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What is an Electric Vehicle Controller?
The world is continuously moving towards sustainable and greener transportation, and in the field of electric mobility, motor controllers play a fundamental role. A motor controller for EVs manages the power utilized by the electric motors. It forms the interface between the vehicle’s battery and motor as well as regulates the amount of power received by the latter in various conditions. Its functions mainly include power conversion, protection of the system including from overheating, torque and speed control, communication between components, regenerative braking, etc.
The EV motor controller market was valued at ₹436.28 billion as of 2024 and is expected to be worth approximately ₹1.996 trillion by 2034, expanding at a CAGR of 16.12% during this forecast period. Major factors driving the growth of these controllers include new Indian governmental regulations such as Faster Adoption and Manufacturing of Electric Vehicle (FAME) that have increased the acceptance of electric vehicles among private and public sector organizations. Also, various incentives for automotive IT solutions through the electric vehicle subsidy system are promoting the development of electric vehicle components, charging infrastructure, and research and development.
Expanding market size of motor controller in electric vehicle during the 2023-2034 forecast period
Brief Account of EV Motor Controller
Types
Choosing the right type of motor controller is directly associated with its specific application in the electric vehicle as well as the characteristics of the motor. This aids in achieving optimal energy efficiency and vehicle performance. Given below are some types of motor controllers –
Brushless DC Motor Controllers
BLDC motor controllers operate on direct and indirect Field Oriented Control algorithms. The DFOC requires sensors for precise torque control, speed control of the rotor and magnetic flux. The IFOC estimates the phase angle of the rotor magnetic field flux and does not require additional sensors. These controllers are cost-effective solutions with sophisticated algorithms for real-time actuating as per safety standards and high-computing capabilities during long-term duty times and complex situations. Although BLDC controllers are efficient and reliable for longer durations, they are slightly expensive to manufacture in comparison to other types of controllers.
AC Induction Motor Controllers
AC IM controllers regulate the operation of AC induction motors that are commonly used for propulsion in electric vehicles. They efficiently manage the motor’s direction, speed, and torque by controlling and adjusting the amplitude as well as the frequency of power received by the motor. Also, these controllers convert direct current (DC) power supplied by the vehicle’s battery into alternating current (AC), as this allows smooth acceleration and deceleration of the electric vehicle. This functionality also supports regenerative braking for returning the energy back to the battery during the application of brakes. They are quite reliable and utilize electromagnetism to run electric vehicles to optimize efficiency, improve performance, and manage energy amongst the vehicles’ components, but they require precision in controlling and continuous monitoring while handling machinery.
Permanent Magnet Synchronous Motor Controller
PMSM controllers use magnets to synchronize power delivery, thus making them the best choice for most of the electric vehicles. They are preferred in terms of energy utilization and conservation but require complex control systems and are made of expensive rare-earth magnets such as Neodymium-Iron-Boron (NdFeB) that offer high magnetic strength for ideal motor performance, or more stable Samarium-Cobalt (SmCo) with high resistance to de-magnetization and operate well in high-temperature environments.
Features
For smooth functioning of an electric vehicle, there are certain factors, such as the electric vehicle controller power rating, that need to match its needs for optimal performance while being compatible with the motor. It should operate on communication protocols that are aligned with other components of the vehicle for the ease of integration. The controller must be capable of thermal management, protecting components from current and voltage fluctuations and supporting regenerative braking. The following are the key features that need to be considered while designing and developing a motor controller for EV –
Power Converter
The controller must be compatible in terms of voltage range and should be able to convert direct current (DC) received from the battery into alternating current (AC) in cases of AC motors, which are most common in electric vehicles. Thus, it is important to choose the motor controller with matching power requirements or the most suitable power rating for an electric vehicle to avoid the risk of overtemperature and otherwise.
Torque Control
It controls the amount of power incoming from the battery as per the input provided by the driver, such as the accelerator pedal, determining the speed of the vehicle and its acceleration. It seamlessly regulates the voltage and the current’s frequency sent to the motor, thus controlling the torque and speed produced by the motor.
Regenerative Braking
This is a common feature of modern electric vehicles where the motor converts kinetic energy back into usable electrical energy during braking. While it acts as a generator, the electric vehicle controller manages this process so that the vehicle gets recharged as and when it is slowed down, thus allowing cost optimization.
Sample workflow of a motor controller for electric vehicle
System Protection
This component ensures that the motor, battery, and the whole system, including the 360 degree camera for car, stay protected against damage caused by overheating, over or under voltage and current, accidental fire, short circuit, or system failure, using certain features by shutting down the system, limiting power received by the motor, thermal management using thermal sensors, isolation monitoring for insulation between high and low-voltage circuits, activating a failsafe mechanism, motor lock in case of stalled motors, and cooling systems like fans or liquid cooling against over temperature.
Communication
It maintains proper communication between vehicle components, such as the battery monitoring system, which helps in energy optimization, maintaining battery health, identifying faults such as faulty sensors and electrical wiring, providing warnings to the driver and onboard diagnostics system regarding the same, and improving the overall efficiency of the vehicle’s performance. For harmonious working of all components and safe driving, the motor controller must be able to communicate vital information through protocols like CAN Bus for seamless integration with the electric vehicle’s control system.
