HMI is an abbreviation for Human Machine Interface, also known as Human Machine Interface. Human-computer interface (also known as user interface or user interface) is a medium for interaction and information exchange between systems and users, which realizes the conversion between the internal form of information and the acceptable form of human beings. Human-computer interfaces exist in all fields involved in human-computer information exchange.

Variable frequency drive (VFD) is a power control device that uses frequency conversion technology and microelectronics technology to control AC motors by changing the frequency of the motor's operating power supply.

Programmable logic controller, which uses a type of programmable memory for storing programs internally, executing user oriented instructions such as logical operations, sequential control, timing, counting, and arithmetic operations, and controlling various types of machinery or production processes through digital or analog input/output.

Circuit breaker ， refers to the switching device that can turn on, carry and break the current under normal circuit conditions and can turn on, carry and break the current under abnormal circuit conditions within the specified time. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their scope of use. The division of high and low voltage boundaries is relatively vague, and generally, those above 3kV are referred to as high-voltage electrical appliances.

Electric machine (commonly known as "motor") refers to an electromagnetic device that converts or transmits electrical energy according to the law of electromagnetic induction. It is represented by the letter M (D in the old standard) in the circuit. Its main function is to generate driving torque as a power source for electrical appliances or various machinery. The generator is represented by the letter G in the circuit. Its main function is to convert mechanical energy into electrical energy. Currently, the most commonly used method is to use thermal energy, water energy, etc. to drive the generator rotor to generate electricity.

During the entire control process, the drive is located in the main controller --> Driver --> The middle section of the motor is changed. Its main function is to receive signals from the main control box (NC CARD), then process the signals and transfer them to the motor and motor related sensors (SENSOR), and feed back the operating conditions of the motor to the main controller.

Relay, also known as a relay, is an electronic control device that has a control system (also known as an input circuit) and a controlled system (also known as an output circuit). It is commonly used in automatic control circuits. It is actually an "automatic switch" that uses a smaller current to control a larger current. Therefore, it plays a role in automatic regulation, safety protection, conversion circuit, etc. in the circuit. Relay coils are represented in a circuit by a rectangular symbol. If the relay has two coils, draw two parallel rectangular boxes. At the same time, mark the text symbol "J" of the relay inside or beside the rectangular frame. There are two ways to represent the contacts of a relay: one is to draw them directly on the side of a rectangular frame, which is more intuitive.

Sensor (English name: transducer/sensor) is a kind of detection device, which can sense the measured information and transform the sensed information into electrical signals or other required forms of information output according to certain rules to meet the requirements of information transmission, processing, storage, display, recording and control.       The characteristics of sensors include miniaturization, digitization, intelligence, multifunction, systematization, and networking. It is the primary link to achieve automatic detection and control. The existence and development of sensors have provided objects with senses such as touch, taste, and smell, allowing them to gradually become alive. According to their basic sensing functions, they are generally divided into ten categories: thermal sensors, light sensors, gas sensors, force sensors, magnetic sensors, humidity sensors, acoustic sensors, radiation sensors, color sensors, and taste sensors.