performance evaluation and damping characteristics of ... · regenerative suspension system (hprss)...

International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 7 (2018) pp. 5436-5442

© Research India Publications. http://www.ripublication.com

5436

Performance Evaluation and Damping Characteristics of Hydro-Pneumatic

Regenerative Suspension System

Magdy N. Awad 1,*, Mohamed Ib. Sokar2, Saber A. Rabbo2, M.E. El-Arabi1

1 Department of Design and Production Engineering, Faculty of Engineering, Cairo University, Cairo, Egypt. 2 Department of Mechanical Engineering, Faculty of Engineering at Shoubra, Benha University, Egypt.

Abstract

This paper presents an evaluation of Hydro-Pneumatic

Regenerative Suspension System (HPRSS) based on Advanced

Modeling Environment Simulations (AMEsim). The general

setup of the HPRSS and the working principle is explained.

The performance of HPRSS is compared to the conventional

suspension system, by using single and double acting cylinder

suspension systems. In addition, the study investigates the

effect of the system parameters on the system performance and

the damping characteristics. The simulation results indicate

that the HPRSS is more comfortable in riding compared to the

other systems due to the reduction of peak oscillation by 20%.

Also, the results show that the optimal accumulator size and

the external load resistance have a significant impact on the

suspension performance and harvested power. Large size of the

accumulator up to 0.75 L increases the stability during the

piston motion.

Keywords: Energy harvesting, regenerative suspension,

hydraulic rectifier, damping characteristics, vehicle dynamics.

INTRODUCTION

Today the energy harvesting is widely used in many

transportation applications such as road tunnels [1], railroad

track [2] and energy recovery systems for automotive

applications [3]. Furthermore vehicle applications such as

braking, crankshaft and vehicle suspension. The oscillation in

automotive wheels is a rich source of green energy and

unfortunately this energy is dissipated in conventional

suspension. Several studies have presented the wasted energy

of shock absorber and proposed many ideas in this field to

convert the dissipated energy to electric power. In addition,

some studies have addressed maximizing the energy harvested

from the suspension system [4-6]. Karnopp [4] studied the

The study was supported by the Faculty of Engineering at Shubra, Benha

University, Egypt. The authors express their gratitude to this supportive

University and the supervisors who provided invaluable advice and

suggestions to this study.

Magdy Naeem, PhD student at the Mechanical Design and Production

Engineering Department, Cairo University, Egypt.

(E-mail: [email protected]).

Mohamed Ib. Sokar, is an assistant Prof. at the Mechanical Engineering

Department, Faculty of engineering at Shubra, Benha University, Egypt.

(E-mail: [email protected]).

S. M. Abdrabbo, is Prof. Dr. at the Mechanical Engineering Department,

Faculty of engineering at Shubra, Benha University, Egypt. (E-mail:

[email protected]).

M.E. El-Arabi, is with the Mechanical Design and Production Engineering

Department, Cairo University, Egypt. (E-mail:

[email protected]).

linear permanent magnet motors application with variable

resistors as variable mechanical vehicle damper. This study

proved that the electromagnetic damper is practical even

though the response time has deteriorated with a long stroke.

[5] Presented a regenerative shock absorber with special

attention to enhancing ride comfort and road handling. An

analytical optimization methodology is presented to determine

the optimal stiffness and damping coefficients to achieve the

best ride comfort and energy regeneration [6]. There are many

different designs and schemes for transmission the forces

subjected from road profile to the regenerative suspension

system. The rack and pinion mechanism is used in the

mechanical regenerative suspension to rectify the direction of

DC motor rotation [7-9]. The linear and rotary electromagnetic

regenerative suspension mechanism was investigated [10-13].

The hydraulic shock absorber is improved based on the

hydraulic rectifier that maintains the unidirectional oil flow

through the system to maximize the energy harvested [14-18].

In this paper, an accurate design for the regenerative

suspension system is proposed, namely Hydro-Pneumatic

Regenerative Suspension System (HPRSS), It is organized as

follows: Section 2 describes the general setup and working

principle for the hydro-pneumatic suspension system and the

effect of the hydraulic rectifier. Section 3 the evaluation of the

HPRSS system performance and damping characteristics is

presented. Section 4 Simulation Model of HPRSS is presented.

Section 5 discussed the simulation results and effect of system

parameters. Finally the conclusion from the results are

provided in section 6.

GENERAL SETUP AND WORKING PRINCIPLE

The system description

The configuration of the HPRSS is shown in Fig.1. The basic

hydro-pneumatic suspension system depends on three main

components: a hydraulic cylinder, hydro-pneumatic

accumulator, and the hydraulic fluid. When the shock absorber

subjected to external force from road profile, this force leads to

increase the hydraulic pressure inside the shock absorber and

compressed the gas inside the accumulators. The accumulator

fluid volume and pressure are changed until the pressure level

reached to the balance inside suspension system. The main

influence of the hydraulic accumulator to absorb the sudden

shocks and minimize pressure fluctuation. The components

that used to harvest energy includes the hydraulic motor,

electromagnetic generator, the hydraulic rectifier and the

external load resistor. The energy harvesting process of the

HPRSS is described in Fig. 2.



