Comparison of several control strategies for DC brushless drives

Two modelings for control of the DC brushless drives or more generally for synchronous motors with nonsinusoidal counter-electromotive forces are presented. Using these modelings, three different kinds of control strategies can be thought out. The reference commutation angles for 120° voltage control strategies are defined using the “abc” modeling and the controller is calculated in the same frame. The reference currents can be also computed using an extension of the Park´s transformation. They can be either controlled in the “abc” frame or in “dq” frame. These three strategies have been implemented on the same test bed driven by a digital signal processor. Comparisons are performed with torque measurement using a quartz torque transductor. It is shown that in order to obtain a good torque quality, a 120° voltage control strategy with a current loop is not enough. A good position estimation is necessary and in this case the control laws in the “abc” frame give good results. This strategy does not need a very powerful microcontroller but the efficiency of the drive does not remain optimal. The best performances are obtained for “dq”-frame vector control which needs the use of a digital signal processor