A servo motor consists of a micro motor, a set of reduction gears, a potentiometer (which is connected to the gear reducer and acts as a position sensor), and a controller (generally including a voltage comparator, input signal, and power supply).
How is Servo Motor Different from Stepper Motor?
A servo motor is a system consisting of a micro motor (usually stepper motors and brushless motors) and various components. The stepper motor attracts the permanent magnet rotor by generating a magnetic field when electrical pulses are applied to the stator coil. Generally speaking, the error of the servo motor is small. Since the power of the micro servo motor comes from the micro motor, there must be a controller that issues commands to the micromotor. Meanwhile, there should be feedback control in the servo motor system.
The output gear of the reduction gear set inside the servo system is connected to a potentiometer to form a position sensor, so the rotation angle of this servo motor system is affected by the rotation angle of the potentiometer. The two ends of the potentiometer are connected to the positive and negative poles of the power supply respectively, and the sliding end is connected to the rotating shaft. The slider rotates with the shaft, causing the voltage between the potentiometer slider end and the negative end of the power supply to change with the shaft rotation. This voltage is the input power supply of the voltage comparator (operation amplifier). The control signal will be sent to the operational amplifier together with the input voltage. The input control signal is a pulse width modulation signal (PWM), which changes the average voltage by the proportion of the high voltage in a medium period.
How to Control the Direction of Micro Motor?
First, it’s to compare the average voltage of the input signal with the voltage of the power supply position sensor, if the input voltage is higher than the voltage of the power supply position sensor, the amplifier outputs a positive power supply voltage, and if the input voltage is lower than the voltage of the position sensor, the amplifier outputs a negative power supply voltage, that is, a reverse voltage. In this way, the CW and CCW direction of the micromotor is controlled, and the servo system is controlled by the reduction gear set. If the potentiometer and output gear coupling is not bound, it is possible to be coupled with other shafts of the reduction gear set to control the gear ratio to achieve a larger range of the servo system, such as 360 ° rotation, etc., and this may cause a greater error, but will not produce a cumulative error.
The servo motor can be applied to various mechanical arms, robots, automatic doors. There are also special high-torque and high-precision servo motors for the areas requiring high accuracy or high torque for a large load. When selecting the model, we need to pay prior consideration to the torque. How to choose carefully and economically and in accordance with the requirements of the servo motor system is also indispensable knowledge that may need more practice.