ENERGY HARVESTING FROM REGENERATIVE SHOCK ABSORBERS WITH SUPERCAPACITOR CHARGING
A seminar report report submitted submitted to the University University of Kerala Kerala in partial fulfilment of the requirements for the degree of Bachelor of Technology Technology In Mechanical Engineering Engineering
by BOBY THOMAS Roll no: 13400044
Department of Mechanical Engineering College of Engineering, Thiruvananthapuram-16 Thiruvananthapuram-16
May – 2017 2017 1
DEPARTMENT OF MECHANICAL ENGINEERING COLLEGE OF ENGINEERING, TRIVANDRUM -16
CERTIFICATE
Certified that this seminar report entitled –‘ Energy Energy Harvesting in Regenerative Shock Absorbers Using Supercapacitor charging’ is a bonafide record of the seminar presented by BOBY THOMAS – 13400044 13400044 on 14 FEBRUARY 2017 under our guidance in partial fulfilment of the
requirement for the award of the Degree of Bachelor of Technology in Mechanical Engineering of the University of Kerala. Shafeek M Assistant Professor Pradheep A Assistant Professor Abhilash R
Dr Krishna Kumar K
Assistant Professor
Head of the Department Dept of Mechanical Engineering College of Engineering Trivandrum
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ACKNOWLEDGEMENT
It is my proud privilege and duty to acknowledge the kind of help and guidance received from several people in presentation of the seminar and preparation of this report. It would not have been possible to prepare this report in this form without their valuable help, cooperation and guidance. First and foremost I’d like to record my sincere gratitude to Prof. Pradheep A, Assistant Professor,
Dept. of Mechanical Engineering CET, for guiding me and for his continuous support and encouragement. I sincerely thank Dr . K Krishna Kumar, HOD Department of Mechanical Engineering, CET for his kind cooperation towards successful completion of the seminar. I express my sincere gratitude to my seminar coordinators Prof. Abhilash R, Assistant Professor, Dept. of Mechanical Engineering, CET, Prof. Shafeek M, Assistant Professor, Dept. of Mechanical Engineering, CET for their valuable assistance and technical guidance for the successful completion of the seminar. Last but not the least, I wish to record my sincere thanks to all my friends for their valuable comments and suggestions for making the work a success
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ABSTRACT The energy source of vehicles is changing rapidly and significantly in recent years with the increase in renewable energy technologies especially in the case of electric vehicles (EVs). A smart solution has emerged in which the wasted energy in a vehicle’s shock absorber is converted to an alternative energy for the cars themselves, and this is called an energy regenerative shock absorber. Hence we introduce a novel high-efficiency energy regenerative shock absorber using supercapacitors. This system collects the wasted suspension power from the moving vehicle by replacing the conventional shock absorbers as these energies are normally dissipated through friction and heat. The proposed system consists of four main components: the vibration of the suspension input module, transmission module, generator module and power storage module. The suspension vibration induced by the road roughness acts as the system excitation to the energy regenerative shock absorber. The vibration is then transmitted through the mechanical transmission module, which changes bidirectional vibration into unidirectional rotation based on gears and a rack to drive the generator module. The power storage module stores the regenerative energy of the shock absorber in the supercapacitor, Higher efficiency up to 54.98% at most and 44.24% on average were achieved in the simulation and bench tests is proof that the energy regenerative shock absorber is beneficial and promising in generating energy used for renewable energy applications.
