ELECTROMAGNETIC SHOCK ABSORBERS

Chapter 1-Introduction

1.1-About shock absorbers

Automobiles and trucks have shock absorbers to damp out the vibration experienced due to roughness of the roads.

Shock absorbers do the following works:

1)     A mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy.

2)      Saves us from unpleasant vibration

3)      Include cushions and springs

4)      Damp out the vibration experienced due to roughness of the roads.

5)      However, energy in conventional shock absorbers gets dissipated as heat and not used in any way.

1.2- Images of Shock absorbers: In fig 1.1(a) and 1.1(b) common types of shock absorbers are shown below

 

 fig 1.1(a) shock absorbers

 fig1.1 (b) shock absorbers

1.3-Need for electromagnetic shock absorbers

Only 10-16 percent of the fuel energy is used to drive the car during everyday usage – that is, to overcome the resistance from road friction and air drag and actually transport the vehicle forward. That amounts to a lot of energy being wasted. Hybrid cars recapture some of the energy usually lost in braking but the dissipation of vibration energy by shock absorbers in the vehicle suspension remains an untapped source of potential energy. To harvest this lost energy the researchers have designed and tested a shock absorber that can be retrofitted to cars to convert the kinetic energy of suspension vibration between the wheels and sprung mass into useful electrical power.

   Also, energy in conventional shock absorbers gets dissipated as heat and not used in any way. Regenerative electromagnetic shock absorbers provide means for recovering the energy dissipated in shock absorbers. Electromagnetic shock absorbers for potential use in vehicles are fabricated and tested for their performance.  Electromagnetic shock absorbers for potential use in vehicles are fabricated and tested for their performance. They transform the energy dissipated in shock absorbers into electrical power.

 An Electro-magnet Shock has been fabricated. The shock consists of three assemblies: the permanent magnet assembly, the coil assembly, and the case assembly. Voltage is induced in the shock windings when the coil assembly moves relative to the magnet assemblies. The case assembly aligns and enables the piston-like motion between the coil and magnet assemblies.

1)      These are also need for Improved Vehicle Fuel Efficiency. 

2)      Passive and Active Vibration and Noise Control (Minimize vibration and Sound)

3) Electromagnetic Shock Absorber (makes more sense with high gasoline prices).

1.4 History and works of different scientists in this field

Goldneret.al proposed electromagnetic shock absorbers to transform the energy dissipated in shock absorbers into electrical power. Gupta has studied the available energy from shock absorbers as cars and trucks are driven over various types of roads. Goldnereret.al studied electromagnetic regenerative damping. They mention that energy regeneration is small and may be relevant only for electric vehicles. They also propose ways to amplify the motion of the shock in order to increase recoverable energy which on the other hand may have a negative effect on vehicle dynamics. Another interesting observation made by them is that device output voltage must be large enough to overcome the barrier potential of the storage device.

Suda and Shiba studied a hybrid suspension system where active control is adopted at low frequency and passive control by energy regenerative damper is adopted at high frequency.

Fodor and Redfield tried to design a regenerative damper. However, they came across the design limitation of amplifying mechanical devices input force which is necessary because available energy is low and a threshold for energy storage exists.

Karnopp studied the electromagnetic involved in designing permanent magnet linear motors used as variable mechanical dampers.

However, until now no practical electromagnetic shock absorbers have been designed for automotive or truck usage.

Chapter 2-Construction

2.1-Electromagnetic shock absorber –

The electromagnetic shock absorber is shown in the following figure (2.1)

  Fig (2.1) Electro-magnetic shock absorber

2.2- Manufacturing of electromagnetic shock absorber

The full scale electromagnetic regenerative shock absorber was fabricated based on the dimensions derived in above section. The permanent magnets NdFeB (grade N32 (Neodymium iron boron, NdFeb magnets, also known as rare earth magnet and neo magnets) 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 resistivity.

