Serge Scavarda

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.

Bond graph representation of multibody systems with kinematic loops

Abstract In this paper we propose a procedure for building bond graph representations of multibody systems with kinematic loops. It is systematic in the sense that no analytical derivation is necessary to construct the bond graph. It also gives a more graphically and analytically exploitable representation compared to the Tiernego and Bos procedure. Our method first considers the kinematic loops globally before building the body bond graphs. Therefore we have to detect a privileged frame for each kinematic loop in which we can express the kinematic constraint. Then we construct the corresponding junction structures of bodies whose variables are projected onto those privileged frames. After having presented criteria and a method for selecting the latter, two examples are given: the forming machine and the flyball governor.

A planar mechanical library in the AMESim simulation software. Part I: Formulation of dynamics equations

Abstract This paper presents the mathematical developments of a planar mechanical library implemented in the AMESim simulation tool. Body and joint components are the basic components of this library. Due to the library philosophy requirements, the mathematical models of the components have required a generic vector calculus based formulation of the constraint equations. This formulation uses a set of dependent generalized coordinates. The dynamics equations are obtained from the application of Jourdain’s principle combined with the Lagrange multiplier method. The body component mathematical models consist of differential equations in terms of the dependent generalized coordinates. The joint component mathematical models are based on the Baumgarte stabilization schemes applied to the geometrical, kinematic and acceleration constraint equations. The Lagrange multipliers are the implicit solution of these Baumgarte stabilization schemes. The first main contribution of this paper is the expression of geometrical constraints in terms of vectors and their exploitation in this form. The second important contribution is the adaptation of existing formulations to the AMESim philosophy.

A planar mechanical library in the AMESim simulation software. Part II: Library composition and illustrative example

Abstract This paper presents the composition of a planar mechanical library for the simulation tool AMESim. This library is composed of 5 body components: one fixed to the frame of reference and the four others corresponding to moving bodies with one to four connecting ports. These body components may be connected to any of the joint components defined in the library. There are four basic joint components for: (1) a translational joint, (2) a revolute joint, (3) a double translational joint, (4) a double translational-revolute joint. Actuated versions of the translational and revolute joints are also available. Two more joint components are also defined for coupling perpendicular motion planes. Finally four more specific components enable a linear actuator in planar motion, a spring-damper, a one dimension to two dimensions coupling and a given action to be modeled. The use of this planar mechanical library is illustrated using the example of a seven-body mechanism.

Equilibrium set investigation using bicausality

The introduction of the bicausality concept in the bond graph language has allowed new analytical methodologies, for instance in the context of model inversion, mechatronic system sizing and control. The bicausality concept is here applied for solving the equilibrium state of a mechatronic system. We propose a new method, which permits us to determine the size of the equilibrium set and the algebraic system to be solved. The proposed method is applied to linear systems in a first step, and a generalization is also given for some non-linear systems. Several examples are included in order to explain the method.

A procedure to match bond graph and scattering formalisms

Abstract A procedure is discussed that matches bond graph formalism to the scattering formalism which is convenient in power transfer analysis. Various concepts of scattering formalism are introduced with the aid of a simple example of interaction between two physical systems represented by bond graphs. The “reduced bond graph” is then defined and a procedure is developed to derive the scattering relations from this reduced graph. This procedure, which links the bond graph formalism to the scattering formalism provides the “analyst” with a bond graph-based complementary tool for the investigation of the power distribution in physical systems.

Alternative Causality Assignment Procedures in Bond Graph for Mechanical Systems

This paper proposes to extend the set of causality assignment procedures. The proposed alternative procedures are mainly inspired by formulations developed in the mechanical domain. They enable Lagrange equations, Hamilton equations, and Boltzmann-Hamel equations to be obtained, as well as formulations with the Lagrange multipliers. In the context of system modeling a varied set of mechanical oriented equations are available in a systematic way from the bond graph representation and the proposed corresponding procedures provide an algorithmic frame for programming these mathematical formulations. The graphical features of the bond graph tool and the causality stroke concept enable formulations to be methodically obtained, formulations that can otherwise be very awkward to express. Also these procedures emphasize certain interesting properties of the bond graph tool e.g.: there is a clear distinction between the energy topology of a system and its dynamic equations; it also enables graphic structural analyses to be undertaken; and finally it can play a pedagogical role in engineering education.

Simulation of the nonlinear behavior of an electrohydraulic exciter

This paper presents a computer simulation of the non linear behavior of an electrohydraulic exciter. The experimental results and the simulated results are compared. The model used takes into account the nonlinearities of the two-stage servovalve and the jack. Major nonlinearities included in the simulation are torque- motor hysteresis, flow forces acting on the servovalve spool, the pressure-flow relationships in the orifices (particularly near the null region), compressibility of the hydraulic fluid, clearance of the mechanical feedback link, fluid leakages, sticking forces, and variations of dead volumes.

A Dynamic Sizing Methodology in the Context of an Automotive Application

This paper deals with the application of a dynamic sizing methodology for car suspensions for different given aims of dynamic behavior aims in braking situations. The methodology is based on the establishment of the inverse model from the bond graph representation of the system by using the bicausality concept. By means of an automotive car suspension example and for specific dynamic trajectories imposed on the inverse model, we show how information on the system variables can be obtained in a dynamical sizing phase.Copyright

Design of an actuating system using Inverse bond graph methodology: Application of FEM to a tow-links flexible manipulator

This paper traits the application of Bond graph approach for the design of an flexible manipulator and it focuses particularly on determining the size of the components for proper operation of the overall system based on dynamic and energy criteria. A numerical approximation method for distributed parameters systems (DPS) is used to represent the flexible links of the robot. The bond graph representation is used to keep a physical-based approach and in order to carry out structural analysis on the system. The proposed method is then applied to validate the actuators of a two-link manipulator for a specified trajectory.