Kerem Karakoc

Bio: Kerem Karakoc is an academic researcher from University of Victoria. The author has contributed to research in topics: Magnetorheological fluid & Torque. The author has an hindex of 5, co-authored 6 publications receiving 293 citations.

Optimized Braking Torque Generation Capacity of an Eddy Current Brake With the Application of Time-Varying Magnetic Fields

Abstract: Unlike conventional hydraulic brakes (CHBs), eddy-current brakes (ECBs) are electrically controlled and noncontact-type actuators. Having such advantages makes ECBs a potential alternative to the conventional systems used in vehicles. However, the braking torque generation of ECBs at low speed is insufficient to stop the vehicle. Thus, such brakes are used for assistive braking. Our previous study showed that braking torque increases with an ac field application compared with the torque generated with a dc field application. To increase the braking torque generation to realize a stand-alone ECB, the braking torque generation of the ECB is optimized, using a stochastic search algorithm, with the consideration of comfort and skin effects, as well as geometric and field-dependent factors. The results show that the application of an ac field with varying frequency on a configuration with multiple pole projection areas (PPAs) results in a significant increase in the braking torque compared with the dc field application, and such optimum ECB configuration can generate a sufficient amount of braking torque comparable with those generated by CHBs.

Application of SEUMRE global optimization algorithm in automotive magnetorheological brake design

Abstract: In this paper, the superior performance of a novel space exploration and unimodal region elimination global optimization algorithm, SEUMRE, is demonstrated through comparisons with other well known global optimization techniques, including genetic algorithm (GA), simulated annealing (SA), and a highly nonlinear design problem--the optimal design of automotive magnetorheological brake (MRB). Unlike the conventional brakes, an MRB employs the interaction between a magnetorheological fluid and an applied magnetic field to generate the retarding braking torque. The SEUMRE design optimization algorithm was used to maximize the braking torque and minimize the weight of the brake structure. The computation time and optimized design parameters illustrated SEUMRE's capability to converge to an accurate result faster than the conventional global optimization methods. However, SA provided significantly better optimization results than GA and SEUMRE in terms of the cost function.

Optimal design of an automotive magnetorheological brake considering geometric dimensions and zero-field friction heat

Abstract: This paper presents an optimal design of a magnetorheological (MR) brake for a middle-sized passenger car which can replace a conventional hydraulic disc-type brake. In the optimization, the required braking torque, the temperature due to zero-field friction of MR fluid, the mass of the brake system and all significant geometric dimensions are considered. After describing the configuration, the braking torque of the proposed MR brake is derived on the basis of the field-dependent Bingham and Herschel–Bulkley rheological model of the MR fluid. The optimal design of the MR brake is then analyzed taking into account available space, mass, braking torque and steady heat generated by zero-field friction torque of the MR brake. The optimization procedure based on the finite element analysis integrated with an optimization tool is proposed to obtain optimal geometric dimensions of the MR brake. Based on the proposed procedure, optimal solutions of single and multiple disc-type MR brakes featuring different types of MR fluid are achieved. From the results, the most effective MR brake for the middle-sized passenger car is identified and some discussions on the performance improvement of the optimized MR brake are described.

A geometrical optimization of a magneto-rheological rotary brake in a prosthetic knee

Abstract: Magneto-rheological (MR) fluids have been successfully introduced to prosthetic devices. One such device is a biomechanical prosthetic knee that uses MR fluids to actively control its rotary stiffness. The brake is rotational, utilizing the MR fluid in shear mode. In this study, the geometrical design of the MR brake is addressed. This includes the design of the magnetic circuit and the geometry of the fluid chamber. Mathematical models are presented that describe the rotary torque of the brake. A novel perfluorinated polyether (PFPE)-based MR fluid is introduced, whose properties are tailored for the prosthetic knee. On-state and off-state rheological measurements of the MR fluid are presented. The finite element method is used to evaluate the magnetic flux density in the MR fluid. The design is formulated as an optimization problem, aiming to maximize the braking torque. A parametric study is carried out for several design parameters. Subsequently, a multi-objective optimization problem is defined that considers three design objectives: the field-induced braking torque, the off-state rotary stiffness and the weight of the brake. Trade-offs between the three design objectives are investigated which provides a basis for informed design decisions on furthering the success of the MR prosthetic knee.

A novel high-torque magnetorheological brake with a water cooling method for heat dissipation

Abstract: The extremely severe heating of magnetorheological (MR) brakes restricts their application in high-power situations. This study aims to develop a novel MR brake with a high-torque capacity. To achieve this goal, a water cooling method is adopted to assist in heat dissipation. In the study, a structural model design of the high-torque MR brake is first developed according to the transmission properties of the MR fluid between the rotating plates. Then, the operating principle of the MR brake is illustrated, which is followed by a detailed design of the water channel. Moreover, theoretical analysis, including the transmitted torque, magnetic field and thermal analysis, is performed as well. After this, an experimental prototype of the proposed MR brake is fabricated and assembled. Then the torque transmission and heat dissipation of the prototype are experimentally investigated to evaluate the torque transmission properties and water cooling efficiency. Results indicate that the proposed MR brake is capable of producing a highly controllable brake torque, and the water cooling method can effectively assist in heat dissipation from the MR brake.