Ferraris sensor - The key for advanced dynamic drives

The positioning features of feed drives in machine tools are nowadays almost always guaranteed by a proportional positioning and a proportional and integral velocity controller with an underlying fast current controller. The achievable dynamics of the positioning control are mainly determined by mechanical oscillations within the structure. In this paper it is shown that the bandwidth of the positioning and velocity controller depends also on the acquisition of the state variables. New methods for measuring the relative acceleration according to the Ferraris principle guarantee a velocity of low quantization together with a conventional cascade control. Based on these improvements it is shown that an underlying acceleration control can increase the dynamic disturbance stiffness further. This requires new control structures. Measuring results of single drive systems and a milling operation with a 5-axis machine tool have shown what potential lies in the improved acquisition of state variables by a relative acceleration sensor to achieve highly dynamic and accurate machining results.