MOTOR CONTROL SYSTEM AND METHOD FOR SKIPPING RESONANT OPERATING FREQUENCIES

摘要

A system and method of avoiding hunting behavior by a motor around disallowed speed ranges. A sensor or sensorless method determines the motor's actual speed. A memory contains lower and upper speed values that define a disallowed range. A control unit determines whether the motor is operating under a limiting condition and engaged in hunting behavior by determining whether the motor is repeatedly moving between an actual speed that is within the disallowed range and an actual speed that is at or below the lower speed value during a first period, and if so, sets a temporary speed limit for the motor at the lower speed value for a second period. The first period may be the time required for the motor to change its actual speed a few times and thereby confirm hunting behavior. The second period may be sufficiently long that the limiting condition may have changed.

主权项

1. An electric motor system comprising:
an electric motor having a shaft for driving a load; and a motor control subsystem operable to control operation of the electric motor, the motor control subsystem including—
a speed determiner operable to determine an actual speed value of the electric motor,a memory element containing a first lower speed value and a first upper speed value which together define a first disallowed speed range for the electric motor, anda control unit in electrical communication with the speed determiner and the memory element, and operable to—
calculate a desired speed value for the electric motor, wherein the desired speed value is not within the first disallowed speed range, and to generate and send an electrical signal to cause the electric motor to attempt to achieve the desired speed value,receive the determined actual speed value of the electric motor from the speed determiner,determine whether the electric motor is unable to achieve the desired speed value due to a limiting condition and is repeatedly changing between a first actual speed value that is at or below the first lower speed value and a second actual speed value that is within the first disallowed speed range over a first predetermined period of time,if so, set a temporary speed limit for the electric motor at the first lower speed value for a second predetermined period of time, andat the end of the second predetermined period of time, remove the temporary speed limit.