Shaft Sensorless Vector Controlled PMSM Servo Drive using Reduced Order Speed Observer

Abstract

The application of vector control techniques in variable speed ac drives demands accurate position and velocity feed back information for the current and speed control loops. A novel method for shaft sensor elimination of the high performance PMSM servo drives is presented in this paper. A reduced order state observer is proposed to be used as a software transducer, which reconstructs the speed and position of the sinusoidal backemf PMSM from the stator current and voltage measurements. The observer is developed from the d-q model of the machine. The state estimation technique used to achieve global stability of the speed observer is discussed along with the design considerations. Since this method totally eliminates the gain scheduling, which is the major difficulty in implementing any conventional observer based scheme, the implementation of the proposed scheme is very simple and easy. The performance of the observer depends on the accuracy of the parameters in the motor model. To take into account these parameter uncertainties along with the load torque variations, a local disturbance torque observer is used. Simulation results using realistic measurement disturbances and drive parameter uncertainties are also presented to investigate the stability and accuracy of the proposed observer. The simulation results show that the proposed scheme gives good results even at near zero speeds.

Indexing terms:

• PMSM servo drives
• Sensorless control
• Reduce order observer

Additional information

Notes on contributors

R Mary Lourde

R Mary Lourde, Received the BSc Engg Degree in Electrical Engg. in 1983 from Kerala University and MTech Degree in Digital Electronics in 1987 from Cochin University of Science And Technology. She has been working as a Lecturer at Cochin University of Science and Technology since 1990. She received the PhD Degree from Indian Institute of Science, Bangalore in 1998. Currently she is a reader in Cochin University of Science and Technology. She has several publications in National and International Journals & Conferences. Her field of interests are Power Electronics and Drives, Control Theory etc…