An automotive Motor Control System is a complex combination of Microcontroller Unit, Gate Driver IC, MOSFETs and motors with clearly defined roles. The blog explores how each of these components work together to drive an automotive BLDC motor.

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Automotive Motor Control System: The Brain Behind the
Brushless DC Motors in an Automotive Application

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In any Mechanical or Electronic system, where ever there is a continuous rotational motion
involved, there is a Motor. And in the modern-day automotive, where comfort is as important as
the driving efficiency, Motors play a pivotal role.
Be it the windows, seats, steering, turbochargers, ventilation flaps or brakes, there are Electric
Motors to be found in each of these components. In fact, there are a few hundred electric motors
in a passenger car. You see, they are called Motor-Cars for a reason!
The motors, however, don’t start and stop on their own. Like many other automotive components
that are controlled by Electronic Control Units (ECU), there are also Motor Control Systems to
drive a Motor.
To understand this system in detail, we met our automotive team members, who were more than
eager to share their knowledge and insights with us.

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Our conversation with the Automotive Team began by discussing the various types of
electric motors deployed in modern-day cars
During this discussion, we realized that Electric Motors have come a long way, as far
as their applications in automotive industry are concerned. And this evolution is still
on-going.
Many safety as well as comforting features in a vehicle, require Electric Motors.
Depending on the applications, there are primarily 3 types of motors that are widely
used in the vehicles:
Different Types of Motors You Would Find in Your Automobile

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• Brushed DC Motors: These DC motors have metallic brushes between the motor
coils and the rotors that complete the circuit. There is no electronic component
required to operate this motor. They are ideal motors for Power Window, Seating
Control, and other such applications where mechanical parts are operated without
any assistance of an electronic systems (like an MCU or a drive logic).
• Brushless DC Motors: These are one of the most widely used DC Motors. A
brushless DC motor has permanent magnets as the rotors. As the current is passed
through the motor coils (stator), the rotor being a permanent magnet starts to
rotate. As there is no physical contact between the stator and rotor, a motor
controller is required to alter the speed of the BLDC motor.

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• AC Induction Motor: Most widely used in Electric Vehicle Drivetrain applications,
an AC Induction Motor works on the principles of Faraday’s law of induction.
There is a rotating magnetic field produced due to the alternating current in the
coils. This moves the rotor. The speed of the motor can be altered by varying the
frequency of the alternating current supplied to the motor.
Understanding the Anatomy of an Automotive Motor Control System
Business use-cases and applications of Electic Motors in automotive, called for
systems which can control the motor according to the application-specific logic. For
instance, a motor deployed in an Electronic Power Steering (EPS) system is required
to alter its speed based on the torque applied by the driver on the steering wheel.

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This system is essentially an Electronic Control Unit (ECU) like all other ECUs in a
vehicle. It comprises of a Microcontroller ported with the Motor Drive Logic
(software) and integrated with some other Motor-Control peripherals (hardware).
The Motor Drive Logic is the software algorithm that drives the motor in the
intended manner. The peripherals like gate driver IC, MOSFETS etc. are part of the
control system that performs auxiliary tasks like error feedback handling, signal
conditioning, current and voltage amplification. We will learn more in detail about
all these components, very soon!
We were also introduced to how a Motor Control System works. But before we get
started with this,.
A Motor Control System is Required to Implement this Logic.

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Let’s first learn about the components of a Motor control system:
• Microcontroller: Microcontroller Unit (MCU) is essentially the component where
the Motor Drive Logic is stored.
For instance, in an electronic power steering application, a steering control
algorithm will be stored in a microcontroller platform. The algorithm is used to
vary the speed of the motor using Pulse Width Modulation (PWM) signals.
• Gate Driver IC: Gate Driver IC also known as a pre-driver is that next core
component! It, receives the PWM signal from the MCU and amplifies it to make
it suitable for the MOSFET.

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• MOSFETs: These are field effect transistors that can amplify a few milliamps
current to ten times and small voltage value to several hundred volts. As electric
motors require minimal switching time in varying the current flow to the motor,
MOSFETs are an indispensable part of the Motor Control System.
• Hall Effect Sensors: The role of Hall Effect sensors in automotive motor control
application is to determine the position of the motor. It is essentially a
transducer that will induce a voltage when the flowing charge comes under the
effect of a permanent magnet.
Hall sensors are fitted to the rotor so that its position is known before the motor
coils are energized.

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The following diagram shows the different components of a motor control system
A Typical Automotive Motor Control System with a 3-phase BLDC Motor

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How a Motor Control System Works?
The signal to start or stop an electric motor comes from the microcontroller. Unlike
a brushed DC motor, where there are brushes to complete the motor circuit, BLDC
motors use Hall-effect sensors to energize the motor coils.
The microcontroller uses the input from Hall-effect sensor to determine the
position of the rotor. Based on the position, it will energize the motor coils thus
creating a rotating electrical field. This field will move the rotor along with it.
This is the Physics and Mechanics Behind the Motor Movement.
Post this, we discussed the electronics behind the motor control system and the
role of MCU and the gate drivers.

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The Microcontroller unit is ported with the motor drive logic, Pulse Width
Modulation module and other algorithms depending on the application. Based on
the logic, the PWM signals will be relayed from the MCU. The Hall-effect sensor will
determine the exact moment when the PWM signal should be sent to the motor.
For example, if the BLDC is deployed in an electronic power steering, the MCU will
have steering control/assist algorithms and PWM signal will be produced according
to that logic. The timing will still be controlled by the Hall-effect sensor.
While the microcontroller unit gives the BLDC motor a start, there are other
components required to keep it running. They are the gate driver IC or the
MOSFETs. Power control and motor drive are two things that the MOSFETs and gate
driver unit are tasked with.

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Some Common Applications of Motors in Vehicles:
• Electronic Power Steering-A BLDC motor works with a MCU with steering control
algorithm, PWM, current loop PI etc.
• Seating Control: Electronically adjustable seats are also driven by electric
motors. Some advanced algorithms in the motor control system ensure that
there is no jerk or sudden start/stop in the seat. It is called soft stop/start.
• Electric Vehicles Drivetrain: Most electric vehicles deploy an AC induction motor
in their drive train. A three-phase AC power input is given to the motor that
produces rotating magnetic field. By altering the frequency of the AC power
supply, the speed of the wheel can be adjusted.

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Concluding Thoughts
The combination of mechanics and electronics has led to various advancements in
automotive motor control system. A simple brushless DC motor is now being
deployed to make some smart moves as it is driven by motor drive logic.
If you drive a modern car, you must have noticed how smooth the power steering,
power window and seat adjustment etc. has become. All this has been possible with
advanced motor control system that not only drive a motor in different speeds and
directions, but also in an efficient and smooth manner.

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Read the complete blog post here: Automotive Motor Control System: The Brain Behind the
Brushless DC Motors in an Automotive Application
Would you like to learn more about the IoT implementation? Contact: sales@embitel.com.