Design and Analysis of of Piezo-wheel for Light Electric Vehicle

SWAPNAJIT PATTNAIK Electrical Engineering

Visvesvaraya National Institute of Technology, Nagpur, India

Abstract—The newest concept for the fulfillment of electrical

energy for light vehicle is the reuse of waste energy. Reusable energy has several advantages such as cheap, safe, maintenance free, flexible, and can be used in various occasions. Energy conversion from vehicle pressure over wheel at the point of contact to the road surface using piezoelectric material is the best option for this purpose. With regular interval in the perimeter of wheel, number of cubic piezoelectric material used to make piezo-wheel which produce medium electrical power to run the vehicle as well as to operate other electrical and electronic equipments.

Keywords— Reusable energy, piezoelectric, piezowheel, light vehicle

I. INTRODUCTION The recent fluctuations on the price of petroleum have

affected worldwide economics which has forced an increased in the price of other items including food. Some even linked the recent collapse of few financial institutions in countries such US and the UK to the recent increased in this price. This shows that we are too dependent to petroleum as a source of electrical power. Besides, petroleum as a source of electrical energy has contributed to severe air pollution problem. Therefore, an alternative method to produce electricity has to be put in place.

Among other solutions which can be explored are nuclear and hydro-electric power generators. However, these options require huge financial capability to run and to maintain. Besides, many countries are not “allowed” to use nuclear power generator due to world political scenario. Thus, photovoltaic cells and wind turbines have been the popular choices and these renewable energy sources are gaining more attention. However, they are expensive and not affordable to many countries to acquire them. As a consequence, other possible energy sources must again be explored [1].

One of the promising options is by using piezoelectric material or PZT. PZT can be used as a mechanism to transfer ambient vibrations into electrical energy. This energy can be stored and used to power up electrical and electronics devices. With the recent advancement in micro scale devices, PZT power generation can provide a conventional alternative to traditional power sources used to operate certain types of sensors/actuators, telemetry, and MEMS devices. An equivalent electrical model of the PZT transforming mechanical impact energy to electrical power is successfully developed [2].

The application of a piezo film in addition to the ceramic to provide power to light up bulbs in a shoe, entirely from walking

motion is examined [3]. Another piezoelectric application is centred on the vibration of a small plate, harnessed to provide a rectified voltage signal to run a small transmitter fixed to migratory birds for the purpose of transmitting their identification code and location [4].

Piezoelectric materials can be used in a system to transfer mechanical energy, usually ambient pressure, into electrical energy that can be stored and used to power other devices. With the limitation of finite life span, conventional batteries at remote location are generally replaced by sensors. Because most sensors are being developed so that they can be placed in remote locations such as structural sensors on a bridge or GPS tracking devices on animals in the wild. Therefore, if a method of obtaining the untapped energy surrounding these sensors was implemented, significant life could be added to the power supply. One method is to use piezoelectric materials to obtain ambient energy at the tyre of wheel in light vehicle. The wasted mechanical energy during movement of vehicle is to be utilized to generate electricity. With proper placement of piezoelectric material, sufficient amount of electricity can be generated, which is to be modulated to run light vehicle [5-11].

The application of piezoelectric as a power generator can be extended to operate daily low power electrical appliances such as tuner, light bulb, mobile phone and so on. The aim of this paper is to develop the piezoelectric material as a power generator for these applications.

Power converters are interfaced with the proposed mechanism to operate light vehicle without fuel. Battery is to be used to start the vehicle and it will be getting charged during ruining mode of the vehicle. Proposed reusable energy system is shown in the figure below in blocks form.

In this paper, reusable energy system is designed and its analysis is presented in following section. The proposed reusable energy system for light vehicle is presented in the Fig. 1. Section II describe about the proposed topology and section III presents the designing procedure. Section IV features about the merits of the topology. Section V gives the result and discussion and in last section includes conclusion.

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II. PROPOSED TOPOLOGY

The proposed topology is presented in the Fig. 2. The input is taken as pulsed voltage as it will be the output of piezoelectric material when appropriate pressure will be provided at equal interval. Conventional buck converter is used for proper conversion and utilization of power in the load, where DC motor and other R-L load connected across the output terminal.

Mosfet switch and schottky diode is used in converter as it can operate at high frequency. Pulsed voltage taken from piezoelectric material is around 800V. It depends upon the weight of the light vehicle. Chargeable battery and ultra capacitor are there in the vehicle for starting of the DC motor, thereafter with the motion of vehicle, piezoelectric material paced at the base of tyre will be pressurized with the weight of the complete vehicle and electricity will be produced.

Fig. 2 Proposed topology for conversion and control of power from output of piezoelectric material to load

III. DESIGN AND ANALYSIS The electric vehicle controller is the electronics package that

operates between the batteries and the motor to control the electric vehicle's speed and acceleration, much like a carburettor does in a gasoline-powered vehicle. The controller transforms dc from the battery current into ac (for ac motors) and regulates the energy flow from the battery. Unlike the carburettor, the controller will also reverse the motor rotation (so the vehicle can go in reverse) and convert the motor into a generator (so that the kinetic energy of motion can be used to recharge the battery when the brake is applied).

