ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

33

REGENERATIVE SUSPENSION

Purushothaman G., Divyaa V.G., Veena Kannan, Subiksha M., Balamurugan M.

SASTRA Racing Team (ESVC19-P-17)

School of Mechanical Engineering,

SASTRA University, Thanjavur.

ABSTRACT

A valuable amount of kinetic energy remains

unutilized in vehicle suspension systems. The

vehicle can be made more energy efficient by

actualizing a regenerative mechanism that works

to render useful the unutilized kinetic energy in

the suspension system.

Regenerative suspensions are unavailable in

current vehicles due to the major design changes

required in the shock absorbers to accommodate

such a mechanism. These vital deviations to the

shock absorber not only intensify the complexity

of the car but could also potentially increase the

vehicle’s retail price drastically. Considering the

stated issues and keeping in mind the benefit of a

regenerative system a suitable mechanism has

been suggested. The regenerative mechanism

proposed in this paper can be attached parallel to

the vehicle shock absorber as a separate device

fixed without influencing the existing suspension

system.

Linear generator system running based on

Faraday’s Law is used to produce electrical

energy from kinetic energy. Dimensions and

specifications (such as coil diameter, number of

windings, type/strength of magnet) of the linear

generator system was defined complementing to

the suspension dimension and outputting

maximum power.

1. INTRODUCTION

The need for alternate energy resources has

skyrocketed overwhelmingly over the past few

decades. Green manufacturing is a process that is

being used to decline waste of resources and various

types of pollution through sequential design and

research. Subsequent growth in green manufacturing

technology in vehicle industry to prognosticate what

the demand for future will be like has played a key

role in development[18].

One extensive energy loss in automobiles isdue to

dissipation of vibrational energy in the suspension

strut. Efficiency of the automobilecan be elevated by

transforming the vibrational energy to useful energy.

The main role of suspension system is to provide

comfort to passengers and driver without making

them feel like they are traveling on rugged roads with

lot of bumps by reducing shock forces and also

preventing the vehicle from bounce, roll and jolt.

Although regenerative suspension systems have been

a research field from 1990 with many papers having

been published since then, it still has a major scope

for improvement. Implementing it in vehicles being

manufactured to meet the demands in commercial

sector is still a challenge today(10).

Rather than dissipating the vibrational energy in the

form of heat, the regenerative system serves as hope

for translating the kinetic energy into electricity with

the help of magnets, hydraulic energy and high-speed

movement of reciprocating parts which can be used

in the future.

Comparatively regenerative suspension system is

easier to use in electrical or hybrid vehicle which

have their own energy source that can control the

peak power and regenerative power due to the inbuilt

electronic circuits in them(17).

2.TYPES OF REGENERATIVE SUSPENSION

In general, the quantity of fuel used for vehicle

motion is very low [13]. The extent of energy wasted

is valuable and can be used for diverse applications.

A regenerative suspension makesa productive use of

this energy possessed by the suspension. There are

many applications for utilizing the energy drawn

from the suspension in which one specific case

suggested by [10] uses the energy for an

electromagnetic active suspension and therefore

eliminating the requirement for a separate power

source. Regenerative suspensions are of two types –

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

34

electromagnetic and mechanical systems. This

classification is done according to its working

principle. Multiple factors such as feasibility, weight

and efficiency are to be taken into consideration prior

to deciding the type of regenerative suspension.

The mechanical regenerative suspension system

works by the basic principle of converting the kinetic

energy drawn from the piston in the strut into

potential hydraulic or pneumatic energy. A realizable

design suggested by [14] is as follows. Through a

hose, a pump is attached to the accumulator cylinder

which is charged by pressurized fluid. A motor,

accumulator and generator are then set up in such a

way that energy from revolution of the generator

shaft can be availed by yielding electricity. Due to

complicated pipeline system, weight and space

constraint the mechanical regenerative suspensions

are not preferred. Moreover, there is a probability for

the system to fail in the occasion of fracture or

leakage of the hose.

