green weight-lifting machine using gear-shifting ...green weight-lifting machine using gear-shifting...

International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:17 No:04 52

173904-5656-IJMME-IJENS © August 2017 IJENS I J E N S

Green Weight-Lifting Machine Using Gear-Shifting

Mechanism and A Power Generator

Vinesh Thiruchelvam

School of Engineering,

Asia Pacific University,

Kuala Lumpur, Malaysia.

E-mail: [email protected]

Syed Abdullah Medni





Cleopatra Musa Yasin Hammad





Abstract— The growth of innovative renewable energy sources is

a worldwide consideration due to the high power demand and the

harmful influence of conventional sources of energy to the

environment. Besides the solar and wind energy, fitness facilities

around the world employed the cardiovascular machines such as

elliptical trainer to generate energy throughout the exercise. As a

further utilization of the gymnasium’s machines, the proposed

project developed a green weight-lifting machine with high

torque generator and gears-shifting mechanism to generate

electricity during the user’s workout. The mechanical design of

the machine focused in altering the linear motion by the user to

rotational motion via pulleys and wheel, which then converted by

the generator to electricity. The power stabilization system was

also introduced to amplify and stable the generator’s output

power with the help of capacitor, voltage converters, and

Arduino controller. Each gear level in the gears-shifting

mechanism represents specific kilograms to be lifted, which were

theoretically derived and then compared with the testing results

where 96.7% accuracy was successfully achieved. The conducted

six tests were designed to find out the lifted kilograms and

generated power in four exercises with six levels of gears.

Index Term– Arduino Controlling, Gears-Shifting Mechanism,

Generator.

I. INTRODUCTION

The importance of energy and its usage has arose in all

around the world, and due to this factor there is an essential

need to create the new technique for the conservation of

energy and power generation that causes least influences on

environment. Therefore, there are some auspicious areas of

application for human power in developing sections where

electric power is not affordable or not obtainable. Similarly at

the most fitness facilities, there are some unused potential for

the requirement of binding the human power also.

In early 2007, the research was started by the fitness

facilities regarding the conversion of human power to

electricity. Initially the first gym that was established to

integrate the human powered machines was California Fitness

facility in Hong Kong, by Lucien Gambarota the French

inventor and the Doug Woodring the entrepreneur. The

program was called “Powered by YOU” which diverts and

converts the excessive energy generated by the members on

13step cycling and cross training machines to the power

lighting fixtures in the gym. Moreover, The Dixon Recreation

Center at Oregon State University (OSU) by Clearwater based

on the Florida Company known to be ReRev that retrofitted in

2008 and 2009. The company diverts the excessive energy

generated by the clients to the electric grid, by retrofitting 22

elliptical machines at OSU. Furthermore, the company states

in the website that “An elliptical machine in regular use at a

gym using ReRev technology will generate one kilowatt-hour

of electricity every two days” (Haji, Laa & Agogino, 2010) [1].

The stability and position of the business plan plays a vital

role in order to evaluate the possibility ratio of execution of

gymnasium’s green technology. By taking this into

consideration and by understanding the responsibility we have

towards our environment, the Green Weight-Lifting Machine

is introduced as a unique opportunity to utilize the human

energy for the good of our environment. The implementation

of green weight lifting machines can be housed within a gym

and used to offset the gym’s energy requirement besides the

cardiovascular machines.

II. METHODOLOGY

Generator Connection: Fig 1 shows the block diagram of

generator connection. The high torque 50W generator is

connected to the weight-lifting machine with the help of

pulley which is connected to the shaft of the generator. The

pulley is connected to the wheel with the help of belt. A 10cm

diameter pulley is connected to the shaft of the generator and

the wheel of 17 inches which is attached to the pulley through

120cm long belt. When the user is working out, the liner

motion produce during the workout is converted to the

rotational motion with the help of pulleys. The string which is

connected to the chain on the other side will allow the wheel

to rotate which will then rotate the pulley connected to the

shaft of high torque generator with the help of belt. Hence the

high torque PM generator will generate electricity. The one

cycle of the 17 inches wheel is equal to the 5 cycles of 10cm

pulley which is connected to the generator. The reason of

using a pulley of large diameter is to limit the maximum force

applied by the user at the smallest gear and to prevent it from

any damage which can be caused due to high tension on the

string and pulleys.



Fig. 1. Generator Connection Block Diagram

Gears-Shifting Mechanism: Another main objective of the

project is the modified gears shifting mechanism (Fig 2). The

gear-shifting mechanism consists of six levels of gears in

order to have more weights options. The moving of the gear-

shifter is dependent on the metal string attached to it. When

the metal string of the gear shifter is pulled, it allows the

shifter to move inside towards the bigger gear. In this way the

shifter changes the position of the chain to different gears.

