Voice coil motor-actuated fast tool servo based on adaptive robust control with cutting force compensation for diamond turning

Abstract

The voice coil motor-actuated fast tool servo (VCM-FTS) is capable of fabricating micro-structured surfaces with ultra-high precision and is widely employed in industrial applications. However, owing to the inherent low axial stiffness of such a system, it is highly susceptible to disturbances caused by cutting forces, resulting in relatively poor machining accuracy. Additionally, parameter variations during machining, such as fluctuations in the force constant of the VCM, can lead to trajectory tracking errors. To address these issues, this paper presents a VCM-FTS controlled by a cutting force compensation-based adaptive robust control (CFC-ARC) controller. Based on prior knowledge of the relationship between the cutting force and uncut chip area from planner trial cutting, the cutting force can be estimated through the ideal uncut chip area and then used as a feedforward term to mitigate disturbances caused by cutting forces. Furthermore, due to the intrinsic properties of ARC, the controller can adjust the system parameters in real time to handle undesired parameter variations. Compared with the traditional controlling method, the adaptation of the CFC-ARC controller improves the system’s positioning resolution, bandwidth and the sinusoidal trajectory tracking accuracy. In the machining of aspheric lens arrays and compound-eye lens arrays, the CFC-ARC controller reduced morphology errors by approximately 30%–45%, confirming its effectiveness in enhancing the machining precision of microstructured surfaces.