Decoupling control of PMA-driven serial link mechanism

Serial link mechanism driven by pneumatic artificial muscles (PMA) usually adopts tendon transmission. In many cases, the torque and position couplings between each joint are obvious, which would affect the control performance. By analyzing the position equation of tendons, this article proposes a decoupling control method for PMA-driven serial link mechanism. First of all, the coupling matrix is calculated. Then combined with the model of PMA, the system coupled dynamics equations are derived. Considering the coupling of tendon-transmitted and the nonlinearity characteristics of PMA, a decoupling control algorithm based on improved computed torque method is proposed and adopted on decoupling control in the PMA-driven and tendon-transmitted system, which can compensate the hysteresis for PMA. Experimental results show that compared with the traditional PID control, the decoupling control method proposed in this article is capable of reducing system coupling, decreasing response time and eliminating the steady-state error to some extent.