Fractional Order Control for the Grasping by Coiling

The paper studies the grasping control by coiling for a class of grippers with continuum arms. First, the fractional order model of continuum arm is proposed. The viscoelastic components are assimilated by the fractional Kevin-Voigt model and the fractional-order dynamics are inferred. A hybrid control technique with two control loops for position and force control, respectively, is proposed. The Lyapunov method for position control is applied. Sector-type constraints for input torque are implemented and frequential conditions, Popov Circle Criterion, that ensure asymptotic stability, are inferred. A conventional PD controller is proposed for the force control. Numerical simulations illustrate the performances of the control system.