Patent ID: 8810163

Claim:
A control system for operating a plurality of electric motors comprising: a first electric motor including a first electric motor control unit, the first electric motor control unit being configured to: operate the first electric motor at a first rate in response to receiving a control signal at a first level and at a second rate in response to receiving the control signal at a second level; and operate the first electric motor at a plurality of intermediate operating rates between the first rate and the second rate in accordance to a first predetermined control curve in response to receiving the control signal at an intermediate level between the first level and the second level; a second electric motor including a second electric motor control unit, the second electric motor control unit being configured to: operate the second electric motor at the first rate in response to receiving the control signal at the first level and at a third rate in response to receiving the control signal at the second level, the third rate being different than the second rate; and operate the second electric motor at another plurality of intermediate operating rates between the first rate and the third rate in accordance to a second predetermined control curve in response to receiving the control signal at the intermediate level between the first level and the second level; and a controller operatively connected to the first electric motor control unit and the second electric motor control unit, the controller being configured to: generate a single control signal as the control signal to operate both the first electric motor and the second electric motor, the control signal being at one of the first level, the second level, and one of a plurality of intermediate levels between the first level and the second level.