Unknown input high-gain observer for internal combustion engine test benches

In the modern world of internal combustion engines, test benches play an important role in the development, the design and the improvement of the engine itself as well as of the control loops implemented in the engine control unit. A test bench replaces the clutch, the gearbox, the shafts and the wheels of a vehicle as well as the load acting on the vehicle. The control of the test bench has to ensure that the internal combustion engine is loaded like in a vehicle, which is best achieved if torque based control is used. As in many cases torque can not be measured and torque estimators are used. However, the internal combustion engines at a test bench are changed frequently due to reduced development cycles and an increased number of different engines. This could require a continuous update of the observer parameters. To take care of this development an enhanced high-gain observer exclusive of a model of the internal combustion engine is proposed in this paper. The proposed method reduces the time required for tuning and parameterization and therefore contributes to a simple and fast change of the internal combustion engine. Measurements on a real test bench show the good performance of the proposed observer compared with measured quantities and quantities determined using an observer including a model of the internal combustion engine.