Multi-axis load-while-track device based on parallel robot for simulating feeding resistance in machine tool test

This paper presents a multi-axis load-while-track (LWT) device based on a parallel robot to simulate 3-axis feeding resistance for machine tool tests. It performs the LWT function which requires the device to load the spindle while tracking the spindle's feeding trajectory. The LWT device was developed based on a 6-PUS parallel mechanism, and its geometric property and kinematics were presented. To perform the LWT function, an explicit force control system was established based on a fuzzy PI controller. A prototype of the device was fabricated, and experiments were conducted on a 5-axis machine tool to validate the feasibility of performing the LWT function to simulate feeding resistance. Results illustrate that the LWT device could exert 3-axis force to the spindle that is executing a 5-degree-of-freedom feeding motion with loading error less than 2%. This suggests that the device could make the machine tool operate in a force field that mimics 3-axis feeding resistant force in a 5-axis machining process, which provides a machining-free loading approach to make the accuracy deterioration and reliability tests of machine tools more economical and environmental-friendly.