Abstract: Aiming at the problem that it is difficult to obtain a constant tracking force when the robot end-effector tracks the contour of a curved-surface workpiece, the contact force between robot end-effector and the curved-surface workpiece is analyzed, the mapping relationship between the normal force of the curved surface and the known sensor coordinate system is established, and a fuzzy iterative algorithm is proposed. Iterative algorithm does not need to get the advantages of the system internal transfer function, which simplifies the modeling design. Meanwhile，the fuzzy iterative algorithm compensates the robot trajectory based on the previous experimental force error and the amount of error change, which accelerates the convergence speed. The bounded convergence of fuzzy iterative algorithm is proved theoretically. The experimental results show that the fluctuation range of contact force is within ±3 N, which verifies the feasibility of this algorithm. Compared with the traditional proportional-derivative (PD) algorithm, the standard deviation of contact force of the fuzzy iterative algorithm is reduced by 42%. Compared with the iterative algorithm without fuzzy compensation, the iteration cycle is reduced at least once in the selected time periods.

Key words: robot, curved-surface tracking, constant force control, fuzzy algorithm, iterative algorithm