Design And Control Method Of Bionic Ankle-foot Mechanism Based On Tensegrity Structure

The stability and adaptiveness of ankle-foot mechanism affect the biomimetic robot’s locomotion performance directly in the complex working environment.Therefore,the research of ankle-foot mechanism-bioinspired has practical application value in human life.Due to the unique structure of human foot and ankle,the bones of foot are coupled to each other by ligaments,and the traditional rigid foot mechanisms are inflexible which lead to incoherent movements.Therefore,to improve the self-adaptability of mechanical structure,the design of a lightweight and morphologically adjustable bionic ankle-foot mechanism is essential to develop the bionic robots.The research in this paper consists of the following four parts:(1)To solve the form-finding problem of symmetric tensegrity structures,an optimization problem is established to acquire the self-equilibrium structure.The group theory is utilized to calculate the analytic relationship of force densities,and the trace of force density matrix is regarded as the objective function.Considering that the noise may influence the form-finding results,a novel form-finding method via noise-tolerant neurodynamic model is exploited to calculate feasible force density,which provides the theoretical basis for form-finding of tensegrity robot.(2)By extracting the biological characteristics and movement patterns of human foot and ankle,the bones and muscles can be simplified as struts or springs.Based on human bionics,an equivalent mapping model is designed by tensegrity structure.(3)As for the dynamics modelling problem of ankle-foot mechanism,the virtual prototype can simulate the plantarflexion and dorsiflexion motions of human foot by ADAMS.The feasibility of equivalent mapping model can be determined by kinematics simulation and the stability of virtual prototype.The dynamics model of ankle-foot mechanism is established to provide a research basis for controlling the motion of bionic ankle-foot mechanism.(4)Combining the model predictive control and robust control,a robust model predictive control algorithm is proposed to handle the trajectory tracking control problem of bionic ankle-foot mechanism.The stability and recursive feasibility of control strategy are demonstrated to ensure that the algorithm can control the motion of ankle-foot mechanism accurately.Several simulations illustrate that the robust model predictive control algorithm can enhance the accuracy of trajectory tracking and overcome the external disturbances effectively.