Robust Nonlinear Control of Two Links Robot Manipulator and Computing Maximum Load

A new robust nonlinear control scheme of a manipulator is proposed in this paper which is robust against modeling errors and unknown disturbances. It is based on the principle of variable structure control, with sliding mode control (SMC) method. The variable structure control method is a robust method that appears to be well suited for robotic manipulators because it requers only bounds on the robotic arm parameters. But there is no single systematic procedure that is guaranteed to produce a suitable control law. Also, to reduce chattring of the control signal, we replaced the sgn function in the control law by a continuous approximation such as tangant function. We can compute the maximum load with regard to applied torque into joints. The effectivness of the proposed approach has been evaluated analitically demonstrated through computer simulations for the cases of variable load and robot arm parameters.

• Hasanifard Goran
• Habib Nejad Korayem Moharam
• Nikoobin Amin

• Variable structure control
• robust control
• switching surface
• robot manipulator.

[1] Utkin VI. "Sliding mode in control and optimization", New York:
Springer- Verlag; 1992.
[2] Hung JY, Gao W, Hung JC. "Variable structure control: A survey".
IEEE Transactions on Industrial Electronics 1993;40:2-22.
[3] Young KD, Utkin VI, Ozguner U, "A control engineer's guide to
sliding mode control", IEEE Transactions on control system
Technology 1999 ;7:328-42.
[4] Huang YJ, Kuo TC, "Robust output tracking control for nonlinear
time varying robotic manipulators", Electrical engineering 2005;
87:47-55.
[5] Utiks, U., "Control Systems of Variable Structure", Wiley: New
York, 1976.
[6] Utkin, V. I., "Sliding Mode and Their Application in Variable
Structure Systems", Mir Publishers: Moscow, 1978.
[7] Hikita, H., "Servomechanism based on sliding mode control", lnt. J.
Control, vol. 48, pp. 435--447, 1988.
[8] Chern, T. L and Wn, Y. C., "Design of integral variable structure
controller and application to electrohydraulic velocity servosystems",
lEE Proc. D, vol. 138, pp. 439-444, 1991.
[9] Leang,T. P., Zhou, Q. J. and Su, C. Y., "An adaptive variable
structure model following control design for robot manipulators"
IEEE Trans. Automat. Control, vol. 36, pp. 347-352, 1991.
[10] Chart, C. Y., "Servo-systems with discrete-variable structure control",
System & Control Letters, vol. 17, pp. 321-325, 1991.
[11] Fu, L. C. and Liao, T. L, "Globally stable robust tracking of nonlinear
systems using variable structure control and with an application to a
robotics manipulator," IEEE Trans. Automat. Control vol. 35, pp.
1345-1350, 1990.
[12] Song, Y. D. and Gao, W. B., "Path tracking control of robot
manipulators via the VSS approach", Int. J. Systems Sci., vol. 22, pp.
151-163, 1991.