Joint motion planning of industrial robot based on hybrid polynomial interpolation

Abstract

To plan an industrial robot's point-to-point joint motion that has velocity constraints, the cubic polynomial interpolation planning method has angular acceleration discontinuity. The quintic polynomial interpolation planning method needs to set in advance the angular acceleration values of target points and easily causes angular velocity fluctuation. Because of the existence of quintic polynomials, hybrid polynomial planning 3-5-…-5-3 also easily causes large angular velocity fluctuation. To solve these problems, a hybrid polynomial interpolation planning method based on cubic and quartic polynomial interpolation is proposed. Cubic polynomial interpolation planning is applied to the first planning, and quartic polynomial interpolation planning is used for the rest of planning. The planning method can not only specify the angular velocities of intermediate target points but also ensure the continuity of angular acceleration. In addition, there is no need to set in advance the angular acceleration values of target points so as to avoid the angular velocity fluctuation caused by the unreasonable presetting of angular acceleration. Furthermore, in order to avoid excessive peaks of angular velocity during the joint motion planning, a calculation method for finding out reasonable motion time is put forward, under which the larger speed at two target points is taken as maximum, thus making the planned angular velocity fluctuation small. A case study is performed to verify the rationality and effectiveness of the planning method. Compared with the other two planning methods used for the case study, our planning method can effectively solve the problems of point-to-point joint motion planning with velocity constrains, therefore being beneficial to the working performance and service life of an industrial robot.