Helmut Kokal

Adaptive Inverse Torque Control of a Diesel Engine Using Adaptive Mapping Update

Torque control is a basic element of engine control systems, in particular since it has become a standard interface for different functionalities. Torque control is also a critical requirement emission test cycle simulation on test benches. This torque control is usually reached by extensive, physical based modeling of the vehicle. This paper presents an approach to avoid this effort and to obtain a dramatic reduction of the parametrization work, by first determining an approximated model and then updating it online during operation. This model is than used for a stable inverse control. To handle model uncertainties and perturbation a correction feedback, with robustifying effect, is added to the control structure. This approach is detailed using data and measurements on a BMW M47D production diesel engine on a dynamic test bench.

Bandwidth extension of dynamical test benches by modified mechanical design under adaptive feedforward disturbance rejection

In this paper we present a mechatronical approach for bandwidth extension of a combustion engine test bench consisting of the reconfiguration of the mechanical design and the introduction of an adaptive feedforward like disturbance rejection scheme. The mechanical design of the test bench is improved by the use of a stiff shaft engine to dynamometer connection. This yields a shift of the resonance frequency of the test bench into the frequency range excited by the combustion oscillations and hence results in the need of a disturbance suppression algorithm. Therefore the repeatability of the almost periodic disturbance is exploited to predict an estimate of future values using an extended FIFO memory to compensate input delays. The algorithm is tested in simulation and furthermore applied to a real test bench. The experimental results will verify the effectiveness of the proposed method.

Online trajectory shaping strategy for dynamical engine test benches

Virtual vehicle testing on combustion engine test benches is becoming increasingly important to enhance testing speed in the automobile industry. To be able to achieve this target, dynamical test benches must be used which allow reproducing the load conditions on the engine crankshaft as occurring in the real vehicle. Dynamical testing usually consists in tracking speed versus torque profiles, which represent the expected vehicle operation. This also allows testing conditions which can not be measured in a real vehicle, and can lead to the situation in which the dynamics limit of the test bench and of the combustion engines are trespassed. This often leads to a chaotic performance of the test bench and to unreliable results. To cope with this problem we present an online capable algorithm which ensures that the test cycle is inside the performance limits. The algorithms are based on prefiltered design, the computation of feasible sets and of the use of augmented Kalman Filters to enforce feasibility. To prove the efficiency of the approach the algorithms are presented and simulation results are shown

Inverse torque control of hydrodynamic dynamometers for combustion engine test benches

Hydrodynamic dynamometers can be used for the entire range of combustion engines from cart engines up to large ship engines, are inexpensive and have a small moment of inertia. Due to their strong nonlinearities and the absence of precise models, they are still rarely used for dynamic testing. Against this background, this paper proposes an inverse control of an approximate form determined experimentally. As the paper shows using measurements on a dynamic truck engine test bench, the proposed approach is able to offer a significantly better performance with respect to the classical implementation thus opening a new path for the intended use for dynamic testing.

Feed forward disturbance rejection by a multiple FIFO approach for transient operation of an engine test bench

Frequency bandwidth is a critical property of engine test benches, and is becoming the longer the more important especially in view of hybrid vehicle applications. A critical limiting factor of the bandwidth is the damping of the connection between engine and brake. To overcome this limit, a setup consisting of a stiff connection and an active rejection of the torque ripple has been proposed. Based on repeatability of a working cycle of a combustion engine, prediction and rejection of disturbance is possible for a given value of the system delay. However the delay is spread in different operating points, and its value is in general non known and subject to drastic changes during transient operations. This problem is tackled here by resorting to a time-shift adaptation based on a bank of FIFO memories along with a switching rule depending on the transient operating points - as opposed to stationary operating points. The algorithm is tested in simulation and furthermore applied to a real test bench. The results show the effectiveness of the proposed method.

Control oriented modeling of a water brake dynamometer

Water brakes combine high power ratings with a low moment of inertia and in case of high power ratings they are a good alternative to other braking systems. Despite these advantages water brakes are not widely used in dynamic testing as their nonlinearities make them hard to control. Mathematical models of hydrodynamic dynamometers are presented in this paper. A first principles approach is compared with a data-based model and a gray box model. The first principles model is hard to parametrize. In contrast a purely databased linear model is easy to tune but is not able to extrapolate. To increase the extrapolation ability it gets necessary to use a gray box approach which combines the simple structure of a first principles model with a data-based part. The resulting gray box model is best suited to the plant, of simple structure and can be used for the design of a model-based controller.

Adaptive Control of Engine Torque with Input Delays

Abstract Control of the inner engine torque of a combustion engine is very crucial for the overall performance of a dynamical combustion engine test bench. The main problem thereby is the usually unknown system behavior of the combustion engine, the time delay of the accelerator actuator which is used to control the combustion engine. In general the combustion engine is mounted on a combustion engine test bench in order to adjust the parameters of the engine control unit (ECU). Hence the system behavior can change quite fast. In this paper we will present an adaptive approach to control the combustion engine torque. Measurements on a dynamical combustion engine test bench will verify the proposed approach.

Speed control of hydrodynamic dynamometers for internal combustion engine test benches

Hydrodynamic dynamometers are primarily used in stationary testing of large internal combustion engines. They are inexpensive, have a small moment of inertia and cover the entire range of internal combustion engines, so their use for dynamical testing would be interesting, but actually they are not used for this purpose due to the strongly nonlinear behavior. Against this background, this paper proposes a cascaded speed control approach based on an inversion of the output nonlinearities. Available degrees of freedom are used to take into account boundaries on fluid temperatures. Measurements on a dynamic truck engine test bench show that the proposed approach is able to offer a significantly better performance with respect to the standard control, allowing an extension of the application of hydrodynamic dynamometers from purely stationary tests to dynamic testing used e.g. in emission legislation.

Goal oriented experiment planning for the optimal use of dynamical engine test benches

The high performance of dynamic engine test benches allows much freedom in arranging engine tests, thus substantially contributing to accelerating vehicle development. However physical limits restrict this freedom. Exploiting these limits as well as examining their effects on the test planning, was the goal of a cooperation between the Institute for Design and Control of Mechatronic Systems of the JKU Linz, the Linz Center of Mechatronics and the AVL Graz, all Austria.

Improved torque tracking on internal combustion engine test benches equipped with EURO 6-engines

Test benches for internal combustion engines are used for many purposes in the automotive industry with strong advantages in terms of reproducibility and costs. The torque and the speed at the crankshaft of the engine must be tracked simultaneously to simulate the operation of an internal combustion engine in a vehicle. Single-input single-output proportional-integral-controllers are usually used to this end. Additional limitations have been introduced in the Engine Control Unit to meet the continuously strengthened emission levels. Especially, for new engines these limitations lead to significant overshoots in the torque tracking which have to be prevented in any case. The limitations are studied and the impacts to the tracking are analyzed in this paper. The existing proportional-integral-controller is extended based on this analysis. In particular, the controller parameters are scheduled with respect to the change of the torque reference and the tracking error. No model of the plant is required for controller design, the controller parameters can be tuned quickly and easily during the set-up of a test bench. Measurements on a test bench equipped with a passenger car Diesel engine confirm the improvements compared to the industrial standard.