Study On Controlling High- Precision Servo System With Gear Backlash

Backlash is one of the most important non-linearities that limit the performance of high-precision motion system in robotics, machine tools, radar, turret, precision micro-machinery, turntable,telescopes and other applications. As the non-differentiable trait of backlash , it is much difficult to compensate. While increasing performance requirements in engineering applications must address the gear backlash issue, research on anti-backlash methods is much important in both theory and engineering.Backlash compensation techniques are analyzed in accordance with the single-motor anti-backlash control and dual-motor backlash eliminating with torque-bias methods. The main contents are concluded as follows:Describing function analysis on dead zone backlash model is used to imply the size of backlash affecting servo bandwidth. The dynamic models of single-motor driving mechanical system with both hysteresis backlash model and dead zone backlash model are buit. Simple analysis on friction is issued and friction model suitable for simulation is established. Two programs by negative feedback from the motor side and load side are discussed, and the advantages and disadvantages of them are compared. The reason of the former superior to the later are listed . Besides, Similar method is implemented with elastic dead zone gear backlash model, and the result is satisfactory. The reasons why the introduction of angle difference works are analyzed qualitatively. For some slow movement occasion, switching control strategy is adopted to minimize the backlash effect on the control performance.According to the concept of torque-bias with dual-motor anti-backlash from engineering, a detailed analysis is given for the principle of the bias torque method eliminating backlash, the model of dual-motor backlash eliminating with torque-bias methods is buit. Specific methods of applying torque bias are studied. Based on the analysis of simulation results, the problem of the existing method of eliminating backlash is pointed and improvements are proposed. New torque bias methods for anti-backlash are propose and simulation results show the effectiveness of them. Anti-windup device is used to solve the current loop saturation problem. Taking into account the actual friction, in order to increase system bandwidth and control accuracy, model-based feedforward scheme is used.