Michael Paulweber

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.

Model-based development methods – What can chassis and powertrain development learn from each other?

The biggest challenge for today’s vehicle development is the increasing number of vehicle variants for different markets, which have to be developed in ever shorter cycles. In addition, customers and governments have high demands when it comes to comfort, driving pleasure, consumption, security and CO2 emissions. The powertrain and the chassis domain have developed their own methods to solve these difficulties. Although there are some important differences, the question arises how one domain can profit from the methods of the other domain. For example, the strict emission legislation in the powertrain sector lead to advanced model-based calibration and testing methods, which could be useful also for other domains.

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.

Virtual reality for automotive radars

Car manufacturers spend quite a lot on the development of driver assistance systems and subsequently on autonomous driving functionality. To ensure the safety and reliability of these functions meet industrial standards it is necessary to verify and validate their functionality. While tests on the road are still the ultimate evidence of correct operation they are associated with huge efforts and risks. Therefore, they have to be complemented by other means like simulations and tests on specialised testbeds. For the latter the car’s sensors have to be stimulated in a way that they perceive a desired – but only virtual – environment. An important type of sensor in cars is the radar due to its various advantages. This article describes the development of a stimulator generating virtual radar targets in order to enable the testing of autonomous driving functions.ZusammenfassungAutohersteller investieren eine hohe Summe in die Entwicklung von Fahrerassistenzsystemen und in autonomes Fahren. Es ist daher notwendig, die sichere und zuverlässige Funktion dieser Systeme zu verifizieren und zu validieren. Dies kann mit Testfahrten auf der Straße erfolgen, was aber mit großen Kosten und hohem Aufwand verbunden ist. Es wird daher daran gearbeitet, zumindest Teile dieser notwendigen Tests mit Simulationen auf Prüfständen durchzuführen. Das Radar ist ein wichtiger Sensor für die erwähnten Systeme, deshalb ist dessen Stimulation von entscheidender Bedeutung. Dieser Beitrag beschreibt die Entwicklung eines Stimulators zur Erzeugung von virtuellen Radarzielen, um autonome Fahrfunktionen auf dem Prüfstand zu testen.

Validation of Highly Automated Safe and Secure Systems

Due to the constantly growing global population and the ageing society, the CO2 production as well as the demand for mobility is constantly rising and hence needs new concepts as offered by advanced driver assistance systems up to fully automated vehicles. If existing approaches were used for these new concepts, the validation of these systems would require unacceptable long validation times and high costs. Therefore, new validation methods are necessary. The extensive use of validation in mixed real and virtual environments together with statistical methods of combinatorial testing offers promising solutions. Standardization of scenarios and learning validation schemes can reduce the validation effort to an acceptable level.

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.