2.3-Generator design

The magnet assembly consists of an inner magnet stack surrounded concentrically by a larger diameter outer magnet stack. Each stack consists of three axially magnetized ring magnets separated by two iron-pole rings and two additional pole rings located at the ends of the stack. Sintered anisotropic NdFeB (Neodymium iron boron magnets, also known as rare earth magnet and neo magnets) permanent magnets are used. The polarity of the magnets is chosen such that radial magnetic flux emanates from both sides of each iron pole and the flux of the inner pole rings adds to that of the outer rings. The radial direction of the flux from the pole rings is opposite at opposite ends of each magnet ring. Also, the flux through the two end pole rings is about half that in the interior pole rings. For purposes of estimating performance, a 1 Tesla (T) radial flux density is assumed to emanate from the interior pole rings and 0.5 T from the end rings.

The coil assembly consists of an inner coil surrounded concentrically by a larger diameter outer coil. Each coil consists of four continuously wound layers of 25 magnet wire with approximately 800 turns. However, each coil is broken into four sections, separated by insulators. In assembly, each coil section is centered on a different iron pole ring. The winding direction is reversed in adjacent section of each coil to accommodate the reversal in radial flux of adjacent pole rings. In other words, the induced voltage in each section of the coil has the same polarity.

The shock absorber uses an electromagnetic linear generator to convert variable frequency, repetitive intermittent linear displacement motion to useful electrical power. The Goldneret.al device uses superposition of radial components of the magnetic flux density from a plurality of adjacent magnets to produce a maximum average radial magnetic flux density within a coil winding array.

Due to the vector superposition of the magnetic fields and magnetic flux from a plurality of magnets, a nearly four-fold increase in magnetic flux density is achieved over conventional electromagnetic generator designs with a potential sixteen-fold increase in power generating capacity. As a regenerative shock absorber, the disclosed device is capable of converting parasitic displacement motion and vibrations encountered under normal urban driving conditions to a useful electrical energy for powering vehicles and accessories or charging batteries in electric and fossil fuel powered vehicles.

Electromagnetic actuators have already been proposed as passive or semi-active shock absorbers or as purely active devices in vehicle suspensions. Such actuators are promising for the flexibility of the configuration. The operation mode can in fact range from fully active to fully passive behavior including the regenerative mode in which part of the mechanical energy that would be otherwise dissipated, is converted in electrical energy. It can then be exploited to drive the device in active mode. Even in passive configuration, electromechanical shock - absorbers allow to easily adapt the damping force using a simple control system. The operating conditions do not affect the performances and the tuning of the design parameters can be obtained easily and with good accuracy. The electromagnetic shock absorber is shown in the figure (2.2)

 Fig (2.2) electromagnetic shock absorber

In order to overcome their weight and cost limitations careful attention must be devoted to the design of electromechanical actuators for suspension systems. Due to the fact that the weight of an electromagnetic actuator is basically determined by its force capacity, the specification about the maximum force should be obtained from the vehicle dynamic performances and not as simple carry-over from the datasheets of hydraulic dampers. The obtained procedure has been applied to design the front suspension damper of a C-segment vehicle. The aim was to analyze the potentialities of electromechanical dampers in automotive applications. The relevant specifications were given in terms of stroke, maximum speeds and damping coefficients. Additional specifications are:

1.     The suspension layout (McPherson) requires a configuration with structural capabilities.

2.     The damper must be connected to the same mechanical interfaces of the conventional one: the upright (wheel hub) and the strut mount (upper connection point to the vehicle chassis).

3.     Its size must fit in the inner diameter of the coil spring with an appropriate allowance.

Chapter 3-Working

3.1-Em shock

An EM Shock has been fabricated. The shock consists of three assemblies: the permanent magnet assembly, the coil assembly, and the case assembly. Voltage is induced in the shock windings when the coil assembly moves relative to the magnet assemblies. The case assembly aligns and enables the piston-like motion between the coil and magnet assemblies.

