Christoph Voser

Analysis and control of high sideslip manoeuvres

This paper presents simple analytical techniques that are used to understand and control high sideslip drift manoeuvres of road vehicles. These are manoeuvres in which a skilled driver stabilises a vehicle beyond its limits of handling, an operating regime responsible for major safety concerns in everyday driving. An analysis of the equilibria of a bicycle model with nonlinear tyres reveals the existence of unstable ‘drift equilibria’ corresponding to cornering at high sideslip angle in a countersteer configuration. Equipped with this information, linearisation about a desired drift equilibrium is used to design a controller that stabilises the vehicle at the equilibrium. The controller is subsequently implemented on a steer- and drive-by-wire testbed and successfully used to achieve autonomous drifts.

Optimal Energy Management and Sizing for Hybrid Electric Vehicles Considering Transient Emissions

This paper investigates the influence of considering transient emissions in diesel hybrid electric vehicles (HEV) on the global optimal energy management strategy (EMS). First, we developed a framework to account for transient emissions in dynamic programming using a simple dynamic emission model adopted from literature. Second, we compared the behavior of three different EMSs which minimize i) fuel, ii) fuel and quasi-static emissions, and iii) fuel, static and transient emissions. Third, we analyzed the total emission reduction potential under use of those three strategies for different sizes of the electric motor in a diesel parallel HEV. The emissions considered in the simulations are nitrogen oxide (NOx) and particulate matter (PM). We found that an EMS accounting for fuel consumption, static and transient emissions can yield a significant lower fuel consumption for a given level of exhaust emissions than an EMS considering only fuel consumption and quasi-static emissions. Moreover, finding the optimal size of the electric motor in the parallel HEV did not require to consider emissions to achieve maximum fuel consumption and emission reduction potentials.

In-cylinder boosting of turbocharged spark-ignited engines. Part 1: Model-based design of the charge valve

Downsizing and turbocharging for retaining the maximal power is a widely used approach to decrease the fuel consumption of spark ignited engines. In general, the trade-off is a substantial driveability loss. In-cylinder boosting has proven to be an effective way to eliminate this problem. Thus far, expensive and complex fully variable valve-trains have been proposed for the air exchange between the air tank and the combustion chamber. This paper is the first of a two-part study that examines the use of a deactivatable camshaft-driven valve with respect to the achievable transient engine performance. The system characteristics and limitations are discussed by using a mean value engine model that is adapted for in-cylinder boosting. A model-based design framework is presented which links the valve system design to a desired engine performance. The companion paper covers control issues and provides experimental verifications.

In-cylinder boosting of turbocharged spark-ignited engines. Part 2: Control and experimental verification

Downsizing and turbocharging is a common approach to improve the fuel economy of spark-ignited combustion engines. However, the inherent turbo lag results in a loss of driveability. In-cylinder boosting is an effective way to eliminate this problem. In the first part of this two-part study, a deactivatable camshaft-driven valve controlling the air mass flow from a pressurised air-tank directly into the cylinder was proposed as the main actuator of such a system, where also a model-based design procedure was demonstrated. In this paper, the torque control during the turbo lag compensation is discussed. The control is complicated by the limited variability of the mechanical valve-train. This limited variability gives rise to a trade-off between fuel and pressurised air consumption. However, the proposed control strategy minimising the consumption of pressurised air (thereby minimising the space required for the pressurised air tank), causes only a small penalty in fuel consumption. This air-mass-based control strategy actuating the throttle, ignition timing and boost mode timing is analysed in simulation and then verified experimentally in various operating conditions.

The pneumatic hybridization concept for downsizing and supercharging gasoline engines

Extensive fundamental research at ETH Zurich has yielded the world’s first fully functional hybrid pneumatic engine. The pneumatic hybridization of gasoline engines primarily aims at maximal downsizing and increased driveability with minimal additional cost. When comparing engines with the same maximum power, the presented engine system proves to be up to 35 % more efficient on the NEDC.

Rapid Start of Hybrid Pneumatic Engines

Abstract Downsized and supercharged hybrid pneumatic vehicles may prove to be a viable and cost-efficient alternative to hybrid electric vehicles since they offer an almost as high fuel saving potential. One part of the fuel saving potential for this concept originates from the start/stop capability. This paper shows that the pneumatic motor mode can be used to start the engine rapidly enough to justify the use of a start/stop functionality. The paper presents fundamental considerations that have to be made for various possible hardware structures. A physics based model is introduced that describes the pneumatic start dynamics for any number of cylinders and any kind of valve profiles. Based on the validated model, the pneumatic engine start has been optimized and the optimal actuations have been implemented at the testbench for the engine under consideration. The experiments were carried out on a downsized and supercharged hybrid pneumatic prototype engine with two cylinders. It was shown that the engines idling speed (1200 rpm) can be reached within 310 ms for a tank pressure of 10 bar.

DAS DOWNSIZING-BOOST-KONZEPT AUF BASIS DER PNEUMATISCHEN HYBRIDISIERUNG VON OTTOMOTOREN

Nach erfolgreich abgeschlossenen Grundlagenuntersuchungen stellt die ETH Zurich den weltweit ersten vollfunktionalen pneumatischen Hybridmotor vor. Die pneumatische Hybridisierung von Ottomotoren dient in erster Linie dazu, mit minimalen Zusatzkosten ein maximales Downsizing zu ermoglichen. Dies erfolgt bei gleichzeitiger Verbesserung des Ansprechverhaltens. Fur dieses Motorkonzept konnte, bei gleicher Nennleistung, ein Verbrauchsvorteil von bis zu 35 % im NEFZ nachgewiesen werden.

System Design for a Direct-Boost Turbocharged SI Engine Using a Camshaft Driven Valve

Downsizing and turbocharging for retaining the maximal power is a common approach to improve the fuel economy of SI internal combustion engines. Due to the additional turbocharger dynamics, small engines suffer from a significant time lag of the torque build-up. The injection of pressurized air into the combustion chamber during the compression phase, also called direct-boost, can recover the driveability. Thus far, expensive and complex fully variable valve-trains have been proposed for the air exchange between the air tank and the combustion chamber. In this paper, a direct-boost system using a camshaft driven valve is designed. An appropriate control strategy is presented. The transient performance of the complete system and the feasibility of the control strategy are demonstrated on a modified 0.75 l turbocharged two-cylinder test bench engine.