Smooth and near time-optimal trajectory planning of industrial robots for online applications

Purpose - The purpose of this paper is to propose a new smooth online near time-optimal trajectory planning approach to reduce the consuming time compared to the conventional dynamics trajectory planning methods. Design/methodology/approach - In the proposed method, the robot path is expressed by a scalar path coordinate. The joints torque boundary and speed boundary are transformed into the plane, which can generate the limitation curves of pseudo-velocity. The maximum pseudo-velocity curve that meets the limits of torque and speed is built up through the feature points and control points in the plane by using cubic polynomial fitting method. Control points used for cubic polynomial construction are optimized by the Golden-Section method. Findings - The proposed method can avoid Range's phenomenon and also guarantee the continuity of torque. Practical implications - The algorithm designed in this paper is used for the controller of a new industrial robot which will be equipped for the welding automatic lines of Chery Automobile Co. Ltd. Originality/value - Compared to the five-order polynomial trajectory optimization method proposed by Macfarlane and Croft, the approach described in this paper can effectively take advantage of joints maximum speed, and the calculation time of this method is shorter than conventional dynamics methods.