Each gear has approximately 2kgs of difference between

them; the first gear allows the user to apply 21kg, whereas the

last gear allows 32kg.

Fig 2. Proposed Gears-Shifting Mechanism

The main purpose of modifying the weight lifting machine

is to generate electricity from the power exerted by the person

during his/her workout. The current weight lifting is modified

in such a way that it converts the linear motion to the

rotational motion with the help of some pulleys and chain,

which is needed at the end to rotate the shaft of the generator,

the overall 2-D mechanical design is shown in the Fig 3. The

reason of developing a suitable gear-shifting mechanism is to

control the intensity of workout, meaning that the force

applied by the person can be controlled without changing or

using the extra weights.

The gears are adjustable and are connected to a wheel. The

machine will rotate the wheel through the gears only in

clockwise direction, whereas the anticlockwise direction will

be free. The spring is attached to the gears-shifting mechanism

in order to support the gear shifter. It is connected to give

more tension on the chain to avoid it to come off the gear.

Power Stabilization System: The block diagram of the

designed power stabilization system is shown in Fig 4. The

Arduino Uno operates as a controller to monitor and control

two circuits in the power optimization system. The program

controls the source of supplying to the system by capacitor

voltage status. The generated output voltage of generator is

connected to the voltage booster. The voltage booster has an

ability to boost the voltage from 4V DC to the 35V DC with

the maximum power of 100W depending on the input current.

This voltage booster is connected in parallel to the capacitor of

24V 3F and voltage sensor 1 which to sense the voltage level

in the capacitor. The Arduino is also controlling the Stable

mode of the circuit that is implemented to exercise easily

without any distortion, and activated when turning the switch

ON (Stable Mode Switch). This is done because the generator

requires more torque to generate enough voltage to turn on the

voltage booster. Once the voltage booster is turned on then the

rotating torque of the generator gets low as the constant flow

of the voltage takes place to boost and charge the capacitor.

To overcome the problem in changing the torque of the

generator, Stable Mode is introduced which is done by taking

the minimum voltage from external source to turn on the

voltage booster and once it turned on the constant voltage is

supplied by the generator.

Fig. 3. Green Weight-Lifting Machine 2-D Design

Fig. 4. Designed Power Stabilization System

Weights Theoretical Derivation: In the testing section, six

gears levels in the gears-shifting mechanism were tested. As

mentioned before, each gear will allow the user to lift specific

amount of kilograms. The lifted kilograms by each gear were

derived theoretically by using engineering fundamentals

related to the mechanical field. Further, the derived parameters

were compared to the actual kilograms displayed on the

attached weight’s meter of the developed weight-lifting

machine design.

Table 1 includes the radiuses in centimeters for each gear

and the wheel which are used to derive the required

parameters. First, it is required to find the torque required to

rotate the gear (τG) by the DC generator. As the radiuses of

gears and wheel are given, and assuming both gear and wheel

have similar speed, no slip and no power losses, the torque can

be found using the ratio of gear power and angular speed in

Equation (4). As no power loss, voltage of gear (VG) and

wheel (VW) are found in Equation (1), and gear power (PG)

and wheel power (PW) are found in Equation (2); where τg is

the DC generator rated torque:

VG = VW = -----------------------------------(1)

PG = PW = -------------------------------------(2)



The wheel’s angular speed (ωw) is found in Equation (3), and

then the value is substituted in Equation (4) with both

Equations (1) and (2):

ωw = ---------------------------------------------------------(3)

τG = = = ---------------------------------(4)

Considering taking the first gear of 0.12m (12cm), 0.22m

(22cm) for the wheel radius, and 80% efficiency of 0.1Nm for

τg then substituting in Equation (4):

τG = = 0.146Nm

By using the torque in Equation (5), τG can be substituted

while considering the first gear of 0.12m radius to convert

torque to force (FG):

τG = FG RG --------------------------------------------------------(5)

FG = = = 1.217N

To find the kilograms of mass to be lifted when selecting the

first gear, Equation (6) is used. Assuming the lifting time is

three seconds (t) and for 50cm (0.50m) of distance (d), mass

(M) is calculated after rearranging Equation (6):

FG = m ---------------------------------------------------------(6)

M = = = 21.906 kg

Using same equations, assumptions and other gears radiuses

from Table 1, Table 2 shows the calculated kilograms versus

each gear to be compared with the testing results when the

actual kilograms are found.

