Anton Hofer

Control of an electronic throttle valve based on concepts of sliding-mode control

This paper deals with the design of controllers for electronic throttle valves, which are used in combustion engines for adjusting the air-fuel-ratio. First a simplified model of the throttle valve is presented. Nonlinear phenomena like stick-slip-friction and gear-backlash are neglected. In order to cope with these uncertainties as well with the modelpsilas discontinuous right hand side, concepts of sliding-mode control are applied. A standard integrating sliding-mode controller is opposed to a higher order concept, namely the super-twisting algorithm. Finally experimental results are presented and discussed.

Modelling and analysis of the non-iterative coupling process for co-simulation

Concerning non-iterative co-simulation, stepwise extrapolation of coupling signals is required to solve an overall system of interconnected subsystems. Each extrapolation is some kind of estimation and is directly associated with an estimation error. The introduced disturbance depends significantly on the macro-step size, i.e. the coupling step size, and influences the entire system behaviour. In addition, for synchronization purposes, sampling of the coupling signals can cause aliasing. Instead of analysing the coupling effects in the time domain, as it is commonly practised, we concentrate on a model-based approach to gain more insight into the coupling process. In this work, we consider commonly used polynomial extrapolation techniques and analyse them in the frequency domain. Based on this system-oriented point of view of the coupling process, a relation between the coupling signals and the macro-step size is available. In accordance to the dynamics of the interconnected subsystems, the model-based relation is used to select the most critical parameter, i.e. the macro-step size. Besides a ‘rule of thumb’ for meaningful step-size selection, a co-simulation benchmark example describing a two degree of freedom (2-DOF) mechanical system is used to demonstrate the advantages of modelling and the efficiency of the proposed method.

IM Torque Control Schemes Based on Stator Current Vector

This paper proposes an induction machine torque control derived from the model in the stator current vector reference frame. The required torque is produced by simultaneously manipulating the magnitude and the rotation speed of the stator current vector, thus forcing the rotor flux linkage vector to change implicitly in such a way that overall stability is preserved. Additional control features include maximal torque-per-ampere ratio in steady state and almost perfect command tracking even if the machine is magnetically saturated. The control adopts a cascaded structure and is based on a partial dynamic inversion of the reduced model that assures existence and uniqueness of the inverse mapping between the required torque, the rotor flux linkage vector, and the stator current vector. Singularity at zero rotor flux linkage represents no restriction for the control performance in the admissible machine operating range. The implementation of the proposed control requires the estimation of the torque-producing rotor flux component and cascaded stator current controllers. Experimental results confirm the key expectations and show the potential and benefits of the proposed control schemes.

Non-Holonomy in Induction Machine Torque Control

In this brief, induction machine (IM) torque control is studied as an example of a 3-D non-holonomic integrator including drift terms. By expanding Brocketts controller derived for the driftless systems, a control structure is proposed that provides simultaneous modulation of both the amplitude and the frequency of the sinusoidal stator current vector. Although not explicitly controlled or programmed, the rotor flux linkage vector is implicitly forced to track natural periodic orbits satisfying non-holonomic constraints of the IM. The proposed control assures high dynamics in the torque response, maximal torque per amp ratio during transients and in steady-state and global asymptotic stability. The overall IM control scheme includes cascaded high-gain current controllers based on measured electrical and mechanical quantities together with rotor flux linkage vector estimator. Simulation and experimental results illustrate the main characteristics of the proposed control.

A Process Environment Toolbox for Matlab/Simulink

Abstract The Process Environment Toolbox for MATLAB/SIMULINK has been created to make laboratory experiments with real time control algorithms very easy. The main goal was to augment MATLAB/SIMULINK in such a way that makes it possible to perform control system design and simulations and control experiments with real word plants within the same program. The application of the toolbox to the stabilization of an inverted pendulum by a special type of fuzzy controller is presented.

