英文版汽车资料.docx

1、英文版汽车资料英文版汽车资料Design considerations for an automotive magnetorheological brake Kerem Karakoca, Edward J. Park, a, and Afzal Sulemana aDepartment of Mechanical Engineering, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC, Canada V8W 3P6 Received 10 October 2007; accepted 22 February 2008

2、. Available online 11 April 2008. Abstract In this paper, design considerations for building an automotive magnetorheological (MR) brake are discussed. The proposed brake consists of multiple rotating disks immersed in a MR fluid and an enclosed electromagnet. When current is applied to the electrom

3、agnet, the MR fluid solidifies as its yield stress varies as a function of the magnetic field applied. This controllable yield stress produces shear friction on the rotating disks, generating the braking torque. In this work, practical design criteria such as material selection, sealing, working sur

4、face area, viscous torque generation, applied current density, and MR fluid selection are considered to select a basic automotive MR brake configuration. Then, a finite element analysis is performed to analyze the resulting magnetic circuit and heat distribution within the MR brake configuration. Th

5、is is followed by a multidisciplinary design optimization (MDO) procedure to obtain optimal design parameters that can generate the maximum braking torque in the brake. A prototype MR brake is then built and tested and the experimental results show a good correlation with the finite element simulati

6、on predictions. However, the braking torque generated is still far less than that of a conventional hydraulic brake, which indicates that a radical change in the basic brake configuration is required to build a feasible automotive MR brake. Keywords: Mechatronic design; Magnetorheological fluid; Aut

7、omotive brake; Magnetic circuit; Finite element analysis; Multidisciplinary design optimization; Brake-by-wire Article Outline 1. Introduction 2. Analytical modeling of MR brake 3. Design of MR brake 3.1. Magnetic circuit design 3.2. Material selection 3.2.1. Magnetic properties 3.2.2. Structural an

8、d thermal properties 3.3. Sealing 3.4. Working surface area 3.5. Viscous torque generation 3.6. Applied current density 3.7. MR fluid selection 4. Finite element modeling of the MR Brake 5. Design optimization 6. Overview of experimental setup 7. Experimental results 7.1. Discussions 8. Conclusion R

9、eferences 1. Introduction The automotive industry has demonstrated a commitment to build safer, cheaper and better performing vehicles. For example, the recently introduced “drive by wire” technology has been shown to improve the existing mechanical systems in automobiles. In other words, the tradit

10、ional mechanical systems are being replaced by improved electromechanical systems that are able to do the same tasks faster, more reliably and more accurately. In this paper, an electromechanical brake (EMB) prototype suitable for “brake-by-wire” applications is presented. The proposed brake is a ma

11、gnetorheological brake (MRB) that potentially has some performance advantages over conventional hydraulic brake (CHB) systems. A CHB system involves the brake pedal, hydraulic fluid, transfer lines and brake actuators (e.g. disk or drum brakes). When the driver presses on the brake pedal, the master

12、 cylinder provides the pressure in the brake actuators that squeeze the brake pads onto the rotors, generating the useful friction forces (thus the braking torque) to stop a vehicle. However, the CHB has a number limitations, including: (i) delayed response time (200300 ms) due to pressure build up

13、in the hydraulic lines, (ii) bulky size and heavy weight due to its auxiliary hydraulic components such as the master cylinder, (iii) brake pad wear due to its frictional braking mechanism, and (iv) low braking performance in high speed and high temperature situations. The MRB is a pure electronical

14、ly controlled actuator and as a result, it has the potential to further reduce braking time (thus, braking distance), as well as easier integration of existing and new advanced control features such as anti-lock braking system (ABS), vehicle stability control (VSC), electronic parking brake (EPB), a

15、daptive cruise control (ACC), as well as on-board diagnostic features. Furthermore, reduced number of components, simplified wiring and better layout are all additional benefits. In the automotive industry, companies such as Delphi Corp. and Continental Automotive Systems have been actively involved

16、 in the development of commercially available EMBs as next generation brake-by-wire technology. These are aimed at passenger vehicles with conventional powertrains, as well as vehicles with advanced power sources, like hybrid electric, fuel cell and advanced battery electric propulsion (e.g. 42 V pl

17、atform). For example, Delphi has recently proposed a switched reluctance (SR) motor 1 as one possible actuation technology for EMB applications. Another type of passenger vehicle EMBs that a number research groups and companies have been developing is eddy current brakes (ECBs), e.g. 2. While an ECB

18、 is a completely contactless brake that is perfectly suited for braking at high vehicle speeds (as its braking torque is proportional to the square of the wheel speed), however, it cannot generate enough braking torque at low vehicle speeds. A basic configuration of a MRB was proposed by Park et al.