TABLE I

GEARS AND WHEEL RAIDUSES IN CENTIMETERES

Symbol Gear Level Radius (cm)

RG

1 12

2 10

3 8

4 6

5 4

6 2

RW Wheel 22

TABLE II

DERIVED WEIGHT FOR EACH GEAR LEVEL

Gear Level Kilograms

1 21.906

2 24.0192

3 25.8004

4 27.9080

5 29.5245

6 31.9940

III. DESIGN IMPLEMENTAION

Power Stabilization System: The designed and actual

constructed circuits of power stabilization system are shown in

Figs 5 and 6. The circuit consists of Arduino Uno, two voltage

sensors and two SPDT relays, to control two scenarios within

the circuit: Supply Switching and Stable Mode. The switching

between the supplies is controlled by using the program flow

in Fig 7. As explained before, the supplies of the stabilization

circuit can be the power generation from the DC generator or

external source such as similar machine or battery charger.

The switching between the sources is determined by

monitoring the voltage level in the voltage sensor which is in

parallel to the 3F capacitor. The capacitor voltage sensor

(CVS) can sense the voltage minimum of 0.5V to the

maximum of 50V DC.

There are three different pins of the voltage sensor which

are (VCC, GND, and SIG). The VCC of VS1 is connected to

the 5V DC output of the Arduino and GND to the ground of

Arduino. Whereas the SIG (signal) pin is connected to (A0)

Analog pin of Arduino Uno. The relay to control the switching

is named capacitor relay where its state is LOW by default and

connected to the digital pin (12) of Arduino. According to the

flowchart in Fig 7 and Arduino code in Fig 8, the capacitor

voltage sensor is continuously monitored to decide the power

supply of stabilization system. If the CVS is less or equal to

10V, the relay will turn on (HIGH) to disconnect the

supplying from the DC generator and connect to supply from

external source. Whereas when the capacitor voltage did not

reach 10V, the DC generator will be the supply of the

stabilization circuit.

Fig. 5. Designed Power Stabilization System



Fig. 6. Actual Power Stabilization System

Fig. 7. Supply Switching Flowchart

For the Stable Mode code, Fig 9 shows the flowchart of the

developed code which monitors voltage sensor (GVS) and

control SPDT relay. The implementation of the stable mode is

done by connecting the wires of generator to the voltage

sensor (GVS) directly. When the Stable Mode switch is turned

on, the voltage sensor (GVS) will start reading the voltage of

generator and send to Arduino Uno via Analog pin (A1). The

voltage sensor is to sense the voltage even if the generator will

produce 0.77V and will send information to Arduino. The

Arduino is programmed in such a way that when it receives

0.77V or greater from the voltage sensor, it will turn on

(HIGH) the relay connected to digital pin (13), thus Stable

Mode is activated. The Arduino code of the Stable Mode is

approximately similar to the Supply Switching code but with

some changes in the variables and values to match the

flowchart’s logic.

Fig. 8. If-Statement to Control Supply Switching

Fig. 9. Stable Mode Flowchart

The developed mechanical design of the power generating

weight-lifting machine is presented in Fig 10. The prototype

was carefully constructed to be identical as much as possible

to the 2D mechanical design in Fig 3. The four possible

exercises that can be performed using the green weight-lifting

are utilized to test the prototype power generation and

performance in testing section. The generator and gears-

shifting mechanism implementations are shown in Figs 11 and

12.



Fig. 10. Green Weight Lifting Machine Prototype

Fig. 11. Generator Connection

Fig. 12. Gears-Shifting Mechanism Connection

IV. TESTING AND RESULTS

The prototype was tested using five experiments where four

tests are to obtain different parameters: lifted weight in

kilograms, voltage, current and generated power for each

exercise and in six gears. The last test is to compare the

average generated power during different exercises, therefore

finding the highest generation of power among all exercises.

Test 1 (Pull-Down Exercise): The actual experimental

setup of Test 1 is showed in Fig 13 which includes the power

stabilization system, multimeter to display current, and 3

Farads capacitor. The setups of the other experiments are

similar to the Pull-Down test but by using different exercises.

The gear levels were changed six times to obtain several sets

of readings to find the generated power when varying the

gears.

Fig. 13. Actual Experimental Setup of Testing

Table 3 shows the experimental data of test 1 where the

Pull Down exercise was tested two times for each gear level

(six gears). The generated power is calculated using the

obtained voltage and current parameters. Kilograms (lifted

weights) column represents the values that were displayed on

the weight meter during each gear level.

TABLE III OBTAINED DATE DURING PULL-DOWN EXERCISE

Fig 14 shows an analysis between the two tests of Pull-

Down exercise where the generated power of each gear level

in test 1 is compared with the second test, to show how well

and stable is the power generation. In gears 1, 4 and 6 the

generation is approximately stable under both tests, whereas

for gears 2, 3, and 5 there is an average 1.433W difference

between the generation level in test 1 and 2. This can be due to

slight change in the applied force during the testing which

caused imprecision in the readings. It is also noticed from the

analysis that when increasing the gears (higher kilograms) the

generation of power is reduced. This is because the lifting

process is slower, thus lower rotation of the generator, which



caused a reduction in the generated current therefore

decreased power generation.

