基于速率观测器的挖掘机器人时延鲁棒控制研究

Time-delayed excavator robust control based on speed monitor

在挖掘机器人运动控制中,控制元件比例阀在零位存在较大的死区,驱动元件非对称液压缸为非线性系统,使得对铲斗关节实现高性能位置伺服控制难度很大.提出一种基于局部线性化模型的时延鲁棒控制方法;考虑到编码器测量精度较低,对液压缸位移及速率信号提出一种在线鲁棒估计方法,通过对扰动输入的补偿来减小估计误差;提出一种新型的比例阀死区补偿策略,依据参考模型位置输出对比例阀零位进行切换,既不牺牲系统的动态品质,又能有效避免比例阀阀芯的频繁切换.计算机仿真结果表明,这一方法对外部力扰动和参数变化均具有很强的鲁棒性,且新型速率观测器和比例阀死区补偿环节能明显增强液压系统输出的平稳性.

In the process of excavator motional control, a widely-ranged dead zone of controlling proportional valves occurs at zero position. Due that the asymmetric hydraulic cylinder actuates as a non-linear system, high-performance servo control on bucket joint still remains problematic. As a result, a time-delayed robust control is proposed using a localized linear model. Owing to the low measuring precision of eneoders, an online linear robust estimation is then postulated regarding displacement and speed signals detected from hydraulic cylinder. Afterwards, a new dead-zone compensation strategy for proportional valves is developed to compensate disturbing inputs and reduce estimation errors. To this end, the zero position of proportional valves is switched according to pre-determined reference position. This can effectively maintain the system dynamic performance and avoid the frequent switch of valve spool. Eventually, it is found from the simulation results that this approach possesses high robustness towards external-force disturbance and parametric varia- tion. Therefore, the new speed monitor and dead-zone compensation strategy will enhance the stability of hydraulic system outputs.