In the early electric vehicles with dc motors, a simple variable-resistor-type controller controlled the acceleration and

speed of the vehicle. With this type of controller, full current and power were drawn from the battery all the time. At slow speeds, when full power was not needed, a high resistance was used to reduce the current to the motor. With this type of system, a large percentage of the energy from the battery was wasted as an energy loss in the resistor. The only time that all of the available power was used was at high speeds.

Modern controllers adjust speed and acceleration by an electronic process called pulse width modulation. Switching devices, such as silicon-controlled rectifiers, rapidly interrupt (turn on and turn off) the electricity flow to the motor. High power (high speed and/or acceleration) is achieved when the intervals (when the current is turned off) are short. Low power (low speed and/or acceleration) occurs when the intervals are longer.

Fig. 3 of sheet 1 shows the schematic views of piezo-wheel used where: 1 denotes rim of the wheel 2 denotes outer surface of rim 3 denotes piezoelectric material strip place over the outer surface of the rim 4 denotes the inner surface of the rim 5 denotes spoke of the wheel 6 denote the tire to be fitted over the rim 7 denotes outer surface of tire 8 denotes inner surface of tire

Fig. 3 Schematic internal view of piezoelectric wheel

There are two theoretical models normally used to predict the power output from piezoelectric film attached to a beam namely pin-force and Euler-Bernoulli methods (Eggborn, 2003). Their main difference is the way to model the interaction between host structure and the piezo-film. The schematic internal view of piezoelectric wheel is presented in Fig. 3. The predicted voltage outputs for pin-force and Euler-Bernoulli are, respectively.

316(3 )b

g MVbt ϕ

=−

(1)

312 2 2

6 (1 )(1 2 (2 3 2 ))a

g M TVbt T T T

ϕϕ ϕ

+= −+ + + +

(2)

where g31, M, ta, ϕ , and T are the voltage constant of the piezo-film, moment of the beam, the width of the piezo-film, thickness of the beam, strain ratio between the beam and piezo, and the stress on the beam, respectively.

The first step in the development process was to verify the characteristics of the cylindrical PZT-5A piezo element selected for the HVG. The simplest and most compact method of obtaining high voltage from the piezo was to compress it axially. The compression was quasi-static, so that the dynamic mechanical processes need not be considered. PZT-5A is a lead zirconate titanate polycrystalline ceramic material [3] that is

Vehicle weight on wheel at the point of contact

Piezoelectric material

Battery and ultra capacitor

Electricity

Shaft of wheel connected by belt

DC Motor

Power Converter for multiple outputs

Electrical and Electronics equipment for lighting

and control

Fig. 1 Proposed reusable energy system for light vehicle

1 2

34

5

6

7

8

2014 IEEE 9th Conference on Industrial Electronics and Applications (ICIEA) 1817

commonly used in igniters in which voltages as high as 20 kV are produced. Large PZT elements were used in order to maximize the available charge, and hence, output voltage, and to account for possible charge leakage during the relatively slow compression process.

The constitutive equations are E

j kj k im mS s T d E= + (3) T

i im m mD d T Eε= + (4) g is the piezoelectric voltage coupling, d contains the piezoelectric coupling terms which relate the electrical and mechanical properties of the material, S is the strain (dimensionless), D is the electric displacement or charge density (C/m2), E is the electric field (V/m), and T is the applied stress (N/m2).

Considering the simple case of a cylindrical piezo element, which is compressed axially in the z-direction, there are two cases of specific interest.

Fig. 4 Charge produced from short-circuited PZT-5A piezo element [4] The first is when the electrodes at each end of the element

are short-circuited together. In this case, E3 = 0 and the charge produced by the piezo element can be calculated readily from Eq. (3):

Q = D3A = d33T3A = d33F, (5) where F is the applied force, A is the cross-sectional area of the element, and the subscripts refer to the location in the respective matrices. Note that the force cannot be increased indefinitely due to a nonlinear piezoelectric effect in the short circuit case, which can lead to irreversible depolarization of the piezo element. This effect occurs when the mechanical stresses in the piezo element are sufficient to cause changes in the ferroelectric domain boundaries. The influence of this nonlinear effect is shown in Fig. 4, which is reproduced from [4]. When the applied stress is an impulse with duration of 50–150 s, the charge produced by the piezo element increases linearly with stress according to the linear theory discussed above. As the stress increases, less charge is produced than predicted by theory. The maximum charge density which can be generated is about 0.275 C/m2. The extent of depolarization is dependent on the duration of the applied stress. If the stress is applied on a time scale much shorter than the relaxation time of the domains, the depolarization is inhibited. For the static case, the nonlinear effect produces more current than predicted at lower stresses. Once a PZT-5A element has produced a charge density of 0.275 C/m2, as for the dynamic case, it is almost completely

irreversibly depolarized. However, it should be noted that for single use applications, the maximum charge produced by either static or dynamic stresses are the same. Since static stresses of 0.5 GPa are readily achievable, quasi-static operation of the piezo HVG is feasible and offers similar performance to more mechanically complicated concepts which exploit impulsive stressing of the piezo.