BOBY THOMAS 13400044
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CONTENTS
1. Introduction................................................................................................................6 2. Suspension system of Automobiles…………...........................................................7 2.1. Functions of A Vehicle Suspension............................................................8 2.2. Passive Suspension.....................................................................................9 2.3. Semi-active Suspension.............................................................................10 2.4. Active suspension......................................................................................11 3. Energy Losses In A Vehicle.....................................................................................13 4. Regenerative Passive Suspension System................................................................16 4.1 System Design……………………………………………………………17 4.2 Suspension Vibration module design……………………………….........18 4.3 Transmission Mechanism Module…………………………………….…19 4.4 The Generator Module…………………………………………………...20 4.5 The Power Storage Module……………………………………….......….21
5. Modelling And Analysis……………......................................................................22 6. Experimental setup…………………………………….........................................24 7. Experimental Results…………………..................................................................25 8. Conclusions……………………............................................................................27
9. References..............................................................................................................28
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1. INTRODUCTION
Vehicle suspension system is a mass-spring-damper system that isolates vehicle body frame from road random disturbance. Springs counter the weight of vehicle body. Dampers, also called shock absorber, undoubtedly they are the key components to damp the vibration which is transmitted from ground. More importantly, dampers are design to reduce the sudden effects of road disturbance such as hitting on a bump to achieve a smooth ride. In general, dampers are categorized into three classes according to their functionalities which are passive damper, semi-active damper, and active damper. As a result, the suspension systems are also divided into passive, semi-active, and active suspension systems. Conventionally, dampers are designed to dissipate vibration energy into heat via viscous fluids or dry frictions. Hydraulic passive dampers are common used in vehicle suspension system due to its simplicity and economic value. Nowadays, as the mechatronics and magnetic materials are well developed, the suspension systems tend toward to semi-active and active co nfigurations to improve the vibration migration performance. Instead of dissipating the vibration energy into heat wastes, electromagnetic damper will transform the energy into electricity and store it for late use. The stored electricity can be used to tune the damping force of the damper to improve the suspension performance or to power car electronics to increase vehicle fuel efficiency. This is so called semiactive suspension and it has advantages over traditional suspension system. Active suspension system has great performance on vehicle body isolation and rider’s comfort. However, the payoff
of this great performance is the exclusive usage of energy. Moreover, the performance will not be achieved when the power is out. Thus, the safety issue is well considered for active suspension system. Electromagnetic dampers are designed to harvest vibration energy as a vehicle travels on a road and at the same time achieve typical damping force. In addition, sensors and micro-controllers can be applied to calibrate damping force while vehicle experiences different road input such as hitting on a bump or rolling over a hole. The semi-active performance of electromagnetic damper will greatly improve rider’s comfort in all kind of situations.
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2. SUSPENSION SYSTEM OF AUTOMOBILE
A system which supports a load from above and isolates the occupants of a vehicle from the road disturbances is called a suspension system. The flexible elements in the suspension system are springs. These components have an ability of storing the energy applied in the form of loads and deflections. The spring is able to absorb energy and bend when it is compressed to a shorter length. It is forced upward and the spring absorbs energy of this upward motion, when a tire meets an obstruction. On the other hand, this energy is observed by spring for a short time only and the energy will release by extending back to its original condition by it. When stored energy is released by spring, it does so with such quickness and momentum that the end of the spring usually extends too far. Until all of the energy in the spring is released the spring will go through a series of 7
oscillations, contractions and extension. The speed of the oscillations will be determined by the natural frequency of the spring and suspension. The energy that spring released, will be changed to heat and dissipated partly by friction in the system via damper. Generally Dampers are in the form of piston working in cylinders which filled with hydraulic fluid. A force which they apply is proportional to the square of the piston velocity. To restrain undesirable bounce characteristic of the sprung mass is the function of damper. Furthermore it used to make sure which the wheel assembly always contact with the road by being excited at its natural vibration frequency. Other mechanical elements in a suspension system are the wheel assemblies and control geometry of their movement. Some of these elements are simple links and multi-role members such as transverse torsion bars used to stabilize the vehicle in corners by restricting roll. A suspension system comprises many elements that include spring, damper, tires, bushes, locating links and antiroll bars are shown in Figure 1.1.
2.1.