19、 3 for automotive applications. As shown in Fig. 1, in this configuration, a rotating disk (3) is enclosed by a static casing (5), and the gap (7) between the disk and casing is filled with the MR fluid. A coil winding (6) is embedded on the perimeter of the casing and when electrical current is app

20、lied to it, magnetic fields are generated, and the MR fluid in the gap becomes solid-like instantaneously. The shear friction between the rotating disk and the solidified MR fluid provides the required braking torque. Full-size image (49K) Fig. 1. Cross-section of basic automotive MRB design 3. View

21、 Within Article The literature presents a number of MR fluid-based brake designs, e.g. 3, 4, 5, 6, 7 and 8. In 4 and 5, Carlson of Lord Corporation proposed and patented general purpose MRB actuators, which subsequently became commercially available 6. In 7, an MRB design was proposed for exercise e

22、quipment (e.g. as a way to provide variable resistance to exercise bikes). More recently, an MRB was designed and prototyped for a haptic application as well 8. In this work, using the Bingham plastic model for defining the MR fluid behavior, its braking torque generation capacity was investigated u

23、sing an electromagnetic finite element analysis. Our previous work 3 E.J. Park, D. Stoikov, L. Falcao da Luz and A. Suleman, A performance evaluation of an automotive magnetorheological brake design with a sliding mode controller, Mechatronics 16 (2006), pp. 405416. Article | PDF (547 K) | View Reco

24、rd in Scopus | Cited By in Scopus (21)3 was a feasibility study based on a conceptual MRB design that included both electromagnetic finite element and heat transfer analysis, followed by a simulated brake-by-wire control (wheel slip control) of a simplified two-disk MRB design. Now, the current pape

25、r is a follow up study to our previous work 3. Here the MRB design that was proposed in 3 is further improved according to additional practical design criteria and constraints (e.g. be able to fit into a standard 13” wheel), and more in-depth electromagnetic finite element analysis. The new MRB desi

26、gn, which has an optimized magnetic circuit to increase its braking torque capacity, is then prototyped for experimental verification. 2. Analytical modeling of MR brake The idealized characteristics of the MR fluid can be described effectively by using the Bingham 10, 11 and 12. According to this m

27、odel, the total shear stress is plastic model 9, (1)where H is the yield stress due to applied magnetic field, p is the no-field plastic viscosity of the fluid and is the shear rate. The braking torque for the geometry shown in Fig. 1 can be defined as follows: (2)where A is the working surface area

28、 (the domain where the fluid is activated by applied magnetic field intensity), z and j are the outer and inner radii of the disk, N is the number of disks used in the enclosure and r is the radial distance from the centre of the disk. Assuming the MR fluid gap in Fig. 1 to be very small (e.g. 1 mm)

29、, the shear rate can be obtained by (3)assuming linear fluid velocity distribution across the gap and no slip conditions. In Eq. (3), w is the angular velocity of the disk and h is the thickness of the MR fluid gap. In addition, the yield stress, H, can be approximated in terms of the magnetic field

30、 intensity applied specifically onto the MR fluid, HMRF, and the MR fluid dependent constant parameters, k and , i.e. By substituting Eqs. (3) and (4), the braking torque equation in Eq. (2) can be (4)rewritten as (5)Then, Eq. (5) can be divided into the following two parts after the integration (6)

31、 (7)where TH is the torque generated due to the applied magnetic field and T is the torque generated due to the viscosity of the fluid. Finally, the total braking torque is Tb = T + TH. From the design point of view, the parameters that can be varied to increase the braking torque generation capacit

32、y are: the number of disks (i.e. N), the dimensions and configuration of the magnetic circuit (i.e. rz, rj, and other structural design parameters shown in Fig. 3), and HMRF that is directly related to the applied current density in the electromagnet and materials used in the magnetic circuit. 3. Design of MR brake In this paper, the proposed MRB was designed considering the design parameters addressed in the previous section. In addition, some of the key practica