How to understand the working principle and control strategy of DC motor?

Principle of work:

Lorentz force principle:

In a DC motor, the stator is energized to produce a magnetic field, while the conductor inside the rotor is energized to be subjected to the Lorentz force in the magnetic field, causing it to produce a rotating torque.

The conductor inside the rotor is energized and subjected to a force in the magnetic field, which causes the rotor to rotate according to the rules of the direction of the Lorentz force.

Principle of commutator:

In order to maintain continuous rotation of the rotor, it is necessary to periodically change the direction of current to the conductors on the rotor.

This is accomplished by means of a commutator, which connects the positive and negative poles of a DC power supply to different windings of the stator, causing the conductors to be energized in different directions, thus producing continuous rotation.

Magnetic field and current interaction:

The operation of a DC motor is based on the interaction between the magnetic field and the current. By varying the magnitude and direction of the current, the speed and torque of the motor can be adjusted.

Friction and load:

In addition to the Lorentz force, the rotor is affected by friction and load, which affect the performance and efficiency of the motor.

Control circuit analysis:

Power electronics:

The key to controlling a DC motor is the use of power electronics (e.g., thyristors, field effect tubes, etc.) to control the magnitude and direction of current and voltage.

PWM Modulation:

Pulse width modulation (PWM) is a commonly used control method to control the average voltage of the motor by varying the width of the pulses, thus regulating the speed of the motor.

Current Feedback:

Current is monitored and fed back in real time through devices such as current sensors in order to realize the current control and improve the stability and efficiency of the motor.

Speed and position feedback:

Encoders, Hall sensors and other devices are used to monitor the speed and position of the motor in real time and send the feedback back to the control circuit to achieve closed-loop control and speed/position regulation.

Protection and fault detection:

Control circuits typically include protection functions such as overcurrent, overload, and overheating, as well as fault detection to ensure that the motor operates within safe limits and that faults are detected and resolved in a timely manner.

Power supply and filtering:

Proper power supplies and filters are also required in control circuits to ensure a stable power supply and reduce electromagnetic interference.