mechatronics design of solar tracking system · tracking system moves the solar panel to the...

750

Research Article

International Journal of Current Engineering and Technology ISSN 2277 - 4106

© 2013 INPRESSCO. All Rights Reserved.

Available at http://inpressco.com/category/ijcet

Mechatronics Design of Solar Tracking System

Farhan A. Salema,b

*

aMechatronics program, Department of Mechanical Engineering, Faculty of Engineering, Taif University, 888, Taif, Saudi Arabia.

bAlpha center for Engineering Studies and Technology Researches, Amman, Jordan.

Accepted 12 April 2013, Available online 01August 2013, Vol.3, No.3 (August 2013)

Abstract

The key element in mechatronics system design is the concurrent synergetic integration, modeling, simulation, analysis

and optimization of multidisciplinary knowledge through the design process from the very start of the design process,

and toward constrains like higher performance, speed, precision, efficiency, lower costs and functionality, resulting in

products with more synergy. This paper proposes the conception and development of smart solar tracking system, based

on mechatronics design approach, such that the solar panel through both day and seasonal changes is accurately

perpendicular to sunlight beam (accurately point towards sun), where illumination is strongest. The whole system and

sub-systems are concurrently selected, designed, integrated modeled, tested and optimized; also, overall system response

is verified for different input types, including actual input altitude angles. The obtained results show the simplicity,

accuracy and applicability of design to meet all design requirements. The proposed design can be used either for

research or educational purposes.

Key words: Mechatronics design, solar tracker, modeling/simulation.

1. Introduction

1Mechatronic system design process can be divided into

systematic, simple and clear design steps including;

Problem statement; Conceptual design and functional

specifications; Parallel (concurrent) design and integration

of system and all subsystems as whole and concurrently

including; selection, design and synergetic integration of

mechanical, electronics, software, control unit, control

algorithm and interface sub-systems; Modeling and

simulation; Prototyping, Testing and Optimization; and

finally Manufacturing, and commercialization (Farhan A.

Salem et al, 2013)( Yu Wang, et al 2012)( Devdas Shetty

et al,2011)( Sarah Brady,2008)( L. Al-Sharif, 2010). This

paper proposes the conception and development of smart

solar tracking system based on mechatronics design

approach.

2. Pre-Study Process-Problem statement.

Among the renewable energy resources, solar energy is the

most essential and prerequisite resource of sustainable

energy because of its ubiquity, abundance, and

sustainability, regardless of the intermittency of sunlight,

solar energy is widely available and completely free of

cost )C.S. Chin,2012) Solar energy is directly converted

into electrical energy by solar photovoltaic modules, made

*Corresponding author: Farhan A. Salem

up of many silicon cells connected in series to get a solar

PV module, the current rating of the modules increases

when the area of the individual cells is increased

(Mohammed S. El-Moghany, 2012). It is known that the

power generated by any solar cell is a function of three

variables: the surface area of the cell exposed to light, the

efficiency of the cell, and an environmental constant

known as irradiance, the best way to increase power

generation would be to increase exposed surface area,

where approximately, each solar cell develops 0.5 V.

Many research studies practically effective methods of

solar energy, one of these methods is solar tracking

system, solar tracker allows the increase of produced

energy amount about 40% in relation to fixed panels.

When solar tracking system is exposed to solar radiation,

it can generate direct current electricity without

environmental impact and contamination and at a lower

maintenance costs.

For optimal operational efficiency of solar energy

receivers, and correspondingly generated electricity, solar

tracking systems are designed such that solar panels are

perpendicular to sunlight, where the illumination is

strongest, to achieve this, an ideal tracker would

compensate for changes in both sun's altitude and

latitudinal angles through both day and seasonal changes

and changes in azimuth angle. In 1986, Akhmedyarov first

increased the output power of a solar photoelectric station

in Kazakhstan from 357W to 500W by integrating the

station with an automatic sun tracking system

Farhan A. Salem International Journal of Current Engineering and Technology, Vol.3, No.3 (August 2013)

751

Akhmedyarov, K.A et al, 1986),also studies show that, a

solar panel of 3m2 with fixed position to surface produces

about 5 kWh of electricity per day, the same installation

but equipped with tracker, can provide

Table 1 Requirements analysis

Requirements type Value/ Unit Requirements

Qualitati

ve Req.

