Resource Efficient Sensorless Control of Low-Power Permanent Magnet Synchronous Machines

• Applicant: Professor Dr.-Ing. Matthias Nienhaus
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives ; Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 458222494

In the recent years, PMS motors have gained wide applicability in both industrial and domestic applications due to their robustness and reduced dimensions joined to a high dynamic behaviour. Nevertheless, it is well known that mechanical sensors such as encoders or resolvers are needed in order to operate such motors. For this reason, sensorless techniques capable of operating within the full speed range, i.e. from standstill to high-speed, are significant for a successful implementation of PMSMs. In particular, for low-power machines, it is crucial to dispose of resource-efficient sensorless techniques, capable of providing reliable operation while requiring low-computational effort, so that space and costs of the driving electronics can be minimized. Several sensorless techniques have been proposed in the last years, being the ones based on machine anisotropies the necessary choice for operating a synchronous machine from stand-still up to high speeds. Within this category, techniques are based on the exploitation of the machine current ripples induced by a switching power stage. This research proposal aims at providing a significant contribution to this field by proposing a hybrid analog/digital technique capable of providing similar performance to state-of-the-art techniques at much lower computational expenses. The main idea of this project stems from the IDIM (Integrator-based Direct Inductance Measurement) technique that has been successfully applied for sensorless control of single-coil electromagnetic actuators. This technique is based on a fast-resettable integrator circuit synchronized to the applied PWM voltage. By measuring the integral of the induced current ripple undergoing a proper reset mechanism, information about the actuator’s coil inductance can be obtained with very high signal-to-noise ratio, thus allowing reliable sensorless drive of the actuator. Nevertheless, a direct application to permanent magnet based rotary machines is challenging due to presence of back-electromotive force, a more complex PWM pattern for multi-phase machines as well as higher influence of nonlinearities of the power stages on the induced current ripples. This project aims at solving these aspects by investigating and modelling the mentioned effects at the aim of designing a proper machine excitation strategy that allows to retrieve the necessary machine information for sensorless operation by implementing a hybrid analog/digital technique while mitigating the effects of the power stage nonlinearities and requiring low computational effort from the driving electronics and microcontroller unit.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Emanuele Grasso