A servo motor consists of a micro motor and a set of reduction gears, plus a potentiometer (connected to the gear reducer, which acts as a position sensor), and a controller (generally including a voltage comparator, input signal, and power supply).
Different from Stepper Motor
Unlike the principle of a stepper motor, it is essentially 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 by applying electrical pulses to the stator coil. In essence, the error is very small, and the power of the micro servo motor comes from the micro motor, so there must be a controller that issues commands to the micro motor, and there is 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 input into the voltage comparator (operation amplifier) together with the control signal, and the power supply of the operational amplifier is connected to the input power supply. 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?
By comparing the average voltage of input signal with the voltage of power supply position sensor, if the input voltage is higher than the voltage of power supply position sensor, the amplifier outputs a positive power supply voltage, and if the input voltage is lower than the position sensor voltage, the amplifier outputs a negative power supply voltage, that is, a reverse voltage. In this way, the CW and CCW direction of the micro motor is controlled, and the servo system is controlled to rotate by outputting the reduction gear set. Just like the picture above. If the potentiometer and output gear coupling are 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.
Wide Application Fields
Various mechanical arms, robots, or automatic doors. various mechanical actions can be realized. There are also special high-torque high-precision servos for the areas requiring high accuracy or requiring high torque and large load for use. When selecting the model, the torque is mainly considered. How to choose carefully and economically and in accordance with the requirements of the servo motor system is also an indispensable knowledge.