A Virtual ECU and Its Application to Control System Analysis - Power Window System Demonstration 2016-01-0022
A virtual power window control system was built in order to look into and demonstrate applications of microcontroller models. A virtual ECU simulated microcontroller hardware operations. The microcontroller program, which was written in binary digital codes, was executed step-by-step as the virtual ECU simulation went on. Thus, production-ready codes of ECUs are of primary interest in this research. The mechanical system of the power window, the DC motor to lift the window glass, the H-bridge MOSFET drivers, and the current sensing circuit to detect window locking are also modeled. This means that the hardware system of the control system was precisely modeled in terms of mechanical and circuit components. By integrating these models into continuous and discrete co-simulation, the power window control system was analyzed in detail from the microscopic command execution of the microcontroller to the macroscopic motion of the window mechanism altogether. The minute microcontroller operation in a few nanosecond time span and slower window lifting were observed in the same time traces. Obviously, the accuracy and the simulation time of the co-simulation were a trade-off. In this paper the techniques to deal with the causes of the timing errors in co-simulation were discussed. Possible use of this technology includes detailed analysis of control operation and verification of the fail-safe response to component failures. As the co-simulation includes both the control system hardware in component level and the control software in execution format, components failures are easily injected in any level. This work was one of the outcomes of the vECU-MBD WG (Virtual ECU Model-Based Development Working Group) in Japan.