Study On A Class Of Backlash Nonlinear Control System

As a main nonlinearity in mechanical drive systems, backlash exists broadly in various systems such as machine tools, robots, astronomical telescopes, radars, artilleries, missile launchers, aerocrafts etc., and is an important factor influencing the dynamic and static properties of drive systems. Due to the non-differentiable trait of backlash, its compensation is much difficult. This brings austere challenge to the high-precision drive systems that have strict demand to quality and reliability. So, making deep study into the backlash nonlinearity in mechanical drive systems is much important both in theory and engineering.In this dissertation, a class of backlash nonlinear control systems is studied. The main ideas are as follows:(1) Drive systems with backlash nonlinearity are studied. First, this paper presents a robust nonlinear control scheme for input backlash systems with parametric uncertainties. A model reference controller is developed and robust global convergence of the tracking error is proved by Lyapunov method. Furthermore, a switching control scheme with PTO (proximate time optimal) compensation is presented for the systems containing inner backlash. With a linear PID controller used in contact period, a sliding control with PTO surface is switched into when system enters the backlash. Then, a supervising mechanism is introduced to find suitable time switching between linear PID control and PTO sliding control, ensuring BIBO stability of the whole system. The design can effectively eliminate the colliding disturbance resulting from the backlash and improve the robustness of the controller.(2) Based on dual-motors drive systems with backlash nonlinearity, the paper present studies on the nonlinearity still existing in the redundant system (consist of dual driving sub-systems with pre-loaded torque bias and one driven sub-system). By selecting control Lyapunov function through Backstepping approach, a state feedback scheme is developed to completely eliminate the influence of backlash in system. Then, an adaptive control scheme for backlash nonlinearity in such system with unknown parameters is proposed in the same way. The scheme can effectively keep tracking to the reference input while ensure the stability of overall system.(3) A model reference adaptive control (MRAC) is proposed for redundantly driven systems with unknown nonlinearities such as friction and backlash. First, the system is...