The ordinary motors, stepper motors, deceleration motors, and servo motors mentioned here refer to micro motors powered by direct current, and the ones we usually come into contact with are mostly direct current. The knowledge of motors is profound, and this article only briefly discusses various motors commonly used in making robots.

Electric motor, commonly known as "motor", refers to an electromagnetic device that converts or transfers electrical energy based on the law of electromagnetic induction. It is represented by the letter "M" (formerly "D") in circuits. Its main function is to generate driving torque as a power source for electrical appliances or various machinery.

Ordinary DC motor

Ordinary motors are the ones we usually use, which are included in electric toys, razors, and more. Generally, there are only two pins, and connecting the positive and negative terminals of the battery to the two pins will cause the motor to rotate. Then, if the positive and negative terminals of the battery are connected in opposite directions to the two pins, the motor will also rotate in the opposite direction. This type of motor has the characteristics of high speed and low torque, and is generally not directly used in smart cars.

When the DC power supply supplies power to the armature winding through the electric brush, the current flowing in the same direction can pass through the N-pole lower conductor on the surface of the armature. According to the left-hand rule, the conductor will be subjected to a counterclockwise torque. The conductor under the S pole on the surface of the armature also flows current in the same direction, and according to the left-hand rule, the conductor will also be subjected to a counterclockwise torque. In this way, the entire armature winding, i.e. the rotor, will rotate counterclockwise, and the input DC electrical energy will be converted into mechanical energy output on the rotor shaft. Composed of stator and rotor, stator: base, main magnetic pole, reversing pole, electric brush device, etc; Rotor (armature): armature core, armature winding, commutator, shaft, fan, etc.

A DC motor is an electric motor that converts DC electrical energy into mechanical energy. Due to its excellent speed regulation performance, it has been widely used in electric drive. DC motors are divided into three categories based on excitation methods: permanent magnet, separate excitation, and self excitation. Among them, self excitation is further divided into parallel excitation, series excitation, and compound excitation.

Gear motor

A deceleration motor is a combination of an ordinary motor and a gearbox, which reduces the speed and increases the torque, making the ordinary motor more widely applicable.

This type of integrated body is usually referred to as a gear motor or gear motor, and is usually assembled and supplied as a complete set by a professional gearbox manufacturer. Deceleration motors are widely used in industries such as steel and machinery. The advantages of using a deceleration motor are simplified design and space saving. After World War II, the rapid development of military electronic equipment promoted the development and production of micro reduction motors and DC reduction motors in countries such as the United States and the Soviet Union. With the continuous development of the deceleration motor industry, more and more industries and enterprises are using deceleration motors, and a group of enterprises have also entered the deceleration motor industry.

Currently, countries such as Germany, France, the United Kingdom, the United States, China, and South Korea maintain a leading position in the global market for micro reduction motors and DC reduction motors. The Chinese micro reduction motor and DC reduction motor industry was founded in the 1950s. Starting from meeting the needs of supporting weapons and equipment, it has gone through stages of imitation, self design, research and development, and large-scale manufacturing. It has formed an industrial system with complete product development, large-scale production, key components, key materials, specialized manufacturing equipment, testing instruments, and continuously improving internationalization.

Deceleration motors are usually used on smart cars, and the control of the motor is usually done using the H-bridge scheme. The L298 chip is based on this principle.

The speed regulation generally adopts PWM (Pulse Width Modulation) mechanism, and the microcontroller uses a timer to control the generation of PWM waves with variable duty cycle or directly outputs different sized waveforms through hardware PWM to control the overall speed of the car.

Stepper motor

A stepper motor is an open-loop control element that converts electrical pulse signals into angular displacement or linear displacement. In non overloaded situations, the speed and stopping position of the motor depend only on the frequency and number of pulses of the pulse signal, and are not affected by load changes. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction, called the "step angle", and its rotation runs step by step at a fixed angle. By controlling the number of pulses, the angular displacement can be controlled to achieve accurate positioning; At the same time, the speed and acceleration of the motor can be controlled by controlling the pulse frequency, thus achieving the purpose of speed regulation.

servo motor

Servo motor, also known as actuator motor, is used as an actuator in automatic control systems to convert received electrical signals into angular displacement or angular velocity output on the motor shaft. It is divided into two categories: DC and AC servo motors. Its main feature is that when the signal voltage is zero, there is no self rotation phenomenon, and the speed decreases uniformly with the increase of torque.

Servo motors mainly rely on pulses for positioning. Basically, it can be understood as follows: when a servo motor receives one pulse, it will rotate the corresponding angle of one pulse to achieve displacement. Because servo motors themselves have the function of emitting pulses, every time they rotate an angle, they will emit a corresponding number of pulses. This forms a response or closed loop with the pulses received by the servo motor. In this way, the system will know how many pulses have been sent to the servo motor and how many pulses have been received back. In this way, the rotation of the motor can be accurately controlled to achieve precise positioning, which can reach 0.001mm.   

DC servo motors are divided into brushed and brushless motors. Brushed motors have low cost, simple structure, large starting torque, wide speed range, easy control, and require maintenance. However, maintenance is inconvenient (such as replacing carbon brushes) and can generate electromagnetic interference, which has environmental requirements. Therefore, it can be used in cost sensitive general industrial and civilian applications.