulation system equivalent to the movement of space robot according to the movement equivalence principle. At last, I analogue successfully the movement that the teleoperating space robot captures target using this system.