Functions Of A Vehicle Suspension
A complicated system as it has to fulfill a large number of partly contradictory requirements is vehicle suspension system. Among the most important requirements that have to fulfill are Ride comfort, safety, handling, body leveling and noise comfort. The acceleration of the vehicle body can determine ride comfort. As a disturbance, the passengers experience acceleration forces and set demands on the load and the vehicle. The task of the suspension system is to isolate these disturbances from the vehicle body, which the uneven road profile caused It. The wheels ability to transfer the longitudinal and lateral forces onto the road can determine the safety of the vehicle during travelling. The necessity of the vehicle suspension system is to keep the wheels as close the road surface as possible. Wheel vibration must be dampened and the dangerous lifting the wheels must be avoided. If between the wheels and the road surface, dynamic forces happening are small, the braking, driving and lateral forces can be transferred to the road in an optimal manner. The cause for the recognized conflict of aims among comfortable and safety tuning is the requirement of dampening the tire system. The isolation of the vehicle body from high frequency road disturbances is a further purpose of the suspension system. In the car, the passengers acoustically note these disturbances and therefore the noise comfort decrease. The suspension system, while 8
there are changes in loading, has to remain the vehicle level as stable as possible therefore for the wheel movements the complete suspension travel exists. In addition, a good suspension design is a lower suspension travel; it means that lower suspension working space. In order to fulfill all these contradict desires confident marginal situation considered. In general, there are three types of the suspension system. They are: 1) Passive suspension 2) Semi-active suspension 3) Active suspension
2.1.1. Passive Suspension
The conventional suspension system is passive suspension system. It has two elements one of them is damper and another is spring. In this passive suspension, the purpose of the dampers is to dissipate the energy and the spring is to store the energy. Often a spring design function is expressed in terms of energy storage capacity. In machines, springs are frequently used to store 9
kinetic energy from moving components during deceleration and release this energy during acceleration to reduce peak loads. If a load exerted to the spring, it will compress until the force produced by the compression is equal to the load force, the spring will oscillate around its original position for a period of time when the load is troubled by an external force. Dampers can absorb this oscillation; therefore, it would only jump for a short period of time. For this type of suspension system damping coefficient and spring stiffness are fixed characteristics therefore this is the main weakness as parameters for ride comfort and good handling vary with different road surfaces, vehicle speed and disturbances. The performance of passive suspension system can be improved by using the semi-active suspension system. 2.1.2.
Semi-active Suspension
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The component in the semi-active suspension system is similar with passive suspension system and where external energy is needed in the system, it uses the same function of the active suspension system. The differentiation with passive suspension system is that the damping coefficient can be controlled .The fully active suspension is modified thus the actuator is only capable of dissipating power rather than supplying it as well. The actuator then becomes a continuously variable damper which is theoretically capable of tracking force demand signal independently of instantaneous velocity across it. While having low system cost, light system weight and low energy consumption this suspension system exhibits high performance. Disadvantage of semi-active suspension: The high frequency harshness that has been observed in road tests and reported in analytical studies of semi active suspension is a significant feature that the performance of ‘semi active’ suspension is not suitable. To get good body isolation for low
frequency inputs a good semi active system should provide high damping, for good comfort, low damping in the mid - frequency range , adequate damping to control the wheel hop, especially under conditions of motion that requires the development of lateral forces and finally increased damping of structural modes. Semi active suspension that use feedback of modal variables reduce s structural vibrations in comparison to the corresponding systems with rigid body based controllers.
2.1.3. Active Suspension
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As early as 1958, the conception of active suspension system was introduced. The differentiation compare to conventional suspension is active suspension system able to add energy into vehicle dynamic system by the use of actuators rather than dissipate energy. Active suspension can use further degrees of freedom in assigning transfer functions and therefore get better performance. The active suspension system consists an additional element in the conventional suspension, which the main component of it, is an actuator that is controlled by a high frequency response servo valve and which involves a force feedback loop. A control law, which is normally obtained by application of various forms of optimal control theory, govern the demand force signal, which typically generated in a microprocessor. In theory, this suspension provides best possible ride and handling characteristics. By maintaining an around stable tire make contact with force, maintaining level vehicle geometry and by minimizing vertical accelerations to the vehicle it is done. On the other hand, due to its complication, cost and power requirements, it has not yet put into mass production. In analysis of suspension system, there are varieties of performance criterion, which require becoming optimal. In designing a suspension system there are three performances criterion, which we should consider carefully; they are body acceleration, suspension travel and wheel 12
deflection. By introducing the appropriate controller into the active suspension system, the performance of the system can be more improved. 3. ENERGY LOSSES IN A VEHICLE
Only about 15 percent of the energy from the fuel you put in your tank gets used to move your car down the road or run useful accessories, such as air conditioning. The rest of the energy is lost to engine and driveline inefficiencies and idling. Therefore, the potential to improve fuel efficiency with advanced technologies is enormous.
Fig 2 Energy losses diagram in a vehicle 3.1.
Engine Losses - 62.4 percent
In gasoline-powered vehicles, over 62 percent of the fuel's energy is lost in the internal combustion engine (ICE). ICE engines are very inefficient at converting the fuel's chemical energy to mechanical energy, losing energy to engine friction, pumping air into and out of the engine, and wasted heat. Advanced engine technologies such as variable valve timing and lift, turbocharging, direct fuel injection,
and
cylinder
deactivation
can
be
used
to
reduce
these
losses.