Key Considerations for Designing EV Motor Controller
While designing a motor controller, it is important to consider the type and topology of the motor, microcontrollers, software involved, power electronics components, driver circuits, communication protocols, and sensors. Given below is a brief account of the key considerations for designing motor controllers.
Control Algorithms
A control algorithm refers to the logic that determines the regulation of power flow, motor speed and torque control by the controller, which is directly dependent on the motor type, its features, expected performance outcome, hardware resources available and other criteria. Few control algorithms are –
1. Direct Torque Control: DTC is a vector control method that directly controls the motor flux and torque without the aid of a current regulator or coordinate transformation. Here, the vector control method refers to separating the current into two components, each for flux and torque for quick, precise motor control and responsiveness. DTC utilizes a hysteresis controller for the motor’s voltage vector selection, alongside a switching table, as per the error between the actual and reference values of the flux and torque. This eliminates the requirement of any complex microcontroller and position sensor and makes it suitable for AC motors like PMSMs and AC IMs. Although they may feature acoustic noise, variable frequency of switching, and excessive torque ripple at times.
2. Field-Oriented Control: This vector control method decouples the stator current of the motor into DC that controls flux and quadrature current, controlling the torque. We discussed earlier that the BLDC electric vehicle controller utilizes FOC algorithms for independent and precise control of the motor’s torque and speed for dynamic response. It is also used for controlling AC IMs, and PMSMs, but requires a fast microcontroller and position sensor for regulating current and implementing coordinate transformation. This transformation basically converts the motor’s three-phase AC currents into a two-axis system using Clarke and Park transforms to simply motor control through independent control of flux and torque components, thus enabling vector control methods.
3. Sinusoidal Control: This is a scalar control method applicable to sinusoidal AC voltage received by the motor that changes the amplitude and frequency of voltage as per the torque and speed input commands. It is suitable for smooth and efficient performance of PMSMs that have sinusoidal back EMF waveforms for regenerative braking. However, they require a position sensor, a fast microcontroller for sinusoidal modulation, and high computations and provide a lower dynamic response in comparison. Here, the back electromotive force (EMF) waveform refers to the voltage induced in the EV motor’s windings or stator cells that opposes the applied voltage, as the rotor spins and the magnets create a changing magnetic field.
4. Trapezoidal Control: This is a scalar control method that is applicable to constant DC voltage supplied to the motor, where the voltage is commutated as per the rotor’s position. Since BLDC motors have a trapezoidal back EMF waveform, this algorithm is suitable for them, while they do require a simple microcontroller and position sensor for implementing the commutation logic and experience poor torque control in comparison. Back EMF increases with motor speed and is utilized by controllers for regulation and energy recovery during regenerative braking.
Robustness
A motor controller’s robustness refers to its ability to maintain optimal performance exhibited by the motor as well as its stability under normal or uncertain conditions. At times, load torque, sensor noise, variations in power supply, certain motor parameters and environmental adversities may cause disturbances and uncertainty in its performance. Through the following methods, the motor controller’s robustness can be increased –
1. Adaptive Control: This technique is useful for dealing with variations, disturbances, and uncertainties in the system, including vehicle control unit, caused by different types of sources. It estimates the state of the system or online identification to adjust the parameters or inputs of motor controller for electric vehicle. This may include regulator gains, voltage changes, motor flux, resistance etc. It improves the overall robustness and adaptability of the motor and requires a sensor, estimator, or identifier for implementing the algorithm.
2. Feedforward Control: In this technique, the effects of disturbances and uncertainties can be anticipated and canceled for improving the motor’s robustness. The disturbance in the system estimated using sensors that can be a part of vehicle detection systems, including motor temperature, load torque, etc., can be utilized to adjust the input of the system, such as frequency or voltage of power electronics in a feedforward loop.
3. Feedback Control: This technique uses the estimated output of the system to adjust the input of the system. For example, the motor’s current or speed can be used to adjust the frequency or voltage of power electronics. It requires a sensor to implement the feedback loop and can compensate for the uncertainties while improving the motor’s stability and accuracy.
Various types of control strategies to be considered in designing electric vehicle controller
Temperature Handling
Thermal control and heat dissipation of power electronics and the motor are managed by motor controller in electric vehicle for ensuring the system’s longevity and required output. It depends on the following factors –
1. Power Losses: Due to mechanical and electrical inefficiencies in the motor, there may be loss of power, resulting in heat generation, such as losses due to friction, switching, resistance, etc. It depends on motor type, features, and operating conditions like voltage, switching frequency, speed, torque, and modulation scheme.
2. Thermal Resistance: The system’s heat flow is determined by thermal resistance as well as the heat transfer from heat sources like power electronics and motors to heat sinks like cooling systems or ambient air. Whereas these properties change with respect to the system’s materials, geometry, insulation between components, thermal contact, and cooling methods like liquid cooling and forced or natural convection.
