Adaptive feedrate planning for continuous parametric tool path with confined contour error and axis jerks

Reduction of contour error plays an important role in improving the machining accuracy. However, as an important means, the feedrate planning mainly focuses on confining the chord error and drive constraints in CNC machining, without taking into account the contour error. To ensure the contour machining accuracy for a given parameter curve and simultaneously release the computational burden in real-time interpolation, this paper proposes an new off-line feedrate planning method constrained by the contour error, axis accelerations, and jerks, as well as the chord error. First, a contour error model is built based on a high-order transfer function, from which the feedrate can be scheduled in the contour error violated zones of tool path. Then, the initial feedrate profile is constructed with confined contour error and chord error using a method based on the direct deformation of target curve. In order to further guarantee the drive performances, an iterative proportional adjustment algorithm is used to update the positions of feedrate sampled from the axis accelerations/jerks violated zones of the path curve, and in each adjustment, a curve evolution strategy is utilized to deform the target feedrate profile to the updated positions without using the re-interpolation of entire feedrate profile. Only through several rounds of iterative operation, the final feedrate profile will be achieved without violated constraints. Finally, simulations are performed on two NURBS curves to validate the proposed method. The results demonstrate the effectiveness and feasibility of the proposed method.