Quantitati

ve Req.

Range or

soft Req.

Fixed

Req.

Qual. Fixed Compact , cost effective. Control unit

Fixed Simple, precise, efficient, and

easy to program. Control

algorithm

Qual Soft 12 -24 V Stand alone or battery Input Power

supply

Qual.

Soft -

12 -24 V

One or two actuators for

adjusting the solar panel

rotating altitude and

latitudinal angles, precise,

simple to interface, control

and inexpensive.

Actuators

Qual. Soft - Light sensors ,simple to

interface, available,

inexpensive

Sensors

Soft n Gears, belt, chain Transmission

Soft 100 Cm Height To supply

maximum electrical

power

Overall

System

dimensions

45 Cm width

50 Cm Length Qual.

Soft

50 Cm Height

:

Depending on solar

sells type , number

and required

electric power

Solar panel

dimensions 38 Cm Width

40 Cm Length

Fixed To supply maximum

electrical power, standalone,

precise, cost-efficient

User

requirements

Qual. Fixed Simple and easy to use and

understand User Interface

Quan. Soft

Attractive, fits user needs. Machine

aesthetics

design

Dri

ve

DC motor GearsSolar

panelController

Position sensor

Error

Light sensor1Light

sensor2

Power supplyComparator

angl

e

Light

sensorsController Actuator

Solar

panel

Position

Feedback

θUser

interface

Power

supply V.R

Dri

ve

Figure 1(a) Figure 1(b)

Figure 1(a)(b) Simplified block diagram representation of proposed solar tracking system

up to 8 kWh per day. Several methods and designs of sun

tracking systems have been proposed, designed and

implemented, main are included in (C.S. Chin, 2012)

(Mohammed S. El-Moghany et al, 2012)( Akhmedyarov

K.A et al, 1986)( Chin CS et ak, 2011)( Ahmad Rhif,

2011)( R. Messenger et al, 2000 )( S.A. Kalgirou, 1996)(

Gustavo Ozuna et al, 2011)( A. Stjepanovic et al, 2010 )(

A. Louchene et al, 2007)( C.S. Chin et al, 2013), a detailed

literature review can be found in (A. Louchene et al, 2007)

Solar tracking systems consist of a photovoltaic generator,


752

actuating unit, control unit, sensing unit, energy storage

devices (such as batteries), and AC and DC elements for

power conditioning. In solar tracking system design, any

light sensitive device, can be used as light detecting sensor

as input sensor unit including phototransistors,

photodiodes, LDR and LLS05-A light sensors. A suitable,

inexpensive, easy to program control unit is

microcontroller; a suitable motion generator is electric

motors and corresponding drive. Target user of proposed

system; Researchers, Educators and wherever such

renewable energy unit is required . User's requirements; it

is required to develop a linear, one/two-dimensional

single-variable solar tracking unit that can be used for

receiving solar energy and to meet the power demands of

supplying maximum electrical power, precise, cost-

efficient, with simple interface. System parameters,

requirements and analysis, are listed in Table 1.

3. Conceptual design

The purpose of design is to propose and develop the

conception and development of solar tracking system

based on mechatronics design approach, such that the solar

User interface

Reading values

Sun position readings

Actuator, electric

energy

Actuator motion

response

Gears ,lever armMotions transmission

Solar panel position

Solar panel angle

measuring

Position sensor

μu-control

Switching system on-off

Control system

Light sensor

Figure 1(c) Functional Structure block diagram

Table 2 Morphological table, analysis and evaluating the

best solution selection

panel through both day and seasonal changes is accurately

perpendicular to sunlight beam (accurately point towards

sun) and fit user's power needs and requirements. The

conception of light tracking system is quite simple, where

light detectors detect position of the sun, based on sensors

readings, and generated sun tracking error, based on error,

the control unit generates the voltage used to command the

drive circuit to drive a low- speed motor, that outputs the

rotational speed or displacement of electric motor, (to

rotate the solar panel via a speed-reduction system) until it

perpendicularly faces the sun. Based on this and on pre-

study process, a preliminary simplified block diagram

representations of solar tracking system is shown in Figure

1(a)(b). Functional structure block is shown in Figure 1(c).

