International Journal of Applied Engineering Research ISSN 0973-4562 Volume 10, Number 8 (2015) © Research India Publications ::: http://www.ripublication.com
Design, Fabrication and Testing of Regenerative Shock Absorber (Linear Alternator Type) S.Gopalakannan1,a, S. Praveen Kumar1,b, V.Premsagar1,c, T.R.Pradeep1,d 1
Department of Mechanical Engineering,Adhiparasakthi Engineering College, Chennai-603319, Tamil Nadu,India. a
[email protected],
[email protected],c
[email protected], d
[email protected]
Keywords: Regenerative shock absorber, Electromagnetic damper, Linear alternator based RSA
Abstract. Almost all the automobiles use shock absorbers to damp out the vibration experienced due to invariably rough roads. The energy in the conventional shock absorbers gets dissipated as heat and is not used in anyway. A regenerative electromagnetic shock absorber was designed, fabricated and tested for the purpose of achieving energy recovery from shock absorbers, which can be further used to achieve battery charging, especially having a high output performance in off-road vehicles.This paper presents design and analysis of an electromagnetic energy regenerative shock absorber which can efficiently recover the vibration energy wasted in vehicle suspension system with due consideration to space limitations in commercial vehicles. Introduction When a vehicle travels on rough road, vibrations are produced. These vibrations have not been yet considered for energy recovery and are wasted through conversion into thermal energy. Experiments have shown that at 90 km/h on good and average roads, 100-400 watts average power is available to recover in the suspension system of a middle-size vehicle [1]. Middle-size passenger vehicle requires 180 watt power to operate continuous loads like ignition, fuel injection and 260 watt power to operate prolonged loads like side & tail lights, head light main lamp etc. Total power requirement of vehicle to operate its electrical components sum out to be 180 to 440 watts. If all the available vibration energy is recovered, it is possible to use regenerative shock absorber to charge the battery of vehicle, instead of alternator. Thus alternator load on vehicle engine can be decreased or removed completely. If say 3% of fuel efficiency of vehicle is improved by this energy recovery scheme, by considering number of vehicles in world, huge amount of fuel can be saved. Thus energy recovery from suspension system is necessary to reduces fuel consumption. Literature References: Lei Zuo, et al. [1] have worked on a prototype design of Electromagnetic energy harvester for vehicle suspension. In this paper they have designed, characterized and tested a prototype retrofit regenerative shock absorber. Gupta et al, [2], (2003) has studied the available energy from shock absorbers as cars and trucks are driven over various types of roads. They fabricated two prototypes of regenerative electromagnetic shock absorber: a linear device (called as Mark 1) and a rotary device (called as Mark 2).Goldner, et al. (2001) [3] have carried out a proof-ofconcept - to evaluate the feasibility of obtaining significant energy savings by using regenerative
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 10, Number 8 (2015) © Research India Publications ::: http://www.ripublication.com
magnetic shock absorber in vehicles. They proposed electromagnetic (EM) shock absorbers to transform the energy dissipated in shock absorbers into electrical power. P. Zhang et al. [4] have presented comprehensive assessment of the power that is available for harvesting in the vehicle suspension system and the tradeoff among energy harvesting, ride comfort, and road handing with analysis, simulations and experiments. Bart Gysen et al., [5] have studied design aspects of an active electromagnetic suspension system for automotive applications which combines a brushless tubular permanent-magnet actuator with a passive spring. Potential energy available in the conventional shock absorber: It is however not possible to exactly predict or determine the amount of energy which can be recovered from a Regenerative shock absorber, but it is possible to determine the energy stored within the spring using theoretical relations. When spring compresses and extends due to excitation supplied vehicle vibrations, energy is stored in the form of strain energy. This energy in compressed spring can be given by equation – ଵ
E = U = ଶ × k × X2
(1)
Using the value of k as 1.2*105 N/m and supporting vehicle mass approximately 1000 kg; vertical displacement stores the amounts of energy in spring as shown below— Table 1: Theoretical calculation for energy stored in a spring used in conventional shock absorbers Displacement(mm) Energy Stored Spring (J) 10 6 30 54 60 216
in Summing over four wheels(J) 24 216 864
Design of regenerative shock absorber: The system consists of a smaller copper tube which slides inside a larger, hollow magnet assembly. The coil component is made of copper coils wound around a stainless steel tube, while the magnetic component is made of ring-shaped magnets separated by ring shaped magnetically permeable spacers. The magnets are aligned with like-poles facing each other to produce a radially emitted magnetic flux. The magnetic tube is also surrounded by a high magnetically permeable material in order to further ―pull‖ the magnetic flux outward. The key factor of the design is to have a higher magnetic flux. Design of Components: Outer diameter of magnet Thickness of magnet Thickness of Spacers No of magnets
: 50 mm : 10 mm : 10 mm : 10
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 10, Number 8 (2015) © Research India Publications ::: http://www.ripublication.com
