Bearingless Reluctant Rotary-Linear Motor

• Applicant: Professor Dr.-Ing. Ralf Werner
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277701070

Bearingless reluctant Rotary-Linear MotorMagnetic levitation systems offer many advantages compared to conventional drives because of contactlessness. There are neither mechanical wear, nor friction or stick-slip effects. Furthermore, no lubricant is necessary. Using an active control, very high bearing stiffness and precision up to the sub-micrometer range are possible.Rotary-linear motors provide independent rotation and translation in one motor unit. However, the versions of this drive known up to this point have mechanical bearings including the corresponding disadvantages.Bearingless motors combine motor and magnetic bearing to one unit with higher utilised volume, better precision and easier assembly. These drives offer all advantages of a magnetic bearing. But however, up to now only either translation or rotation is possible.The construction of the above-mentioned drives often is sophisticated and expensive due to both bearings and geometries of the magnetic circuits, or due to the use of permanent magnets.Objective of this research work is the development of a bearingless reluctance motor, which can execute both rotation and translation. Thus an easy, robust and cost-effective construction will be possible. The motor is controlled by a novel control algorithm that is adapted for the motor specifics. It is based on finding an optimal inverse to the motor model.At first, the control method will be elaborated theoretically and implemented into a DSP. Using numeric computation of fields, the parametrisation of the motor model will be done. After the construction of a test station, it will be started up and the control parameters will be set.First step of the investigations will be an analysis of the response behavior to setpoint changes and to disturbances. According to the results, further optimisation of the control algorithm will be done.Next step will be an analysis of the tolerance against differences between the motor model and the real motor.Furthermore, the control method shall be modified in order to obtain minimal transverse forces in the rotor. This leads to less deformation and to further increase of precision.An additional modification of the control leads to a minimisation of the effective winding currents. Thus, ohmic loss will be reduced and efficiency will be improved.The bearingless reluctant rotary-linear motor combined with the flexible control method provides a very universally usable drive system. Very high positioning accuracies in every degree of freedom can be achieved. The construction of the bearingless drive is robust, compact and, because of its simplicity, tends to be more cost-effective than conventional drives.

• DFG Programme: Research Grants