Morphological Table analysis and evaluating the best

solution are listed in Table 2.

4. Parallel (concurrent) selection, design and

integration of sub-systems and overall system.

Mechatronics system design is Modern interdisciplinary

design procedure; it is a concurrent selection, synergetic

integration and optimization of the system and all its

components as a whole and concurrently, all the design

disciplines work in parallel and collaboratively throughout

the design and development process to produce an overall

optimal design. Mechatronics design approach tends to

develop products with synergy and integration toward

constrains like higher performance, speed, precision,

efficiency, lower costs and functionality.

4.1 Mechanical construction and components selection:

Depending on desired performance, precision, efficiency,

speed, cost, functionality and required maximum energy

receiving of solar panel, different solar tracking system's

types and arrangements exist, there are three main types

particularly; Passive tracker, Chronological tracker and

active tracker, also, there are many system's arrangements,

most applied are shown in Figure 5 . In this paper two

system arrangements are considered; one-axis (one

directional) using two light detectors (Figure 6(a)) and

two-axis (two directional) using four light sensitive

sensors (Figure 6(b) and). A simple and optimal

mechanical design could be as shown in Figure 5, this

arrangements can be used for either or both a one-axis and

two-axis motion control, the vertical axis is perpendicular

to the ground and horizontal axis normal to vertical axis,

by the combinations of two axes any position and location

of solar panel in upward hemisphere could be achieved,

correspondingly, the motions can be manipulated such that

the solar panel is perpendicular to sun light. The proposed

mechanical design shown in Figure 5(c), the Overall

System and solar panel dimensions are listed in Table 1 ,

the system consists of aluminum steel base frame (2), onto

which the solar panel is to be mounted, the steel frame

with solar panel is mounted onto rotating head derived by

first DC motor for horizontal motions (3), and all are

mounted onto a vertical steel beam (4), this steel beam is

also a vertical axis for azimuth control derived by second

DC motor (5). System CAD model is shown in Figure


753

5(b). To make sure the structure is stable and the load is

constant for the rotation of motor, the center of gravity of

tilting structure is aligned at rotating center, this is shown

in Figure 5(c). The system uses external power supply, but

also can be modified to be standalone solar tracking

system.

4.2 Sensor selection: a solar tracker can be built using

sensing unit, or can be built to be senseless (chronological

tracker), where the sun coordinates are calculated for the

any moment of the day, during all year, using this data, the

tracking system moves the solar panel to the optimum

calculated position. For smart precise solar tracker, a

suitable, inexpensive, simple and easy to interface sensor

is analog light dependent resistor (LDR), The LDR sensors

can be used to detect light intensity to which it is exposed,

also to differ from day and night, Different LDR sensors

available in the market, the biggest size is used to

construct the sensor because the more area of the sensor,

the more its sensitivity or less time taken for output to

change when input changes (Mohammed S. El-Moghany

et al, 2012). In both proposed system's configurations,

sensors are integrated with the solar panel, screened from

each other by opaque surfaces; and each is placed in an

enclosure, so that the light will only hit LDR when it is

facing directly at the sun.

The LDR sensor circuitry is designed as a voltage

divider circuit as shown in Figure 4. The desired resistor

value should provide a voltage that covers the sunny and

cloudy conditions, a 100 ohm could be suitable; the output

of the sensor circuit is an analogue voltage that is used as

an input to the control unit ( e.g. microcontroller, PIC) to

calculate error between two LDRs. An extra LDR, located

on panel's front surface, can be used to ensure that solar

panel is perpendicular to the sun.

A variable resistor (potentiometer) can be, also used to

determine the location of the solar panel to prevent the

panel from the impact when it reaches the edges (also, in

case of measured sequence of angle change), When the

potentiometer reaches the value corresponding to edge, the

controller stopped the motor and immune it from rotating

in that direction.