Relative to the commonly used hydraulic shock absorbers, electromechanical ones are based on the use of linear or rotary electric motors. If electric motor is of the DC-brushless type, the shock absorber can be devised by shunting its electric terminals with a resistive load. The damping force can be modified by acting on the added resistance. An integrated design procedure of the electrical and mechanical parameters is presented in the article. The dynamic performance that can be obtained by a vehicle with electromechanical dampers is verified on a quarter car model.

Electromechanical dampers seem to be a valid alternative to conventional shock absorbers for automotive suspensions. They are based on linear or rotary electric motors. If they are of the DC-brushless type, the shock absorber can be devised by shunting its electric terminals with a resistive load. The damping force can be modified by acting on the added resistance. To supply the required damping force without exceeding in size and weight, a mechanical or hydraulic system that amplifies the speed is required. This paper illustrates the modeling and design of such electromechanical shock absorbers. This paper is devoted to describe an integrated design procedure of the electrical and mechanical parameters with the objective of optimizing the device performance. The application to a C class front suspension car has shown promising results in terms of size, weight and performance.

3.2-PRINCIPLE OF ELECTROMAGNETIC SHOCK ABSORBER

Electromagnetic shock absorber is to use a new type of intelligent electromagnetic response independent suspension system. It uses multiple sensors detect road conditions and a variety of driving conditions, transfer to the electronic controller ECU, control of transient response of electromagnetic shock absorber, vibration suppression, maintain vehicle stability, particularly in high speed, Tu Yu obstacles show its advantages when more. Response speed of up to Electromagnetic Absorber 1000 Hz, 5 times faster than conventional shock absorbers, shock absorber completely solved the existence of traditional comfort and stability cannot be both the problem and can adapt to changing driving conditions and any road incentive, even in the most bumpy roads, the electromagnetic shock absorber also ensure the smooth running motorcycle, on behalf of the shock absorber development.

Hitachi of Japan developed electromagnetic shock absorber, for example, this is the electromagnetic shock absorber from the sensor, the electronic controller ECU, cylinder-type linear motor and the spring hydraulic shock absorbers 4 major components of the active suspension system.

System sensors are acceleration sensors and suspension travel sensors. Acceleration sensor to detect the extent of rugged road, transport to the electronic controller ECU, an order generation and shock absorber control the linear motor moving direction completely opposite reaction movement stroke to reduce the vibration of vehicles up and down. Suspension stroke sensor to detect the actual movement of shock absorber stroke, then back to the electronic controller ECU timely correction of linear motor reaction sports trip.

The core component of the system of linear motor and electronic controller ECU, the linear motor is actually a movement by the stator coil and magnet linear motor, it works the same as ordinary rotary motor. General Motors is the use of rotary current changes, so that the motor stator windings produce a rotating magnetic field, sensing the rotor magnet rotation. Linear motor can be regarded as the common rotary motor along the radius from the center cut, the flat start is made, so that the original rotation direction of the magnetic field becomes a moving magnetic field lines, while the rotation of the rotor into linear movement also.

Hydraulic shock absorbers installed in the spring the lower part of the linear motor, the stator coils fixed in the shock absorber cylinder, the coil current strength of the direct control by the electronic controller ECU, the electronic controller ECU acceleration sensor according to the actual road test Suspension travel conditions and the actual movement sensors to detect trip, an order in precise control of input current strength of the stator coil, linear motor to precisely control the direction of movement of anti-damping force and damping force, to ease road shock and vibration. Input current increases, the magnetic field generated in the stator coil stronger, linear motors have the opposite direction of the damping force and the greater damping force, we can see that the current size of the control system complete with driving acceleration and bumpy road conditions adapt.

