“The paper analyzes the drive control of brushless DC motor in detail, and designs a dual rear-wheel drive control system for electric vehicles based on ARM7 LPC2132 microprocessor. The intelligent controller can realize electric vehicles such as forward, backward, automatic cruise, and Electronic differential. The basic functions of the car, and the hardware has the functions of motor overcurrent protection, battery undervoltage protection and serial communication, which well meet the actual use requirements.
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Abstract: The paper analyzes the drive control of the brushless DC motor in detail, and designs a dual rear-wheel drive control system for electric vehicles based on the ARM7 LPC2132 microprocessor. The intelligent controller can realize the forward, backward, automatic cruise and electronic differential of the electric vehicle. It can basically perform functions such as electric vehicles, and the hardware has functions such as motor overcurrent protection, battery undervoltage protection and serial communication, which well meet the actual use requirements.
1 Overview
Today’s lack of petroleum resources and the urgent needs of environmental protection have put forward new requirements for the development of the automobile industry, that is: low noise, zero emission and energy saving. The most important way for sustainable development, and the electric vehicle driven by the in-wheel motor can not only eliminate the mechanical wear and loss in the traditional transmission, improve the transmission efficiency, but also have the advantages of small size and light weight, so that while improving the efficiency, the wheel The space can also be effectively used, which is more conducive to the realization of mechatronics and modern control technology; ARM7 series microprocessors, as 32-bit embedded processors, are characterized by their extremely high performance, low power consumption, abundant on-chip resources, and small size. It has been widely used in mobile phones, handheld computers, automobiles and other fields, and has become a processor with great market competition and prospects. This design scheme is based on PHILIPS’ ARM7TDMI-STM processor LPC2132, which controls two wireless The brushed DC motor realizes the independent drive of the two rear wheels of the electric vehicle, and the control system is designed reliably to ensure the stability of the system, and finally verified in practice.
2. Brushless DC motor and drive control
The brushless DC motor is composed of the rotor position sensor, the motor body and the electronic switch circuit. Its working principle is as follows: the position of the rotor is dynamically detected by the position sensor (Hall sensor), and the switch tube is controlled according to the position signal. It is turned on or off to control the energization and de-energization of the stator winding, which realizes the electronic commutation function and makes the motor run continuously.
Figure 1 is a three-phase connected full-bridge drive circuit, in which the switch tubes Q1, Q3, and Q5 are P-channel MOSFET power tubes. When the gate is low, the MOSFET tubes are turned on, and VD1, VD3, and VD5 are the corresponding protection diodes; Tube Q2.Q4.Q6 adopts N-channel MOSFET power tube. When the gate is high, the MOSFET tube is turned on, and VD2.VD4.VD6 is the corresponding protection diode. The three output ends of the position sensor control Q1 through a specific logic circuit. -Q6 switch tube works (on or off), there are two control methods: “three-three conduction mode”
And the “two-two conduction mode”. The windings driven by the full bridge are divided into star connection and angular connection, and the connection method is shown in Figure 2.
Three-to-three conduction mode “means that three switches are turned on at the same time each time. In Figure 1, the conduction sequence of each switch is: Q1.Q2.Q3CQ2.Q3.Q4CQ3.Q4.Q5CQ4.Q5. Q6CQ5.Q6.Q1CQ6.Q1.Q2. “Three-three conduction mode” can be divided into six control modes in actual work. The conduction state is changed every 60°, and a switch tube is replaced every time the state is changed. Each switch is turned on for 180°. In each state, the magnitude of the combined torque is 1.5 times that of the single-phase torque.
In this paper, the three-phase full-bridge star connection is used, and the “three-three conduction mode” is adopted. The conduction or cut-off of the MOSFET in the drive circuit is controlled by the corresponding software, that is, the corresponding MOSFET is extracted according to the detection signal of the position sensor. The corresponding control word of the tube is controlled, and the MOSFET tube is controlled by a specific logic circuit to realize the on or off control of the MOSFET tube, so as to realize the commutation control of the brushless DC motor, so that the motor can run continuously. The control of the motor direction is only the above The conduction sequence of the power MOSFET is different, that is, the extracted control word is different. The speed control of the brushless DC motor can use the PWM (pulse width modulation) method to control the energization current of the motor, which will not be described in detail here.
3. Hardware design of dual-drive electric vehicle control system
The design idea of the control system in this paper is to use one CPU to control two brushless DC motors, which is designed to realize the independent driving of the rear wheels of the electric vehicle. In the electric vehicle control system, the control system is mainly responsible for the two brushless DC motors. Motor speed regulation of the motor. Forward and reverse control, start and stop control and other functions. Here LPC2132 from PHILIPS’ LPC2100 series is used as the central processing unit.
LPC2132 is a microcontroller based on a 32-bit ARM7TDMI-STMCPU that supports real-time simulation and tracking, with embedded high-speed 64K-byte Flash memory, a wide range of serial communication interfaces and rich on-chip resources (such as 32-bit timer x4 10-bit 8-channel ADC and 10-bit DAC, plus 47 general-purpose I/O ports and 9 edge or level-triggered external interrupt sources) make it have powerful processing functions, and has a very high Strong anti-interference ability, especially suitable for industrial control. The overall block diagram of the intelligent control system for electric vehicles is shown in Figure 3, and the hardware design diagrams of several functions are given below.
3.1 Power Design
The power supply of this control system is provided by 4 12V large-capacity lead-acid batteries connected in series to provide 48V direct current, and the working voltage in the system is also +3.3V, +5V and +15V, so the commonly used regulated power supply chip LM7824.LM7815 is used. 1117-3.3 and 1117-5 generate the required voltages, which are reliable, stable and simple. As shown in Figure 4.
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