(a) LDR sensor simulation in Proteus

(b) Physical implementation (Chin CS,2011)

(c) connecting to PIC, Figure 4 LDR sensor circuitry

4.3 Control unit selection: Over the years, tests and

researches had proved that development of smart solar

tracker maximizes the energy generation. For

implementing smart precise solar tracker, an embedded

Microcontroller is optimal selection, since it is

inexpensive single chip computer, easy to embed into

larger electronic circuit designs, also, because of their

versatility, Microcontrollers add a lot of power, control,

and options at little cost, capable of storing and running

programs and can be programmed to perform a wide range

of control tasks. Optimal and available microcontroller is

PICmicro Microcontroller (e.g. PIC16F877A), supplied

with 6VDC. Selected PICmicro microcontroller type is

supported with ADC pins, to convert the analog input

sensor readings to digital value, fed to microcontroller.

Microcontroller can be easy programmed, using C

language; C offers unmatched power and flexibility in

programming microcontrollers. MikroC adds even more

power with an array of libraries,

4.4 Control algorithm selection: a review of literature

shows that, different control algorithms can be used to

achieve desired performance of solar tracking system,

where: (M. A. Usta et al, 2011 ) presented a one-axis

tracker using three light resistors (LDRs). The first LDR

detect the desired state of the collector, the second and

third LDRs were designed to establish the presence of

cloud and to make difference between day and night. (S.A.

Kalogirou, 1996) implemented a fuzzy logic control for

sun tracker on a computer controlled the nonlinear

dynamics of the tracking mechanism. (H.A. Yousef, 1999)

modeled and designed a first order fuzzy inference system

for tracking system. (M. Singh et al, 2007) developed a

correction control system made by an artificial technique

vision based on the capture of pictures of the sun

positions. (M. Berenguel et al, 2004) presented a robust

control with MPPT system based on a sliding mode


754

controller (SMC). In this paper we will propose a simple

and easy to implement control algorithms to achieve

desired output position, particularly PID / PD with

deadbeat response. In the transient mode, PD-controller

speeds up the transient response, and it will decay faster,

resulting in less settling time TS, less time constant T, less

peak time TP, and reduced maximum overshoot MP, while

deadbeat response means the response that proceeds

rapidly to the desired level and holds at that level with

minimal overshoot, combining both characteristics will

desired and satisfactory system response.

The microcontroller can, also, be programmed to apply

the Pulse Width Modulation (PWM) signal to drive the

motor at a controlled speed correspond to a maximum

voltage of 5V. A proposed flowchart of PIC16F877A

programming, is shown in Figure 4(d) , where LDR

readings is converted and compared, and based on

generated error , microcontroller will drive the motor until

the error is zero.

Sun position readings

(LDR1 and LDR2)

Switching system on-off

Converting and

comparing LDR readings

Error= LDR1 - LDR2

Error == 0 & Vs ~== edge

Set RB? to 1

Set RB? to 0

Position sensor reading

Vs

Error, Vs

Error ~= 0 & Vs ~== edge

Error ~= 0 & Vs == edge

Set RB? to 0Set RB? to 1

End

Yes

Yes

Yes

No

No

No

No

Figure 4(d) Flowchart of microcontroller programming

4.5 Actuator selection: Actuator converts an information

signal from the microcontroller control unit, into energy

acting on the basic system, the solar tracking system

requires movement in different directions, the proper

selection of actuator and drive combination can save

energy and improve performance. Mechatronic systems

often use electric motors to drive their work loads, due to

simple principle of working, quick instantaneous and

accurate torque generation, available, inexpensive,

reversible, and ease of designing and implementing

controller to achieve optimal instantaneous, precise motion

control performance, a suitable electric motor is low-

speed DC motor, therefore the control of proposed solar

tracking system is simplified to eclectic motor control. The

driving mechanism includes the motor and the gears with

gear ratio, n

4.6 Output signal and conditioning: LDRs are used as

current sources and connected in opposite polarity to the

input of an op-amp, any difference in the short-circuit

current of the two cells is sensed and amplified by the op-

amp. Because the current of each cell is proportional to the

illumination on the cell, an error signal will be present at

the output of the amplifier, this error voltage, is fed to

microcontroller to generate signal to cause the motor to

drive the system back into alignment, the op-amp is given

by RF

A voltage regulator (the IC UA723chip) is to be used

to regulate the supply voltage (12 V) lowered to a level

suitable for use in the microcontroller (6V), the charge

controller and the LDR sensors. a heat sink is to be used to

dissipate the heat generated by the long duration used.