Solving the issues put forward in the case of

mechanical regenerative suspensions, the

electromagnetic regenerative suspension is a better

substitute. Alternatively, the electromagnetic

regenerative suspension converts the kinetic energy

into electrical energy. Electric energy can be

conveniently accumulated, employed, necessitates

fewerroom, undemanding in design and has a more

pronounced efficiency [15]. Under the

electromagnetic regenerative suspension there are

two categories linear and rotary in which the rotary

type can further be classified according to the

mechanism implemented as follows: rack-pinion

transmission, ball screw transmission and hydraulic

transmission [16].

The subsequent tabulation is a collation of the

different electromagnetic regenerative suspensions

asidentified by [6]:

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

35

Figure 1: Electromagnetic regenerative suspension - types

3. EXPERIMENTAL DESIGN

In the front suspension, the ends of the strut are fixed

at the frame and the lower control arm. The lower

control arm is attached at two points to the car frame.

A linear electromagnetic energy harvesting system is

stationed parallel to the strut in the front suspension.

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

36

A telescopic cover model is used for the regenerative

set up. The coil is wound around AISI 1018 mild

steel pipe, which moves up with the lower control

arm, on encountering a jolt. A mild steel core

(ferromagnetic) is inserted for the length of the

winding. The external cover encompasses a set of

twelve magnets positioned in its inner surface with

like poles adjacent to one another.

The displacement of the coil wound ferromagnetic

(steel) coreresults in a change in the magnetic flux

that will induce a current flow. The usage of steel

core increases the magnetic field strength due to its

ferromagnetic properties.

Current is generated according to Faraday’s law as

the coil wound ferromagnetic (steel) core oscillates

with respect to the stationary magnets. A

ferromagnetic core is specifically used as it magnifies

the magnetic field. In addition, magnets with good

magnetic attributes were requisited, hence

Neodymium [NdFeB] magnets were designated.

The magnets are fixed on the inner side of the PVC

pipe.It is ensured thatthe cover is constructed of a

good material with optimum insulation. Enamel

coated copper wires are wound on a central

reciprocating rod made of AISI 1018 steel material.

Stepped billets (steel caps) of the required

dimensions encloses the set up at the top and bottom

of the PVC pipe.

A LM2UU linear bearing is fixed at the bottom to

maintain a constant air gap between the coil and the

magnet, and for a constant linear motion of the

reciprocating rod. Permanent magnets with repelling

poles are placed at the top of the reciprocating rod

and the top billet to push the coil back to the original

position.

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

37

Figure 2: Solidworks model of regenerative system

Figure 3: Prototype of regenerative suspension

4. DIMENSIONS

The front suspension has an eye to eye length of 15

inch. The dimensions of the regenerative system was

fixed accordingly to get same eye to eye length.

PVC pipe

Outer Diameter : 2 inches

Inner Diameter : 47 mm

Total length : 30 cm

Central reciprocating rod - steel 1018

Diameter : 1 inch

The neodymium magnets used are

rectangular having dimensions : 50 *25*2.5

mm

Taking into account the magnet dimensions

and the available surface area within the

pipe to place it , 12 magnets can be

optimally placed for maximum output, per

pipe. Proximate magnets are 1.3 cm apart.

Upper travel of the strut used in front

suspension : 2.2 inches

Lower travel of the strut : 2.1 inches

Total travel : 4.3 inches

Giving allowance for the travel length, the

steel rod length is fixed at 31.3 cm.

30 AWG enamel coated copper wire

Diameter of the enamel coated copper wire:

0.3 mm

No. of layers of wire wound for max output

possible: 6

The length of the coil wound over the steel

rod for optimum output: 5.42 inches

The coil wire has been wound over the

above-mentioned length such that it is

always within the magnetic field.

5. EXTERNAL CIRCUIT

An alternating output is produced due to oscillatory

motion of the rod. A W10 full bridge rectifier is used

to rectify the alternating voltage. This voltage is to be

used to charge the 12V secondary battery. A

XL4015E1 DC to DC converter is used to convert the

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

38

rectified output to 12V to efficiently charge the

battery.

6. SIMULINK MODEL

The regenerative system was modelled in Simulink.

