Sliding Mode Impedance Control of Flexible Base Moving Manipulators Using Singular Perturbation Method

In this paper, the general problem of impedance control for a robotic manipulator with a moving flexible base is addressed. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base mobile manipulator is rather new and is being considered for first time using singular perturbation and new sliding mode control methods by authors. Initially slow and fast dynamics of robot are decoupled using singular perturbation method. Slow dynamics represents the dynamics of the manipulator with rigid base. Fast dynamics is the equivalent effect of the flexibility in the base. Then, using sliding mode control method, an impedance control law is derived for the slow dynamics. The asymptotic stability of the overall system is guaranteed using a combined control law comprising the impedance control law for the slow dynamics and a feedback control law for the fast dynamics. This proposed Sliding Mode Impedance Controller (SMIC) was simulated for an advanced 10 DOF’s Flexible Base Moving Manipulator (FBMM) composed of a 4 DOF’s manipulator and a 6 DOF’s moving base with flexibility. This controller provides desired position/force control accurately with satisfactory damped vibrations especially at the point of contact.