The principle of operation of a servo motor is relatively simple, but its efficiency is relatively high. The servo circuitry is built inside the motor unit, which uses a flexible shaft usually equipped with gears. Electrical signals control the motor and also determine the amount of movement of the shaft. The internal setup of a servo motor is simple: a small DC motor, a control circuit and a potentiometer. The DC motor is connected to the control wheel via a gear, and as the motor rotates, the resistance of the potentiometer changes, and the control circuit is able to accurately regulate movement and direction.
When the shaft is in the correct (desired) position, the motor stops supplying power. If the shaft does not stop at the target position, the motor keeps running until it goes into the correct direction. The position of the target is transmitted via a signal line using electrical impulses. Therefore, the speed of the motor is proportional to the actual and desired position. As the motor approaches the desired position, the motor begins to rotate slowly, but the motor rotates quickly as it turns farther away. In other words, servo motors just need to get the job done as fast as possible, which makes them efficient devices.
When an AC servomotor has no control voltage, there is only a pulsating magnetic field generated by the excitation windings in the air gap, and the rotor is stationary without a starting torque. When there is a control voltage and the control winding current and the excitation winding current are in different phases, a rotating magnetic field is generated in the air gap and an electromagnetic torque is produced to rotate the rotor in the direction of the rotating magnetic field. However, the servo motor requires that not only can it be started under the action of control voltage, but also the motor should be able to stop immediately after the voltage disappears. If the servo motor control voltage disappears like a general single-phase asynchronous motor to continue to rotate, then the phenomenon of runaway, we call this phenomenon due to the loss of control of their own rotation phenomenon known as spinning.
The basic working principle of the traditional DC servo motor is exactly the same as that of the ordinary DC motor, relying on the action of the armature current and the air gap flux to generate electromagnetic torque to make the servo motor rotate. The armature control method is usually used, that is, under the condition of keeping the excitation voltage unchanged, the speed is adjusted by changing the armature voltage. The smaller the armature voltage is, the lower the speed is; when the armature voltage is zero, the motor stops. As the armature voltage is zero, the armature current is also zero, the motor does not produce electromagnetic torque, there will be no “spin”.
Post time: Apr-21-2025