Roy Perryman

Comparison of sliding mode and forced dynamics control of electric drive with a flexible coupling employing PMSM

The paper presents comparison of two control techniques (a) sliding mode and (b) forced dynamics for control of electric drives employing permanent magnet synchronous motors with flexible coupling. The designed controllers are of the cascade structure, comprising an inner speed control loop and an outer position control loop. The inner speed control loop for both controllers is based on forced dynamics and respects the principles of vector control. The outer position control loops are designed to control load mass angle in the presence of a vibration mode with an external load torque. Derived control laws requires estimates of the load torque and the second one also its derivatives, which are estimated in the especially designed load torque observer. The simulations presented indicate that the control systems operate according to theory and therefore further investigations including experimental implementation are recommended.

Analytical thermal modelling for permanent magnet synchronous motors

This paper concentrates on the development and analysis of a new generic steady state thermal model for mapping the heat transfer throughout a permanent magnet synchronous motor by considering its individual components as elements of an overall thermal equivalent circuit. This model includes (a) conduction resistances for the stator laminations and housing, conduction resistances between the copper winding and the stator teeth and yoke, between the housing and the stator, and between the housing and the flange, (b) heat flow in the air-gap for vortex and turbulent flow, (c) natural convection and forced cooling for the housing surface and the mounting flange surface, and (d) radiation resistance for the housing surface and mounting flange. The results obtained from the model are compared with corresponding experimental tests for the stall and rated performance with natural and forced cooling for two different motors, one with a rated speed of 1500 r/min and 130 Nm stall torque having 30 slots and 10 poles, and the other with a rated speed of 3000 r/min, and 15 Nm stall torque having 18 slots and 6 poles. The results achieved demonstrate a good correlation between the experimental results and the theoretical results obtained from the thermal model.

Forced dynamics control of electric drives employing pmsm with a flexible coupling

A control system based on the principle of forced dynamics control for an electric drive with a permanent magnet synchronous motor and a flexible coupling is presented and verified by simulations. The controller is of the cascade structure, comprising an inner speed control loop and an outer position control loop. The inner forced dynamics speed control loop respects the principles of vector control and requires an estimate of the load torque, which is estimated in an observer. The outer position control loop based on the same principle is designed to control the rotor angle or load mass angle in the presence of a vibration mode due to the flexible coupling and with an external load torque. The derived control law requires estimates of the load torque and its derivatives, which are estimated in the load torque observer. The simulations presented indicate that the control system operates according to theory and therefore further investigations including experimental implementation are recommended.

Cogging analysis for fractional slot/pole permanent magnet synchronous motors

Analytical and FEA predictions of cogging torque are compared with experimental results for a range of non-skewed PMSMs of similar size but with slot/pole ratios of 18/8, 12/10 and 30/8 (fractional) together with 30/10 and 18/6 (integer). The two analytical methods and the experimental data show close agreement and predict that stator or rotor skewing would be required to reduce the cogging torque to acceptable levels for the motors with the integer ratios, but the cogging torques for the fractional ratios are sufficiently small to obviate the need for skewing, thereby reducing the manufacturing operations. Finally the 12/10 ratio is recommended since this yields a higher stall torque than the 18/6 or 30/8 ratios. The explanation of this is that the 12/10 ratio enables a higher slot fill to be obtained than the 30/8 ratio. Also the winding overhang can be significantly reduced for the 12-10 design with a segmented stator in contrast with all the other slot pole combinations.

Forced dynamics position control of the drive with linear PMSM

Design and verification of forced dynamics position control of a drive with a linear permanent magnet synchronous motor is presented. This control method is a relatively new one and using the principles of feedback linearisation offers an accurate realisation of a dynamic speed and position response, which can be selected for a given application by the user. In addition to this, the primary part current vector and the moving part flux vector are maintained mutually perpendicular as in conventional vector control. The control system has the cascade structure with an outer position control loop and an inner speed control loop. To achieve the defined speed response, the derived control law requires estimation of an external force, which is obtained from an observer. The overall control system is verified by simulations and experimentally. Preliminary experimental results confirmed that the moving part position response follows the prescribed one fairly closely.