Daniel Thomasset

Control of an electropneumatic actuator: comparison between some linear and non-linear control laws

Abstract The aim of this paper is to present and to compare some linear and non-linear control laws for an electropneumatic positioning system both for point-to-point control and for tracking control. The experimental results are presented in terms of repeatability for each control law implemented on the same device: an in-line electropneumatic servo-drive. Different kinds of model, namely a non-linear affine model, linearized tangent model and a reduced linearized tangent model, are presented to synthesize the different control laws. For this a new mathematical modelling of the servo-distributor flow stage is described.

Influence of the process design on the control strategy: application in electropneumatic field

Abstract This article proposes an example of electropneumatic system where the architecture of the process is modified with respect to both the specifications for position and velocity tracking and a criterion concerning the energy consumption. Experimental results are compared and analyzed using an industrial bench test. For this, a complete model of the system is presented, and two kinds of nonlinear control laws are developed, a monovariable and a multivariable based on the flatness theory.

Physical model-based inversion in control systems design using bond graph representation:

Abstract In Part 1, a graphical and physical approach to the inversion of dynamic systems using the bond graph representation was presented. Two applications of inverse bond graph models are presented in this paper: the sizing of actuators for the control of a given system with pre-defined output performance specifications and the zero-dynamics analysis of a system from a physical viewpoint.

Optimal control problem in bond graph formalism

This paper presents a new way to derive an optimal control system for a specific optimisation problem, based on bond graph formalism. The procedure proposed concerns the optimal control of linear time invariant MIMO systems and can deal with both cases of the integral performance index, these correspond to dissipative energy minimization and output error minimization. An augmented bond graph model is obtained starting from the bond graph model of the system associated with the optimal control problem. This augmented bond graph, consisting of the original model representation coupled to an optimizing bond graph, supplies, by its bicausal exploitation, the set of differential-algebraic equations that analytically give the solution to the optimal control problem without the need to develop the analytical steps of Pontryagins method. The proof uses the Pontryagin Maximum Principle applied to the port-Hamiltonian formulation of the system.

Robust position control of an electropneumatic system using second order sliding mode

First order sliding mode control is an important robust control approach. For the class of systems to which it applies, first order sliding mode controller provides a systematic approach to the problem of maintaining stability and consistent performance in the face of modeling imprecision. On the other hand, the chattering phenomenon is one of the major problems in first order sliding mode control. This paper introduces a second order sliding mode control approach in the context of position control of an electropneumatic system. The main objective is to demonstrated through this approach the undesired chattering phenomenon can he avoided while retaining the same robustness of first order sliding mode control.

A Solution to the “Stick-Slip” Problem for an Electropneumatic Drive

Abstract This paper describes a solution to the problem of “stick-slip” for an electro-pneumatic system. The phenomenon of “stick-slip” may appear during the mechanical static state when the position is fixed but the pressures continue to evolve in each actuator chamber, until exceeding the dry friction zone. The system is then in partial equilibrium. The idea to avoid this phenomenon is a switching control law between the tracking position control and the pressure regulation.

HYBRID FORCE CONTROL WITH ON/OFF ELECTROPNEUMATIC STANDARD DISTRIBUTORS

Abstract This paper presents a new control method applied to the electro-pneumatic field. This strategy originates from the hybrid control theory recently developed for the control of asynchronous or synchronous electrical motors, e.g. Retif (2004). The interest of this strategy concerns the possibility of using standard on/off distributors instead of the usual servodistributors (components issued from proportional technology) for the force control of a pneumatic cylinder. Distributor components have less performance but are cheaper than a servodistributor. The aim is to obtain, with a distributor, the same performances as servodistributors on the global system. Based on both cylinder and distributor models, the hybrid control presented here chooses the best state for each on/off distributor to reach the desired force value. Experimental results are presented and discussed.

Determination of Essential Orders From a Bond Graph Model

The notion of essential orders was first introduced for the handling of decoupling problems. This paper focuses more on their interpretation, namely on the fact that each essential order corresponds to the highest time-differentiation order of a specific output appearing in the inverse model. During inverse modeling, this can in particular be useful for checking whether the specifications are appropriate to the structure of the given model. The aim of this paper is to define two procedures to graphically determine the essential orders directly from a bond graph (BG) model of a linear time-invariant system. Their usefulness is then justified in the context of a bond-graph based methodology for design problem analysis.

Nonlinear Passivity Based Control Law with Application to Electropneumatic System

Abstract This paper presents a synthesis of a nonlinear controller to an electropneumatic system. Nonlinear passivity based control law is applied to the system under consideration. First, the nonlinear model of the electropneumatic system is presented. It is transformed to be a nonlinear affine model and a coordinate transformation is then making possible the implantation of the nonlinear controller. A nonlinear control law is developed to track desired position. Experimental results are also presented and discussed.

On the role of essential orders on feedback decoupling and model inversion : bond graph approach

The essential orders have an important role in the study of the systems decouplability as well as in the inverse model characterization. The aim of this paper is first to define essential orders on the bond graph model. Secondly, static and dynamic decoupling by bond graph approach is discussed and the dynamic extension order is defined. Finally, the dynamic compensation is physically located on the bond graph model and an approach to synthesize a model statically decouplable is suggested in order to define an adequate structure to the control requirements.