In addition, diesels are about 30-35 percent more efficient than gasoline engines, and new advances in diesel technologies and fuels are making these vehicles more attractive.
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3.2.
Idling Losses - 17.2 percent
In urban driving, significant energy is lost to idling at stop lights or in traffic. Technologies such as integrated starter/generator systems help reduce these losses by automatically turning the engine off when the vehicle comes to a stop and restarting it instantaneously when the accelerator is pressed. 3.3.
Accessories - 2.2 percent
Air conditioning, power steering, windshield wipers, and other accessories use energy generated from the engine. Fuel economy improvements of up to 1 percent may be achievable with more efficient alternator systems and power steering pumps. 3.4.
Driveline Losses - 5.6 percent
Energy is lost in the transmission and other parts of the driveline. Technologies, such as automated manual transmission and continuously variable transmission, are being developed to reduce these losses. This also includes the losses happening in the suspension of the automobile. 3.5.
Aerodynamic Drag - 2.6 percent
A vehicle must expend energy to move air out of the way as it goes down the roadÑless energy at lower speeds and progressively more as speed increases. Drag is directly related to the vehicle's shape. Smoother vehicle shapes have already reduced drag significantly, but further reductions of 20-30 percent are possible. 3.6.
Rolling Resistance - 4.2 percent
Rolling resistance is a measure of the force necessary to move the tire forward and is directly proportional to the weight of the load supported by the tire. A variety of new technologies can be used to reduce rolling resistance, including improved tire tread and shoulder designs and materials used in the tire belt and traction surfaces.
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For passenger cars, a 5-7 percent reduction in rolling resistance increases fuel efficiency by 1 percent. However, these improvements must be balanced against traction, durability, and noise. 3.7.
Overcoming Inertia; Braking Losses - 5.8 percent
To move forward, a vehicle's drivetrain must provide enough energy to overcome the vehicle's inertia, which is directly related to its weight. The less a vehicle weighs, the less energy it takes to move it. Weight can be reduced by using lightweight materials and lighter-weight technologies (e.g., automated manual transmissions weigh less than conventional au tomatics. In addition, any time you use your brakes, energy initially used to overcome inertia is lost.
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4. REGENERATIVE PASSIVE SUSPENSION SYSTEM
a. System Design
Fig 3 Architecture of Regenerative Shock Absorber with Supercapacitor Charging The general architecture of our energy regenerative shock absorber using supercapacitors, which is applied to extend the battery endurance of EVs, as shown in Fig. 1, has four main parts: (1) suspension vibration input module, (2) transmission module, (3) generator module and (4) power storage module. Acting as the energy input, the suspension vibration input module is shown in Fig. 4 1. When an EV is driving on a road, the road roughness will induce suspension vibration and there will be a linear motion between the two cylinders of the regenerative shock absorber. Therefore, the two cylinders of the energy regenerative shock absorber are defined as the suspension vibration input module. The function of the transmission mechanism module is to convert the bidirectional vibration between the two c ylinders to unidirectional rotation for the input shaft of the generator, which greatly improve reliability and increase efficiency. The generator module will be driven in one direction to generate electricity and to convert the kinetic energy into electrical energy. The purpose of the power storage module connected to the generator module is to store the regenerative energy of the shock absorber in the supercapacitor, which is applied to an EV to improve the cruising mileage.
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4.1.1
Suspension vibration input module
Fig 4.1 Suspension Vibration Input Module
Fig 4.2
Prototype
This paper is devoted to the design of a novel energy regenerative shock absorber used to harvest the kinetic energy caused by suspension vibration. The shock absorber is installed in a position between the vehicle frame and the chassis, as shown in Fig. 4.1. The outer cylinder is connected to the vehicle frame and the inner cylinder is fixed to the chassis. As a result, when suspension vibration occurs, there will be a linear motion between the two cylinders of the shock absorber. There are many factors that induce suspension vibration, such as road roughness, acceleration and deceleration. However, research shows that road roughness is the main source of excitation of suspension vibration. Road roughness is generally random and can be modelled as a white-noise velocity input to the tires. In addition, the vehicle speed is also the main factor influencing suspension vibration, as data recorded. Road roughness causes the vibration and the vehicle speed largely effects the performance of suspension. Therefore, a conclusion can be drawn that the suspension velocity highly depends on the road roughness and vehicle’s speed.
