MPS II – Multi-Coordinate Positioning System for Machining Tools

Conventional multi-axis systems realize motion by serially arranging individual feed axes. This results in high moving masses, limited acceleration, and the accumulation of geometric and positioning errors. Compliance is direction-dependent, and the overall path dynamics are constrained by subordinate axes. Multi-coordinate drives with integrated guidance overcome these drawbacks by reducing moving masses, increasing stiffness, and eliminating frictional contacts. The approach developed at IFW combines a synchronous planar motor with an electromagnetic surface guidance system, providing a compact and practice-oriented solution for highly dynamic machining tools.

Objectives

The project aims to develop and validate a friction-free multi-coordinate positioning system that combines a synchronous planar motor with electromagnetic surface guidance. This enables highly precise and dynamic feed motions in six degrees of freedom. Separate control of eight motor windings provides fine rotational positioning about the B-axis. A current-based feed-forward strategy derived from measured force maps compensates periodic cogging forces and improves path quality. Magnetic guidance is controlled using a model-based state controller augmented by an observer and a Kalman filter to increase bandwidth, levitation stability, and robustness. The complete system is implemented in an industry-grade control environment with high-precision position measurement and validated for practical use in machining tools.

Benefits

Because all motions are executed directly without mechanical coupling, the system increases path and positioning accuracy. Eliminating frictional contacts avoids wear effects and enables reproducible dynamic behaviour. Friction-free magnetic guidance raises system stiffness and stability, while separate actuation of the planar motors enables precise fine rotational positioning. As a result, higher dynamics and smoother feed motion are achieved – particularly beneficial for high-precision machining processes.

Approach

The system employs four planar-motor modules with decoupled actuation to realize translational motions and fine rotational positioning about the B-axis. One focus is the optimization and commissioning of the drive units and the development of a feed-forward strategy that compensates position-dependent cogging forces to improve path quality. Another focus is the model-based control of magnetic guidance in the Y-, A-, and C-directions using a state controller with observer, which increases overall stability and dynamic performance. High-resolution grating encoders and capacitive sensors provide precise measurement of all degrees of freedom.

Are you also interested in a cooperation project?

Contact Hamed Roham via email at roham@ifw.uni.hannover.de or by phone at +49 511 762 833.