CONTACTLESS EDDY BRAKING SYSTEM P.Krishnan 1, A.Rex kerpy 2, A.Ranjith kumar 3, B.Ravi kumar 4, S.Rogith sabari 5 1 Assistant Professor, 2,3,4,5 UG Scholar, 1, 2,3,4,5 Department of Mechanical Engineering, K.S.R. College of Engineering Tiruchengode. ABSTRACT Electromagnetic braking systems use electronic and magnetic power to apply wheel brakes. Our system utilizes concept of electromagnetism in order to achieve braking without friction. Eddy braking improves reliability &life of brakes since y do not wear out over time due to friction. This needs comparatively very less maintenance and no oiling. This leads to a very low maintenance cost due to no friction and no oiling. Also traditional braking systems are prone to slipping while this one is guaranteed to apply brakes to vehicle. So without friction or need of lubrication this technology is a preferred replacement for traditional braking. Also it is quite smaller in size compared to traditional braking system. KEYWORDS 1. Electromagnets 2. DC Motor 3. Battery 4. Supporting Frame 5. Wheel. INTRODUCTION When electromagnets are used, control of braking action is made possible by varying strength of magnetic field. A braking force is possible when electric current passed through electromagnets. The movement of metal through magnetic field of electromagnets creates eddy currents in discs. These eddy currents generate an opposing magnetic field, which n resists rotation of discs, providing braking force. The net result is to convert motion of rotors into heat in rotors. EDDY CURRENTS A metal sheet moving to right under a magnet, illustrating how linear eddy current brake work. In drawing magnet is drawn spaced apart from sheet to reveal vectors; in an eddy current brake magnet is normally located as close to sheet as possible
BRAKE STRUCTURE The braking force of an eddy current brake is exactly proportional to velocity V, so it acts similar to viscous friction in a liquid. The braking force Eddy currents (I, red) induced in a decreases as velocity decreases. When conductive metal plate (C) as it moves to conductive sheet is stationary, right under a magnet (N). The magnetic field magnetic field through each part of it is (B, green) is directed down through constant, not changing with time, so no eddy plate. The increasing field at leading currents are induced, and re is no force edge of magnet (left) induces a between magnet and conductor. Thus counterclockwise current, which by Lenz s an eddy current brake has no holding force. law creates its own magnetic field (left blue There are two types of eddy braking system, arrow) directed up, which opposes y are Linear and Cirucular Eddy Current magnet s field, producing a retarding force. brakes Similarly, at trailing edge of magnet (right), a clockwise current and downward counter field is created (right blue arrow) also producing a retarding force. LITERATURE REVIEW N. Paudel, S. Paul, and J. Z. Bird in his paper general 2-D analytic based transient formulation for a magnetic source 52
moving above a conductive plate has been applied to a high-speed eddy current braking derived. The formulation is written in a system. Based on analytical 2-D field general forms of magnetic source can be solutions considering dynamic end effect, utilized. The derived field and force magnetic field, eddy current distribution, equations by and forces according to secondary evaluating a single integral. The conductive relative permeability and conductivity were region was solved for vector potential presented. It was observed that air-gap whereas air region was solved for flux density has a non-uniform distribution magnetic scalar potential. The inverse for high speed. Comparisons between Laplace transform of vector potential numerical simulations and experimental data was obtained by using Heaviside were also presented.. expansion orem. The transient solution Authors: Andrew H. C. Gosline, Student for normal and tangential forces along Member, IEEE, and Vincent Hayward, surface of conductive plate were Fellow, IEEE The pertinent background to obtained by using Maxwell s stress tensor dissipative actuation and passivity control of need to be computed of haptic interfaces were first discussed to Parseval s orem circumvented need familiarize reader with focus of this for The paper. Basic eddy current brake physics by were presented, design of an ECB comparing m with two different 2-D FEA damper for Pantograph haptic interface transient models. was and Parseval s inverse derived orem. Fourier equations Authors: The use transforming. were Virendra validated Kumar Maurya, described, experimental and results optimization of from an damping RiturajJalan, H. P. Agarwal, S. H. Abdi, hardware were discussed. A prior existing Dharmendra Pal, G. Tripathi and S. Jagan time domain passivity control methodology Raj. of was adapted for use of physical electromagnetic brakes over friction brakes, damping, rar than virtual. The physically y have been widely used on heavy damped passivity controller was shown to vehicles where brake fading problem improve stability of virtual stiff wall. The is serious. The same concept is being authors would like to note that virtual walls developed lighter rendered using physical dampers do not vehicles. A Hal bach magnetized mover was have characteristic sticky feel that is With all for advantages application on 53
