New control techniques based on state space observers for improving the precision and dynamic behaviour of machine tools

This paper describes control techniques based on state space observers that have been developed to improve the precision and dynamic behaviour of machine tools. To improve precision, an accelerometer located close to the tool centre point (TCP) is used, so that its position is estimated by an state space observer and used as position feedback instead of the position read by the linear scale. This way, the structural deformation from the slide to the tool is compensated. Dynamic behaviour is improved estimating the acceleration of the TCP by the aforementioned observer and feeding this noiseless signal into the control system, rather than the noisy signal of the accelerometer itself. These techniques provide a simple way to achieve considerable improvements without using complex and expensive TCP position measurement devices. Tests on actual machines have shown that errors produced by deflections between the slide and the TCP can be reduced by 70%.