I started out my career on the G.M. project SimuCar; a full vehicle simulation for Hardware in the Loop validation which models transmissions and HVAC systems. The project introduced me to the requirements and rigor of Real-Time simulation as well as the practical limitations of hardware “bucks.” From there I transitioned to Applied Dynamics International (ADI) a Hardware in the Loop vendor; in that role I developed a passion for rigorous simulation based testing. Since that time I’ve had a chance to work with all of the major vendors: Speedgoat, dSpace, Opal-RT, and NI. Each vendor has unique strengths, but they all share common requirements in getting you “up that H.I.L.”(1)
Planning your summiting
A H.I.L. system has 5 principal components:
- The target controller: the unit under test.
- The physical H.I.L. system: the environment that provides signals to the controller
- The plant model: the simulated environment used to stimulate the controller.
- The test runner: infrastructure for running the system, collecting data, and evaluating the results.
- Wires and signal conditioning: the physical connections and mechanical/electrical conditioning used to “close the loop” between H.I.L. and controller.
Today I want to talk about how to plan out your first foundational stones of the H.I.L., the signal conditioning.
The wiring and signal conditioning
In my first year at SimuCar by my estimates my “initial” physical models would have destroyed close to 3 million dollars in GM proto-type hardware if we hadn’t first validated the wiring and signal conditioning. So here is how to commission your H.I.L. system:
- Run the loopback harness: most H.I.L. companies provide a stand-alone loop back tests that enable initial validation of the hardware.
- Beep your harness: the wiring harnesses connects the H.I.L. system to the controller. A wire connection test ensures that the H.I.L. and controller are correctly exchanging information.
- Open loop connection validation: connect the controller to the H.I.L. system with a no-controls version of the controller to validate signals are correctly red on the controller.
What is a “no-controls” model?
The basic model architecture for a H.I.L. system plant model decomposes the system into three top-level components: Inputs, Plant and Outputs. Likewise, the controls model is decomposed into the OS, I/O, and control algorithms. The no-controls algorithm pairs a H.I.L. model without plant and a controls model without controls algorithms present. The test system then exercises the outputs and validates that they are correctly read into the controls system via the monitoring stack.
Once the signal connections and scaling are validated the same “no-controls” H.I.L. model can be reused in the testing environment.
- The initial commissioning of H.I.L. systems is critical for long-term success. This blog post aims at providing the tips for your base camp.