4.1.2
Transmission Mechanism Module
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The transmission mechanism module is the core of the novel energy regenerative shock absorber, which is the bridge between the suspension vibration input module and the generator module. The 18
function of the transmission mechanism module is to convert the up-and-down linear motion between the two cylinders to a uni-directional rotation for the input shaft of the generator. The detailed parts of the regenerative shock absorber are shown in Fig. 5. The primary parts are two pairs of rack-pinions, two overrunning clutches, two bevel gears, two cylinders and a generator. The transmission mechanism module, which overrunning clutches, two bevel gears and a shaft, as shown in Fig. 5, can convert the linear oscillation of the two cylinders to unidirectional rotation for the input shaft of the generator. The racks are fixed in the end of the outer cylinder, and the assemblies of the pinions, bevel gears, shaft, clutches, bearings and generator are mounted on the inner cylinder that is enclosed by the outer cylinder. There will be a linear motion between the outer cylinder and the inner cylinder when the suspension vibration input occurs. As a result, the racks will move upwards and downwards along with the outer cylinder. In the design, two pinions are assembled on the shaft without being fixed, whereas the overrunning clutches are embedded into the pinions. The overrunning clutch is connected with the pinion using a key. Moreover, the overrunning clutches are fixed to the shaft through a key. In the design, the CSK-PP type overrunning clutch is used, which mainly consists of the outer race, inner race, wedge, roller, spring, end cover, etc. Due to the raceway that is placed between the inner ring and outer ring with eccentric wedges, the clutch can transfer torque in one direction and is overrunning in the opposite direction. When a linear motion between the outer cylinder and the inner cylinder occurs, both of the racks will move up and down at the same moment. The racks transmit vertical upward and downward motions to the two pinions. The rack pinion assembly causes the two pinion gears to rotate in opposite directions with respect to one another. The pinions are fitted with unidirectional overrunning clutches. Under the effect of dual-overrunning clutches, on e of the pinions will engage the input shaft and the other pinion will disengage it. Therefore, the shaft will always rotate in one direction regardless of whether the racks move down or up.
4.1.3
The Generator Module
The generator, which is one of the most important parts of the shock absorber, converts the suspension vibration energy into electrical energy. To improve the installation of the energy regenerative shock absorber, the generator should have a small volume and a light weight. To 19
improve the energy harvesting efficiency, the rotor inertia of the generator should be low and the copper loss should be small. Therefore, it is most suitable to select the brushless DC motor as the energy harvesting generator. Brushless DC motor can be utilized as generator directly
Fig. 6 The Generator Module
4.1.4
The Power Storage Module
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Fig 7.1 The output power storage circuit
Fig 7.2 Supercapacitor Charging System
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The frequency and amplitude of suspension vibration depends highly on the road roughness and the vehicle’s speed. When these condition changes rapidly, the rotating speed of the generator
changes drastically, so that the current generated becomes unstable. A brushless DC motor was used as the generator in this regenerative shock absorber, and the brushless generator will generate three- phase alternating current. Therefore, the current produced by the generator is unconscious and unsteady. This current is neither suitable for electrical loads nor battery charging before the current rectifier and voltage regulator. To rectify the three phase alternating current into a pulselike current, an electrical rectifying circuit was designed, as shown in Fig. 7.1. The super capacitor could be rapidly charged and had a high power density and is suitable for the rapid storage of a pulse-like current, so a super capacitor was selected to store the electric energy. The voltage regulator was built using stabilivolt to achieve better power stability for loads. Fig. 7.2 shows the circuit board of the proposed circuit.
5. Modelling and analysis
The energy regenerative shock absorber has several parts, such as the generator, planetary gearbox, bevel gear, and rack pinion. The objective of this session is to investigate the influence of these components and the parameters on the dynamics of the system. The damper in the shock absorbers is analysed in this section and is influenced by friction damping between meshing gears and electromagnetic damping in the motor. Then, a dynamic analysis was also conducted based on the damper analysis to determine out the properties of the regenerative shock absorbers and the ride comfort, which is important to consider when determining whether the regenerative shock absorbers are able to replace the conventional shock absorbers.
