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Automotive Brushless Motor Controller Summary

2018-04-30 11:47:17 8

In any mechanical or electronic system, as long as there is a continuous rotational motion, there is a motor.In modern automobile, comfort is as important as driving efficiency, and motor plays a key role.Whether it's the Windows, the seats, the steering wheel, the turbocharger, the hood or the brakes, every part has an electric motor. However, the motor does not start and stop on its own.Like many other automotive components controlled by electronic control units (ECU), there are motor control systems that drive motors.Below is the experience of automotive engineers on these motor control systems.

Main Motor Types Used In Automotives

Motor is widely used in automobile industry, which is mainly used to improve the safety and comfort of automobiles.According to different applications, there are three main types of motors:

1. Brush dc motor: there is a carbon brush between the coil and rotor of these dc motors, which plays the role of reversing.Automotive dc motors are widely used for electric Windows, seat control, and other similar applications of mechanical parts that operate without any auxiliary electronic system (such as the MCU or drive logic).

2. Brushless dc motor: the rotor of brushless dc motor adopts permanent magnet. When the current passes through the motor coil (stator), the rotor as permanent magnet starts to rotate.

3, ac induction motor: ac induction motor is most widely used in the transmission system of electric vehicles, its working principle is Faraday induction law.The alternating current in the coil creates a rotating magnetic field, which moves the rotor, and the speed of the motor can be changed by changing the frequency of the alternating current supplied to the motor.

The Structure of Aotomotive Brushless Motor Montroller

A brushless motor in a car consists of a motor and a controller, which is essentially an electronic control unit (ECU) like all other ecus in a vehicle.It includes a microcontroller migration with motor drive logic (software) and integration with some other motor control peripherals (hardware).The motor controller is the software algorithm that drives the motor in the expected way.Peripherals such as door driver chips, mosfet, etc. are part of the control system and perform auxiliary tasks such as error feedback processing, signal conditioning, current and voltage amplification.Components of motor control system:

1.Microcontroller: microcontroller unit (MCU) is essentially a component that stores motor drive logic.For example, in electronic power steering applications, the steering control algorithm will be stored in the microcontroller platform.The algorithm USES pulse width modulation (PWM) signal to change the speed of the motor.Input and output buttons can interface with this MCU.The output PWM signal is connected to the next core part of the motor control system.

2.door drive IC: door drive IC is also known as the front drive, is the next core component!It receives PWM signal from MCU and amplifies it to make it suitable for MOSFET.This was a bit confusing to us, knowing that mosfet is usually used to amplify voltages, so what is the purpose of using gate driver chips in motor control systems.We were told that there was a threshold voltage value that a MOSFET needed to work;Gate driver IC provides a threshold voltage.In addition, there are some signal conditioning algorithms in the gate driver chip, which can remove the noise in the signal and make it smooth.

3.Mosfet: these are field-effect transistors that can amplify a current of a few milliamps up to ten times and small voltages up to a few hundred volts.Mosfet is an indispensable part of the motor control system because the motor needs the minimum switching time to change the current flow to the motor.

4.Hall effect sensor: the role of hall effect sensor in automobile motor control application is to determine the position of the motor.It is essentially a sensor that generates a voltage when a flowing charge is applied to a permanent magnet.Hall sensors are mounted on the rotor to know the position of the rotor before the motor coil is energized.

The following figure shows the composition of brushless motor control system:

Automotive Brushless Motor Controller.png

Working Principle of Brushless Motor Control System

The signal to start or stop the motor comes from the microcontroller.The brushless dc motor USES a hall effect sensor to drive the motor coil.The microcontroller USES the input of the hall effect sensor to determine the position of the rotor.Depending on the position, it will excite the motor coil, thus creating a rotating electric field.This magnetic field will move the rotor with it.

Some Common Applications Of Motor In Automotive

The brushless dc motor is controlled by single chip microcomputer, with steering control algorithm, PWM, current loop PI and other functions.

Seat adjustment: electronically adjustable seats are also driven by electric motors.In the motor control system, some advanced algorithms can ensure no bumps or sudden start/stop in the seat.This is called soft stop/soft start.

Electric car drivetrain: most electric cars have an ac induction motor in the driveline.A three-phase ac power supply is supplied to the motor which generates the rotating magnetic field.The speed of the wheel can be adjusted by changing the frequency of the ac power supply.

The most prominent role of motor can be seen in electric vehicles. The core components of electric vehicles are made up of DC and AC motors, among which the most cutting-edge is brushless DC motor. Power Motor is investing heavily in Automotive Brushless Motor Controller, which can obtain the maximum motor output with the least investment.

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