•Introduction
This article primarily discusses ordinary motors , geared motors, stepper motors, and servo motors, which refer to DC miniature motors, the most common type we encounter in daily life. The subject of motors is quite complex; this article only provides a general overview of the various motors commonly used in robot manufacturing for beginners.
An electric motor, commonly known as a "motor," is an electromagnetic device that converts or transmits electrical energy based on the law of electromagnetic induction. Electric motors are also called motors (or simply motors), and are represented by the letter "M" (formerly "D") in circuit diagrams. Their main function is to generate driving torque, serving as a power source for electrical appliances or various machines. Generators are represented by the letter "G" in circuit diagrams.
Ordinary motor
Ordinary motors are the most common type of motor we encounter daily, found in electric toys, razors, and so on. These motors are characterized by excessively high speed and insufficient torque. They typically have only two pins; connecting the positive and negative terminals of a battery to these two pins will make them rotate, and connecting the battery's positive and negative terminals in reverse will cause the motor to rotate in the opposite direction.
Gear motor
A geared motor is simply a regular motor with a gearbox added, which reduces the speed and increases the torque, giving the regular motor a wider range of applications.
Stepper motor
A stepper motor is an open-loop control unit that converts electrical pulse signals into angular or linear displacement. Under non-overload conditions, the motor's speed and stopping position depend only on the frequency and number of pulse signals, and are unaffected by load changes. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in a set direction, called the "step angle." Its rotation occurs step by step at fixed angles. The angular displacement can be controlled by controlling the number of pulses, thus achieving accurate positioning; simultaneously, the motor's speed and acceleration can be controlled by controlling the pulse frequency, thus achieving speed regulation.
Servo
A servo motor mainly consists of a housing, circuit board, coreless motor, gears, and position detector. Its working principle is as follows: a receiver sends a signal to the servo motor, the IC on the circuit board determines the direction of rotation, and then drives the coreless motor to start rotating. Power is transmitted to the swing arm through the reduction gears. Simultaneously, the position detector sends back a signal to determine whether the desired position has been reached. The position detector is essentially a variable resistor; its resistance changes as the servo motor rotates, and the angle of rotation is determined by detecting the resistance value.
The specifications provided by manufacturers for servo motors include basic information such as dimensions (mm), torque (kg/cm), speed (seconds/60°), test voltage (V), and weight (g). Torque is measured in kg/cm, meaning the weight (in kilograms) that can be lifted at a distance of 1 cm from the lever arm. This is the concept of lever arm; therefore, the longer the lever arm, the lower the torque. Speed is measured in sec/60°, meaning the time required for the servo motor to rotate 60°.
Servo motors, also known as actuator motors, are used as actuators in automatic control systems to convert received electrical signals into angular displacement or angular velocity output on the motor shaft. They are divided into two main categories: DC and AC servo motors. Their main characteristic is that they do not rotate when the signal voltage is zero, and their speed decreases uniformly as the torque increases.
Servo motor
Servo systems primarily rely on pulses for positioning. Essentially, a servo motor receives one pulse and rotates by the angle corresponding to that pulse, thus achieving displacement. Because the servo motor itself has the function of emitting pulses, it emits a corresponding number of pulses for each rotation angle. This creates a feedback loop, or closed loop, between the pulses received by the servo motor and the pulses sent. In this way, the system knows how many pulses were sent to the servo motor and how many were received, enabling precise control of the motor's rotation and achieving accurate positioning down to 0.001mm .
DC servo motors are divided into brushed and brushless motors. Brushed motors are low in cost, simple in structure, have high starting torque, wide speed range, and are easy to control. However, they require maintenance, which is inconvenient (replacing carbon brushes), generates electromagnetic interference, and has environmental requirements. Therefore, they can be used in cost-sensitive general industrial and civilian applications.