Different drives (servo-amplifier) can be used

including, Relay driver and H-bridge. A most suitable and

simple to implement drives for PMDC motor for

bidirectional driving are H-bridge Or H-Bridge in IC’s,

e.g. L293D, L293D is a dual H-Bridge motor driver, it is

a 16 pin chip, so with one IC we can interface two DC

motors which can be controlled in both clockwise and

counter clockwise direction .a common carrier,(see Figure

5-6). The gain of the servo-amplifier –K. A voltage

regulator circuit was used to bring the supply voltage

down to a level suitable for use in the microcontroller and

the LDR sensors.

4.7 Sub-systems placement and integration: The overall

solar tracking system consists of the selected mechanical,

sensing, actuating and electrical subsystems, shown in Fig

2 and Fig 3, all these subsystems are to be integrated with

synergy into the solar tracking system. To make sure the

structure is stable and the load is constant for the rotation

motor, the center of gravity of tilting structure is aligned at

rotating center , electronics, data outputting and control

circuitry to be located inside the a housing, that will

include slots for user interface and input/output ports.

For one-axis sun tracking system, one light tracking circuit

consisting of two similar LDR-sensors, and one electric

motor are to be used, meanwhile for two-axis sun tracking

system, two light tracking circuit consisting of four similar

LDR-sensors which are located at the east, west, south,

and north and two electric motor, each for each axis, are

used, the two drive motors are decoupled, the sensors are

configured in a way that sensor1 and sensor2 are used to

track the sun horizontally meanwhile sensor3and sensor4

allow tracking the sun vertically, in order to achieve

constantly solar panel aligned perpendicularly to sun light,

it is required to find balance between the two light sensors,

both sensors must receive the same light, and

correspondingly produce the same voltage, when one

sensor receives more light than the other, this means the

solar panel is not aligned perpendicularly to sun light and

an error voltage results. When sun's position changes, the

light source intensity received by different sensors is

different, the system then determines which sensor

received more intensive light based on the sensor output

voltage value interpreted by voltage type A/D converter.


755

The system drives the motor towards the orientation of this

sensor. If the output values of the two sensors are equal,

the output difference is zero and the motor’s drive voltage

is zero, which means the system has tracked the current

position of the sun. Based on desired accuracy, a control

system is to be designed (particularly, PID / PD with

deadbeat response), and correspondingly the PICmicro

unit can programmed to continuously track the sun’s

position by continuously scanning the sun location and

continuously drive the system in both directions or a

control system is to be designed to scan the sun's position

every one minute in the horizontal plane and every 1.5

minute in the vertical plane, calculate the error and use it

to drive the system in both directions. It is important to

consider that for each sensor pair the both LDR must be

quasi-identically as possible, because the measurement

method assumes identical currents in the case of

identically irradiance. At the night the LDR-sensors

resistance are maximum, in this case the microcontroller

will rotate the solar panel until the position sensor has the

starting point value. For two axis system, Figure 1 can be

modified to have the arrangement shown in Figure 6(d).

Figure 5 (a)( Mohanad Alata, 2005)

Figure 5(b)

(ba

tter

ies)

sto

rag

e

dev

ices

First

motor

Second tilt

motor

Control and

circuitry

Light

sensors

Figure 5(c) Proposed design

Figure 5(d) One and two DOF system (Ahmad Rhif, 2011)

Figure 5(e) One and two DOF system (Ahmad Rhif, 2011)

Light sensor

Sun

Shadow

Enclosure

Figure 6 (a) One-axis sun tracking system

sensor1

sensor4

sensor3

sensor2

North

West

East

South

Figure 6 (b) Two-axis sun tracking system

Lig

ht

sen

sor1

Lig

ht

sen

sor2

Co

mp

arat

or

Mic

roco

ntr

oll

er

Figure 6 (c) Light sensor

Figure 6 light detecting and tracking circuit and

arrangements.


