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为了简单、高效地实现对由单根气动人工肌肉(pneumatic artificial muscle,PAM)驱动的仿生关节的轨迹跟踪控制,提出了一种基于鲁棒建模方法的级联控制策略.首先,通过解析法建立比例方向控制阀输入电压与PAM腔内驱动气压之间的非线性模型.其次,将PAM的驱动气压输入和关节角位移输出之间的非线性关系等效为一个含有参数摄动的2阶线性时不变模型,并通过鲁棒建模方法辨识模型参数.再者,对应由以上两个模型(即非线性模型和线性时不变模型)组成的混合模型,提出一种级联控制器,其外环是一个采用回路成形设计程序(loop-shaping design procedure,LSDP)法设计的用于角度位置跟踪的H∞控制器,内环是一个基于反馈线性化理论的用于PAM腔内驱动气压控制的非线性控制器.最后,在回转角度小于90?且工作频率上限小于1.25 rad/s的实验条件下,关节对参考轨迹实现了稳态误差小于2%的跟踪.本研究表明,在工作频率相对较低的情况下,采用所提策略可以对高度非线性系统实现有效的轨迹跟踪控制.
In order to realize the trajectory tracking control of a biomimetic joint driven by a single pneumatic artificial muscle (PAM) simply and efficiently, a cascade control strategy based on a robust modeling method is proposed.First, The nonlinear model between the input voltage of proportional directional control valve and the driving air pressure in PAM cavity is established.Secondly, the non-linear relationship between the driving pressure input of PAM and the output of joint angle is equivalent to the second order with parameter perturbation Linear time-invariant model, and identify the model parameters by robust modeling method.Furthermore, corresponding to the hybrid model consisting of the above two models (that is, the nonlinear model and the linear invariant model), a cascade controller , The outer ring is a H∞ controller designed for loop position tracking using the loop-shaping design procedure (LSDP) method. The inner loop is a feedback loop-based theory for PAM cavity drive Pressure controller.Finally, under the experimental conditions that the rotation angle is less than 90 ° and the upper limit of operating frequency is less than 1.25 rad / s, the joint achieves a steady-state error of less than 2% Track. This study shows that, at the operating frequency is relatively low, the use of the proposed strategy can achieve effective control of highly nonlinear trajectory tracking system.