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a. Equivalent Spring Constant
6. EXPERIMENTAL SETUP 23
Fig 8 Experimental Setup The experimental setup for the bench test of the energy regenerative shock absorber is shown in Fig. 8. The bench tests were conducted on a Bionix 858 material testing system from Mechanical Testing and Sensing (MTS), shown as Fig. 8(a). The prototype of regenerative shock absorbers is manufactured for the test in Fig. 8(b) and (g). A UTD2102CEX-EDU digital oscilloscope from UNI-T was used to record the voltage signal from the generator. Force and displacement signals were measured using a displacement sensor and a load cell (integrated in the Bionix 858 MTS testing system as shown in Fig. 8(c)). Due to the limited height, the greatest amplitude of excitation tested in the prototype was Fig. 11. Damping coefficients with different external loads. Because the suspension vibration was over a broad spectrum, which was primarily 1 – 10 Hz, we also investigated the performance at different frequencies from 1 to 2.5 Hz. Therefore, the prototype was tested with sinusoidal displacement inputs for different amplitudes and frequencies in the above ranges. Next, three external resistors of Re ¼ 3X were connected to the generator, as shown
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in Fig. 8(e). The signal of generated power is recorded in a digital oscilloscope, as shown in Fig. 8(f) and (h).
7. EXPERIMENTAL RESULTS
Figure 9 RMS voltage output versus input frequency for 0◦ phase coil set (eight coils) at different shaker excitation voltages.
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Fig 10 Force v/s displacement response at an amplitude of 7.5 mm
Fig 11 Voltage v/s time response t a frequency of 2 Hz and amplitude of 7.5 mm
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8. CONCLUSIONS
An energy regenerative shock absorber is able to harvest the kinetic energy from the vehicle suspension vibration. This paper presented the design, modelling, simulation and test of a novel energy regenerative shock absorber based on dual-overrunning clutches for electrical vehicles. The shock absorber consists of four main components: the suspension vibration input module, the transmission module, the generator module and the power storage module. The suspension vibration input module is used to obtain a relative linear motion, and the function of the transmission mechanism module is to convert the up-and-down linear motion of the suspension vibration to a unidirectional rotation for the input shaft of the generator. The generator will be driven in one direction to generate electricity and convert the kinetic energy into electrical energy. The power storage module is used to store the power in the supercapacitor and will be used by the EV to improve the cruising mileage. A prototype shock absorber was manufactured, and its performance was evaluated on a bench-test subject to sinusoidal displacement. The results demonstrate that the energy regenerative shock absorber can provide damping for a typical passenger car. Furthermore, vibration energy can be regenerated with a measured average mechanical efficiency of 44.24%. An average power of 4.302 W was attained by this prototype shock absorber at a vibrational input of 2.5 Hz and an amplitude of 7.5 mm. The prototype can achieve 54.98% efficiency at a frequency of 2.5 Hz and an amplitude of 7.5 mm. In addition, the energy regenerative shock absorber can provide variable damping coefficients by changing the external loads, i.e., this novel shock absorber can be applied to different types of vehicles.
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9. REFERENCES
1. Z Zhang, X Zhang, W Chen, Y Rasim, W Salma- A high-efficiency energy regenerative shock ‘
absorber using supercapacitors for renewable energy applications in range extended electric vehicle’, Applied energy, Volume 178, 15 September 2016 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. Zhen Longxin and Wei Xiaogang, ‘Structure and Performance Analysis of Regenerative Electromagnetic Shock Absorber’, Journal of networks, vol. 5, no. 12, December 2010 6. S. Mirzaei, S.M. Saghaiannejad, V. Tahani and M. Moallem, ‘Electromagnetic shock absorber’,
Department of Electrical and Computer Engineering, IEEE 2001. 7. 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. 8. N. Bianchi, S.Bolognani, F. Tone1,’ Design criteria of a tubular linear IPM motor’, Department
of Electrical Engineering, University of Padova,2001, IEEE 9. Babak Ebrahimi, Mir Behrad Khamesee, M. Farid Golnaraghi, ‘’ Feasibility Study of an Electromagnetic Shock Absorber with Position Sensing Capability’’, IEEE 2008, P age 2988-91 10. Shakeel Avadhany, Zack Anderson, U S patent 260935,’ Regenerative shock absorber
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