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The Significance of the Hydraulic Rectifier

The main function of the hydraulic rectifier is to keep the

hydraulic motor rotation in the one direction during

compression (positive half cycle) and extension (negative half

cycle) that maximizes the power of the electromagnetic

generator. The hydraulic flow path through the system which

subjected to external sinusoidal road input signal is shown in

Fig 3. It can be seen that the flow rate during the extension

cycle is lower than the compression cycle due to the different

size of the cylinder chambers.

EVALUATION OF THE HPRSS SYSTEM PERFORMANCE

The HPRSS performance was evaluated by comparing it with

the corresponding conventional mechanical suspension and

hydro-pneumatic suspension with single and double acting

cylinder. A step input signal is used to simulate the road profile

with an amplitude 0.05m and simulation time 0.1 to 10 seconds

generated by the signal and control library to study suspension

performance and system efficiency to isolate road shocks. The

schematic diagram of the quarter car model with the

conventional mechanical suspension and hydro-pneumatic

suspension based on single and double acting cylinder is

shown in Fig 4. The quarter vehicle parameters used in this

study are listed in table1.

Figure 1. Schematic diagram for Hydro-Pneumatic Regenerative Suspension System

Figure 2. The HPRSS energy harvesting process through the system.

Figure 3. The Hydraulic flow path through the system.



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Damping Characteristics for HPRSS

In order to analyze the system performance and evaluate

damping characteristics of HPRSS, force-displacement and

force-velocity response for the HPRSS system were compared

with the corresponding conventional mechanical damper. The

HPRSS model was built with and without accumulators to

investigate the significance of the accumulators on the

performance of the suspension system. Furthermore, a number

of tests were performed using different standard accumulator

sizes, road profiles and external load resistance to explain their

effect on the system performance and the harvested

power. The AMESim models of the conventional mechanical

damper and the HPRSS model with and without accumulators

with different sizes (0.75 L, 0.5 L, 0.35 L and 0.16 L) are

shown in Fig 5.

SIMULATION MODEL OF HPRSS

AMEsim is one of the most powerful simulation programs that

can accurately simulate the combined system, it contains

various libraries such as hydraulic, mechanical and electrical

libraries. The control library used to simulate the road profile

test signals. The mechanical library is used to construct the

main components of quarter car such as wheel tire model,

spring, sprung and unsprung masses. The hydraulic library is

used to build the hydraulic component such as double acting

cylinder, check valves, accumulators, hoses and hydraulic

motor. Lastly the electric circuit and electromagnetic generator

were selected from the electric library. The block diagram of

the regenerative suspension model was illustrated in Fig 6.

Figure 6. The Hydro-Pneumatic Regenerative Suspension

System (HPRSS) model.

RESULTS

The displacement of sprung and unsprung masses of the

conventional mechanical suspension system is shown in Fig. 7,

where the amplitude of sprung mass is greater than the

unsprung mass also the damping time of the unsprung mass

about 1 second while the sprung mass is about 3 seconds. Fig.

8 illustrates the displacement of sprung and unsprung masses

of the hydro-pneumatic suspension based on the single acting

cylinder. The sprung and unsprung masses took about 9

seconds and 2 seconds respectively to reach the steady state

zone and the maximum overshoot of the sprung mass is larger

than unsprung mass. It can be noted that the behavior and the

frequency characteristics of the hydro-pneumatic system and

mechanical system are totally different. Similarly, Fig. 9 shows

the displacement of sprung and unsprung masses of the hydro-

pneumatic suspension based on the double acting cylinder. The

TABLE I

THE QUARTER VEHICLE PARAMETERS

Symbol Parameter value

V1 Accumulator 1 size 5 e-4 m3

P1 accumulator 1 pre-charge pressure 20 Bar

V2 Accumulator 2 size 7.5 e-4 m3

P2 accumulator 2 pre-charge pressure 5 Bar

Da Accumulator inlet port diameter 0.012 m

Dcv check valve nominal diameter 0.01 m

Pcv check valve opening pressure 0.7 Bar

RL External load resistor 8 Ohm

X0 Hydraulic cylinder balance position 0.1 m

XFull Hydraulic cylinder Full stroke 0.2 m

DM Hydraulic motor displacement 8.2 e-6 m3/rev

DP Piston diameter 0.05 m

Dr rod side piston diameter 0.02 m

Ks Spring rate 15000 N/m

Ms Sprung mass 300 kg

Wnom Typical speed of hydraulic motor 500 rpm

Mus Unsprung mass 30 kg

Dw Wheel damping 1000 N/(m/s)

