A robust multivariable control for an electropneumatic system using backstepping design

International audienceDuring the last twenty years, the parallel development of pneumatic systems and control theory has lead to the implementation of modern control laws in pneumatic devices. This paper deals with the robust control problem of a pneumatic actuator subjected to mass flow leakage inside the servodistributor and load disturbances. The control strategy is based on backstepping design. For this, backstepping is presented in an informal setting. The nonlinear model of the electropneumatic system is presented. This one is transformed to be nonlinear affine model and a coordinate transformation is then related to make possible the implementation of the nonlinear controller. Control laws are developed using backstepping design to control position and pressure. The robustness visa -vis modeling errors and some unknown terms is proved. Finally, the experiment results are presented and discussed

Control design for energy saving

International audienceThis paper presents the interest of including control strategy into electropneumatic design. For this certain experimental results obtained in an electropneumatic process have been presented. Using two servo-distributors leads to a system with one degree of freedom. This opportunity is exploited for in two objectives. The first concerns positioning control and the second attempts to optimise energy efficiency. With this aim an energy optimisation algorithm has been presented. The chosen control algorithm issues from the flatness concept. KEY WORDS nonlinear control, flatness, energy saving, electropneumatic

Hybrid control for switching between position and force tracking

International audienceThis paper is the logical result of previous researches about advanced control in electropneumatic systems. After different works in feedback control of electropneumatic actuators in position tracking [1] or in force tracking [2], this study led about a method to switch between these two different focuses. This question is an important problem in many industrial systems, for example in the case of vehicle active suspension or for pneumatic or hydraulic pliers, fingers and spot welding, fatigue test. Indeed, some dangerous damages could occur when the aim is to move a load near a structure and to apply a force against this structure. The major difficulty is to know when and how to switch between the position control and the force control (this is here the notion of hybrid control). A classical occurrence is due to a static position error when the control algorithm switches from position feedback to force feedback. The result leads very often to an undesirable impact to the structure. KEYWORDS Force / position tracking, hybrid control, pneumatic

Design of a compliant positioning control using an inverse method

International audienceThe design of new system requires generally achieving different objectives. The choice of the right system and control architecture is crucial and they can be judiciously exploited. The proposed approach is dealing with the efficient use of a pneumatic cylinder controlled by two servovalves. The control objectives are independent position and stiffness tracking. A Bond graph approach gives, in a first step, a general methodology to check the accessibility of the specifications on energetic and dynamic criteria. Then a control algorithm issued from the flatness concept and the nonlinear control theory is developed. Simulation and experimental results illustrating the proposed principle are finally presented. Concerning the tracking performance, it is shown that the new strategy does not decrease tracking errors, or the static errors, or the standard deviation in term of position and velocity tracking. The performance of the stiffness control is finally illustrated in simulation

A solution to the stick slip problem for an electropneumatic drive

International audienceThis 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

Limited energy consumption in positioning control of an electropneumatic actuator

International audienceThis paper shows the possibility of using two three-way servo-distributors in place of one five-way for position control of an electropneumatic actuator. Two nonlinear control laws are developed and compared. The aim is to prove the advantage of a multi-input control law in terms of stability and energy consumption due to the flatness property

Strangeness S=−2S=-2 baryon-baryon interactions in relativistic chiral effective field theory

We study the strangeness $S=-2$ baryon-baryon interactions in relativistic chiral effective field theory at leading order. Among the 15 relevant low energy constants, eight of them are determined by fitting to the state of the art lattice QCD data of the HAL QCD Collaboration (with $m_\pi=146$ MeV), and the rest are either taken from the study of the $S=-1$ hyperon-nucleon systems, assuming strict SU(3) flavor symmetry, or temporarily set equal to zero. Using the so-obtained low energy constants, we extrapolate the results to the physical point, and show that they are consistent with the available experimental scattering data. Furthermore, we demonstrate that the $\Lambda\Lambda$ and $\Xi N$ phase shifts near the $\Xi N$ threshold are very sensitive to the lattice QCD data fitted, to the pion mass, and to isospin symmetry breaking effects. As a result, any conclusion drawn from lattice QCD data at unphysical pion masses (even close to the physical point) should be taken with caution. Our results at the physical point, similar to the lattice QCD data, show that a resonance/quasi-bound state may appear in the $I=0$ $\Lambda\Lambda$/$\Xi N$ channel.Comment: 20 pages, 8 figure

An accurate tracking control of an electropneumatic actuator

International audienceSynopsis: Due to low cost, clean working environments, linear power transfer facilities and good performance, pneumatic systems play a significant role in industrial processes. During the last twenty years, the parallel development of pneumatic systems and control theory has lead to the implementation of modern control laws in pneumatic devices [Edge 1997]. The aim of this paper is to present and to compare experimental results for an electropneumatic positioning system. A classical linear control law with scheduling gains, established with the tangent linearized model, is compared with a more sophisticated nonlinear control law based on input-output linearization [Isidori 1989]. The tests are realised with two different admissible trajectories. The first one is a trajectory with a constant stage, which is usually used in robotic, to control painting system for example. The second one is a trajectory with constant acceleration and deceleration stages, often used for positioning systems which carry delicate loads or dangerous liquids in containers (as in the chemical industry). This choice of the trajectories has also to be related to a problem of sizing. The experimental results are presented in terms of repeatability for each control law implemented on the same device: an in line electropneumatic servo-drive. The statistical comparisons between nonlinear and linear control laws are shown in terms of static error: mean value, standard deviation value, minimum and maximum values. The precision and the repeatability are deduced from these results. All these indicators are also processed during the dynamical stage. The customer for choosing an appropriate control law for its desired specifications may use all these results

A bond graph representation of an optimal control problem: the example of the DC motor

International audienceOptimization has become of great importance in present day Systems Engineering. Also, bond graph language proves to be a very efficient tool for modelling, analysing and designing mechatronic systems from an energy and dynamic point of view. The idea presented in this paper is to combine an optimization formulation in the optimal control context with bond graph language. The objective is to transpose the optimization problem into bond graph formalism so that its exploitation will solve this optimization problem. This paper, being a primary investigation, restricts itself to an optimal control problem formulation applied to the example of the classical DC motor. Developments are based on the use of Pontryagin's classical Maximum Principle where the cost function is expressed as the integral of a quadratic form of the state space vector and the control input to be determined. This type of expression may correspond to a certain energy loss-minimization. It is shown that the formulation of this optimal control problem in bond graph makes logical use of the adjoint system concept. Later variable mapping enables an augmented bond graph representation of the whole problem to be set up. Finally the bicausality assignment to this augmented bond graph representation furnishes the solution to the optimal control problem under consideration

Adaptive Higher Order Sliding Modes for Two-Dimensional Derivative Estimation

International audienceIn this paper, some recent technical of the derivatives noisy transient signals estimation is extended to the two-dimensional case. This technique, which called higher order sliding modes is mostly used in the synthesis of robust controllers and is also shown a good results in the synthesis of the rth order robust dierentiators. In this work, such dierentiators are used as an edge detection method into image application. The proposed algorithm use an adaptive mechanism for tuning up its parameters in real time, in order to increase the efficiency of basic scheme. Some comparative study with a conventional methods of edge detection is performed