液压驱动单元基于力的阻抗控制系统前馈抗扰控制研究

液压驱动单元(Hydraulic drive unit,HDU)是液压驱动型足式机器人常用的关节驱动器，具有集成度高、功率密度大等特性。机器人顶层规划后，需依靠其完成具体动作，实现机器人的行走、对角小跑、奔跑等步态。HDU所受外负载会随机器人腾空相和着地相频繁大幅变化，严重影响系统性能。若HDU具备高性能基于力的阻抗控制，则可有效减小机器人在运动过程中足地接触时的碰撞力，保证机器人运动的平稳性。为提高基于力的阻抗控制系统的抗外扰动能力，研究一种前馈抗扰控制(Feedforward disturbance rejection control,FDRC)。介绍HDU基于力的阻抗控制系统及其数学模型，推导其非线性状态空间表达式。针对系统的外扰动推导等价输入矩阵，设计前馈抗扰控制器，并估算伺服阀流量系数。利用HDU性能测试试验台，针对不同工况和典型信号进行试验。试验结果表明，FDRC可大幅提高HDU基于力的阻抗控制系统的抗外扰动能力，且工况适应性良好。该控制方法可降低外扰动对液压驱动型机器人的影响，提高机器人的适应性。

Research on Feedforward Disturbance Rejection Control for Force-based Impedance Control System of Hydraulic Drive Unit

Hydraulic drive unit(HDU) is a common joint driver of the hydraulic drive legged robot, which has the characteristics of high integration and high power density. After the top-level planning of the robot, it need to rely on it to complete specific actions, to realize the gait of the robot, such as walking, diagonal trot, running and so on. The external load on the HDU will change greatly with the suspension phase and touchdown phase of the robot, which will seriously affect the system performance. If HDU has high performance force-based impedance control, it can effectively reduce the collision force when the foot end contacts with the ground in the process of motion, and ensure the stability of the robot movement. In order to improve the ability of force-based impedance control system to resist external disturbance, a feedforward disturbance rejection control(FDRC) is studied. Firstly, the force-based impedance control system of HDU and its mathematical model are introduced, and its nonlinear state space expression is derived. Secondly, according to the external disturbance of the system, the equivalent input matrix is derived, the FDRC is designed and the flow coefficient of the servo valve is estimated. Finally, the HDU performance test platform is used to test different working conditions and typical signals. The experimental results show that FDRC can greatly improve the ability of resisting external disturbance of the force-based impedance control system of HDU, and it has good adaptability to operating conditions. This control method can reduce the influence of external disturbance on the hydraulic drive legged robot and improve the adaptability of the robot.