Design of electric vehicle brushless motor controller detection based on STCl2C5410AD

0 Introduction
With the process of urbanization, the distance of people's lives is constantly expanding. The popularity of electric vehicles that replace fuel vehicles and bicycles has greatly improved the utilization efficiency of electric resources and promoted the healthy development of the national economy. Electric bicycles are powered by electricity, do not produce pollution during riding, and do not damage the air quality. From the perspective of improving people's travel methods, protecting the environment, and economic conditions, electric bicycles have broad development space at present and in the future. The DC motors used in electric bicycles are divided into brushed motors and brushless motors. Among them, the control of brushed motors is relatively simple. However, its easily worn brushes bring disadvantages such as relatively large maintenance workload and relatively short service life. The brushless DC motor itself has no easily worn parts, long motor life, and small maintenance workload. However, the brushless DC motor works on the principle of electronic commutation, and its control process is much more complicated than that of the brushed motor, so the requirements for the quality of the controller are also much higher.
At present, the brushless DC motors used in electric bicycles are all three-phase motors, with two electrical angles of 60° and 120°. Most of the motor poles are 18 poles, and there are also 16 poles, 20 poles, etc. The controller controls the opening or closing of the corresponding power drive tube according to the motor electrode position fed back by the Hall effect, generates a rotating magnetic field in the stator, and drives the motor's rotor to rotate.
In order to determine whether the brushless controller can operate normally, that is, to detect whether the handlebar and brake functions are normal, determine whether the angle of the controller is 60° or 120°, and determine the correspondence between the winding A, B, C phases and the position signals a, b, c, and correctly connect the controller to the motor, many detection instruments now use analog circuits, which makes the results not very accurate, and the required circuits are also very complex and costly. The design uses the STCl2C5410AD microcontroller as the control chip, which greatly simplifies the hardware circuit and is implemented by software programming.

l Introduction to brushless motor controller for electric vehicles
The controller consists of peripheral devices and main chip (or single chip microcomputer). Peripheral devices are some functional devices, such as execution, sampling, etc. They are resistors, sensors, bridge switch circuits, and devices that assist single chip microcomputers or special integrated circuits to complete the control process; single chip microcomputers are also called microcontrollers. They are integrated with memory, decoders with signal language conversion, sawtooth wave generators and pulse width modulation functional circuits, as well as drive circuits that can turn on or off the power tube of the switch circuit, and control the motor speed by controlling the conduction time of the power tube through square waves, input and output ports, etc., to form a computer chip. This is the intelligent controller of electric bicycles.
The design quality, characteristics, functions of the microprocessor used, power switch device circuits and layout of peripheral devices of the controller are directly related to the performance and operation status of the whole vehicle, and also affect the performance and efficiency of the controller itself. Controllers of different qualities, used on the same vehicle, equipped with the same set of batteries with the same charge and discharge status, sometimes show large differences in driving range.
At present, the circuit principles of controllers used in electric bicycles are basically the same or similar. Most brushed and brushless DC motors use PWM control method to adjust the speed, but the difference is in the selection of drive circuit, integrated circuit, switch circuit power transistor and some related functions. The difference in components and circuits constitutes the difference in controller performance.

2 System Hardware Circuit Design
In order to determine whether the brushless controller is normal, measure whether the output signals of each part of the controller meet the standards, and be able to receive the signals of the motor, handle, and brake, and determine whether the controller can achieve the functions it needs to achieve, the system needs to detect whether the controller's handle and brake have a stable 5 V voltage output, determine the angle of the controller, and determine whether the phase sequence of the Hall control line and the corresponding motor power supply phase sequence are consistent. Only when the position sensor signal and windings A, B, and C are correctly connected can the motor operate normally. Figure 1 is the overall circuit design schematic diagram. The system uses the STCl2C5410AD microcontroller as the main control chip. The STCl2C5410AD series microcontroller is a single clock/machine cycle (1T) microcontroller produced by Hongjing Technology. It is a new generation of 8051 microcontrollers with high speed, low power consumption, and super strong anti-interference. The instruction code is fully compatible with the traditional 8051, but the speed is 8 to 12 times faster. It integrates MAX810 dedicated reset circuit, 4-way PWM, and 8-way high-speed 10-bit A/D conversion, which is specifically designed for motor control in strong interference situations.

2.1 Bridge rectifier circuit
Because the controller needs direct current to work, a rectifier circuit is needed. The system uses a single-phase bridge rectifier circuit. This circuit has the advantages of a full-wave rectifier circuit as long as the four diode ports are connected into a "bridge" structure.
2.2 Detection of brake and throttle signals
The change in the high and low potential of the brake signal is the basis for the controller to identify whether the electric vehicle is in a braking state, and thus determine whether the controller supplies power to the motor. As long as the output ends of the brake and throttle signals are connected to the A/D conversion terminals P16 and P17 of the STCl2C5410AD microcontroller, it can be detected whether the output is normal.
2.3 Judgment of controller angle and phase sequence
As shown in Figure 2, first determine the output of the winding voltage A, connect the two optical couplers to the end of the controller, and connect them in parallel with the upper and lower tubes of A. When the upper tube of A is turned on, A outputs a high voltage, turning on the optical coupler below. Thus, a voltage value is output and sent to the single-chip microcomputer through the A/D conversion terminal P11 port of the STCl2C5410AD single-chip microcomputer; when the lower tube of A is turned on, A outputs a low voltage, which turns on the upper optocoupler, thereby outputting a voltage value and sending it to the single-chip microcomputer through the A/D conversion terminal P10 port of the STCl2C5410AD single-chip microcomputer. B and C use the same connection method as above. There is no direct output when outputting, but it is output after being isolated by the optocoupler. The reasons are as follows: the signal of the optocoupler is transmitted unidirectionally, the input end and the output end are completely electrically isolated, the output signal has no effect on the input end, it has strong anti-interference ability, stable operation, no contacts, long service life, and high transmission efficiency.

3 System software design
3.1 Overall design flow chart
The overall design flow chart is shown in Figure 3.

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Measure the impedance of the controller input terminal. When it is greater than 10 Ω, it is normal. Otherwise, the power input terminal is short-circuited. The detection of the turning handle, brake handle, and Hall power supply terminal must ensure that the output voltage is greater than 4.5 V. The judgment of the controller angle and phase sequence is judged and detected according to the brushless truth table. The following is only an example of the controller angle judgment.
3.2 Controller Angle Judgment Program Design
It can be seen from Table 1 that when a, b, and c are all "0" and the controller angle is 120°, the upper and lower tubes of A, B, and C are not turned on; when the controller is 60°, the upper tube of A and the lower tube of B are turned on. In this way, the angle of the controller can be judged according to the output signals of A, B, and C when a, b, and c are all "0". The flow chart is shown in Figure 4.

4 Conclusion
The system design uses STCl2C5410AD single-chip microcomputer as the control chip. The circuit is simple and the measurement is accurate. It meets the various requirements of electric vehicle brushless motor controller detection. It can detect whether the controller is connected to the handlebar and brake handle. It can judge whether the controller angle, Hall control phase sequence and the corresponding motor power supply phase sequence are consistent. It is hoped that this design will be better improved and perfected in future applications.