Stepper motors and servo motors are the two most widely used products in the industrial control field, and their core components are stepper motor controllers and servo motor controllers, respectively. This article will explain the differences between these two devices.
I. Differences in working principles
Stepper motor controller: It is an electronic product that can emit uniform pulse signals. The signals it emits enter the stepper motor driver, which converts them into the strong current signals required by the stepper motor, driving it to rotate. The stepper motor controller can accurately control the stepper motor to rotate through each angle. The driver receives pulse signals; each pulse received causes the driver to send a pulse to the motor, causing it to rotate through a fixed angle. Because of this characteristic, stepper motors are widely used in various industries today.
Servo motor controller: This is a controller used to control servo motors. Its function is similar to that of a frequency converter for ordinary AC motors. It is part of a servo system and is mainly used in high-precision positioning systems. Generally, it controls the servo motor through three methods: position, speed, and torque, achieving high-precision positioning of the transmission system. Currently, it represents a high-end product in transmission technology.
Second, the composition is also different.
1. The three main circuits of a stepper motor controller
Motor drive circuit: A stepper motor drive circuit is designed based on the H-bridge circuit. Using discrete MOSFETs to build a dual H-bridge drive circuit is a mature motor control solution. The circuit is not complex, and depending on the different operating currents of the MOSFETs, the upper limit can even reach tens of amperes, making it an ideal stepper motor driver solution.
Motor parameter measurement circuit: A constantan resistor is used for motor current sampling, with one end connected to the bottom of the H-bridge and the other end connected to GND. The voltage and current signal conditioning circuit is built using an LM324 operational amplifier. The voltage signal is fed into the MCU after following the signal, and the MCU's built-in 10-bit A/D converter performs A/D sampling. The chassis temperature monitoring uses a DS18B20 digital temperature chip, which is attached to the surface of the motor chassis to monitor the temperature parameters in real time and send them 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 power supply . Traditional linear regulators are inefficient, large in size and generate a lot of heat. Therefore, a DC-DC switching power supply is used to provide 3.3V to ensure the normal operation of the devices.
2. Circuit composition of the servo motor controller
Motor rectifier circuit: The main topology of the rectifier unit is a three-phase full-bridge uncontrolled rectifier circuit, which is essentially a series connection of a set of common cathode and a set of common anode three-phase half-wave controlled rectifier circuits. Conventionally, the three thyristors with their cathodes connected together are called the common cathode group; the three thyristors with their anodes connected together are called the common anode group.
Power drive circuit: The power drive unit generally uses intelligent power modules, which rectify the input three-phase power or mains power through a three-phase full-bridge rectifier circuit to obtain the corresponding DC power. The power unit is a high-voltage frequency converter component that uses power electronic devices for rectification, filtering, and inversion, and mainly consists of rectifier bridges, thyristors, electrolytic capacitors, IGBTs, and other devices. The entire process of the power drive unit can be simply described as an AC-DC-AC process.
Motor control circuit: The main circuit uses a digital signal processor as the control core, which can implement relatively complex control algorithms and perform intelligent control.