Kw Wheel stiffness 180000 N/m

Figure 4. (a) The conventional mechanical vehicle

suspension system. (b) The hydro-pneumatic suspension

based on single acting hydraulic cylinder, (c) The hydro-

pneumatic suspension based on double acting hydraulic

cylinder

Figure 5. (a) The conventional mechanical damper (b)

The HPRSS model with accumulator, (c) The HPRSS

model without accumulator



5439

maximum overshoot of both sprung mass and unsprung mass

response are less than the previous systems, but the

conventional mechanical suspension has less damping time to

reach the steady state zone. As shown in Fig. 10, it can be

observed that the HPRSS achieves the best overshoot and

damping time of sprung and unsprung masses compared to

other suspension systems considered in this study.

Figure 7. The displacement of sprung mass and unsprung mass

for the conventional mechanical suspension system.

Figure8. The displacement of sprung mass and unsprung mass

for hydro-pneumatic suspension based on the single acting

hydraulic cylinder.

Figure 9. The displacement of sprung mass and unsprung

mass for hydro-pneumatic suspension based on the double

acting hydraulic cylinder.

Figure 10. The displacement of sprung mass and unsprung

mass for HPRSS.

Fig. 11 and Fig.12 shows the comparison of the damping force

and force-displacement response for the conventional

mechanical and HPRSS with and without accumulator

respectively. For conventional mechanical and HPRSS without

the accumulator, the damping force gradually changes with the

shock absorber motion to reach the maximum value at the

maximum displacement and then gradually decrease. The

maximum damping force only appears for a short period in

conjunction with the maximum speed of absorption. On the

other hand, the accumulators play an important role to

conserve the energy in HPRSS, the effect of the accumulators

appears in maintaining the maximum damping force most of

the oscillation time and minimizing the pressure fluctuation to

ensure the stability of the hydraulic motor rotation.

Figure 11. Comparison of the damping force between the

conventional mechanical and HPRSS with and without the

accumulator

Figure 12. Comparison of the force-displacement response

between the conventional mechanical and HPRSS with and

without the accumulator.

The effect of the accumulator size on the damping

characteristics was tested using different accumulator sizes

(0.75 L, 0.5 L, 0.35 L and 0.16 L). Fig.13 and Fig.14 shows the

force-displacement response and force-velocity response for

the HPRSS system. It is clear that the large size of the

accumulator increases the stability of the damping force during

the piston motion.



5440

Figure 13. Variation of the force-displacement response for

the HPRSS system with different accumulator sizes

Figure 14. Variation of the Force-velocity response for the

HPRSS system with different accumulator sizes.

Fig. 15 and Fig. 16 shows the force-displacement response for

the HPRSS system with an initial pressure 20 bars and 10 bars

respectively for accumulator 1, which subjected to different

road inputs.


the HPRSS system with different road inputs at initial

accumulator pressure 20 bar.


the HPRSS system with different road inputs at initial

accumulator pressure 10 bar

In order to explore the impact of external load resistance on

system performance and energy harvesting, different resistance

values have been tested. The force-displacement and force-

velocity response are shown in Fig. 17 and Fig. 18

respectively. It can be observed that the values of load

resistance have a significant impact on the damping forces. The

optimum resistance value is necessary to maximize absorption

shock for each type of vehicle. Fig. 19 and Fig. 20 shows the

variation of the electric generator output power and voltage

respectively. The increasing the value of external load

resistance leads to reduce the regenerative power.


the HPRSS system with the different load resistance

Figure 18. Variation of the Force-velocity response for the

HPRSS system with the different load resistance.

Figure 19. Variation of the electric generator output power

with the different load resistance.



5441

Figure 20. Variation of the electric generator output voltage

with the different load resistance.

CONCLUSION

In this paper, the study of Hydro-Pneumatic Regenerative

Suspension System (HPRSS) is discussed. The HPRSS and its

damping characteristics are assessed by comparing its

performance with the conventional mechanical suspension and

hydro-pneumatic suspension with single and double acting

cylinder. The results show that HPRSS has better performance

than other suspension systems in both reducing vibration and

increased harvested energy by approximately 19%.. The effect

of the presence of accumulators is studied by building the

HPRSS simulation model with and without accumulators. In

addition, the effect of using different standard accumulator

sizes, road profiles, and external load resistance is investigated.

The accumulators could maintain the maximum damping

force with the oscillation time and ensure the stability of the

hydraulic motor rotation. The large size of the accumulator

increases the stability of the damping force during vehicle

vibration. Moreover, the appropriate selection for both external

load resistance and accumulator size have a significant effect

on the damping force of the suspension system and harvesting

energy from road vibrations.

