Robust control of a throttle body for drive by wire operation of automotive engines

In recent years, ever more stringent requirements in terms of emissions control, driveability, and safety of automobiles have led to the development of the drive by wire (DBW) concept, a new architecture for engine control systems, with the purpose of managing air, fuel and ignition in an integrated way. The throttle control plays an important role in the development of DBW systems. Despite its apparent simplicity, the position control of the throttle valve is quite a complex problem, due to application constraints and system characteristics. Very high robustness must be linked with limited cost, as required by a mass production device. A cascaded control structure including a nonlinear trajectory generator filter is adopted, allowing each different control problem to be solved with the most suitable control algorithm and implementation technology. In this regard, the use of variable structure control techniques is the key element to reaching the solution. Extensive simulation tests are reported to show the performance of the proposed control algorithm. A throttle step from 0.5° to 89.5° indicates good position tracking under realistic operating conditions, with a position error smaller than 1°. The same simulation is performed at a battery voltage of 9 V to check the controller robustness. A prototype controller is presented. The experimental implementation of the controller for a step from 2.5° to 85.5° indicates a very smooth position trajectory with a maximum dynamic position error of 7°. A small throttle step from 1° to 7° (which contains the nonlinearity of the limp home mode spring) was also tested and resulted in very good position response with the maximum position error of 2°. Application specifications are fully satisfied both in terms of control performance and controller cost.