Trajectory tracking control of the pneumatic muscle knee joint under uncertain disturbance

ObjectiveConsidering the impact of modeling errors and external disturbances on the trajectory tracking of pneumatic muscle knee joints, a fuzzy sliding mode control strategy based on a disturbance observer was proposed.MethodsIn this control strategy, the disturbance observer was added to the sliding mode control to estimate and compensate for disturbances, and the fuzzy control was used to adaptively adjust the switching gain <inline-formula><alternatives><math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mi>K</mi></math><graphic specific-use="big" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="alternativeImage/B74EE16F-7D30-434c-A081-36B50D69C071-M002.jpg"><?fx-imagestate width="2.45533323" height="2.28600001"?></graphic><graphic specific-use="small" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="alternativeImage/B74EE16F-7D30-434c-A081-36B50D69C071-M002c.jpg"><?fx-imagestate width="2.45533323" height="2.28600001"?></graphic></alternatives></inline-formula> according to the real-time interference and tracking error values. Finally, the stability of the system was proved according to the Lyapunov stability theory. In order to verify the effectiveness of the control strategy, the simulation and physical trajectory tracking tests of pneumatic muscle knee joints were designed.ResultsThe results show that the pneumatic muscle knee joint can stably track the target trajectory, and the average error and variance are both close to 0°, indicating that this control method has good accuracy and stability for the trajectory tracking control of flexible knee joints.