Jean-Paul Hautier

Inversion-based control of electromechanical systems using causal graphical descriptions

Causal ordering graph and energetic macroscopic representation are graphical descriptions to model electromechanical systems using integral causality. Inversion rules have been defined in order to deduce control structure step-by-step from these graphical descriptions. These two modeling tools can be used together to develop a two-layer control of system with complex parts. A double-drive paper system is taken as an example. The deduced control yields good performances of tension regulation and velocity tracking

Control structures for multi-machine multi-converter systems with upstream coupling

A multi-machine multi-converter system formalism has been proposed to describe systems composed of several electrical machines and converters. This description points out coupling elements, which have to distribute energy. Control structures have already been proposed for systems with downstream coupling. This paper is focused on control structures for systems with upstream coupling. Several solutions can be found by moving control blocks.

Multi-machine multi-converter system for drives: analysis of coupling by a global modeling

More and more electrical systems are composed of several electrical machines and several electrical and/or mechanical converters. Such systems are called multi-machine multi-converter systems (MMS) and are described by a specific formalism. Specific coupling structures are defined in order to distribute the energy. Three coupling structures are pointed out in drive applications: electrical, magnetic and mechanical coupling devices. Despite allowing a better energy distribution, these coupling structures also induce also some constraints on power components and some perturbations between the associated conversion chains. Decoupling control strategies may be developed in order to minimize these interactions. Three examples of the different couplings are presented according to this specific formalism.

Torque tracking strategy for antislip control in railway traction systems with common supplies

The traction system of the subway VAL 206 is ensured by DC machines connected in series. A common chopper supplies the armature windings and a double-chopper supplies the field windings. Another power structure is suggested in order to increase performances during losses of adhesion. A specific control strategy is defined in order to obtain different torque on both machines despite their common armature current. An antislip control can thus be developed in applying the desired torque to each bogie at just the right time. This torque tracking strategy is validated on a 1.5 kW experimental set-up.

High performance control of the permanent magnet synchronous motor using self-tuning resonant controllers

The permanent-magnet synchronous motors (PMSM) have been widely used in high-performance variable speed drives. However, any non-ideal conditions, such as nonsinusoidal distributed rotor permanent magnet flux or the cogging effects, may bring on ripples in the output torque. In this paper, we propose to suppress the torque ripple of the PMSM in the stationary reference frame by using self-tuning multiple-frequency resonant controllers. This kind of controller is usually used to track the non-sinusoidal command and/or reject some kind of higher-order harmonic disturbances in AC current control system. We first present how to design the robust self-tuning resonant controller using pole assignment technique, in which the influence of unit time-delay is compensated. After that, the optimal excitation current waveforms are designed to suppress the torque ripples caused by the back-EMF harmonics. The torque ripples can be completely eliminated up to an arbitrary order. By using the self-tuning multiple-frequency resonant controllers, the regulated currents can perfectly track the optimal excitation currents, and the undesired torque ripple is therefore efficiently suppressed. The experimental results confirm the validity and effectiveness of the proposed method

Multi-phase System Supplied by SVM VSI: A New Fast Algorithm to Compute Duty Cycles

Summary Multi-phase drives are more and more often used in industry, especially for high-power applications [17, 18, 20]. Space Vector Modulation (SVM) is now widely implemented and possesses many advantages over carrier-based pulse width modulation (PWM): – natural overmodulation implementation; – easy solution for saturation treatment; – fast and convenient to compute; – easy implementation of switching constraints for example to reduce harmonic currents [19]. Many authors proposed SVM VSI applied to multi-phase drives. For example, [2] and [15] have chosen instantaneous vectors to control dual 3-phase induction machines with low generated harmonic currents, [4] and [6] to control 5-phase machines. The initial space is split onto orthogonal subspaces (d-q and zero-sequence) and the initial reference vector can be expressed at any sampling time in terms of several reference vectors, each one belonging to one subspace (plane and/or line). Each reference vector is located onto a sector, bounded by two active vectors, and decomposed onto these vectors. Once the two vector components are known, duty ratios are determined. Then, zero vectors are chosen and switching sequencing is imposed. Due to the high number of phases, a high number of sectors exist and the location of the different reference vectors leads to a great computational requirement (Fig. 1a). Using the equivalence between a multi-phase machine and a set of fictitious one-phase or two- phase machines which are magnetically independent but mechanically and electrically coupled [1, 13], we propose a new fast algorithm to compute the duty cycles of each VSI leg. This algorithm, based on a vectorial approach of inverters developed in [3, 5, 7, 22], thereby reduces computation time and allows to use low computational requirements. This paper shows that, compared to classical techniques [9, 10, 11, 12], it is no more necessary to find the location of the reference vectors to get explicitly the duty cycle of each leg. Fig. 1 shows the difference between classical algorithm (Fig. 1a) and proposed one (Fig. 1b). This proposed technique is at first illustrated on a 3-phase drive. Geometrical representations allow then to establish links with usual 3-phase SVM. The implementation of the proposed SVM is achieved in the vector control of a 5-phase drive. Experimental results are presented and confirm the theoretical approach.

Minimum Torque Ripple Control of Permanent Magnet Synchronous Motor in the Stationary Reference Frame

To suppress torque ripple caused by non-sinusoidal back electromotive force (EMF), non-sinusoidal currents should be injected into the PMSM. Direct torque control (DTC) has been proposed to achieve this aim. Nevertheless it has many unavoidable drawbacks, especially the large torque ripples produced at low speed. The multiple reference frame theory can be applied to track the desired currents with a number of harmonics, while the control scheme is too complex and requires too many computations. In this paper, we propose a novel approach to suppress the torque ripple of PMSM in the stationary reference frame. A closed form solution is suggested in order to design the optimal excitation current waveforms, with which the torque ripple caused by the back-EMF harmonics up to an arbitrary degree can be completely eliminated. By using the self-tuning multiple-frequency resonant controllers, the regulated currents can perfectly track proposed optimal excitation current waveforms, and the undesired torque ripple is efficiently suppressed. The simulated and experimental results confirm the validity and effectiveness of the proposed approach

Modelling and Axis Control of Machine Tool for High Speed Machining

Abstract The main objective of an efficient axis control is to reproduce on the tool (or the workpiece), the reference wished for machining accuracy. Every process control requires the knowledge of its input-output relationships. One problem is looking for a compromise between a model, a real system and a dynamic control performances. The present paper proposes an energetic approach in which the control specifications are directly deduced from the inversion of the process causalities.

Behaviour model control for cascaded processes: Application to an electrical drive

Behaviour model control (BMC) is known to increase the robustness of a process control. It has already been applied to electrical drives for single-loop controls. This paper introduces the BMC among others model control strategies and extends its single-loop structure to more complex controls, which need several loops. This extension is applied to a double loop control of a DC machine drive. Simulations and experimental results show that the suggested double-loop BMC yields better results than a classical control, increasing robustness against parameter variations and external disturbances.

VIBRATION REDUCTION ABILITIES OF SOME JERK-CONTROLLED MOVEMENT LAWS FOR INDUSTRIAL MACHINES

Abstract Vibration-free positioning is a basic objective in industrial high-speed systems, i.e. systems for which axes are submitted to significant dynamical demands. The focus of this paper is on the pragmatic formalisation of the influence of some jerk-controlled movement laws on the residual vibrations. Analysis of limited-jerk, harmonic-jerk and minimum-jerk laws is conducted on a simplified axis drive model that accounts for axis control parameters and for predominant mode effects. Experimental measurements performed on industrial test-setups demonstrate the effectiveness of the proposed approach in estimating the evolution of the vibration level according to each movement law.