756

Dri

ve2

DC motor1 Gears

Solar panel

& mechanism

Controller

Position sensor

an

gle

Dri

ve2

DC motor2 Gears

an

gle

sensor1

sensor4

sensor3

sensor2

North

West

East

South

Position sensor

Error

Error

Charge controller

storage devices

(DC-batteries)

DC/AC converter

Load

Figure 6(d) Two axis solar tracker system arrangements

5. Modeling and simulation

The key essential characteristics of a mechatronics

engineer are a balance between two skills;

modeling/analysis skills and experimentation/hardware

implementation skills. The mechatronics design approach

challaenge conventional sequancial design approach, by

connecting machine design tools and creating a virtual

machine prototype before designing the physical machine,

to take all advantages that can result from an integrated

design, this approach offers less constrains and shortened

development, also allows the design engineers to provide

feedback to each other about how their part of design is

effect by others

Two very important characteristics that determine the size

of electric motor for a particular application are torque and

horsepower. Torque is the turning effort. Horsepower

takes into account how fast the system is turned.

5.1 Electric motor sub-system modeling

Solar tracking system motion control is simplified to an

electric motor motion control, in terms of output angular

displacement; therefore, the conception of solar tracking

system can be presented as position control of one eclectic

motor, considering the system operation is accomplished

by one of two used two motors.

The DC motor is an example of electromechanical

systems with electrical and mechanical components. Based

on (S. Kim et al,2007), the DC motor open loop transfer

function without any load attached relating the input

voltage, Vin(s), to the output angular displacement, θ(s), is

given by Eqs(1)(2). The total equivalent inertia, Jequiv and

total equivalent damping, bequiv at the armature of the

motor are given by Eq(3), for simplicity, the solar panel

can be considered to be of cuboide shape, with the inertia

calculated by Eq(4), also the total inertia can be calculated

from the energy conservation principle, correspondingly,

the equivalent mobile robot system transfer function with

gear ratio, n, is given by Eq(5)

3 2

( )( )

( )

( )

( ) ( ) ( )

t

angle

in a a m m t B

t

in a m a m m a a m t b

KsG s

V s s L s R J s b K K

Ks

V s L J s R J b L s R b K K s

(1 )

Armature inductance, La is low compared to the armature

resistance, Ra (discussed later). Neglecting motor

inductance by assuming, (La =0), manipulating and gives:

( )

( ) 1

t

a a

in t bm

m a

K

R Js

V s K Ks s b

J R

(2) 2 2

1 1

2 2

equiv m Load equiv m Load

N Nb b b J J J

N N

(3)

2 2

2

2 2

2

( ), ,

12

* 0.5* * 0.5* *

load

total

total load load

m h aJ

mm J J

(4)

2

/( )

( ) ( ) ( )

t

angle

a equiv a equiv equiv a a equiv t b

K nG s

s L J s R J b L s R b K K

(5)

5.2 Sensor sub-system modeling: the system is to be built

with a unity feedback such that the control system insures

that the output position is met, as noted, a variable resistor

(potentiometer) can be, also used to determine the location

of the solar panel to prevent the panel from the impact

when it reaches the edges. Potentiometer is a sensor used

to measure the actual output position, θL, convert into

corresponding volt, Vp and then feeding back this value,

the Potentiometer output is proportional to the actual

position, θL, this can be accomplished as follows: The

output voltage of potentiometer is given by: Vp = θL * Kpot.

Where: θL :The panel position. Kpot the potentiometer

constant; It is equal to the ratio of the voltage change to

the corresponding angle change, and given by:

potK (Voltage change) / (Degree change), Depending on

maximum desired output angle, the potentiometer can be

chosen, for case Vin= 0:12, and angle = 0:180 degrees,

substituting, we have Kpot by:

12 0 / 180 0 0.0667 V / degreepotK

The gain of the servo-amplifier –K. The op-amp, for

sensors' reading difference, is given by RF

5.3 Control system selection, modeling and design

The main function of designed control system is to achieve

a fast response to a step command with minimal

overshoot; this can be achieved applying different control

algorithms, including PID/PD with deadbeat response.