This means that all kinds of road conditions and loads can choose the optimal damping force. When the vehicle in rugged driving on bad roads or single drive to double riding, pounding the wheel, the system control input greater stator coil current, so that linear motor produces the opposite direction of movement and shock absorber greater damping force and damping force shock absorber of the violent vibration of the buffer offset. Electronic controller ECU 1 S period in the resistance to shock absorber damping force and the continuous changes in 1 000, with hydraulic spring shock absorbers alone compared to both improve the response speed, but also improve the comfort, called the world's quickest and most advanced smart suspension system.

       Using a linear motor and non-use of linear motors can be compared to the vibration frequency of vibration in the vicinity of 1.5 Hz to reduce 8 dB. Currently, the electromagnetic shock absorber has been installed in the SUV (Sports Utility Vehicles) sport utility vehicle were experimentally obtained a large number of real driving data. By 2009, small quantities can be installed on SUV large displacement sports car and motorcycle.

For the modern sport utility motorcycle, the traditional spring-hydraulic shock absorber sports comfort and cannot be solved the contradiction between, there are many difficult to overcome the drawbacks:

1) The coil spring will be the impact of vibration and continuous vibrations easily lead to rider fatigue and irritability, potential hidden dangers.

2) shock absorber damping force increases, the faster the vibration reduction, but to parallel external coil spring in the shock absorber cannot be fully effective, while the damping force is too large, may result in shock absorber components and connections frame damage;

3) hydraulic damping force changes with temperature changes, prolonged use, the hydraulic oil with a small hole between the wall friction and internal friction of liquid molecules produce large amounts of heat, causing hydraulic oil temperature, viscosity decreases rapidly damping force decreased, the shock absorber damping performance of the resulting deterioration.

4) The adjustment is very limited, the existing multi-adjustable shock absorber coil spring generally only pre-load adjustment, increasing the spring stiffness, cannot really meet the different surface and different load driving cycle requirements.

3.3-Nomenclature

The different notations have been given below along with their units which are later useful for understanding the topic easily.

B_i = Magnetic flux in tesla

f = Frequency in Hz

F = Force in N

h = Height of pole ring in mm

I = Current in amp

K = Constant (nhBi) in volt-s/m

L = Length in mm

n = Number of turns / mm

P = Power generated in watts

R_c = Total resistance of coils in ohms

R_i = Resistance of external load in ohms

v = Velocity in m/s

V = Voltage in volt

                  

3.4-Primary equation for regenerated voltage

Faradays law of electromagnetic induction states that when an electric conductor is moved through a magnetic field, a potential difference is induced between the ends of the conductor. He proposed the principle that electromotive force induced in a conductor is proportional to the time rate of change of the magnetic flux change of that conductor.

V = n h v Bi                                                                                                     (1)

Voltage is generated in each section of the coil. Assuming B_i = 1 T and the coil is at 0.01 m/s, then each middle section of the outer coil will generate an open-circuit voltage of 0.169 volts. Each middle section of the inner coil will produce, in proportion to its smaller diameter, a smaller voltage of 0.062 volts. The bottom and top sections of each coil will generate only half these voltages, since their B_i = 0.5 T. For both coils the total voltage is

V = K v (m/s) = 68.9v = 0.69 volts.                                                                (2)

3.5-Damping force

When a straight wire of length L (m) conducts a current, I(A), and is subject to a magnetic field, B_i(T), normal to the wire, a force, F(N), is exerted on the wire of magnitude

F = I L B_i                                                                                                       (3)

The direction of the force is normal to the wire and field. The damping force developed on the coil assembly of the EM shock is the sum of the forces exerted on each section of the coil and (3) is applicable because of the coil geometry and the radial directions of the flux. Already, L = n h and

B_i = 0.5 T or 1 T are known for each section of the coils. The current I will be the same in all sections of the coils, but its magnitude depends on the impedance of the coil and the external load.

