Performance Evaluation and Damping Characteristics of ... · Regenerative Suspension System (HPRSS)...
Transcript of 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:
M.E. El-Arabi, is with the Mechanical Design and Production Engineering
Department, Cairo University, Egypt. (E-mail:
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.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 7 (2018) pp. 5436-5442
© Research India Publications. http://www.ripublication.com
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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.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 7 (2018) pp. 5436-5442
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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
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 7 (2018) pp. 5436-5442
© Research India Publications. http://www.ripublication.com
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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.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 7 (2018) pp. 5436-5442
© Research India Publications. http://www.ripublication.com
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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.
Figure 15. Variation of the force-displacement response for
the HPRSS system with different road inputs at initial
accumulator pressure 20 bar.
Figure 16. Variation of the force-displacement response for
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.
Figure 17. Variation of the force-displacement response for
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.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 7 (2018) pp. 5436-5442
© Research India Publications. http://www.ripublication.com
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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.
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