基于力的电动静液作动器阻抗控制

阻抗控制作为一种柔顺控制方式,能够实现力与位置的协同控制,在作动系统需要与外部环境发生接触的应用中具有一定优势。在集成、高效的电动静液作动器(EHA)上实现基于力的阻抗控制具有良好的应用前景,其中核心问题是EHA力伺服控制器的设计。针对阻抗控制中外部负载特性不确定,EHA部分结构参数时变等问题,采用定量反馈理论(QFT)的方法对力伺服控制器进行设计。在对EHA数学模型及参数进行分析的基础上,通过QFT方法将被控对象的不确定范围与系统性能设计指标相结合,并以定量的方式在Nichols图上形成边界,在使标称对象的开环频率特性曲线满足各边界约束条件的同时完成力伺服控制器的设计。通过不同外部负载条件下的力伺服控制实验以及静、动态阻抗控制实验对EHA的力伺服控制器与阻抗控制系统进行了验证。实验结果表明:通过QFT方法设计得到的力伺服控制器对外部环境具有较强的鲁棒性,从而确保了EHA阻抗控制的成功实现。

Force based impedance control of electro-hydrostatic actuator

As a kind of compliance control method, impedance control can realize force and position coordination control. So it has obvious advantages in the applications that the actuating systems are required to interact with the environments. Because of high energy efficiency and compact structure, electro-hydrostatic actuator (EHA) with force based impedance control has an extensive prospect. The force controller of EHA is the foundation of the impedance control. Due to the uncertain external load characteristics in impedance control and the time-invariant parameters of EHA, the quantitative feedback theory (QFT) was employed to design the force controller. The mathematical model of EHA was analyzed first. Then the uncertainty range of the controlled plant was combined with the performance specifications of the system to quantitatively plot the boundaries on the Nichols chart. The open-loop frequency characteristic curve of the nominal element was adjusted to satisfy the limitations of boundaries and the force controller was completed simultaneously. The force control and static/dynamic impedance control experiments under various load characteristics were conducted to examine the efficacy of the system. The experimental results demonstrate that the force controller designed by QFT method has sufficient robustness and the impedance control of EHA is achieved successfully.