System Identification for Time Optimal Turbocharger Testing with an Unknown Map 2019-01-0321
Turbocharger testing is a time consuming process, and as rapid-prototyping technology advances, so must other areas in the development chain. In one example, a compressor map took over 34 hours to measure. In this paper, an effort to combat the main bottleneck of turbocharger testing, namely the thermal inertia, is made. When changing operating point during the measurement process, several minutes can be required before the turbocharger components reach temperature steady state. In an earlier paper, an optimal control method was developed that significantly reduced the testing time required to produce compressor performance maps. The time was reduced by a factor of over 60, compared to waiting for the system to reach steady state with constant inputs. However, the method required a model of the turbocharger. This paper extends the optimal control method with system identification. This is an important step in order to be able to use the optimal control method when only geometric information of the turbocharger is known, such as new prototypes. In addition to the time reduction benefit, corrections to the efficiency map can be made using the estimated heat transfer model parameters. To demonstrate the effectiveness of the optimal control method, it is applied to a virtual gas-stand implemented as a Simulink model with a Mitsubishi TD04 turbocharger. The data that was used to create the model was originally collected at Saab Automobile in Trollhättan, 2011. The results show that on-line system identification captures the behaviors of the turbocharger. A compressor map of 27 points is measured (in the virtual gas-stand) with the developed optimal control method, taking 6.6 minutes to measure, compared to 1.54 hours if the standard waiting method is employed. Real time implementation of the Matlab/Simulink based algorithm is planned for testing in a real gas stand.