Control of Synchronous Motors

Chapter 8

Characterization of Control without a Mechanical Sensor in Permanent Magnet Synchronous Machines ¹

8.1. Introduction

If the industrial development of the permanent magnet synchronous machine (PMSM) is mostly linked to the placing on the market of reliable and efficient position sensors, it is still true that today we are witnessing a second wind for these devices, due to the possibilities of functioning without a mechanical sensor.

These structures help to meet new requirements concerning operation in difficult conditions (temperatures, vibrations, etc.) or else for cost reduction, while maintaining satisfying dynamic performances for a large number of applications. To this effect, many solutions appeared in recent years, in order to rebuild the information “mechanical position of the shaft” necessary for piloting the associated drives. Interested readers can also refer to Chapter 4 of this book or to many other publications such as [CHA 00] or [BOL 99].

Whatever the chosen observation method, the “position” information, rebuilt with a certain precision and above all with certain dynamics, will be injected into the autopilot loop of the machine, in order to ensure drive control. In the search for high dynamic performances, modern drives generally integrate a device that can evaluate the applied load torque, in order to compensate for its harmful effects on the adjustment quality [FOR 10], [BRA 87]. These devices are characterized by certain dynamics, imposed by the designer, ...