PID controllers are commonly used to regulate the time-

domain behavior of many different types of dynamic

plants (L. Al-Sharif, 2010). The transfer function of PID

control is given by:

2

( )

P I

D

D DI

PID P D

K KK s s

K KKG s K K s

s s

(6)

Proportional Derivative, PD-controller, The transfer

function of PD-controller is given by:


757

( )PD P DG s K K s , Rearranging, we have the following

form:

( ) ( )P

PD P D D D PD

D

KG s K K s K s K s Z

K

(7)

The PD-controller is equivalent to the addition of a simple

zero at/PD P DZ K K

. The addition of zeros to the open-

loop has the effect of pulling the root locus to the left, or

farther from the imaginary axis, resulting in speeding up

the transient response, where it will decay faster. a suitable

choice is a combination, PD-controller with deadbeat

response

Designing and applying Proportional Derivative

controller with deadbeat response :Deadbeat response

means the response that proceeds rapidly to the desired

level and holds at that level with minimal overshoot(Wai

Phyo Aung et al,2007). The characteristics of deadbeat

response include; Zero steady state error, Fast response,

(short rise time and settling time) , percent overshoot

greater or equal to 0.1% and less or equal 2 % and

minimal undershoot, less than ±2% error band. PD-

controller transfer function is given by Eq.(7). Using

simplified first order form of PMDC

Current

Torque

5Angular Acceleration

4 Torque13 Curent1

2 Angular position

1Angular speed

speed.

Sum.4

Sum.1

Product9

Product8Product7

Product4Product11

Product10

Product1Product

1

s

Integrator.2

1

s

Integrator..4

1

s

Integrator..1

du/dt Derivative

1

Constant

8

bm

7T, Load torque

6

Ra

5

Input Voltage1

4Kt, Torque constant

3

Kb, EMF constant

2Jm

1La

Figure 7(a) actuator sub-system

angular position.

Torque

Motor5.mat

To File2

Motor4.mat

To File1

Tl

Tload

La

Jm

Kb, EMF constant

Kt, Torque constant

Input Voltage1

Ra

T, Load torque

bm

Angular speed

Angular position

Curent1

Torque1

Angular Acceleration

Subsystem

Ra

Ra

La

La

Kt

Kt

Kb

Kb

Jm

Jm

Input Volt

Current.

bm

Bm

Angular speed.

Angular acceleration

Motor1.mat

.

Motor3.mat

.

Motor2.mat

Figure 7(b) Open loop one DOF solar tracker system, motor function block model


758

R4

DC7

Q3

GN

D1

VC

C8

TR2

TH6

CV5

U1

NE555

C?

0.1uF

R5

33

Changing the value of variable resistor, will chnage the speed

B?12V

RV1100K

D11N4001

D21N4001

R21k

Q?BD139

C50.1uF

-204

B3120VD?

1N4007

R4

DC7

Q3

GN

D1

VC

C8

TR2

TH6

CV5

U1

NE555

R1100

R2500

C1

5uF

B29V

+88.8

R5

10k

D1

LED-GREEN

R6

220

A

B

C

D

Changing the value of R1, R2, and C1, will chnage the width of the pulse: TIME=0.7*(R1+R2)*C1=1.620370257844658e-005

