New energy electric vehicle motor controller composition and working process

The motor controller, as one of the core components of electric vehicles, is a decisive factor in the vehicle's power performance. It obtains the vehicle's requirements from the vehicle controller, obtains power from the power battery pack, and obtains the current and voltage required to control the motor through modulation of its own inverter, which is then provided to the motor so that the motor's speed and torque meet the requirements of the vehicle.

The motor controller is the nerve center connecting the motor and the battery, and is used to adjust the performance of the entire vehicle. Sufficiently intelligent electronic control can not only ensure the basic safety and precise control of the vehicle, but also allow the battery and motor to fully exert their strength.

1. Position and function of motor controller in electric vehicles

1. Location

From the outside, a general motor controller has at least two pairs of high-voltage interfaces. One pair of input interfaces is used to connect to the high-voltage interface of the power battery pack; the other pair is a high-voltage output interface, which connects to the motor and provides control power. There is at least one low-voltage connector, and all communications, sensors, low-voltage power supplies, etc. must be led out through this low-voltage connector and connected to the vehicle controller and power battery management system.

Low voltage connector

Including the low-voltage power supply and low-voltage signal of the motor controller: low-voltage power supply, 12V is commonly used for passenger cars, 24V is commonly used for commercial vehicles, connected to the vehicle's small battery; CAN signal, including the vehicle CAN and the internal CAN network, generally has two or more; resolver signal: connected to the motor's resolver, responsible for detecting the motor's speed, the resolver is installed at the motor end; some DI and DO are reserved according to different customer needs.

High voltage busbar connector

Connected to the power battery.

Waterproof breathable valve

Prevent the formation of moisture and condensation inside the controller.

2. Working process

(1) Instructions and responses The motor controller, the trigger signal of the speed control command, and the command from the vehicle controller. The vehicle controller reflects the driver's intention on the one hand, and on the other hand, evaluates whether the response to the driver is reasonable from the perspective of safety and the operating status of the vehicle's electrical system, and finally executes or discounts the execution. The driver's intention is expressed through the accelerator pedal and the brake pedal and transmitted to the vehicle controller. The specific instructions given by the vehicle controller to the motor controller are related to the power system and are as follows: acceleration, deceleration, braking, and parking. The response made by the motor controller is to change the power supply current, voltage, frequency and other parameters so that the operating state of the motor meets the needs of the vehicle controller. (2) Closed-loop The motor controller itself is a closed-loop control system that adjusts the target parameters and detects whether the controlled function value reaches the expected value. If it does not meet the requirements, it is fed back to the controller to adjust the target parameters again. After repeated closed-loop feedback, high-precision control is achieved.

The vehicle controller collects important status parameters such as the speed sensor, temperature and voltage of each electrical component, and determines the overall condition of the vehicle to see whether it meets the needs of the driver without affecting the health of the entire system. This process is a closed-loop control at the vehicle level.

(3) Directions for improvement On the one hand, a good control strategy will have a significant impact on control accuracy and response speed, and is therefore an important area for R&D personnel to focus their efforts.

On the other hand, as the control and computing capabilities of various components improve, the driving experience of electric vehicles will become more and more "free and easy".

2. Basic components of motor controller

The motor controller system consists of a central control module, a power module, a drive control module, and various sensors.

1. Central control module

Including PWM wave generation circuit, reset circuit, sensor signal processing circuit, interaction circuit. The central control module obtains the instructions and status information of other components on the vehicle through the external interface. Internally, it transmits the translated instructions to the inverter drive circuit and detects the control effect.

2. Power module

The main body of the motor controller is an inverter, which controls the motor current and voltage. Commonly used power devices include MOSFET, GTO, IGBT, etc.

3. Drive control module

The instructions of the central control module are converted into on-off instructions for the thyristors in the inverter, and as a protection device, it has the monitoring and protection functions for overvoltage, overcurrent and other faults.

4. Sensors

The sensors used in the system include current sensors, voltage sensors, temperature sensors, motor shaft angular position sensors, etc., which can be increased or decreased according to design requirements.

