Abstract: This paper studies electric pumps and designs an electric pump control system based on the 83C552 microcontroller. The hardware composition and software design of the electric fuel pump control system are presented. Keywords: Electric pump, MCU, Control system 1. Introduction A pump is a machine that transports or pressurizes liquids . An electric pump is a type of pump, a combination of a mechanical pump and an electric motor. As a product of mechatronics, it transfers the mechanical energy of the electric motor to the liquid, increasing the liquid's energy and thus achieving the purpose of transporting or pressurizing the liquid. Electric pumps are mainly used to transport liquids including water, oil, emulsions, and suspensions. Therefore, electric pumps can be used in automobile engines to pressurize fuel, in aircraft turbojet engines with continuous fuel injection, and in food processing machinery and other applications requiring liquid transport or pressurization. Therefore, controlling the flow rate of an electric pump is a very practical topic. Controlling an electric pump is essentially controlling the electric motor. Traditional methods of controlling motor speed require the installation of a speed measuring device. Whether using a magnetoresistive magnetoelectric sensor, a photoelectric tachometer, or other types of sensors like Hall effect sensors, the size and cost of the motor increase. Furthermore, any error in the sensor leads to increased armature current and reduced motor efficiency, resulting in increased heat generation and higher requirements for motor manufacturing processes. Therefore, after studying the structure and working principle of the electric pump, this paper proposes an electric pump control system that differs from traditional control methods. 2. Structure and Working Principle of an Electric Fuel Pump The electric fuel pump studied in this paper consists of three parts: the pump body, the permanent magnet motor, and the housing. The motor part of the electric fuel pump includes a permanent magnet fixed to the housing, an armature that generates electromagnetic torque, and a brush assembly mounted on the housing. The brushes contact the commutator on the armature, and their leads are connected to terminals on the housing, leading the voltage controlling the electric fuel pump to the armature windings. The electric fuel pump's housing has its ends crimped and riveted, assembling all components into a non-removable assembly. Its working principle is as follows: when the permanent magnet motor is energized, it drives the pump body to rotate, drawing fuel in through the inlet, through the interior of the electric fuel pump, and then expelling it through the outlet to supply fuel to the fuel system. The fuel flowing through the electric fuel pump cools the armature of the permanent magnet motor, hence it is also called a wet fuel pump. 3. Overall Design Concept From the above structural analysis of the electric pump, it can be seen that the operation of the electric pump is mainly achieved by a DC motor. Controlling the electric pump is therefore transformed into controlling the DC motor. Therefore, to implement the single-chip microcomputer control system design for the electric pump, the motor speed must be measured. However, the DC motor is integrated within the electric fuel pump assembly, making traditional methods of speed measurement, such as DC tachogenerators, impossible unless the electric pump structure is modified to incorporate a motor speed measurement mechanism. This would increase the manufacturing cost of the electric pump, making it somewhat uneconomical. So, since the motor speed cannot be directly obtained and the original structure of the electric pump cannot be changed, in order to achieve the single-chip microcomputer closed-loop control of the electric pump, other control schemes need to be used to replace the speed negative feedback control scheme. According to the relationship formula between DC motor and other motor parameters, where: U-armature voltage; I[sub]a[/sub]-armature current; R[sub]a[/sub]-motor armature resistance; c[sub]ε[/sub]-motor structural parameter, which is a constant; Φ-armature flux, which is also a constant; it can be concluded that the motor speed can be indirectly reflected by the armature voltage and the current through the armature, and these two parameters of the electric fuel pump can be measured. Therefore, this paper adopts the method of feedback armature voltage and current signals to replace speed feedback, and selects a bipolar H-type reversible PWM power amplifier circuit as the motor drive circuit. 