For the frequency range of interest, 0<f<100 Hz, the inductive reactance of the EM coils are negligible in comparison to its resistance. The resistance of the inner coil is 9 ohms and the outer coil has a resistance of 22 ohms, for a total of R_c = 31 ohms. By combining (2) and (3) for every section of the coils, the total damping force is

F = K² v / (R_l + R_c)                                                                               (4)       

here the impedance of the external load is assumed to be entirely resistive R_l. The power developed in the shock coil is given by

P = K² v² R_c / (R_l + R_c)²                                                                                                    (5)

The maximum damping force is developed when the external load is zero, Rl = 0. Maximum power occurs at the external load when Rl = Rc, and is equal to the power that occurs at the coil of the EM shock.  

3.6 Design considerations

Based on the requirements of the design, the energy harvester is modeled as a linear induction generator that incorporates shock absorber functions. Analysis will be used to guide the design and more comprehensive element analysis (FEA) is used.

3.7-Analysis and experiments

Experiment set-up and mathematical modeling. The 1:2 scale regenerative shock absorbers was fabricated based on the parameters derived from section 2. The magnet field intensity averaged over one coil direction in one space cycle 2H along the axial direction. was designed to characterize the voltage output and power output of the generator at various road conditions, as shown. The magnet assembly of the shock absorber was mounted in the mover of a vibration shaker. The coil assembly was mounted to the top plate, which is fixed on the base of the vibration shaker. The position of the coil assembly can be adjusted via a ¼ -20 threaded rod. The shaker drives the relative motion between the magnet and coil assemblies via a 5× power amplifier. Road conditions were simulated with a wave function generator. Waves at different frequencies and amplitudes were sent through the power amplifier to the vibration shaker. An oscilloscope was used to measure the output voltage, both peak and RMS values, of the shock absorber. The oscilloscope was also used to view the output waveforms generated from the shock absorber. A multi meter was used to measure current output.

Since the technology actively uses the weight of a vehicle for energy recovery, it could help speed the expansion of the hybrid and battery electric vehicle market from cars to vehicles of greater size, weight and payloads, such as SUVs, pickup and delivery trucks, mail trucks, school and city buses and other light and medium duty trucks.

The regenerative magnetic shock absorber sounds to like an electromechanical active suspension. If we feed energy into this device in the right manner, it can counter unwanted body motion. But then, energy can flow in either direction so we can use it as a shock absorber, which regenerates body motion energy rather than just converting it into heat like a conventional shock absorber.

An electromagnetic shock absorber according to the present invention has a shock absorber body 1 which makes telescopic motion in response to an input from outside. The shock absorber body 1 comprises a ball screw mechanism 15, which converts the telescopic motion into rotary motion and is composed of a ball nut 16 and a screw shaft 17, and power transmitting sections 13 and 24 having elastic bodies which transmit the rotary motion of the ball screw mechanism 15 to a rotary shaft 11 of a motor 10 while shifting a transmission phase when transmission torque of the rotary motion is changed. The motor 10 generates electromagnetic resistance to oppose against rotations which input into the rotary shaft 11. Thus, vibration or the like which inputs into the shock absorber body 1 from outside is damped by the electromagnetic resistance of the motor 10. Due to the power transmitting sections 13 and 24 which delay a rotary phase, moment of inertia of a rotor of the motor 10 is eased when a shocking load inputs into the shock absorber body 1. Therefore, it is possible to make a vehicle more comfortable to drive when the electromagnetic shock absorber is applied as a shock absorber of the vehicle.

The shock absorber body (1) comprises a ball screw mechanism (15) consisting of a ball nut (16) and a screw shaft (17) for converting a telescopic motion into a rotational motion, and power transmitting sections (13,24) provided with a resilient body for transmitting the rotational motion of the ball screw mechanism (15) to the rotary shaft (11) of a motor (10) while shifting the transmission phase upon variation in the transmission torque of the rotational motion. The motor (10) generates an electromagnetic force resisting against a rotation entering the rotary shaft (11). An external vibration entering the shock absorber body (1) is thereby damped by the electromagnetic resisting force of the motor (10). The power transmitting section delaying the rotational phase relaxes the inertial moment of the rotor of the motor when an impact load enters the shock absorber body, and the absorber enhances riding comfortableness when it is applied to a vehicle as a shock absorber.

