Feedrate scheduling method for 3-PRS hybrid machine tools considering kinematic constraints

Hybrid machine tools (HMTs), known for their fast response speed, high stiffness, and accuracy, have found wide applications in aerospace and other industries. However, maintaining stability and durability during high-speed machining necessitates careful feedrate scheduling. This study introduces a novel feedrate scheduling method for 3-prismatic-revolute-spherical (3-PRS) HMTs, ensuring that the velocities and accelerations of the drive axes remain within predefined ranges. Initially, the velocity and acceleration dynamics of the 3-PRS mechanism were scrutinized using the screw theory. Subsequently, a virtual axis programming method was introduced, transforming the HMT into a virtual double-pendulum five-axis serial machine tool. In addition, the space of the master-slave movement (SMM) concept is proposed to define the toolpath. Moreover, a strategy for constraining the tool center point rate and acceleration was devised based on the kinematic relationships between the drive axes, virtual axes, and tool center points. Simulation and experiment validated the efficacy of the feedrate scheduling method, demonstrating compliance with the kinematic constraints of the drive axes and enhanced machining efficiency.