REFERENCES

[1] Zhang, Z., et al., 2016. Design, modelling and practical

tests on a high-voltage kinetic energy harvesting (EH)

system for a renewable road tunnel based on linear

alternators. Applied Energy. 164: p. 152-161. DOI:

10.1016/j.apenergy.2015.11.096.

[2] Zhang, X., et al., 2016. A portable high-efficiency

electromagnetic energy harvesting system using

supercapacitors for renewable energy applications in

railroads. Energy Conversion and Management. 118: p.

287-294 DOI: 10.1016/j.enconman.2016.04.012.

[3] Gabriel-Buenaventura, A. and B. Azzopardi, 2015.

Energy recovery systems for retrofitting in internal

combustion engine vehicles: A review of techniques.

Renewable and Sustainable Energy Reviews. 41: p. 955-

964 DOI: 10.1016/j.rser.2014.08.083.

[4] Karnopp, D., 1989. Permanent Magnet Linear Motors

Used as Variable Mechanical Dampers for Vehicle

Suspensions. Vehicle System Dynamics. 18(4): p. 187-

200 DOI: 10.1080/00423118908968918.

[5] Zuo, L. and P.-S. Zhang, 2011. Energy Harvesting, Ride

Comfort, and Road Handling of Regenerative Vehicle

Suspensions. p. 295-302 DOI: 10.1115/dscc2011-6184.

[6] Huang, B., et al., 2015. Development and optimization of

an energy-regenerative suspension system under

stochastic road excitation. Journal of Sound and

Vibration. 357: p. 16-34 DOI: 10.1016/j.jsv.2015.07.004.

[7] Li, P. and L. Zuo, Equivalent Circuit Modeling of

Vehicle Dynamics With Regenerative Shock Absorbers,

in Volume 1: 15th International Conference on Advanced

Vehicle Technologies; 10th International Conference on

Design Education; 7th International Conference on

Micro- and Nanosystems. 2013.

[8] Li, Z., et al., 2013. Electromagnetic Energy-Harvesting

Shock Absorbers: Design, Modeling, and Road Tests.

IEEE Transactions on Vehicular Technology. 62(3): p.

1065-1074 DOI: 10.1109/tvt.2012.2229308.

[9] Li, Z., et al., 2013. Energy-harvesting shock absorber

with a mechanical motion rectifier. Smart Materials and

Structures. 22(2): p. 025008 DOI: 10.1088/0964-

1726/22/2/025008.

[10] Zhang, G., J. Cao, and F. Yu, 2012. Design of active and

energy-regenerative controllers for DC-motor-based

suspension. Mechatronics. 22(8): p. 1124-1134 DOI:

10.1016/j.mechatronics.2012.09.007.

[11] Gysen, B.L.J., et al., 2011. Efficiency of a Regenerative

Direct-Drive Electromagnetic Active Suspension. IEEE

Transactions on Vehicular Technology. 60(4): p. 1384-

1393 DOI: 10.1109/tvt.2011.2131160.

[12] Zuo, L., et al., 2010. Design and characterization of an

electromagnetic energy harvester for vehicle suspensions.

Smart Materials and Structures. 19(4): p. 045003 DOI:

10.1088/0964-1726/19/4/045003.

[13] Hao, L. and C. Namuduri, 2013. Electromechanical

Regenerative Actuator With Fault-Tolerance Capability

for Automotive Chassis Applications. IEEE Transactions

on Industry Applications. 49(1): p. 84-91 DOI:

10.1109/tia.2012.2228834.

[14] Fang, Z., et al., 2013. Experimental Study of Damping

and Energy Regeneration Characteristics of a Hydraulic

Electromagnetic Shock Absorber. Advances in

Mechanical Engineering. 5 DOI: 10.1155/2013/943528.

[15] Zhang, Y., et al., 2015. Study on a novel hydraulic

pumping regenerative suspension for vehicles. Journal of



5442

the Franklin Institute. 352(2): p. 485-499 DOI:

10.1016/j.jfranklin.2014.06.005.

[16] Li, C., et al., 2014. Integration of shock absorption and

energy harvesting using a hydraulic rectifier. Journal of

Sound and Vibration. 333(17): p. 3904-3916 DOI:

10.1016/j.jsv.2014.04.020.

[17] Wang, R., et al., 2016. Modelling, Testing and Analysis

of a Regenerative Hydraulic Shock Absorber System.

Energies. 9(5): p. 386 DOI: 10.3390/en9050386.

[18] Zhou, Q., et al., 2015. Simulation based Evaluation of the

Electro-Hydraulic Energy-Harvesting Suspension

(EHEHS) for Off-Highway Vehicles. 1 DOI:

10.4271/2015-01-1494.

performance evaluation and damping characteristics of ... · regenerative suspension system (hprss)...

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