Research On The Force-position Coordination Control Method Of The Antagonized Joint Of The Fluidic Muscle Bundle

With the rapid development of the new generation of intelligent robot technology,the concept of human-machine integration is deeply rooted in the hearts of the people.It requires that the new generation of robots should have better human-machine interaction,that is,robots can achieve human-machine collaboration more safely.However,the traditional driving methods such as motors and hydraulics cannot meet this requirement due to structural complexity and high rigidity.Pneumatic related products are increasingly used in various fields of production and life due to their unique low rigidity and other characteristics.Pneumatic muscle actuator,a new type of air-driven structure,is similar to biological muscles in performance indicators and working methods.The characteristics of simplicity,high power-to-weight ratio,and good compliance have attracted extensive attention of experts and scholars at home and abroad,and have been applied in production research fields such as rehabilitation medicine and flexible robotic joints.In this paper,the coordinated control strategy of the position and environmental interaction forces of the pneumatic muscle actuator antagonistic joint is studied.The main contents are summarized as follows: Firstly,the working principles and similarities of the two muscles are analyzed from the biological muscle and pneumatic muscle structures.The pneumatic muscle actuator of the Festo company in Germany was taken as the specific actual object.Combined the theoretical model and the three-elements equivalent model of the pneumatic muscle actuator,the dynamic model of the single muscle was established.The model parameters of the single muscle were obtained through parameter identification and fitting experiments.Based on the dynamic model of a single muscle,combined with the principle of biological knee joint movement,a variety of antagonistic joint configurations were analyzed.And,a dynamic model of the state-space equation of the pneumatic muscle actuator antagonist joint was established in combination with Newton's second law.Secondly,considering the constraints and time-varying parameters of the joint dynamics model,an antagonistic joint position controller based on model predictive control is designed.The principle of model predictive control and the derivation of the predictive control rate of the antagonized joint model are derived.and the feasibility of the designed controller is analyzed through mathematical simulation.Then,based on the principle of impedance and admittance control,and on the basis of the position control of the antagonistic joint,a coordinated control strategy for antagonistic joint compliance was designed with model predictive position control as the inner loop and environmental interactive force admittance control as the outer loop.On the basis of ensuring the accuracy of the position control of the antagonistic joint,the joint output has good compliance.The feasibility of the designed controller is showed by simulation Finally,the software and hardware integration of the designed test platform for the antagonistic joint is completed.On the experimental platform,the position trajectory tracking experiment and the experiment under the influence of environment interaction force are carried out by using the above model predictive position controller and the admittance compliance controller respectively.The experimental results show that the coordinated control strategy proposed in this paper can be effectively applied to the pneumatic muscle actuator antagonistic joints,which can not only ensure the trajectory tracking accuracy of the antagonistic joints,but also effectively adapt to the situation of interaction with the external environment.