Hardware in the loop for electronic speed limiter

Electronic controller unit (ECU) used for controlling sub-systems of complex real life applications like automotive vehicles can pose several challenges. Many times one needs to plan development and testing of controller, when the end vehicle is also under development and hence not available. In such case, hardware in the loop (HIL) approach for testing such controllers emulates the external application environment and allows concurrent development of the electronic controllers. Even when the end vehicle is available, if design iterations are to be carried out using "in-vehicle" testing approach, then the same can be time-consuming. Such an approach may also possess safety hazards if malfunction of the ECU impacts occupants/vehicle safety. Many cases require simulation of a range of use-case scenarios as well as system operation under diverse set of environments. For example, for a power-train related application various road conditions / road-grades / frictional coefficients will have to be simulated. HIL set-up allows us to do this on-the-fly. This paper describes a case-study of how HIL testing approach was gainfully employed for an electronic road-speed limiting application. The control system uses an electronic throttle controller as its heart. The HIL system can simulate vehicle dynamics for the end vehicle as well as road-grade, vehicle load etc. This allowed us rapid development of the core control algorithm, which minimized vehicle testing time. Another novel feature of this particular testing was, that the HIL system was implemented on a low cost hardware based on the target controller to be tested. The paper describes the basic scheme in detail and also records our experiences/ lessons learnt etc.