4. Hardware structure Considering the kinetic energy of the electric fuel pump and the nature and characteristics of the control system, and taking into account the following factors: (1) Considering the reduction of the system's performance-price ratio, only an 8-bit single-chip microcomputer is needed. (2) It should have a program memory (ROM) of more than 4K to store the control program; expandable FLASH memory chip to facilitate real-time adjustment of control parameters. (3) In order to facilitate real-time adjustment of control parameters during the testing phase and considering the scalability of the system, it should have an I2C bus. (4) Considering the portability of the program and the compatibility of the hardware circuit interface, the selected microcontrollers must all be 51 core. The 8-bit microcontroller of PHILIPS, 83C552, is initially selected. In addition to meeting the above basic requirements, 83C552 also has the following features: it is compatible with MCS-51, has the same CPU and instruction system, pin functions are compatible, and it is easy to master and use; it has a built-in PWM signal output port, which simplifies the system hardware circuit and program; it integrates 8 channels of 10-bit A/D converters, which can meet the requirements of the number of sampling channels and sampling accuracy of the system analog signal, so there is no need to select another A/D converter, which simplifies the circuit and reduces the cost; it has a built-in watchdog circuit to ensure the stability of the system. The overall hardware schematic diagram of the control system is shown in Figure 1. [align=center]Figure 1[/align] Its working principle is as follows: The motor speed command signal is given by the host computer through an asynchronous communication interface. The armature voltage and current sampling signals are sent to the microcontroller after passing through the feedback preprocessing circuit. The microcontroller cyclically detects the voltage and current values ​​of the A/D sampling channel and the speed command signal value. The resulting deviation signal is modulated and amplified by the PID controller, and then loaded into the form of a PWM signal by the PWM register on the microcontroller and output to the analog circuit section. After being delayed by the delay circuit and amplified by the gate drive circuit, a PWM gate drive voltage with a certain power and duty cycle is formed, which controls the on and off time of the PWM power transistor, thereby changing the magnitude of the average voltage on the armature of the DC motor. The width of the control pulse is determined by the speed command signal and the current and voltage sampling values. The parts within the dashed box in the figure can all be implemented by the microcontroller. In this way, the discrete domain controller is designed by microcontroller software programming, and a closed-loop control system is formed through voltage and current feedback, ensuring the performance of the control system. By using the PWM motor drive circuit, the purpose of voltage regulation and speed regulation can be achieved by changing the PWM signal pulse width. 5. Software Design The design of the motor speed control program should mainly consider the following issues: (1) Loading the microcontroller's PWM signal; (2) Sampling and digital filtering of voltage and current feedback signals; (3) Implementing the voltage PID control algorithm; (4) Converting all numbers to fixed-point pure decimal two's complement form during data processing, and then converting the 10-bit voltage and current sampling values ​​to 16 bits for calculation, taking the 8-bit effective value of the calculation result; (5) Communication with the host computer. The motor control program consists of two parts: the main program and the T0 interrupt service program. The main program includes the initialization of the 83C552 itself and the initialization of each parallel I/O port. Its important subroutines include: sampling subroutine, serial communication subroutine, digital filtering subroutine, PID calculation subroutine, etc. The flowchart of the main program (Figure 2) and the flowchart of the T0 interrupt service program (Figure 3) are shown in the figures respectively. [align=center]Figure 2 Figure 3[/align] 6. Conclusion The innovation of this paper: Through the analysis of the working mechanism of the electric fuel pump, a bipolar H-bridge PWM (Pulse Width Modulation) motor drive control hardware system was designed using the PHILIPS 83C552 microcontroller as the main control chip. Voltage negative feedback current compensation control was used instead of speed negative feedback control to form a complete closed-loop control system. This is a bold attempt at the practical application of control theory and lays the foundation for the development of the entire engine control system. Preliminary tests using a principle-based experimental system consisting of a PC as the host computer and the microcontroller system as the slave computer showed that the newly designed control system can basically realize the flow regulation of the electric fuel pump. However, due to the limitations of the voltage and current feedback signals from the sampling resistor, the microcontroller bit width, and the selection of PID parameters, there is still room for further improvement. Therefore, repeated experiments should be conducted according to the actual situation in specific applications to achieve the best control effect. References: [1] Chen Boshi, ed. Electric Drive Automatic Control System (Second Edition). Beijing: Machinery Industry Press, June 2004. [2] Qin Jirong and Shen Anjun, eds. Modern DC Servo Control Technology and Design. Beijing: Machinery Industry Press, 1993. [3] Hu Hancai, ed. Single-chip Microcomputer Principles and System Design. Beijing: Tsinghua University Press, 2002. [4] Wang Xiaoming, ed. Single-chip Microcomputer Control of Electric Motor. Beijing: Beijing University of Aeronautics and Astronautics Press, May 2002. [5] Yang Hongli. Fuzzy Control System Based on 80C196 Single-chip Microcomputer. Microcomputer Information, 2005, (03).