Many auto mechanics vaguely feel that pure electric vehicles will drive in the streets in the future. For the sake of environmental protection, every city has formulated a promotion plan for related pure electric vehicles; but if you still don't know anything about him, then your technology is waiting for the hind feet of the auto mechanic. Today, I will talk about the problems related to the detection of pure electric vehicle drive motor resolver sensors for your reference.

The drive motor system is one of the three core systems of electric vehicles and is the main drive system of the vehicle. Its characteristics determine the main performance indicators of the vehicle and directly affect the vehicle power, economy and user driving experience.

1. Introduction to the drive motor system

The drive motor system consists of a drive motor and a drive motor controller (MCU), which are connected to other systems of the vehicle through high and low voltage wiring harnesses and cooling pipelines.

The vehicle controller (VCU) sends instructions to the motor controller MCU through the CAN network according to the signals of the accelerator pedal, brake pedal, gear position, etc., and adjusts the torque output of the drive motor in real time to realize the idling, acceleration, and energy recovery of the vehicle. Function.

The motor controller can monitor its own temperature, the operating temperature of the motor, and the rotor position in real time, and transmit relevant information to the vehicle controller VCU, and then adjust the work of the water pump and cooling fan to keep the motor working at an ideal temperature.

The technical parameters of the drive motor, as shown in Table 1, the technical parameters of the drive motor controller

1. Drive motor

Permanent magnet synchronous motor is a typical drive motor (Figure 2). It has the advantages of high efficiency, small size and high reliability. It is the actuator of the power system and the carrier of converting electrical energy into mechanical energy. It relies on the built-in resolver and temperature sensor (Figure 3) to provide the working state information of the motor, and send the motor running state information to the MCU in real time.

The resolver detects the rotor position of the motor. After decoding by the resolver decoder in the motor controller, the motor controller can know the current rotor position of the motor, so as to control the corresponding IGBT power tube to conduct, and energize the three coils of the stator in sequence to drive the motor. rotate.

The function of the temperature sensor is to detect the temperature of the motor winding, and provide the information to the MCU, and then the MCU transmits it to the VCU through the CAN line, and then controls the operation of the water pump, the circulation of the water circuit, the operation of the cooling electronic fan, and adjusts the working temperature of the motor.

There is a low-voltage interface and three high-voltage lines (V, U, W) interfaces on the drive motor,

The definition of each terminal of the low-voltage interface is shown in Table 3, and the motor controller also obtains the motor temperature information and the current position information of the motor rotor through the low-voltage port.

2. Drive motor controller

The structure of the drive motor controller MCU is shown in Figure 5. It uses a three-phase two-level voltage source inverter inside, which is the control core of the drive motor system. It is called an intelligent power module. It uses IGBT (insulated gate bipolar type) transistor) as the core, supplemented by driver integrated circuits and main control integrated circuits.

The MCU processes all the input signals, and sends the operating status information of the drive motor control system to the vehicle controller VCU through the CAN2.0 network. The drive motor controller contains a fault diagnosis circuit. When the motor is abnormal and certain conditions are met, it will activate an error code and send it to the VCU vehicle controller, and also store the fault code and related data.

The drive motor controller mainly relies on the current sensor (Figure 6), voltage sensor, and temperature sensor to monitor the motor running state, and adjust and control the voltage and current according to the corresponding parameters, as well as the completion of other control functions. The current sensor is used to detect the actual current of the motor, including bus current and three-phase AC current. The voltage sensor is used to detect the actual voltage supplied to the motor controller, including the power battery voltage and the 12V battery voltage. The temperature sensor is used to detect the operating temperature of the motor control system, including the temperature of the IGBT module.

The drive motor controller is divided into low-voltage interface and high-voltage interface

2. Function of the drive motor system

The basic functions of the new energy vehicle drive system can be understood through the working state of the drive motor, and the working state of the drive motor according to the driver's wishes: when accelerating driving in D gear, decelerating braking, reversing in R gear, and driving in E gear. its working process.

1. D gear accelerates driving

The driver hangs the D gear and steps on the accelerator pedal. At this time, the gear information and acceleration information are transmitted to the vehicle controller VCU through the signal line. The VCU transmits the driver's operation intention to the drive motor controller MCU through the CAN line, and then the driver The motor controller MCU combines the resolver sensor information (rotor position), and then passes three-phase alternating current to the stator of the permanent magnet synchronous motor, and the three-phase current produces a voltage drop on the resistance of the stator winding.

The rotating armature magnetomotive force and the established armature magnetic field generated by the three-phase alternating current, on the one hand, cut the stator winding and generate an induced electromotive force in the stator winding; As the accelerator pedal stroke continues to increase, the conduction frequency of the 6 IGBTs controlled by the motor controller increases, and the torque of the motor increases with the increase of the current. Therefore, it basically has the maximum torque when starting. As the speed of the motor increases, the power of the motor also increases, and the voltage also increases.

In electric vehicles, the output power of the motor is generally required to be kept constant, that is, the output power of the motor does not change with the increase of the rotational speed, which requires the voltage to remain constant when the rotational speed of the motor increases. The output characteristic curve of the permanent magnet synchronous motor is shown in Figure 8 .

At the same time, the motor controller will also sense the current power, current consumption and voltage of the motor through the current sensor and voltage sensor, and transmit these information data to the instrument and the vehicle controller through the CAN network. The specific working principle is as follows: shown in Figure 9.

2. When reversing in R gear

When the driver is in R gear, the driver's request signal is sent to the VCU, and then sent to the MCU through the CAN line. At this time, the MCU combines the current rotor position (resolver sensor) information to change the WVU power-on sequence by changing the IGBT module, and then control the motor. Invert.

3. Energy recovery during braking

When the driver releases the accelerator pedal, the motor is still rotating due to inertia. Let the wheel speed be the V wheel, the motor speed be the V motor, and the fixed transmission ratio between the wheel and the motor is K. When the vehicle decelerates, the V wheel K<V When the motor is turned on, the motor is still the power source. As the speed of the motor decreases, when the V wheel K>V motor, the motor rotates due to being dragged by the vehicle, and the driving motor becomes a generator at this time (Figure 10).

The BMS can calculate the corresponding maximum allowable charging current according to the battery charging characteristic curve (the relationship between the charging current, the voltage change curve and the battery capacity) and the collected battery temperature. According to the maximum allowable charging current of the battery, the MCU controls the IGBT module to keep the angular velocity of the rotating magnetic field of the "generator" stator coil and the angular velocity of the motor rotor until the generating current does not exceed the allowable maximum charging current, so as to adjust the current that the generator charges the battery. Also controls the deceleration of the vehicle