The shock absorber comprising the above all mentioned things is shown in the figure (3.1).

 Fig 3.1 Electromagnetic shock absorber

Chapter 4- Testing

4.1-Electromagnetic testing machine

The lab testing of electromagnetic shock absorbers is shown in the fig (4.1).

    

  Fig (4.1) Electro-magnetic testing machine

EM shock fabricated at ANL was tested on a 300 lb electro dynamic shaker. The base of the shock was supported from a stand and the moving rod was attached to a stinger through an impedance head as shown in Fig 4.1. The shaker was run using sine dwell at certain frequencies. One end of the inner coil and one end of the outer coil were connected such that combined voltage can be measured. The other ends were connected with various resistances (0.1 Ω, 30 Ω, 50 Ω or open circuit). The EM shock was excited at two different levels 0.5g and 1 g at frequencies ranging from 10 Hz to 100 Hz. The EM shock was tested at 1 g level with a 33-Ω external resistance (close to optimum resistance).

Table 4.1 Results for 33-Ω external resistance

                                                        

Frequency in Hz	Velocity in mm/sec	Displacement in mm	Voltage across 33 ohm  in volt	Power Generated in watts
10	110.38	1.757	3.082	0.2878
11	100.35	1.452	2.276	0.1570
12	91.99	1.22	2.09	0.1324
15	73.59	0.781	1.47	0.0655
20	55.19	0.439	1.333	0.0538
30	36.79	0.195	0.883	0.0236
40	27.60	0.11	0.673	0.0137
50	22.08	0.07	0.553	0.0093
60	18/40	0.049	0.475	0.0068
70	15.77	0.036	0.417	0.0053
80	13.80	0.027	0.372	0.0042
90	12.26	0.022	0.34	0.0035

Chapter 5-Types

5.1-Types of electromagnetic shock absorbers                                   

These are of two types:

1)      Linear type electromagnetic shock absorbers

2)      Rotary type electromagnetic shock absorbers

5.2-Linear electromagnetic shock absorber

An electromagnetic linear generator and regenerative electromagnetic shock absorber is disclosed which converts variable frequency, repetitive intermittent linear displacement motion to useful electrical power. The innovative device provides for superposition of radial components of the magnetic flux density from a plurality of adjacent magnets to produce a maximum average radial magnetic flux density within a coil winding array. Due to the vector superposition of the magnetic fields and magnetic flux from a plurality of magnets, a nearly four-fold increase in magnetic flux density is achieved over conventional electromagnetic generator designs with a potential sixteen-fold increase in power generating capacity. As a regenerative shock absorber, the disclosed device is capable of converting parasitic displacement motion and vibrations encountered under normal urban driving conditions to a useful electrical energy for powering vehicles and accessories or charging batteries

The linear generator comprises an assembly of magnet arrays, high magnetic permeability spacers and coil winding arrays with an innovative magnet-spacer-coil configuration and geometry which uniquely provides for vector superposition of the magnetic fields.

Unlike conventional devices, such as a linear motion generator, a regenerative shock absorber, or a reciprocating linear motor, the Goldner device provides substantially more uniform and higher average radial magnetic flux density throughout coil winding volumes, according to the inventors, resulting in the increase in electrical power regeneration.

In their patent filing, the inventors claim that the regenerative electromagnetic shock absorber system is capable of peak power generating capacity of between about 2 to 17 kW, average power generating capacity ranging from about 1 to 6 kW, and power contribution efficiencies ranging from 8-44% for passenger vehicles traveling at relatively moderate speeds on typical roads encountered under normal urban driving conditions.

For rough roads with bump slopes as high as 0.10 and displacement velocities greater than 1.0 m/s, they claim that the system may generate nearly 50 kW of peak power and nearly 16 kW of average power with a power contribution efficiency approaching 70%.