Guidelines for the Application of a Coupling Method for Non-iterative Co-simulation

Modular simulation requires efficient coupling of the involved subsystems. Subsystems are independently solved and synchronized at coupling time instants. By the commonly used non-iterative coupling approach the extrapolation of some coupling quantities is necessary because of bidirectional dependencies between subsystems. Thus, a coupling step-size dependent coupling error is introduced. Required sampling of the coupling signals may lead to aliasing effects and unintentional discontinuities at coupling time instants occur. A recently developed coupling error compensation approach seems to be able to solve the typical problems concerning non-iterative co-simulation. However, for adequate usage of the available functionalities proper settings of the proposed coupling scheme are mandatory. In this work, the basic nearly energy-preserving coupling approach is explained and significant extensions are proposed. Especially, the resulting enhanced coupling performance enables smoothing of the coupling signals without degradation of the overall system behavior. The resulting effects as well as the specific adjustments are discussed, which leads to supporting parameterization guidelines.

A contribution to the control of the non-holonomic integrator including drift

In this paper a three-dimensional non-holonomic integrator (NI) with drift terms is considered. For this type of plant, the question how to obtain desired piecewise constant output functions with minimum norm control inputs is explored. It is shown that this can be achieved by a nonlinear controller that provides simultaneous modulation of both the amplitude and the frequency of the harmonic input vector. The internal states are implicitly forced to follow natural periodic orbits satisfying the non-holonomic constraints of the plant. Global asymptotic stability and high dynamics in the output response are achieved. The problem of singularity at zero initial state is solved by a time optimal control scheme for the internal states. By combining the nonlinear controller and the time-optimal controller using an appropriate switching strategy, a powerful control concept can be established. The torque control of an induction machine is considered as an illustrative example for the application of the control scheme. Experimental results of the closed loop feedback control system are presented.

A Contribution to Energy Optimal Thermal Management for Vehicles

Abstract Hybrid electric vehicles are regarded as a possible solution for the reduction of pollutant emissions and for improving the fuel economy. Besides the conventional cooling circuit for the engine, hybrid vehicles need cooling for the electrical drives and for the energy storage systems as well. The development of appropriate cooling systems has the consequence that the number of auxiliary components involved, the weight and above all the energy consumption is increased. Therefore in order to minimize the energy consumption an optimal strategy for the operation of the cooling aggregates is required. In this paper an approach for finding the optimal control strategy of the electric auxiliaries over an apriori defined driving cycle is introduced. An energy minimization problem with constraints given by the maximum allowed temperature of the components is stated. This problem is based on a nonlinear mathematical model of the cooling system. It is shown how the nonlinear continuous time model can be equivalently replaced by a suitable linear discrete time model where some of the variables are confined to take integer values. This allows us to cast the optimization problem as a mixed integer linear program. The proposed approach is demonstrated by an example. For this purpose a cooling system is considered where an electrically driven water pump and an electric cooling fan are involved. As a result the optimal interaction of the water pump and the fan is computed such that the energy consumption of these components is minimized subject to given temperature constraints.

Control of an Electronic Throttle Valve for Drive-by-Wire Applications

Electrically actuated control devices for regulating the amount of air entering gasoline engines play an essential role in drive-by-wire applications. In this paper an approach to the control of so-called electronic throttle valves is outlined. First a standard sliding-mode controller is presented. It is shown that the performance of the feedback loop can be improved significantly by incorporating time-variable boundary layers

Two controller reduction methods based on convex optimization

This article outlines two approaches for the computation of a suitable low order controller if a linear discrete-time control system with a high order controller is given. Actually this step is of significant importance in the case of the so-called Q-design procedure and especially in l 1-optimal control system design. Since the main focus during controller reduction is to maintain the performance of the closed loop system this task is quite different from the general order reduction problem and thus requires special methods. In this article two controller reduction methods are presented, which lead to linear programs. It is intended to augment the Q-design approach by a suitable controller reduction step and in this way it should become possible to utilize the full power of Q-design and to get controllers of reasonable order. The performance of the proposed methods is demonstrated by an example.