NURBS curve interpolation strategy for smooth motion of industrial robots

Smooth motion is crucial for industrial robots to efficiently execute accurate path tracking tasks. This paper proposes a NURBS curve interpolation strategy for smooth motion of industrial robots to reduce roughness and contour error. The strategy ensures smooth motion through two stages: feedrate planning and interpolation point parameter calculation. During the feedrate planning stage, kinematics and dynamics constraints, including torque and torque change rate, are considered in the parameter domain. Round-off error is considered, and an S-curve feedrate planning approach is employed to ensure the planned feedrate is smooth after transitioning from the parameter domain to the time domain. In the interpolation point parameter calculation stage, the displacement guidance curve is generated and updated based on the current situation. Interpolation point iteration compensation is conducted to ensure the interpolation output feedrate is smooth. Simulations and experiments are conducted to validate the effectiveness of the proposed strategy. The simulation results indicate that the proposed strategy effectively smooths the interpolation output feedrate while maintaining efficiency. The experimental results show that the strategy effectively reduces roughness and contour error.