Compliant control of a two-link flexible manipulator featuring piezoelectric actuators

This paper presents a control strategy for the position and force control of flexible manipulators exploiting the characteristics of actuators fabricated from smart materials. The governing equations of motion of a planar two-link flexible manipulator which features piezoceramic actuators and piezofilm sensors bonded on each flexible link are derived via Hamiltonʹs principle. A nominal control torque of the motor to command the desired position and force is determined by a sliding mode controller based on the rigid-mode dynamics. In order to take uncertainties into account, the sliding mode controller with perturbation estimation (SMCPE) is adopted. The routine is then incorporated with the fuzzy technique to determine the appropriate control gains while maintaining the stability of the system. A set of fuzzy parameters and control rules is then obtained from the estimated perturbation. During the commanded motion, undesirable oscillations are actively suppressed by applying feedback control voltages to the piezoceramic actuators. These feedback voltages are determined by the SMCPE, and they permit accurate position and force control of the two-link flexible manipulator to be achieved. Computer simulations are undertaken by taking two different surface constraints in order to demonstrate the effectiveness of the proposed control methodology.