Application Modeling and Simulation of a new Hydraulic Piezo Valve

Transcription

1 Application Modeling and Siulation of a new Hydraulic Piezo Valve Introduction and Overview This study is related to the iproveent of hydraulic drives perforances for circuit-breaker. The response tie is a ajor characteristic for the circuit-breaker control. Usually, solenoids are used for their activation. They have an iportant idle period (a few s), which is a ajor disadvantage. The use of piezoelectric syste is an alternative way to iprove the response tie. Their very large bandwidth allows very short response tie (about 1s even less). The idle period is consequently reduced. Contrary to the solenoids, their control is delicate. This is why their study in the shape of a virtual prototype is particularly interesting. Figure 1: Hydraulic Piezo Valve ounted on a hydraulic drive for circuit-breaker application (Source: ETNA Industrie) Multi-doain Model Representing of the physical behavior by signal blocks and 2D-Maps Association of specific eleents and standard eleents odel allows to perfor several configurations Effect of paraeters can be studied It is also necessary to develop specific odels to study precisely the whole coand. Various odels have been developed to deterine the behavior of: the piezoelectric valve; the whole hydraulic coponents, taking into account dynaics of these coponents. static and dynaic behavior can be optiized Modeling of Control valves Using Signal Blocks and 2D-Maps During opening transitional stages, the control valves have a dynaics which represents balance between: Effects of inertia; Hydraulic forces; Return spring force. Control valve opening, pressure drop and flow rate are cobined together. The use of signal blocks and 2D-Maps allows representing this physical behavior, and so building this coponent behavior. A finite eleent odel is then used to deterine the hydraulic characteristics of the check valve (see Figure 2).

2 Page 2 of 5 Figure 2: Finite Eleent Siulation of control valve: Left: Velocity vector Right: Pressure field These calculations have been lead for several values of opening and pressure drop. It allowed establishing a 2D-Map giving the hydraulic forces value versus the control valve opening and to the pressure drop. Throttle valve properties give us the choice between various flow description odels. A very suitable odel has been chosen aong this list. The finite eleent calculation allowed to adjust the paraeters of the chosen odel. This set of results gives a description of the control valve hydro-echanical behavior (see Figure 3). Figure 3: Siulation odel of control valve, including dynaic, using signal blocks and 2D-aps for describing the hydraulic force and the flow description

3 Page 3 of 5 Figure 4: SiulationX not only offers coprehensive libraries for physical odeling, it also includes a large library of signal blocks Modeling of piezoelectric valve Piezoelectric aterials are crystalline solids whose asyetric structures create an electric dipole oent in the crystal lattice, which is sensitive to both elastic strain and applied electrical field. Stresses and Strains are related to each other by the Young's odulus of the ceraic. In addition, a stress generates an electrical field through the inverse piezoelectric effect. Since the ceraic is a dielectric ediu, the electrical displaceent is related to the electrical field. These relationships can be cobined in several sets of equations. Static behavior of piezoactive valves: The displaceent U is in the priary interest: it depends on both the applied voltage V and the generated force: NV F U = where N is the force factor of the actuator and is the stiffness. Dynaic behavior of piezoactive valves: If either the applied voltage or the external force varies with the tie, the displaceent still follows the excitations until dynaic behaviors appear. The previous relationships reain valid in the quasistatic bandwidth, which is liited by about half the resonance frequency f r 0 : f r 0 = 1 2π where is the effective ass of the piezoelectric valve

4 Page 4 of 5 At resonance, considering constant voltage aplitude, displaceents are agnified by the echanical quality factor U 0 = Q NV Q : This phenoenon is taken into account through a daper. Figure 5: Siulation odel of a piezoelectric valve. The odel deonstrates the possibility of taking into account: - Static behavior of the coponent - Dynaic behavior of the coponent Figure 6: Coparison between experiental results (on the left Source: CEDRAT Technologies) and siulation results for the piezoelectric in Figure 5 (on the right). The electric voltage is turned on at t=0.2s and turned off after 25s. The ain characteristic of piezoelectric actuators is their very sall response tie. In this exaple, the axiu displaceent is obtained after about 1s.

5 Page 5 of 5 Modeling of entire circuit-breaker Once the specific eleents have been developed, they can be associated with standard eleents of the library. This allows building the odel of the hydraulic circuit-breaker. Figure 7: Model of a hydraulic circuit-breaker, actuated by a hydraulic piezo valve. This odel allows perforing several configurations of the coand. Effect of paraeters such as strokes, clearances, friction, asses can be studied. Choices could have been ade for an optial design of the circuit-breaker piezo valve. SiulationX A potential solution for odeling of piezoelectric actuators Coprehensive libraries for signal block odeling as well as for hydraulic circuit odeling Efficient integration of electronic, agnetic, echanical (1D/3D), hydraulic, pneuatic and theral coponents in one odel Open odeling environent: all eleents can be extended or new eleents can be created using the object-oriented odeling language ITI -MDL together with the ITI TypeDesigner Suary of the project task written by Mr. P. Martini and Mrs. M.A. Meyer-Warnod, under direction of Dr. C. ühl, Ecole Nationale Supérieure d Arts et Métiers (ENSAM Paris), Service Production, Recherche et Développeent (PRD), research progra with ETNA Industrie, 81 pages, June 2004