Magnet Material : Permanent Magnets (NdFeB) Wire material : Copper wire 27 AWG (Average Diameter-0.0142‖) Length of coil component : 180 mm Design of spring: There are many different types of springs and spring materials. In the design calculations, the following assumptions are considered: 1. The type and form of the spring will be the compression spring ground. 2. The material must be chosen for the maximum energy and mass, such as the spring steel, Chromium Vanadium or Chromium Silicon steel wire. 3. The ends of the spring are to be closed and ground. 4. The spring operates periodically. Outer diameter of spring, Do Inner diameter of spring, Di Young‘s Modulus of the material Diameter of coil wire, d Number of turns, N Total height of the spring
= 60 mm = 43 mm = 2×105 N/mm2 = 6 mm = 14 = 220 mm
Table 3: Properties of spring: Load
Scale reading at loading (cm)
Deflection
Stiffness
(Kg)
100
Initial
Final
Mean
(mm)
(N/mm2 )
1.5
3.4
1.9
19
51.63
Fabrication and Testing of Regenerative shock absorber The full scale regenerative shock absorber was fabricated based on the dimensions derived in above section. The Fig. 1 and Fig. 2. shows the exploded and assembled view of the shock absorber. The permanent magnets NdFeB (grade N32) were chosen due to their high magnetic density. Copper wire of 27 AWG were chosen to wound coils because of its superior conductivity and low resistivit y. A test set-up was designed to characterize the voltage output and power output of the generator at various road conditions. The output generated by the regenerative shock absorber is given in table 3. The machine was having the mechanism for variation of amplitude & frequency of excitation to simulate road profiles. Waves at different frequencies and amplitudes were modeled using mechanism in shock absorber testing machine. A multimeter was used to measure current output. The regenerated voltage was in alternating current form and required to be rectified to convert it into direct current voltage so as to use in vehicle battery. Output voltages were recorded.
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 10, Number 8 (2015) © Research India Publications ::: http://www.ripublication.com
Fig. 1 Exploded view of the shock absorber
Fig. 2 Assembled view of the shock absorber.
Table 3: Output power recorded by regenerative shock absorber: Displacement in cm 1.75 0.75 0.45 0.20 0.10
Voltage in volt 3.082 1.47 1.333 0.883 0.673
Power Generated in watts 0.2561 0.0619 0.0570 0.0236 0.0137
Stabilization of voltage: The step-up/step-down voltage regulator is a switching regulator (also called a switched-mode power supply (SMPS) or DC-to-DC converter) with a single-ended primary-inductor converter (SEPIC) topology. It takes an input voltage from 1.5 V to 16 V and increases or decreases the voltage to a user-adjustable constant output voltage between 2 V to 12 V. The input voltage can be higher, lower or equal to the set output voltage, and the voltage is regulated to achieve the set output voltage. This flexibility in input voltage is especially well-suited for battery-powered applications in which the battery voltage begins above the desired output voltage and drops below the target as the battery discharges. This voltage regulator has a shutdown feature that can also be used as an under-voltage protection mechanism. Results and Conclusion The results of experiment carried out for the variationin regenerated vo ltage against varying displacements was found out and a maximum of 0.2561 W of energy recovery was achieved.By using the method of charging the battery through the use of Regenerative shock absorbers we can meet a large amount of energy requirement and can increase the engine efficiency slightly. This
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 10, Number 8 (2015) © Research India Publications ::: http://www.ripublication.com
method cannot remove the alternator setup completely as the output from this system is subjected to extreme fluctuations, but the size of the alternator can be reduced which will result in a slight contribution towards fuel economy. References 1. Lei Zuo, Brian Scully, JurgenShestani and Yu Zhou, ‗Design and characterization of an electromagnetic Energy harvester for vehicle suspensions‘, Journal of Smart Materials and Structures, Volume 19, Number 4. 2. Gupta A, Jendrzejczyk J A, Mulcahy T M and Hull J R , ‗Design of electromagnetic shock absorbers‘, International Journal of Mechanics & Material Design, Volume 3, Number 3. 3. Goldner R B, Zerigian P and Hull J R, ‗A preliminary study of energy recovery in vehicles by using regenerative magnetic shock absorbers‘, SAE Paper #2001-01-2071. 4. Pei-Sheng Zhang and Lei Zuo, ‘Energy harvesting, ride comfort, and road handling of regenerative vehicle suspensions‘, ASME Journal of Vibration and Acoustics, 2012. 5. Bart L. J. Gysen, Jeroen L. G. Janssen, Johannes J. H. Paulides, Elena A. Lomonova, ‗Design aspects of an active electromagnetic suspension system for automotive applications‘, IEEE transactions on industry applications, vol. 45, no. 5, September/October 2009 6. Graves, K.E., Iovenitti, P.G., and Toneich, D., ―Electronic Regenerative Damping in Vehicle Suspension Systems,‖ International Journal of Vehicle Designs, Vol. 24, Nos. 2/3, 2000, pp. 182-197. 7. Suda, Y. and Shiba, T., ―A New Hybrid Suspension System with Active Control and Energy Regeneration,‖ Vehicle System Dynamics Supplement, Vol. 25, 1996, pp. 641-654. 8. Fodor, M.G., and Redfield, R., ―The Variable Linear Transmissions for Regenerative Damping in Vehicle Suspension Control,‖ Vehicle System Dynamics, Vol. 22, 1993, pp. 1-20.
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