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ABSTRACT
This paper investigates the hydraulic
regenerative braking system for a bicycle. The
purpose of implementing this system is to lower
the human effort required for driving a bicycle.
The regenerative braking system can capture and
reuse the energy that is normally lost due to
braking. This paper represents a model of novel
configuration for hydraulic regenerative braking
system based upon the Matlab Simulink
Environment. The influence of the key component
parameters on the performance, braking and rate
of energy recovery is analyzed. The simulation
result helps in selecting proper components which
will suit the proposed system most appropriately.
Though the overall cost of the system is high the
amount of human effort saved makes it worth of
being implemented in real life.
INTRODUCTION
According to the Environmental Protection
Agency (EPA), an agency of the U.S. government, a
report has been made in 2006 on Clean Automotive
Technology Program [1], transportation is
responsible for 30% of national CO2 emissions. As a
fuel- and- emission-free option to traditional modes
of travel, bicycling remains an important means of
transportation in cities and high-traffic areas. They
are reliable, convenient, and sometimes faster than
driving. However, because they require more work to
operate, they are frequently dismissed for a car. In
order to increase attraction to bicycles, a modification
can be done to the bicycle which will consume less
amount of human effort. A hydraulic regenerative
system can be added to the conventional bicycle
which can store the wasted energy, generally lost
during braking and reuse it during accelerating the
bicycle.
In a conventional bicycle system, during
braking the kinetic energy is lost to the environment
in the form of heat. This happens every time when we
stop the bicycle. During acceleration we again have
to invest energy to overcome the inertia of the bicycle
and rider, thus requiring more effort to drive. In the
mid of a city, where we require frequent stopping, the
energy lost is considerable.
In hydraulic hybrid bicycle, instead of chain
drive a hydraulic circuit is used to drive the rear wheel of the bicycle. During normal cycling mode
human power is given as an input to the hydraulic
pump. Then pump pressurizes the fluid and sends it
to the hydraulic motor which is connected to the rear
wheel of bicycle. During braking the motor acts as a
pump for a short time and consumes bike momentum
to pump the fluid. This pressurized fluid is stored into
the accumulator which can be used as input to the
motor during accelerating mode. This arrangement is
also called as series hydraulic hybrid system.
This system is currently used in heavy
vehicles such as dump trucks and busses, the
efficiencies of the system have been measured
experimentally and analytically. [9] the results
indicate that the average efficiency of energy
recovery of the system was 66%. The overall
regeneration efficiency of the proposed hydraulic
system (consists of three 2.5 litter accumulators, a
Vickers fixed displacement 4.11 cm3/rev, an axial
piston pump/ motor, and two 0.847 kg.m2 moment of
inertia flywheels) is 73% [10]. Generally overall
efficiency of the hydraulic system varies from 32% to
66% [4]. Although the result variation is high, yet it
indicates that hydraulic regenerative braking system
possesses a high potential of energy recovery [5].
In this paper a new configuration of
hydraulic hybrid system is established. The model
consists of a hydraulic gear pump, gear motor,
accumulator, and a reservoir. These components are
connected with hose and solenoid actuated valves.
This model is also simulated with the help of Matlab
Simulink environment. Based on simulation, the
regenerative braking process will be investigated
with regarded to the effects of main component
parameters. The rate of recovery energy during
regenerative braking is calculated.
Working of System
Complete ride of a bicycle can be classified in 4 basic
modes like peddling mode, no peddling or cruising
mode, braking mode and launching mode. In
peddling mode the power provided by a human is
directly utilized in propelling the bicycle. In cruising
mode bicycle maintains its motion due to inertia. In
case of braking mode, momentum of the bicycle is
used to drive the pump which in turn fills the
accumulator, and in case of launching mode the
energy stored in the accumulator is used to propel the
bike to gain the momentum without human effort.
These different modes can be achieved with the help
of actuation of different valves in the hydraulic
circuit. The following diagram shows symbol of
hydraulic direction control valve, the left block is
considered as I position and right block is considered
as II position. To activate the different modes during
riding the valve position is shown in following table.
Conclusion
In this paper, a simple hydraulic circuit is
proposed which can be remotely actuated with the
help of electric circuit. Based on different
manufacturer’s catalogue a variety of components are
selected to suit the hydraulic circuit. The relationship
among the components involved in regenerative
braking and propelling modes have been analyzed.
Simulation model for the hydraulic regenerative
braking system has been established. Influences of
the main factors to the braking performance were
investigated. Based on the above analysis final
component specification can be given as,