Real-Time Iterative Compensation Based Contouring Control Method for Polar Coordinate Motion Systems

For precision planar contouring control systems widely applied in industrial scenarios, additional contouring control action is usually added to two axes respectively to enhance contouring motion performance. In this article, planar motion is innovatively described in the polar coordinate system but not Cartesian one, and a novel definition of polar-radius error (PE) is proposed to evaluate contouring performance. Compared to traditional contouring error defined in Cartesian coordinate system, PE is more suitable for describing the deviation between the actual contour and the reference one, especially at contour vertexes where the traditional definition is defective. Based on the definition of PE, a real-time iterative compensation method is subsequently designed for radial motion axis to improve its trajectory tracking performance and to suppress the contouring error indirectly. The compensation mechanism is merely implemented on only one axis rather than both axes of planar motion, which makes it simpler for practical applications than other existing contouring control algorithms. Comparative experiments with different error definitions and control modes are carried out on machine tool systems to illustrate the effectiveness of the proposed contouring control framework.