Research On Pneumatic Muscle Joint Tracking Based On Adaptive Backstepping Control

Currently,the robot industry is developing rapidly,and robots have been applied in the fields of manufacturing,medical,military and other fields.With the appearance of flexible robots,how to improve robot bionics and flexibility has become a key issue in research.Pneumatic muscle drivers are widely used in flexible robots because of their clean,lightweight,supple,and bionic characteristics,however the strong nonlinearity and uncertainty of pneumatic muscle drivers make their control difficult.In this paper,for the pneumatic muscle joint,the adaptive backstepping control algorithm is used to improve the accuracy of joint trajectory tracking.First,a second-order differential model of the pneumatic muscle joint is established.Because the theoretical model of pneumatic muscle is more deviated from the actual joint model,this paper uses experimental modeling method to model the pneumatic muscle joint.The experimental model needs to identify the model parameters and disturbances,but the test experiments are complex and the identification has errors.Therefore,this paper uses an adaptive algorithm to estimate the unknown model parameters and unknown disturbances online,simplifying the experimental modeling process.Secondly,an adaptive backstepping state feedback controller is designed for the pneumatic muscle joint,and stability analysis and simulation experiments are carried out.For the second-order strict feedback nonlinear pneumatic muscle joint system in measurable states,an adaptive backstepping state feedback controller is designed to perform trajectory tracking control.The stability of the controller is proved by the Lasalle invariant principle,and the effectiveness of the controller is proved by simulation experiments.The state feedback structure is simple,the backstepping method solves the strong nonlinear problem of the system,and the adaptive method solves the problem of unknown model parameters and unknown disturbances.Then,an adaptive backstepping output feedback controller is designed for the pneumatic muscle joint,and stability analysis and simulation experiments are carried out.For the second-order strict feedback nonlinear pneumatic muscle joint system in unmeasurable states,an adaptive backstepping output feedback controller is designed to perform trajectory tracking control.The output feedback reorganizes the states of the system by designing the state observer,and designs the controller for the pneumatic muscle joint with only output measurable.The stability of the controller is proved by the La Salle invariance principle,and the effectiveness of the controller is proved by simulation experiments.Finally,the pneumatic muscle joint platform is built,and the adaptive backstepping state feedback controller and adaptive backstepping output feedback controller designed in this paper are experimentally verified.The effectiveness of the controller is demonstrated by comparative experiments of pneumatic muscle joint of the same diameter and different lengths pneumatic muscle.The comparative analysis of the experimental results proves that the adaptive backstepping control algorithm improves the tracking accuracy of the pneumatic muscle joint.