Cooperative compliance control of the dual-arm manipulators with elastic joints

Abstract

Cooperative compliance control of dual-arm manipulators with elastic joints carrying a constrained object is addressed in this paper. The well-known inner/outer loop hybrid control strategy was used as the overall control scheme. The inner loop control method of each manipulator with elastic joints is a global tracking control approach, which is based on highorder inverse dynamics and the passivity theory; high-order inverse dynamics can be efficiently computed with modern high-order Newton-Euler algorithms, and the passivity-based theory can be robust against model uncertainties and input disturbances. The outer loop control approach enforces a desired impedance between the two end-effectors with the object, aimed at avoiding large internal forces to damage the robot or the object. The proposed control scheme is simulated on a dual-arm cooperative system which contains two 7-DOF elastic-joint manipulators and a manipulated object, and simulation results illustrate the high-precision tracking capabilities of the proposed control scheme, and robustness to bounded dynamic parameters uncertainties can be achieved. Meanwhile, the internal forces converge to the desired values.

Cooperative multiple elastic‐joint arms control using the (p, q)‐analogue of Bernstein operators as the uncertainty approximator

“…For cooperative multiple elastic joint robots, a hybrid control strategy including an inner/outer loop is utilized. 11 The inner loop control law is a global tracking controller, in agreement with the high-order inverse dynamics concept and the passivity theorem, while the control law related to the outer loop inserts desired impedance between the two end-effectors and the object. Reference 12 investigated an efficient and different compliance modeling theory for cooperative elastic joint robots.…”

“…Hence, Equations ( 24), (11), and (12) give the overall cooperative multiple elastic-joint arms dynamics.…”

“…According to (35), using (11) and the above-mentioned equation, the following error dynamics can be obtained.…”

“…Theorem 1. Consider the dynamic system (11), (12), and (24) with the control inputs (33), (49), and (59). Assume that, the system's uncertainties are approximated using ( 38), ( 52), and (62).…”

“…For the flexible robots, Reference 10 investigated a dynamic control, on the basis of rigid‐flexible coupling dynamics. For cooperative multiple elastic joint robots, a hybrid control strategy including an inner/outer loop is utilized 11 . The inner loop control law is a global tracking controller, in agreement with the high‐order inverse dynamics concept and the passivity theorem, while the control law related to the outer loop inserts desired impedance between the two end‐effectors and the object.…”