Brushless dc motor, ac servo system with small inertia, large output torque, simple control, the advantages of good dynamic response, rapid development, has a broad application prospect, in the field of high performance, high precision servo drive, will gradually replace the traditional dc servo system. Brushless dc machine, however, still exists the torque ripple, unable to realize more position control and speed control, better performance of phase current commutation is one of the main reasons for torque ripple.
in the adoption of the reversing of the phase current feedback ac servo system, the commutation torque ripple at low speed can be controlled, but the inability of high-speed non commutation phase current is not controlled. Therefore, to seek optimization of directional control scheme, and to get better performance of the commutation torque.
the reversing of the inverter in the process of effective switch state shall, in accordance with the rules of the selection:
rule 1: follow the rotor position of the current is shut off should disappear corresponding switch, and shall establish corresponding to the switch.
rule 2: on the premise of rule 1, can use single or double polarity control.
rule 3: allow should disappear corresponding switch delay shut off.
the reversing switch control strategy under the pros and cons of consists of the following two indicators to evaluate:
1. Caused by the commutation torque ripple small (as much as possibleThe commutating current pulse as small as possible)；