3. Thermal Stress: This system’s thermal and temperature-related stress is caused by thermal expansion and heat distribution. Their dependency is mainly on thermal gradient, equilibrium, coefficients of components, protection, temperature limits, and fault detection mechanisms. It directly affects the system’s reliability and overall performance.
Safety
It is of utmost importance to ensure that the motor controller for electric vehicle operates reliably and safely to prevent and mitigate damage caused by system failure. One can consider the below aspects for safety and fault detection mechanisms –
1. Fault Type: These include classification of various types of faults and their causes, such as overtemperature, overvoltage, overcurrent, failure of sensors, error in software, ground fault, short or open circuits, environmental conditions, human intervention, load, etc. that lead to the origin of undesired conditions.
2. Fault Detection: This includes techniques that are used to identify and locate system failures observed through its signals and symptoms, including error codes, voltage, current, temperature readings, etc. Fault diagnosis is directly dependent on measurement devices, sensors, fault models, indicators, detection algorithms, and methods that may be AI-enabled, threshold-based, or model-based.
3. Fault Recovery: All the strategies and actions required for mitigating impacts such as damage, downtime, or injury caused by system failure. Fault protection depends on protection devices, driver circuits, fault isolation, tolerance mechanism, recovery methods like reconfiguration, restart, shutdown, self-healing etc.
Controller Design
Let us explore further on how to design and develop a motor controller and the factors to consider in the below section –
1. Motor Type: Choosing the characteristics and requirements of the motor controller directly depends on the type and topology of the motor, including its size, cost, weight, and efficiency. Let us take an example, PMSM and BLDC motors are dependent on three-phase inverters consisting of size switches to convert direct current voltage supplied by the battery to alternating current voltage received by the motor. On the other hand, IMs need variable frequency drives for controlling the amplitude, and frequency of AC voltage.
2. Control Strategy: Choosing control algorithms directly impacts the regulation of power flow, motor torque, and speed by the electric vehicle controller. Some common control methods for AC motors include vector control, direct torque, scalar control, and FOC, Sinusoidal and trapezoidal controls are for PMSM and BLDC motors that directly affect the complexity, computations, and performance of the controller.
3. Components: The safety, integration, networks, reliability, cost, power density, and functionality of the motor controller are determined by the appropriate software (libraries, firmware, development tools) and hardware (microcontrollers, transistors, voltage sensors, gate drivers, communication interface) components chosen.
Applications of EV Motor Controller
In the above sections, we have talked about how these controllers are necessary for the optimal operations and performance of electric vehicles. Let us now delve into the various applications of the same in different industries.
1. Electric Cars: Motor controllers regulate motor torque, speed, and power sent to the electric vehicle as per the driver’s input or otherwise, such as in the case of autonomous driving systems. They optimize battery usage and manage energy flow between the motor and regenerative braking system.
2. Electric Bicycles: eBikes utilize these controllers to adjust the motor’s power output to assist with pedaling speed within legal limits and effort for smooth acceleration and safety.
3. Electric Scooters: Electric scooters and mopeds regulate efficient power delivery to wheels and ensure driver safety and protection against overcurrent, overtemperature, faults, etc., by using motor controller in electric vehicle.
4. Electric Boats: Electric marine vehicles and boats utilize these to manage propulsion systems over water for efficient boat speed, power optimization, and electricity flow between the components.
5. AGVs: These are used in electrified automated guided vehicles (AGVs) for managing the vehicle’s speed and movement, energy consumption during the transportation of material around warehouses and manufacturing units.
6. Electric Trains: These controllers regulate electric traction motors to manage power for starting, stopping, maintaining speed, and regenerative braking on railway tracks.
7. Electric Aircraft: Electric vehicle take-off and landing (eVTOL) utilize these controllers to manage propulsion systems such as lift and thrust motors of aircraft and balancing power consumption between motors as per the flight phase.
8. Electric Forklifts: Material handling equipment such as electric forklifts ensure energy efficiency while lifting heavy loads alongside operational cost reduction.
9. Public Transit: Automated transportation systems such as electrified trams and metro systems are assured of smooth acceleration, deceleration, braking, energy management, and performance optimization over long distances using these controllers.
10. Electric Construction Equipment: These controllers are also used in various construction machinery, equipment, and vehicles like bulldozers and excavators for energy efficiency, management of large motors, and reduction of emissions in construction sites.
Conclusion
KritiKal has assisted various automotive companies with varied portfolios in designing, developing, and integrating PMSM, BLDC, or AC IM motor controller in electric vehicle. These controllers manage power flow for efficient operations, and it is of utmost importance to consider factors such as power rating, motor compatibility, communication protocols, thermal management properties, safety features, programming, and the extent of regenerative braking etc., while designing a controller. One needs a thorough understanding of motor controllers transitioning to cleaner and more efficient transportation. Please get in touch with us at sales@kritikalsolutions.com to know more about our solutions and products and realize your automotive requirements.
Manoj Kumar currently works as a Senior Manager – Embedded at KritiKal Solutions. With extensive experience in handling industry-agnostic embedded systems and proficiency in C, C++, Python, JavaScript, debugging, Selenium, robotics, and more, he has assisted KritiKal in delivering various projects to some major clients.