The inputs for the system are the force (F), number of

layers of winding (n), diameter of coil (D), diameter

of wire (d), length of winding (L), length of magnet

(z), magnetic field intensity of magnet (B) and

external resistance (R). The output of the system is

the emf induced (e), current (i) and opposing force

developed (F*).

The value of various parameters issummarized:

Diameter of coil (D) : 0.0254 m

Diameter of wire (d) : 0.25 mm = 0.0003 m

Magnetic field intensity (B) :1 T

Layers of winding (n) : 6

Length of winding (L) : 0.1148 m

Dimensions of magnet: 50 x 25 x 2.5 mm

First the suspension system was modelled and based

on known parameters the damping coefficient was

determined. Then the model was modified to

determine the output emf, current and opposing force.

Figure 4: Simulink model of suspension system

The maximum bump force on the wheel = 1040 N

Motion ratio = 0.6

Maximum force on the suspension = 1040/0.6 =

1733.33 N

Maximum bump height considered is 5 inch. The

time required to pass halfway through the bump at a

speed of 15 Km/hr is 0.3175 seconds. The time taken

for the force to reachpeak value is taken as 0.3175

seconds. This force is given as a sine wave, with a

bump in the first 5 seconds and a droop in the next 5

seconds.

When the coil advances past the magnets, an

opposing force will begin to originate. This opposing

force is calculated and is subtracted from the bump

force to get the actual force acting on the system.

The total unsprung mass is 60 Kg. Mass considered

for 1 wheel is 15 Kg.

The suspension travel from mean position is

represented by x. The corresponding acceleration and

velocity are represented by a and v.

ma = F – kx – Cv

k represents suspension stiffness. C represents

damping coefficient.

k = 25 N/mm

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

39

C = 0.2 Ns/mm

a = 1/m * (F – kx – Cv)

v = ∫ 1/m * (F – kx – Cv) dx

x = ∬ 1/m ∗ (F – kx – Cv) dx

The emf induced is,

emf = dɸ/dt

ɸ = NB.A cosϴ

dɸ/dt = NB cosϴ x dA/dt

dA/dt = D x dx/dt = Dv

∴ emf, e = NBDvcosϴ = n x (L/d) x BDv cosϴ

In order to account for the cosϴ factor and to account

for efficiency the emf obtained is multiplied by a

factor of 0.5.

The external resistance is represented by R.

The current induced, i = e/R

The system will generate an opposing force. This is

generated due to the coils present in the region of

magnetic field.

The opposing force, F* = i x B x (z/d) x ПD sinϴ

This force is subtracted from the bump force and

given as input to the system.

Figure 5: Bump force

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Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

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Figure 6: Opposing force

Figure 7: Simulink model of regenerative suspension

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

41

Figure 8: Emf induce

The emf plot shows an instantaneous surge in the

voltage initially which can’t be used as it occurs for a

very short period of time. It occurs due to a very high

instantaneous force of 1733.33 N. After the initial

damping the amplitude of the damped signal reduces

as slower rate which can be rectified and stored in the

battery

7. RESULT AND DISCUSSION

A prototype of the regenerative suspension was

prepared. The emf and current values were measured.

The average value of emf measured was 2.5V with

peak being 3.2V. The emf output from the Simulink

model shows an instantaneous emf of nearly 10V

initially, which occurs for a very short period of time.

Once damping ensues it shows emf values in the

range of 2.5V to 5V.

8. CONCLUSION

The work has successfully modelled system for

regeneration of energy from suspension system. A

sample prototype has also been manufactured as

proof of concept

9. SCOPE FOR DEVELOPMENT

The regenerative suspension is relatively a new

development and has a high scope for future

enhancement. Many scholars have made the effort to

commence the development of regenerative

suspension and bring this into attention for numerous

potential researchers. Being at its state of infancy,

regenerative suspension is definitely a budding topic

of research in the automobile industry. It can be

installed in commercial cars, trucks and multi utility

vehicles for energizing the auxiliary electrical

components. Such a system will be even more

effective in case of off roading vehicles.

ISSN 2457-0931

Imperial International Journal of Eco-Friendly Technologies (IIJET)

Vol.3, Issue – 1 (2018), pp. 33-43

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Imperial International Journal of Eco-Friendly Technologies (IIJET)

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