It is anticipated that, with devices fabricated with high permeability materials having a saturation magnetization of greater than 2.5 Tesla, even greater peak and average power outputs and power contribution efficiencies may be realized from additional increases in radial magnetic flux density in the coil windings.

5.3-Rotary electromagnetic shock absorbers

Rotary electromagnetic shock absorbers are gear-like devices designed to limit the movement of a moving piece of equipment. It absorbs and slows down rotary motion for the vibration, noise, and machine component wear. It enables products to perform with a smooth mechanical motion. Rotary shock absorbers control vertical and lateral motion in rail suspension applications. It is built to outlast and outperform linear type shock absorbers. It is designed to slow down the rotary motion within the machine. It is used to provide a smooth, controlled retraction of a movable mechanical device. It contains different grades or blends of silicone to produce varying torque values to offer specific limitations or speeds of the moving piece.

These are found in a variety of industries such as furniture, cabinets, automotive, and the electronics industry (e.g., CD door or tray opens slowly). These are commonly used for deployment systems by the aerospace industry, i.e. for solar panels on satellites. When solar panels open in space, they are opened by a spring and there has to be some type of damper in the system to stop excessive acceleration and prevent it flying off into space. It can protect delicate electronics and extend the life of certain products by helping to prevent lid and access panel closure damage. Superior noise suppression is achieved as a direct result of the smooth flowing motion provided by dependable rotary dampers.

Chapter 6-Importance and Scope

The project undertaken has bright scope for future study in the areas of different aspects of mechanical engineering. There is the scope for research in electromagnetic shock absorbers and to have better utilization of energy and in industries in order to reach more accurate conclusion and suggest remedial methods.

The energy dissipated in shock absorbers can be recovered with the help of electromagnetic shock absorbers. The vehicle fuel efficiency can also be increased.

Sometimes products are designed so that vibrations are min. and sometimes products are designed so that sound is minimum (or maximum).  Eventual goal is to either make human being more comfortable or make a machine or building last longer

Now may be the time to take apart a product and think all engineering aspects of it.  Vibration and acoustics may be one concern, material and manufacturing issues are also of concern and sometime there may be interdisciplinary i.e. electrical or industrial engineering issues need to be addressed. 

Thus the topic has bright scope in the future.

Chapter 7- Advantages and Disadvantages

7.1 Advantages

It has the following advantages

1) It converts the energy wasted due to vibration into useful electrical power.

2) It increases the vehicle fuel efficiency.

3) It Produces 8 watts of power per wheel when the vehicle runs at 72.5 kmph.

4) It is very economical

5) It has made possible to recover the waste heat energy wasted in the conventional shock absorbers

7.2 Disadvantages

The only disadvantage is that the initial cost of installing the EM shock absorbers is higher than the conventional sock absorbers.

Chapter 8-Conclusion

Electromagnetic actuators have already been proposed as passive or semi-active shock absorbers or as purely active devices in vehicle suspensions. Such actuators are promising for the flexibility of the configuration. The operation mode can in fact range from fully active to fully passive behavior including the regenerative mode in which part of the mechanical energy that would be otherwise dissipated, is converted in electrical energy. It can then be exploited to drive the device in active mode. Even in passive configuration, electromechanical shock - absorbers allow to easily adapt the damping force using a simple control system. The operating conditions do not affect the performances and the tuning of the design parameters can be obtained easily and with good accuracy.

The testing demonstrated that in typical driving conditions, traveling at a speed roughly equivalent to 45 mph (72.5kmph) the regenerative shock absorber was able to harvest 2-8 watts of power. A system would be able to harvest approximately 64 watts per wheel. So with the regenerative shock absorbers put on all four wheels it should be possible to recover a total of around 256 watts under such driving conditions. Driving on rough surfaces such as a corrugated dirt track the system should be able to harvest considerably more.