Method for controlling ECM motor to output constant torque

1. A method for controlling an ECM motor to output a constant torque, the ECM motor comprising:

a stator assembly, a rotor assembly, a housing assembly, and a motor controller;

the motor controller comprising: a power supply circuit, a microprocessor, an inverter, and a rotor position detection circuit;

the power supply circuit supplying power to each circuit;

the rotor position detection circuit detecting a rotor position signal and inputting the rotor position signal into the microprocessor;

the microprocessor controlling the inverter circuit; and

the inverter circuit controlling each coil winding of the stator assembly to be in a power-off state or a power-on state;

the method comprising the following steps:

1) entering a target torque value T0 from an external device; when the motor is in a non-use state, starting the motor, and allowing the microprocessor to acquire an original output voltage value P chopped by a PWM signal; when the motor is in a running state, allowing the microprocessor to acquire a current output voltage value P chopped by the PWM signal;

2) enabling the microprocessor to calculate a target bus current value Itad using the function Itad=F(T,P) according to the target torque value T0 and the output voltage value P chopped by the PWM signal, in which, Itad represents a target bus current, T represents a torque value output by the motor, P represents the output voltage value chopped by the PWM signal input to the inverter circuit by the microprocessor; and detecting a real-time bus current Ibus; and

3) allowing the microprocessor to compare the target bus current value Itad with the real-time bus current Ibus for conducting a closed-loop control: when the target bus current Itad is larger than the real-time bus current Ibus, increasing the output voltage value P chopped by the PWM signal; when the target bus current Itad is smaller than the real-time bus current Ibus, decreasing the output voltage value P chopped by the PWM signal; and when the target bus current Itad is equal to the real-time bus current Ibus, stopping regulating the output voltage value P chopped by the PWM signal, and allowing the ECM motor to enter a running state, and repeating step 2) for conducting a constant control state.

2. The method of claim 1 , wherein that the target bus current Itad is equal to the real-time bus current Ibus means that an error of a deviation of the real-time bus current Ibus from the target bus current Itad is within 1%.

3. The method of claim 2 , wherein the function Itad=F(T,P) in step 2) is Itad=K1+K2*T+K3*P+K4*T*P, in which, K1, K2, K3, and K4 represent coefficients, T represent the torque, and P represents the output voltage value chopped by the PWM signal.

4. The method of claim 2 , wherein the function Itad=F(T,P) relating to the torque value output by the motor and a DC bus current is established by experimental means.