Design of Brushless DC Motor Control System Based on

Design of Brushless DC Motor Control System Based on 11:22:37 on Source: foreign electronic components Author: Zheng haoxin, Zheng Bin, Li Jianmin

1 Introduction

In public cycles, the brushless DC motor has the advantages of simple AC motor, reliable operation, convenient maintenance, and high operation efficiency of the DC motor. It is not limited by Mechanical reversing, and has good speed performance, easy to achieve large capacity, high conversion
Speed and other features. TI's Digital Signal Processor (DSP) has the architecture required for high-speed signal processing and digital functions. It also provides a single-chip solution for motor control applications.
The peripheral device required by the solution. With TMS320F2-812 as the core of the digital motor control system greatly simplifies the hardware design, improve the reliability of the system, reduce the cost, and the Brushless DC Motor
Application popularization has a good prospect. Therefore, a digital Permanent Magnet Brushless DC Motor Control Scheme Based on is proposed.

2 System Design Scheme
The
The system design adopts three-phase PWM control scheme of Y-type Permanent Magnet Square wave brushless motor, and the power-on mode is power-on. Figure 1 shows the schematic diagram of the control system. It adopts full digital three closed loop control. Among them, the current ring uses PI Adjustment
The PID control algorithm of integral separation is adopted for the speed loop, and the output polarity determines the direction of forward and reverse, so that the four quadrant operation of the motor can be realized. Position ring uses PI regulator. Inverter Used
Full bridge PWM modulation.

3 system hardware design
Figure
2. A Brushless DC Motor Control System Based on is provided. Using as the controller, it is used to process collected data and send control commands.
The Controller first captures the high-speed pulse signals of Hall Elements H1, H2, and H3 on the DC motor through three I/0 ports, detects the Rotation Position of the rotor, and sends the signal according to the position of the rotor.
To change the current value of the PWM signal, and then change the turn-on sequence of power tubes in the DC Motor Drive Circuit (IGBT, control the motor speed and rotation direction. Motor
The code disk signal a and B pass through
The CAPL and cap2 ports of the DSP controller are captured. The captured data is stored in the register and the and B pulse values are captured by comparison to determine the positive and reverse states and speed of the current motor. In the system
During operation, the drive protection circuit detects the operating status of the current system. If there is an over-current or under-voltage condition in the system, the PWM signal Driver (ir12001) starts the internal protection circuit and locks the subsequent PWM signal.
At the same time, the pdpinta pin voltage of the DSP controller is reduced through the fault pin to enable the power supply drive protection of the DSP controller. At this time, the output pins of all EV modules will
The hardware is set to a high-impedance state to protect the control system. The following describes the rotor position detection circuit, phase current detection circuit, driving circuit, and system protection circuit in the system.

3.1 rotor position detection circuit
When the brushless DC motor is controlled, the DSP controller sends corresponding control words based on the current Rotation Position of the rotor, by changing
PWM Pulse Signal duty cycle control motor. The rotor position of the brushless DC motor is detected by the position sensor. The system is designed with three photoelectric position sensors (Hall Elements), which are
It shall be made up of the Shadow board that rotates along the rotor of the motor, the fixed light source and the optical tube and other components.

With the rotation of the motor rotor, the optical tube receives intermittent light from the light source, and continuously guides and ends, thus generating a series of "0" and "L" signals. These pulses are transmitted
DSP and DSP read the state value of the Hall element to determine the current position of the rotor. Then, by changing the duty cycle of the PWM signal, the driving circuit is controlled to change the conduction sequence of the IGBT, and the phase change control of the motor is realized.
And adjust the motor speed. The turn-on sequence of power tubes on the Bridge Arm is
Vq1, vq2 → vq2, vq3 → vq3, vq4 → vq4, vq5 → vq5, vq6 → vq6, vq1 (powered on ). The motor rotor is rotated once every second.
The following six States are displayed: 10l → 100 → 110 → 010 → 011 → 00l. The DSP sends corresponding control words to each State. Change the power-on sequence of the motor to achieve continuous operation of the motor. Figure 3
Schematic diagram of the motor driving circuit control.

3.2 phase current detection circuit
Electricity
The stream feedback channel consists of a Hall element, an operational amplifier, and A/D converter. Current feedback ratio:
000 magnetic balanced Hall element. The output of this element is a current signal, and the signal is weak. It must be converted into a voltage signal through a Precision Resistor and then amplified, obtain the bipolar signal of current. Because DSP
The input range of A/D conversion unit is 0 ~ 3.3 V (single polarity), the design of the bipolar signal into a single polarity circuit, and then sent to the/D converter. Figure 4 shows the circuit diagram.

3.3 Drive Circuit
Electricity
The driver circuit of the controller is ir12001 (see figure 5 ). Ir12001/ir2132 is a high-voltage, high-speed actuator and IGBT driver. Ir12001 can be the same
Control the switching and shutdown of six power tubes. The output ports h01, h02, and H03 are used to control the pilot and shutdown of the upper half-bridge vq1, vq5, and vq5 in the three-phase full-bridge drive circuit respectively.
L0l, L02, and l03 respectively control the guidance and shutdown of the lower half-bridge vq4, vq6, and vq2 of the three-phase full-bridge driving circuit, so as to control the motor speed and forward and backward.

3.4 System Protection Circuit
The protection circuit plays an important role in the brushless DC motor control system. It can protect the DSP core device of the control system from the impact of high voltage and overcurrent, and also protect the drive circuit of the motor from damage. The protection circuit of the entire system consists of circuit isolation, signal isolation, and drive protection.
3.4.1 Isolation Circuit
The signal isolation circuit isolates the control signal and the driving signal between the control circuit and the driving circuit through the photoelectric isolator to realize signal transmission between different voltages, as shown in figure 6. This isolating circuit can be used to isolate the 6-way PWM output signal of the DSP from the IGBT, and implement the drive and level conversion functions.

3.4.2 Protection Circuit
Is
To ensure the safe and reliable operation of the power conversion circuit and Motor Driving Circuit in the system, also provides the pdpint input signal, which can be used to conveniently implement various protection functions of the servo system.
Figure 7 shows the specific implementation circuit. Various fault signals are integrated by CD8128 and input to the PDPINT pin through photoelectric isolation. CD8128 output low power when any fault occurs
Flat and PDPINT pins are also pulled to a low level. At this time, the timer in the DSP immediately stops counting, and all the PWM output pins are in high-impedance status. At the same time, an interrupt signal is generated to notify the CPU of exceptions.
Occurred. The entire process is completed automatically without any intervention, which is very useful for quick troubleshooting of various fault states.

4. Communication between the system and the host computer
The system uses the SCI interface to complete the communication function with the upper PC, using RS-232 communication, through the upper PC given the location. the speed, current, location feedback, and other parameters of the motor are also controlled to send the host computer display in real time. The SPI interface completes the serial drive digital display function. you can use the numeric I/0 extended keyboard to set the position for the quantitative display.

5. Experiment results
Based on the hardware circuit, two experimental results shown in Figure 8 are obtained through software programming. Figure 8 (a) shows the system tracking characteristic curve under the conventional PID control, and figure 8 (B) shows the test curve of the system under the tracking characteristics of the fuzzy PID system.

6 conclusion

The digital servo system, designed with as the core, solves the problems of PWM signal generation, motor speed feedback and motor current feedback in the servo system, and conveniently realizes the protection function.
The system hardware design is simplified, the system reliability is improved, and the volume of the servo system is reduced. Reduced costs (reduced by about 20% ). The experimental results verify the effectiveness of this method.