Research On Position Servo Control Of Underwater Manipulator With Time Delay

Along with the development of human society and the advancement of technology, many countries have begun to attach importance to the exploitation and utilization of marine resources. Underwater manipulators work in the complex ocean (water) environment, the control performance of underwater manipulator will be affected by pressure, corrosion, current, tide, swell, and so on. The research of underwater manipulator has great theoretical and practical significance to improve the level of intelligence and operational capability.Architecture and operating control technology is one of the key issues to underwater manipulator. On the basis of analysis and research to the overall structure, motion analysis and control system of the underwater manipulator, the double closed loop position servo controller is presented for the underwater manipulator based on the speed inner loop and the position outer loop. Regarding the double closed loop control system, the speed loop is helpful in suppressing the vibration, reducing the over modulation and enhancing system's dynamic property. And the position loop is helpful to the guarantee of system static state precision and the dynamic track performance. The underwater manipulator position servo-control experiment indicated that the double closed loop position servo control which based on the speed inner loop and the position outer loop, suits the request of the submarine complex working environment; it has high control precision and good anti-jamming ability, while it has confirmed the validity and feasibility of this kind of control system.Taking account into the background of underwater manipulator to autonomous underwater vehicle (AUV) and the work environment, the big time delay in the control system will affect the stability of the whole control system, and reduce the quality of the control system. When the time delay occurs in the closed-loop control system, the time delay buffer and compensator are added into the forward path and the feedback path to reduce the influence which was attached to the control system of the underwater manipulator by time delay. The time delay compensator to the forward path uses Smith compensation. Smith compensation is adding a compensator in the closed-loop system, to compensats the delay links in the control path, and the denominator of the system's transfer function, so as to improve the performance and stability of the control system. The time delay compensator to the feedback path is adding compensator in the forward path to be equivalent to the system without time delay after compensation, to reduce the influence to the control systems. Because the time delay to the underwater manipulator in the deep sea is random, variable and unpredictable, we use a time delay buffer to change the variable time delay into a fixed time delay, and further to compensate control. The experimental results in the water pool show that the time delay compansention method is feasible and effective.