3. What should a good motor controller look like?

1. Characteristics of a good motor controller

The difference in the working principles of the motor directly affects the complexity and accuracy of the control process.

Arranged from easy to difficult to control, they are brushless DC motor, permanent magnet synchronous motor, switched reluctance motor, and asynchronous motor.

The difficulty of electronic control includes not only the scale and cost of the hardware system design, but also the control accuracy achieved by the software algorithm and the robustness of the strategies and methods used to achieve this accuracy.

What people expect is a control system with simple hardware structure, concise software algorithm, high control accuracy and good system stability.

2. The motor controller has national standards

There are national standards for electric vehicle motors and controllers:

GB /T 18488.1-2015 "Electric vehicles and their controllers Part 1: Technical requirements";

GB /T 18488.2—2015 “Motors and controllers for electric vehicles Part 2: Test methods”.

The 2015 version is the latest version. The standard mainly puts forward specific requirements for safety and environmental resistance, such as the insulation and withstand voltage performance of each part and various environmental resistance. As for the technical parameters of the motor, as a verification item, it only needs to comply with the manufacturer's own statement.

As shown below: Audi e-tron three-in-one powertrain control part open cover explosion diagram:

As shown below: An exploded view of the internal structure of the Audi e-tron three-in-one powertrain control unit:

(1) Driver board, (2) Driver board bracket, (3) High-voltage bus sampling harness, (4) Three-phase output laminated copper busbar, (5) Three-phase copper busbar, (6) Bus integrated Hall, (7) Hitachi double-sided water-cooled IGBT module, (8) Laminated busbar, (9) Water outlet cover, (10) IGBT cooling water channel, (11) Bus capacitor, (12) Positive (or negative) busbar, I don’t know which one is positive or negative, (13) Water inlet cover, (14) Control board, (15) Capacitor pin welding point, (16) IGBT middle four pin welding point, (17) IGBT thick pin welding point, (18) IGBT water channel other end cover.

Controllers from different manufacturers may be different, but they basically include all of the above components, but the appearance may be different depending on the manufacturer or model.

Control board analysis: The control board mainly includes: power supply circuit, control chip, CAN network, resolver circuit and various sampling circuits.

Power supply circuit: The power supply circuit mainly converts 12V or 24V electricity into the voltage required by DSP and some circuits. It is marked by transformers, electrolytic capacitors, large-volume ceramic capacitors, large-volume inductors, and thick wiring. Commonly used solutions: Infineon's DSP generally uses Infineon's power supply chips, and some use Infineon's TLF35584; TI's DSP generally uses the power supply chips recommended by TI's DSP.

DSP is commonly used as the control chip, which is usually the largest chip on the board. In addition, FPGA and CPLD will be used together with DSP. Commonly used DSP chips are from Infineon and TI, and some low-end models also use STMicroelectronics.

CAN network: marked by a small common-mode inductor, which can be easily confused with a resolver circuit. We can determine whether it is a CAN network by judging the nearby ICs.

Resolver circuit: The hardware decoding circuit is marked by a resolver decoding chip, and the chips are mainly ADI's 12XX series chips. If it is software decoding, it is marked by a small common-mode inductor and a push-pull circuit, which can easily be confused with the CAN network, which does not have a push-pull circuit.

Various sampling circuits: cannot be judged directly.

Driver board analysis: There are high-voltage and low-voltage parts on the driver board. There will be obvious isolation zones on the board. The driver part includes: driver power supply, high-voltage sampling and driver circuit.

Driving power supply: With transformer as the symbol, different schemes will have different setting schemes, generally there are flyback power supply, forward power supply and half-bridge power supply, transformers are 6, 3, 2 and 1 difference, 6 transformers, three-phase upper and lower bridge each have a transformer, each bridge arm has a power supply for the upper and lower bridge, 3 transformers, one transformer for each phase, 2 transformers, generally there will be one transformer for the upper bridge and one transformer for the lower bridge, 1 transformer is a transformer that plays the role of 2, 3 and 6 transformers. The more transformers, the more conducive to PCB wiring.