| 摘要 |
A surface cleaning appliance comprising a cleaner head including an agitator and a motor 11 for driving the agitator. The appliance further comprises a switch 40 coupling the motor 11 to a supply voltage 9, a voltage sensor 23 for measuring the magnitude of the supply voltage 9, a current sensor 42 for measuring the magnitude of current through the motor 11, and a controller 24 configured to output a PWM signal for controlling the switch 40. The controller 24 then adjusts the duty cycle of the PWM signal in response to changes in the supply voltage 9 and in response to changes in the current through the motor 11. The controller 24 preferably stores a voltage lookup table and a current lookup table, the controller 24 indexes the voltage lookup table using the measured supply voltage to select a first value, the controller indexes the current lookup table using the measured motor current to select a second value, and the duty cycle is defined by the sum of the first value and the second value. The appliance may include a battery pack 9 that provides the voltage supply. As the battery pack 9 discharges the performance of the brush remains constant. |