typical of walls increases considerably. provides a fast braking response because it There are also limitations to use of is capable of fast anti-lock braking. physical dampers for passivity control. First, as this method is dependent on additional hardware, a haptic interface would have to be equipped with programmable physical dampers to make use of this method. Second, dampers actuate slower than motors, system energy could be in active region longer than if virtual damping was used. Baoquan Kou et al [2015] [2], in this paper, a novel hybrid excitation linear eddy current brake was presented. The hybrid excitation linear eddy current brake has advantages of high force density and low excitation loss compared to electric excitation linear eddy current brakes. The validity of analytical model was verified by Authors:- Kapjin Lee, Kyihwan Park In order to solve and experimental tests, refore analytical model can be used in of preliminary design of eddy current conventional hydraulic systems such as time brakes. Parametric analysis was performed delay response due to pressure build-up, to explore influence of design brake pad wear due to contact movement, parameters on eddy current brake bulky size, and low braking performance in performance. Moreover, experimental a high speed region, an eddy current brake results show that eddy current brake can system is developed and its performance is generate objective braking force using investigated by using a scaled model. controller proposed in this paper. It has been Braking torque analysis is performed by found that proposed eddy current brake using an approximate oretical model and system can be used in road and rail vehicles. Effect of parameters on performance of braking torque problems FEM is experimentally compensated. Optimal torque control which ECBS can shorten braking distance is achieved Experimental results show very good slip by maintaining a desired slip ratio which regulation in a braking event on low gives force friction coefficient surface when compared coefficient. A sliding mode controller is with non-abs braking condition. The used for optimal torque controller. From results show that proposed ABS simulation and experimental results, it is controller provided a smooth ABS stop as observed that eddy current brake (ECB) evident from vehicle speed plots. maximum braking has also been discussed. 54
current. A disc brake is a type of brake that MAIN COMPONENTS OF THE CONTACTLESS EDDY BRAKES uses calipers to squeeze pairs of pads against a disc in order to create friction that retards The main components that are used in rotation of a shaft, such as a vehicle axle, fabrication of our project is listed in eir to reduce its rotational speed or to below, hold it stationary. The energy of motion is 1. Electromagnets converted into waste heat which must be 2. Rotor Disc dispersed. 3. DC Motor DC MOTOR 4. Battery 12V DC Series motor is used in this 5. V-Belt. experiment, which converts electrical energy into mechanical energy. Its location is based ELECTROMAGNETS on principal that when a current carrying Electromagnets are DC type that can be Conductor is placed in magnetic field, it powered by battery. Electromagnets are experiences a mechanical force whose selected instead of permanent magnet as direction is given by Fleming s left hand electrical actuation is faster than mechanical rule. actuation with lower losses. ROTOR DISC BATTERY Despite having a very low energy-to- The figure for disc is given in below. weight ratio and a low energy to volume This disc is main component which ratio, ir ability to supply high surge supports whole blade arrangement which currents means that cells maintain a is made up of mild steel. It is used for relatively large power to weight ratio. 12V Lead acid battery are used which are connected in series. They could deliver 4Amps. V-BELT V belts solved slippage and alignment problem. They provide best combination of traction, speed of movement, load of breaking purpose and generating Eddy bearings, and long service life.. The V shape 55
of belt tracks in a mating groove in pulley, belt cannot slip off. The belt also 2. ROTOR DISC THICKNESS tends to wedge into groove as load The thickness of rotor disc, increases greater load, greater d, must also be optimized in wedging torque order to minimize time transmission and making V-belt an constant, τ and minimize effective solution, needing less width and disc s moment of inertia, I. The tension than flat belts. Optimal speed range inertia of disc is linearly is 300 2,130 m/min. proportional to thickness, so action improving minimizing DESIGN PARAMETER: disk radius minimizes disk inertia. The The design of an eddy current brake time constant does not depend on reduced to five optimization problems which disc thickness. Thus, are discussed in proceeding sections. optimization problem reduces to 1. ROTOR MATERIAL The material of rotor disc minimizing disc thickness while maintaining structural rigidity. must also be optimized in order to minimize time constant, τ and minimize disc s moment of inertia, I. There are two strong 3. ROTOR DISC RADIUS candidates in our selection of The radius of rotor disc, R, material which are copper and must also be optimized in order aluminum. to minimize time constant, τ and minimize disc s moment of inertia, I. The inertia of Material Density Specific [Kg/m3] conductivity disc is proportional to radius to fourth [S/m] minimizing minimizes disk inertia. copper 8.9 58.0 Aluminium 2.7 38.5 power, disk so radius 56
