The Difference Between Stepper Motor Controller And Servo Motor Controller

- Feb 27, 2019-

The difference between stepper motor controller and servo motor controller



Stepper motor and servo motor are the two most widely used products in the industrial control field, and their cores are stepper motor controller and servo motor controller. This article will explain the difference of these two kinds of products.

First, the working principle is different

Stepper motor controller: It is an electronic product that can emit a uniform pulse signal. When the signal sent from the stepper motor driver, it is converted by the stepper driver into a stepper motor needed  strong current signal,and make stepper motor operate. The stepper motor controller accurately controls the stepper motor to rotate through each angle. The driver receives a pulse signal, and each time a pulse is received,stepper drive will give the motor a pulse to turn the motor through a fixed angle. Because of this feature, the stepper motor will be widely used in various industries.

Servo motor controller: It is a kind of controller used to control the servo motor. Its function is similar to that of the inverter acting on the common AC motor. It is part of the servo system and is mainly used for high precision positioning system. Generally, the servo motor is controlled by three modes: position, speed and torque to realize high-precision transmission system positioning. At present, it is a high-end product of transmission technology.

Second, the composition is not the same

1. Three major circuits of stepper motor controller

Motor drive circuit: Design a stepper motor drive circuit based on the H-bridge circuit. The use of discrete component MOS tube to build a double H-bridge driver circuit is a mature motor control scheme, and the circuit is not complicated.

The upper limit of the operating current according to the MOS tube can be as high as tens of amps, which is an ideal stepper motor driver solution.

Motor parameter measurement circuit: The motor current sampling resistor uses a constant copper resistor, one end is connected under the H bridge, and the other end is connected to GND. Voltage and current signal conditioning circuit is built with LM324 op amp, voltage with and sent to the MCU for A/D sampling by the MCU's built-in 10Bit A/D converter. The temperature monitoring of the casing uses the digital temperature chip DS18B20, which is attached to the surface of the motor casing to monitor the temperature parameters in real time,and sent to the MCU.

Power supply and MCU control circuit: The drive circuit in the system is powered by the input voltage. The MCU and Bluetooth module require an additional 3.3V supply. The traditional linear regulator is low in efficiency and large in size,also heat is severe, so the DC-DC switching power supply is used to provide 3.3V voltage to ensure the normal operation of the device.

2. The circuit composition of the servo motor controller

Motor rectifier circuit: The main topology circuit of the rectifier unit is a three-phase full-bridge uncontrolled rectifier circuit, which is essentially a series of three-phase half-wave controllable rectifier circuits with a common cathode and a common anode.The three intergranular tubes in which the cathodes are connected together are referred to as a common cathode group; the three thyristors to which the anodes are connected together are referred to as a common anode group.

Power drive circuit: The power drive unit generally adopts an intelligent power module, and rectifies the input three-phase electric or commercial power through a three-phase full-bridge rectifier circuit to obtain a corresponding direct current. Power unit is a high-voltage inverter component that uses power electronics for rectification, filtering, and inverter. It is mainly composed of rectifier bridge, thyristor, electrolytic capacitor, IGBT and other devices. Power drive unit process can be simply the process of AC-DC-AC.

Motor control circuit: The main circuit uses digital signal processor as the control core, which can realize more complicated control algorithms and intelligent control.

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