Fig. 14. Data Analysis of Pull-Down Exercise

Test 2 (Chest Press Exercise): The collected data during the

testing are listed in Table 4 and analysed in Fig 15.

TABLE 4. OBTAINED DATA DURING CHEST PRESS EXERCISE

Test 3 (Butterfly Exercise): Table 5 and Fig 16.

TABLE V

OBTAINED DATA DURING BUTTERFLY EXERCISE

Fig. 15. Data Analysis of Chest Press Exercise

Fig. 16. Data Analysis of Butterfly Exercise

Test 4 (Legs Exercise): Table VI and Fig 17.

TABLE VI

OBTAINED DATA DURING LEGS EXERCISE

Test 5 (Comparison Test): The average power generation

values of the two trials in each gear level in each exercise are

calculated and listed in Table 7. The column chart in Fig 18

illustrates the average power generation of each exercise under

specific gear level. It is clear that the first gear level has the

highest generation of watts, and the generation decreases as

the gear level is increased.

Pull-Down exercise generates the highest amount of power

when same weight is lifted by other exercises which can be

noticed in Fig 18. This finding is true except when the third

gear is selected, as Chest Press exercise has higher power



generation of 0.245W when compared to Pull-Down exercise.

Another outcome of this comparison is that the power

production in the different exercises and under fifth and sixth

gear levels is slightly reduced in each exercise.

Fig. 17. Data Analysis of Legs Exercise

TABLE VII

AVERAGE POWER GENERATION FOR EACH EXERCISE

Gear

Level

Pull-

Down

(W)

Chest

Press

(W)

Butterfly

(W)

Legs (W)

1 31.36 30.735 31.01 29.025

2 27.64 27.2 27.37 26.165

3 21.805 22.05 20.795 20.49

4 17.655 17.43 16.54 15.86

5 13.78 13.53 13.41 13.21

6 11.91 11.565 11.335 10.915

Fig. 18. Average Power Generation Comparison

V. DATA INTERPRETATION

Table 8 shows a comparison between the theoretically

calculated kilograms in each gear (Table 2) and the actual

kilograms obtained by the weight meter during the testing.

From the testing tables of each exercise, the average actual

kilograms were calculated. The error column represents the

error level in percentage between the calculated and actual

kilograms. Fig 19 is an analysis between the derived

kilograms by each gear level with the average actual

kilograms obtained during the four exercises testing. The data

are showing high degree of accuracy as the average lifted

kilograms are close to the original values. The highest

similarity level is caused by gear level 5 as the average

obtained kilograms value is less by 0.7495kgs as compared to

the original value (29.5245kgs) with a percentage error of

2.54% only.

TABLE VIII

DATA COMPARISON & PERCENTAGE ERROR

Gear Level Calculated

Kilograms

Actual

Average

Kilograms

Error (%)

1 21.906 21.075 3.79

2 24.0192 23.15 3.62

3 25.8004 25.0125 3.05

4 27.9080 27.00 3.25

5 29.5245 28.775 2.54

6 31.9940 30.825 3.65

Fig. 19. Calculated versus Actual Average Kilograms

VI. CONCLUSION

The aim of modifying the available weight-lifting machine

to be a power generating unit was successfully accomplished

by satisfying the project’s three objectives. The mechanical

design of the green weight-lifting machine was developed by

using high torque generator and suitable gears-shifting

mechanism instead of the original weights of the machine.

Several components were also utilized to construct the

mechanical design such as chains, weight meter, springs,

pulleys, wheel, and L-shape aluminums bars to interconnect

all the mechanical parts. The last objective was achieved by

integrating a power stabilization system which amplifies and

stabilizes the output power of the weight-lifting machine with

the help of 3 Farads capacitor, buck-boost convert, voltage

sensors, relays and Arduino Uno. The testing of the developed

machine showed 96.7% of accuracy when comparing the

attained results to the theoretical findings. The project can be

further improved as follow: reducing the machine’s size by

incorporating built-in generator in the wheel, and introducing

electronic clutch for the gears-shifting mechanism to shift the



gears freely without jerking therefore decrease the chances of

damaging the gears.

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Wind Turbine. In Power Electronics Conference (IPEC). Sapporo and

21st – 24th June 2010. pp. 258-263. [4] Lee, G. & Jung, T. (2013) Design of Dual Structural Axial Flux

Permanent Magnet Generator for Small Wind Turbine. In TENCON

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[5] Neto, J. et al. (2013) DSP Based Fuzzy Controller Applied to a DC-DC

Boost Converter. In IEEE Conference on Intelligent Signal Processing

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green weight-lifting machine using gear-shifting ...green weight-lifting machine using gear-shifting...

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