Different types of Hardware-In-the-Loop Simulation for Electric Drives

Hardware-in-the-loop (HIL) simulation, also known by various acronyms such as HiL, HITL, and HWIL, is a technique that is used in the development and testing of complex real-time embedded systems. HIL simulation provides an effective testing platform by adding the complexity of the process-actuator system, known as a plant, to the test platform. The complexity of the plant under control is included in testing and development by adding a mathematical representation of all related dynamic systems.

Hardware-in-the-loop simulations are more and more used to assess the performances of electric drives. Software simulations lead to the development of control of the studied system. In this case, generally, a lot of simplifications are assumed to reduce the computation time. Before a real-time implementation of the control, HIL simulations could be a very useful intermediary step. Thus a hardware device is introduced in the loop in order to take its real constraints into account.

When to Use Hardware-in-the-Loop Simulation

When performing model-based design (MBD), use HIL simulation to test the design of your controller. The figure shows where HIL simulation fits into the MBD design-to-realization workflow.

Validation involves using actual plant hardware to test your controller in real-life situations or in environmental proxies (for example, a pressure chamber). In HIL simulation, you do not have to use real hardware for your physical system (plant). You also do not have to rely on a naturalistic or environmental test setup. By allowing you to use your model to represent the plant, HIL simulation offers benefits in cost and practicality.

There are several areas in which HIL simulation offers cost savings over validation testing. HIL simulation tends to be less expensive for design changes. You can perform HIL simulation earlier than validation in the MBD workflow so you can identify and redesign problems relatively early in the project. Finding problems early includes these benefits:

• Your team is more likely to approve changes.

• Design changes are less costly to implement.

In terms of scheduling, HIL simulation is less expensive and more practical than validation because it can be set up to run independently.

HIL simulation is more practical than validation for testing your controller’s response to unusual events. For example, you can model extreme weather conditions like earthquakes or blizzards. You can also test how your controller responds to stimuli that occur in inaccessible environments like deep sea or deep space.

 This is crucial in electric drives as it enables testing of motors, inverters, controllers, and other key components before they are deployed in real-world systems.

1. Controller HIL (C-HIL) for Electric Drives

Purpose: The primary focus of Controller HIL testing is to test and validate the electric drive's controller (e.g., motor controller, inverter controller).

How It Works:

• In C-HIL, the controller is connected to a real-time simulation of the electric drive system.

• The controller sends commands to the virtual models of the electric motor, power converter, and other components.

• Real-time feedback is provided, allowing the controller's performance to be analysed under various operating conditions.

Applications:

• Motor controllers: Testing of algorithms that manage the speed, torque, and direction of electric motors.

• Inverter controllers: Validation of inverter behaviour and performance, especially in applications like electric vehicles.

Benefits:

• Provides a safe environment to test controller algorithms before integrating them with physical systems.

• Helps in identifying issues in control strategies like overcurrent, overheating, or inefficient switching behaviour.

2. Plant HIL (P-HIL) for Electric Drives

Purpose: Plant HIL testing focuses on simulating the real-world dynamics of the electric drive’s physical plant, including the electric motor and power electronics.

How It Works:

• The actual electric drive hardware (e.g., motor, inverter, sensor) is connected to a virtual model of the plant.

• The system operates as it would in real-world conditions, but the surrounding environment (like load, torque, and temperature) is simulated.

Applications:

• Motor testing: Real-time validation of electric motors in various load conditions.

• Power converter testing: Examining how power electronics, like inverters or converters, handle different input and output scenarios.

Benefits:

• Helps in understanding how physical components interact with each other.

• Identifies inefficiencies or potential failure modes in the drive system's physical plant.

3. Integrated HIL (I-HIL) for Electric Drives

Purpose: Integrated HIL combines both the controller and the plant hardware into a unified simulation platform. This type is ideal for testing the interaction between hardware components and their control systems.

How It Works:

• The hardware controller (such as a motor controller) is linked with the physical plant (e.g., motor and inverter), while virtual models of the environment simulate external conditions like battery levels or load.

• The system operates in real time, with continuous feedback exchanged between the controller and plant hardware.

Applications:

• EV development: Testing the full electric drive system, including controller and motor dynamics, to optimise vehicle performance.

• Robotics: Testing robot actuators, including motor and power systems.

Benefits:

• Provides a complete test environment that mimics real-world scenarios, ensuring that both control algorithms and hardware components perform as expected.

• Reduces time-to-market by identifying integration issues early in development.

4. Real-Time HIL (RT-HIL) for Electric Drives

Purpose: Real-time HIL simulation is critical when testing electric drives in systems that require immediate feedback, such as automotive or aerospace applications.

How It Works:

• The system operates in real-time, meaning the simulation processes data and responds as the electric drive system would in actual operation.

• This type of testing ensures that the controller and plant components function with the exact timing and synchronisation as in a real-world scenario.

Applications:

• Electric vehicles: Simulating and testing how an EV’s electric drive system behaves under different driving conditions.

• Wind turbines: Real-time testing of electric drive systems used in turbines to optimise performance and efficiency.

Benefits:

• Guarantees system behavior is consistent with real-time operation, which is vital for safety-critical applications.

• Ensures high-performance standards are met in applications with strict timing requirements.

5. Rapid Prototyping HIL (RPHIL) for Electric Drives

Purpose: Rapid prototyping HIL is used for testing and validating early-stage prototypes of electric drives, enabling quick iterations and faster development.

How It Works:

• The physical prototype (e.g., motor, inverter, or controller) is tested using a real-time simulation model.

• This allows engineers to immediately evaluate the prototype's performance in a virtual environment, making modifications and improvements rapidly.

Applications:

• Prototype electric vehicle drivetrains: Quickly validating different motor and controller configurations.

• New inverter designs: Prototyping and testing new inverter topologies before full production.

Benefits:

• Accelerates the development cycle by enabling quick feedback and testing of new concepts.

• Reduces development costs by minimising physical testing and prototyping.

Conclusion

For a brand like Suzuki R&D, which is renowned for producing reliable and efficient vehicles, leveraging HIL simulation in the development of electric drives is essential to maintaining high standards of quality and performance. Whether it's testing motor controllers for electric vehicles, validating power electronics, or ensuring the integration of complex drive systems, HIL testing helps Suzuki engineers ensure that every component is optimised for real-world conditions.