CALCULATION DISSIPATION BY OF POWER CONTACTLESS CALCULATION OF BRAKING TORQUE: EDDY CURRENT BRAKES: Under certain assumptions (uniform material, uniform magnetic field, no skin effect, etc.) power lost due to eddy currents per unit mass for a thin sheet or wire can be calculated from following equation Where, electrical conductivity of rotating disk and sheet thickness rotating disk should be known, r = radius of electromagnet, m = distance of disc axis from pole-face center, BZ = Magnetic flux density, a = disk radius CALCULATION Where: OF TORQUE GENERATED IN DISC: P is power lost per unit mass (W/kg), The magnitude of braking torque, B is peak magnetic field (T), [N m] can be oretically derived to be a d is thickness of sheet or function of number of magnets around diameter of wire (m), wheel, specific conductivity of f is frequency (Hz), material, σ [Ω 1 m 1], diameter of k is a constant equal to 1 for a thin magnet core D, thickness of disk (d), sheet and 2 for a thin wire, ρ is resistivity of material (Ω m), magnetic field B, effective radius R, and instantaneous angular velocity. However, equation shown above is D is density of material (kg/m3). given under assumption that primary magnetic field is sufficiently greater than induced magnetic field. 57
WORKING OF CONTACTLESS EDDY spinning, stronger effect, meaning that as BRAKING SYSTEM vehicle slows, braking force is When vehicle is moving, reduced producing a smooth stopping action. rotor disc of eddy current brake which is The magnetic field of this eddy current coupled to wheels of vehicle rotates, produces a breaking force or torque in in close proximity to stationary magnetic opposite direction of rotation disc. This poles. When we want to brake vehicle, a kinetic energy of rotor is converted as heat control switch is put on which is placed on energy and dissipated from rotating disc to steering column in a position for easy surrounding atmosphere. Current in field operation. can change by changing position of When control switch is operated, current flows from a battery to field controls switch. Thus we can change strength of braking force. winding, thus energizing magnet. Then rotating disc will cut magnetic field. When disc cuts magnetic field, flux changes occur in disc which is proportional to strength of magnetic field. The current will flow back to zero field areas of metal plate and thus create a closed current loop like a whirl or eddy. A flow of current always means re is a magnetic field as well. Due to Lenz s law, magnetic field produced by eddy currents, work against movement direction. Thus instead of mechanical friction, a magnetic friction is created. In consequence, disc will experience a drag or braking effect, and thus disc stops rotation. The wheels of CONCLUSION The use of eddy current braking system we can reduce wear, maintenance cost, increased durability is achieved. Hence, due to all se factors, overall cost is reduced. Eddy current braking system is used for dynamic braking. Due to its various applications as discussed earlier, it can use as a secondary braking system. vehicle, which is directly coupled to disc, also stop rotation. Faster wheels are 58
REFERENCES 1 Kapjin Lee, Kyihwan Park Optimal 6. Arunesh Kumar Singh, Ibraheem, Amit robust control of a contactless brake system Kumar Sharma, Parameter Identification of using an eddy current, Department of Eddy Current Braking System for Various Mechatronics, Kwangju Institute of Science Applications, International Conference on and Technology, 500-712,South Korea, 20 Innovative Applications of Computational October, 1998. Intelligence on Power, Energy, and Controls 2. Henry A. Sodano, Jae-Sung Bae, Daniel J. Inman, W. Keith Belvin Concept with ir Impact on Humanity (CIPECH14) 28 & 29 November 20147. and model of eddy current damper for 7. vibration suppression of a beam 27th Analysis of an eddy current brake using an January, 2005. air track, American Journal of Physics, vol. 3. Yasuaki Sakamoto, Takayuki L.H. Cadwell, Magnetic damping: 64, no. 7, pp. 917-923, 1996. Kashiwagi, Takashi Sasakawa, Nobuo Fujii, 8. Member IEEE, Linear Eddy Current Brake Antilock-Braking Algorithm for an Eddy- for Railway Vehicles Current-Based Braking, Using Dynamic Proceedings International of Conference on 2008 Electrical Machines. 4. Lee, and Sang-Sub Jeong. Characteristic analysis of eddy current brake system using Linear Halbach Array. September, 2002 5. Henry A. Sodano, Jae-Sung Bae, Daniel J. Inman, W. Keith Belvin Concept Brake-By-Wire Transactions On System, Vehicular Technology, Vol.56, No. 3, May 2007. 9. Seok-Myeong Jang, member, IEEE, Sung-Ho IEEE Sohel Anwar and Bing Zheng, An P. J. Wang and S. J. Chieuh, Analysis of Eddy-Current Brakes for High Speed Railways Transactions On Magnetics, VOL 34, NO.4, JULY 1998 10. Manuel I Gonzalez, Experiments with eddy currents: eddy current brake, Department of physics, spain. 20th April, 2004. and model of eddy current damper for vibration suppression of a beam 27th January, 2005.. 59