外文翻譯---壓電液壓驅(qū)動器的設(shè)計和測試（英文）

1、Presented at SPIE Smart Structures and Materials Symposium, Industrial and Commercial Applications of Smart Structures Technology, San Diego, March 2003, Paper No. 5054-11. 1 DESIGN AND TESTING OF PIEZOELECTRIC-HYDRAULI

2、C ACTUATORS Jason E. Lindler, and Eric H. Anderson CSA Engineering Inc., 2565 Leghorn St., Mountain View, CA 94043 Marc E. Regelbrugge Rhombus Consultants Group, 2565 Leghorn St., Mountain View, CA 94043Abstract This pap

3、er describes design methodologies for construction of an actuator that uses smart materials to provide hydraulic fluid power. In the class of actuators described, hydraulic fluid decouples the operating frequency of th

4、e output cylinder from the drive frequency of the piezoelectric or other smart material. This decoupling allows the piezoelectric to be driven at high frequency, to extract the maximum amount of energy from the materi

5、al, and the hydraulic cylinder to be driven at low frequencies to provide long stroke. However, due to fluid compressibility and structural compliance, the fundamental impedance match between the fluid and the piezoel

6、ectric make it difficult to convert energy from the piezoelectric into pressurized hydraulic fluid flow. The basic design tradeoffs and major technical issues are discussed in the areas of materials, mechanical design

7、, and fluid-mechanical interface. Prototype devices and component measurements are presented. Test methods are described, and test results quantifying pump pressure and flow, and actuator force and velocity are summa

8、rized. The series of tests show the potential of these devices for high force long stroke devices powered by smart materials. Keywords: Piezoelectrics, smart materials, piezohydraulic, actuation, power by wire, pumps I

9、ntroduction Smart materials such as piezoelectrics, magnetostrictives and electrostrictives have a long history of use in precision control applications. Because of their limited shape change capability, these material

10、s are not normally used in actuators requiring large linear motion. Over the last several decades there have been dozens of designs that achieve increased motion from smart material cores by various techniques. Among

11、 the common ones are mechanical amplification or transformation, for example those using lever and pivots,1 and step-and-repeat types, for example the Inchworm?.2 More recently, researchers have recognized the potenti

12、al of integrating smart materials and fluids, making the pump a fundamental element to be exploited for linear actuation.3-8 This newer approach holds promise for high power actuation with long stroke. The piezoelectr

13、ic-hydraulic or “piezohydraulic” actuation brings advantages and disadvantages compared to other types of actuation, including conventional servo-hydraulic and various electromagnetic types.9 The primary advantage com

14、pared to traditional hydraulics is the power-by-wire aspect, i.e. the elimination of hydraulic distribution lines. Compared to electromagnetic methods including motor-driven ball screws, the piezohydraulic actuation p

15、rovides the high force of hydraulics and a potentially more rapid response time. The new class of actuators has disadvantages compared to conventional hydraulics in the areas of heat distribution and tolerance for flu

16、id loss. Compared to electromagnetic actuators, the new class, despite the small amount of fluid used, still requires both electrical and hydraulic integration. Many of these features of piezohydraulic actuation are c

17、ommon to electrohydrostatic actuators (EHAs), such as those used on the Joint Strike Fighter. Where piezohydraulic actuation has a potential advantage over other EHAs is in the energy density of the piezoelectric mate

18、rial itself. Extracting this energy is a difficult task, and this paper attempts to describe some of the many challenges in a current development effort. The overall design goal is to convert power input from a piezoe

19、lectric stack element, through various stages, to mechanical power delivered by an actuator output cylinder to an external load. The design starts with the piezoelectric smart material, extends to the piezoelectric-fl

20、uid interface, through valves, and finally to the output cylinder. Electronic drive of the actuator is also a consideration, though it is discussed elsewhere.9 Like many systems, the overall design is an integrated a

21、nd iterative one, where individual components can be designed, but then require redesign to work well with other subsystems. Testing at the component, subsystem and system level aids in Presented at SPIE Smart Structur

22、es and Materials Symposium, Industrial and Commercial Applications of Smart Structures Technology, San Diego, March 2003, Paper No. 5054-11. 2 this process. Tests can be conducted to characterize individual elements, t

23、heir interaction, and their collaboration. Measurement and maximization of total mechanical output of the device (force, velocity, or power) is the ultimate goal. The remainder of the paper describes basic concepts in

24、 solid-fluid actuation, illustrating operation and highlighting limitations. The actuator design concept is presented next, and various key subsystems are described. Important properties of piezoelectrics for this ap

25、plication are considered. Design of the pressurization chamber is addressed and prototype devices are described. The various test approaches, for partial or complete device characterization, are enumerated, with the

26、value of each is highlighted. The paper concludes with test results and interpretation for multiple generations of piezohydraulic devices. Solid-Fluid Hybrid Actuation In more general terms, piezoelectric-hydraulic or

27、smart material-hydraulic actuation can be termed “solid-fluid hybrid” actuation. Energy sent to the smart material produces pressurized fluid. Then mechanical valves rectify the oscillating fluid pressure to create p

28、ressurized fluid flow. With hydraulic accumulators and another valve, the solid element can operate at a frequency different from the frequency required by the load. In general, the solid actuator operates at a frequ

29、ency much higher than that required by the load, perhaps 100 times as high. While theoretically attractive, practical limitations arise that limit the efficacy the solid-fluid hybrid actuation approach.8 In particular,

30、 fluid viscosity and compressibility combine with loss mechanisms inherent in the active material to limit the effective bandwidth of the driving actuator and the total actuator output power. Also, great care must be

31、taken in design to match the characteristics of the driving actuator to the fluid transmission and output actuator if maximum power is to be available to drive the mechanical load. Figure 1 illustrates the generic cla

32、ss of devices considered by the present development. As this figure shows, the device considered here comprises several elements: a solid-state element of stiffness k driving a piston of area A1 to pressurize the worki

33、ng fluid, and fluid passages connecting the pressurization chamber with an hydraulic output cylinder and accumulator volume through four valves. Figure 1: Hybrid solid-fluid actuator concept Figure 2 shows the hybrid ac

34、tuator’s sequence of operation. Valve openings are timed to allow pressurized fluid into one of the output cylinder’s chambers. During the stroke of the solid state actuator, the alternate output-piston chamber is po

35、rted directly to the accumulator volume to allow the output piston to displace different volumes in each chamber. Once the pressurization stroke has reached its limit, valve openings are adjusted to allow the pressuri

36、zation chamber to take fluid in from the low-pressure volume of the output cylinder and the accumulator volume. This displacement of fluid from one side of the output piston to the other moves the piston in the directi