液压驱动单元位置控制系统前馈补偿控制研究

Feedforward Compensation Control for Hydraulic Drive Unit Position Control System

液压驱动型足式机器人在运动过程中各关节液压驱动单元(Hydraulic drive unit,HDU)多采用基于液压控制内环的外环阻抗控制方法,其中液压控制内环可分为位置闭环控制和力闭环控制。当液压控制内环采用位置闭环控制时,其位置控制性能直接决定了外环阻抗控制性能,所以,一种针对HDU的高精度的位置控制方法具有重要研究意义。针对以上研究意义,首先对HDU位置控制系统6阶数学模型进行简化,求出位置控制系统中各部分传递函数。其次,推导位置控制输入前馈补偿控制器,该控制器中含有液压系统固有非线性和负载特性。最后,在HDU性能测试试验平台上,在多种典型输入信号以及对角小跑输入信号下,对系统的位置控制性能进行试验研究并给出定量分析。试验结果表明,在不同输入信号下,加入所提出的输入前馈补偿控制器可以大幅提高系统位置控制性能,并且该控制器具有良好的多工况适应性。以上研究成果可结合相应的针对位置控制系统的抗干扰控制策略,一起为基于位置的阻抗控制液压内环控制提供控制策略重要参考和试验基础。

During the motion process of the hydraulic driven legged robot, the outer loop impedance control method, based on the hydraulic control inner loop, is applied in the hydraulic drive unit(HDU) which drives the robotic joints. For this control method, the hydraulic control inner loop can be selected from two different control loops, position closed loop and force closed loop. When the position closed loop is adopted, the impedance control performance of outer loop is directly decided by the position control performance of the inner control loop. Therefore, it is significant to design a position control method with high accuracy for HDU. Thus, the paper is organized as follows according to the design idea. First, the six order mathematical model of HDU position control system is simplified and the corresponding transfer functions are figured out. Then, the mathematical expressions which describe the input feedforward compensation controller of position control are derived out. This controller has the natural nonlinear characteristics and load characteristics of the hydraulic system. At last, the position control performance is researched through experiments, where the multiple typical input signals and trotting gait input signals are applied in the control system, on the HDU performance test platform. Then, the experimental results are analyzed quantitatively. It is found that the application of the feedforward compensation controller designed in this paper can improve the position control performance greatly under different input signal. Besides, this controller shows good robustness. Combined with the corresponding anti-disturbance strategy, the research results can provide the valuable reference and experimental foundation for the hydraulic control inner loop of position-based impedance control.