IV. BASIC FEATURES OF THE PROPOSED REUSABLE SYSTEM The proposed reusable energy system with the help of

piezoelectric material has certain advantages such as:

• External fuel is not used for operating light vehicle • Maintenance cost is reduced • Provides pollution free environment • Weight of light vehicle is reduced • Overall efficiency of the system is increased • Severe modification is not required in the existing

light vehicle system

With the proper designing of reusable system with the above features, this system is going to be on demand in near future.

V. RESULTS The proposed system is simulated in PSIM by taking

piezoelectric transducer (PZT) output 800V, frequency 1000Hz as input for the system. Rating of the system under verification is 12kW, 120V/100A, torque 60 N/m. The variations of speed and torque with respect to time are plotted, which shows that speed and torque maintained constant at steady state. From the waveform it can be seen that rating of converter is achieved. Torque vs speed graph shows that higher starting torque at low speed and lower starting torque at higher speed is achieved.

The parameters designed for the simulation is give in the table I.

Table I Sl no

Name of the parameters

Values

1 Inductor 2mH 2 Capacitor 1000 F 3 DC Motor 2000rpm, 200V, 200A Armature

current 4 RL Load 10 , 1mH 5 Mosfet 6 Schottkey Diode

The waveforms are shown in the figures below:

0 0.5 1 1.5 2Time (s)

0

20

40

60

80

100

TORQUE

Fig.5(a)

1818 2014 IEEE 9th Conference on Industrial Electronics and Applications (ICIEA)

0 0.2 0.4 0.6 0.8 1Time (s)

0

50

100

150

200

Vo

Fig. 5(b)

0 1 2 3 4Time (s)

0

-200

200

400

600

800

1000

1200

N(SPEED)

Fig.5(c)

0 0.2 0.4 0.6 0.8 1Time (s)

0

50

100

150

200

250

Ia

Fig. 5(d)

0 0.2 0.4 0.6 0.8 1Time (s)

0

0.5

1

1.5

2

2.5

Field Current If

Fig. 5(e)

0-200 200 400 600 800 1000 1200N

0

-20

20

40

60

80

100

Torque

Fig. 5(f) Fig. 5(a) to fig. 5(f) are shown the waveforms of torque, speed, output voltage, armature current, field current, and torque-speed characteristics of the proposed system.

VI. CONCLUSION The proposed system is verified in simulation results. With

proper placement of piezoelectric material in between outer rim and tyre of the wheel of light vehicle, required power can be generated and light vehicle can be operated effectively. Generated DC voltage is directly provided to the motor which can be placed inner side of the wheel. This concept can be extended to any type of transport. Only drawback is initial power should be there for starting purpose the system.

REFERENCES [1] J. Dayou, C. Man-Sang, M. N. Dalimin, and S. Wang, “Generating

electricity using piezoelectric material,” Borneo Science 24: March 2009 [2] Umeda, M., Nakamura, K. & Ueha, S. “Analysis of Transformation of

Mechanical Impact Energy to Electrical Energy Using a Piezoelectric Vibrator”. Japanese Journal of Applied Physics, 1996, 35(1) 3267-3273

[3] Kymissis, J., Kendall, C., Paradiso, J. & Gershenfeld, N., 1998. “Parasitic Power Harvesting in Shoes”, Second IEEE International Conference onWearable Computing, 132-139.

[4] Kimura, M, Piezoelectric Generation Device, US Patent Number 5,801,475, 1998.

[5] U. S. Patent 8610335 “Electricity producing tire” describes an electricity producing tire for generating electrical current from the rotation and compression of the tire as vehicle moves. This invention describes the placement of piezoelectric inside the tire.

[6] U. S. Patent 8247952 “Wheel with piezoelectric ring and vehicle having same” describes a wheel with piezoelectric ring which produces electric power under pressure.

[7] U. S. Patent 8415861 “Wave power generator” consists of a transmitting module and a piezoelectric generator which can generate power by reciprocating waves.

[8] U. S. Patent 8189431 “Piezoelectric drive device and electronic device” describes a piezoelectric actuator that generate power by vibration and rotational motion.

[9] U. S. Patent 7784336 “Load cell” based on the piezoelectric measurement principle to detect wheel forces.

[10] U. S. Patent 7429801 “System and method for generating electric power from a rotating tire’s mechanical energy” presents a tire assembly with piezoelectric devices to generate power.

[11] U. S. Patent 6725713 “System for generating electric power from a rotating tire’s mechanical energy using reinforced piezoelectric materials” is a system for generating electric power from a rotating tire’s mechanical energy.

2014 IEEE 9th Conference on Industrial Electronics and Applications (ICIEA) 1819