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What is HIL-Testing?

HIL(Hardware In the loop) testing, designed to test the performance of the actual control system of built-in control algorithm, is a method of evaluating the performance of the controller by using the virtual environment that responds the same as the actual system. The concept of HIL Test was first proposed in the 1990s and applied in areas where it is difficult to test a real system, such as vehicles and aircrafts, to reduce the time and cost of developing the controller and enhance reliability.

In general, a close loop control system can be divided into a controller, an actuator that receives the order of signal and performs operations, and a sensor that provides a feedback signal to the controller by measuring the status value. To perform HIL simulation, actual sensor and actuator of the closed loop control system are replaced with a virtual sensor and actuator. When the simulation is started, the controller sends an appropriate signal to the actuator, and the actuator performs the operation accordingly. Virtual sensor predicts status change to the actuator operation and uses it as feedback signals. Tester verifies the reliability of the controller while performing a case study on a variety of circumstances such as signal abnormality and actuator breakdown by controlling feedback signals or actuator operation.

Why Do HIL-Testing?

1. IMPROVE RELIABILITY & QUAILTY

The reliability of the control system can be improved with HIL simulations. Controller’s performance can be easily verified with virtual machine. The evaluation is possible as to whether the control system operates correctly in accordance with condition signals of the virtual machine system and, when a control function problem arises, the error is corrected and the correction applied to the actual product. Through this process, control system errors are removed before being applied to the product, resulting in the improvement of reliability and quality.

2. INCREASE SAFETY

HIL simulation allows safe testing of the control system in place of the actual machine. Through HIL simulation, the performance of the control system beyond the operation range of the machine can be verified. When the system is verified with a virtual mechanical model, tests can be performed safely without any problems even if there is an error with the controller.

3. SAVE TIME & MONEY

When errors are identified in advance by the verification of control functions through HIL simulation, problems such as the loss from suspension of operation and the extension of commissioning period can be prevented. A control system has many potential errors due to the nature of its production process. The earlier such problems are identified, the more time and costs are reduced.

What Do We Test?

By using the virtual machine, validation is performed to verify whether the control system was designed to be fit for its purpose, and it is verified whether appropriate operations are performed by the functions mentioned in the FDD.

1.NORMAL STATE TEST

  • Normal state, where everything is functioning normally
  • This test verifies the controller function on normal state
  • Example) L/D(Load dependent) start function test
    • 1)Thruster and Drilling system consumed power increase
    • 2)If the generator loading is over the limit, PMS will start to L/D start function
    • 3)Check : Whether the generator starts in time or not

2.DEGRADED STATE TEST

  • Degraded state, with some defect in the function on the controlled system such as degraded communications(signal loss, wrong value feedback, etc@)
  • This test is performed to check whether the controller operates the system in a stable manner even when it receives wrong feedbacks or the controller’s command signals are not sent normally to the system.
  • Example) One thruster is uncontrollable, DP positioning test
    • 1)Failure on the thruster driver control signal - one thruster is uncontrollable
    • 2)Check : Can the controller stabilize vessel and generate alarms?

3. ABNORMAL(FAILED) STATE TEST

  • Failure state, where the target control fails to execute the control system programming. The description is to include the programmed error handling routine
  • for the degraded and failure states.
    This test verifies controller function on abnormal state.
  • Example) Low Frequency State
    • 1)Low frequency occurs on the HV SWBD (it can occur as a result of generator trip, overload, and generator fuel supply fault)
    • 2)Check : How can PMS stabilize the power system?