Figure 8(a) Chronological solar tracker, two different circuits

X18MhzC1

22pF

C2

22pF

+88.8

1

5

MODFILE=DCMOTOR

D1

1N4370A

IN12

OUT13

OUT26

OUT311

OUT414

IN27

IN310

IN415

EN11

EN29

VS

8

VSS

16

GND GND

U1

L293D

RA0/AN02

RA1/AN13

RA2/AN2/VREF-/CVREF4

RA4/T0CKI/C1OUT6

RA5/AN4/SS/C2OUT7

RE0/AN5/RD8

RE1/AN6/WR9

RE2/AN7/CS10

OSC1/CLKIN13

OSC2/CLKOUT14

RC1/T1OSI/CCP216

RC2/CCP117

RC3/SCK/SCL18

RD0/PSP019

RD1/PSP120

RB7/PGD40

RB6/PGC39

RB538

RB437

RB3/PGM36

RB235

RB134

RB0/INT33

RD7/PSP730

RD6/PSP629

RD5/PSP528

RD4/PSP427

RD3/PSP322

RD2/PSP221

RC7/RX/DT26

RC6/TX/CK25

RC5/SDO24

RC4/SDI/SDA23

RA3/AN3/VREF+5

RC0/T1OSO/T1CKI15

MCLR/Vpp/THV1

U?

PIC16F877A

B112V

B25V

LDR2TORCH_LDR

RV110k

R4

1.5k

LDR1TORCH_LDR

RV110k

R2

1.5k

Figure 8(d) microcontroller based solar tracker using L293D and Relay driver

-16.72

speed in rad/sec

-159.6

speed in RPM

XY Graph2

XY Graph1

XY Graph

X(2Y)

Graph1

31.1288

s+31.1288

Transfer Fcn Torque

solar6.mat

To File5solar.mat

To File4

solar4.mat

To File2

solar3.mat

To File1

TL

Tload

La

Jm

Kb, EMF constant

Kt, Torque constant

Input Voltage1

Ra

T, Load torque

bm

Angular speed

Angular position

Curent1

Torque1

Angular Acceleration

Subsystem

Step

time1

Signal From

Workspace4

theta

Signal From

Workspace2

time1

Signal From

Workspace1Ra

Ra

RPM

s+Z0

s+P0

Lead compensator

La

La

Kt

Kt

Kb

Kb

Jm

Jm

-K-

-K-

-K-

[output]

Goto

theta

From

Workspace

[output]

From

Error signal

Current.

Control_signal

bm

Bm

Angular speed (rad/sec)

Angular position Rad2 -0.05004

Angular position Rad

Angular acceleration-K-

Angle feedback, Ktac

.3

.2.1

solar5.mat

.

PD(s)

,

Kp

''

PID(s)

'

solar2.mat

.

solar1.mat

Figure 9 (a) The simulink model of overall solar tracker system, with main sub-systems

motor transfer function in terms of output angle given by

Eq.(2): /( )

( )( ) 1

t a m

angle

in t b

m

m a

K R JsG s

V s K Ks s b

J R

The system forward transfer function is given by:

2

( )

( )

p D t

a m

forward

t bm

m m a

K K s K

R JG s

K Kbs s

J J R

The system overall closed loop transfer function transfer

function is given by:


759

2

( )

( )

p D t

a m

p tt b D tm

m m a a m a m

K K s K

R JT s

K KK K K Kbs s

J J R R J R J

(8)

Referring to Wai Phyo Aung,2007 The controller gains KP

and KD depend on the physical parameters of the actuator

drives, to determine gains that yield optimal deadbeat

response, the overall closed loop transfer function T(s) is

compared with standard second order transfer function

given by (9), and knowing that parameters α and ωn are

known coefficients of system with deadbeat response

given by (L. Al-Sharif, 2010), α = 1.82 and ωnTn = 4.82 , Tn

=2 and gives the following:

ωnTn = 4.82 , ωn = 4.82/2=2.41

2

3 2 2( ) n

n n

G ss s

(9)

Equating and comparing the actual and desired

characteristic equations, the gains of controller are found: 3 2 2 2 p tt b D tm

n n

m m a a m a m

K KK K K Kbs s s s

J J R R J R J

Systems design with prefilter: Prefilter is defined as a

transfer function Gp(s) that filters the input signal R(s)

prior to calculating the error signal. Adding a control

system to plant, will result in the addition of poles and/or

zeros, that will effect the response, mainly the added zero,

will significantly inversely effect the response and should

be cancelled by prefilter, therefore the required prefilter

transfer function to cancel the zero is given by (10). In

general. The prefilter is added for systems with lead

networks or PI compensators. A prefilter for a system with

a lag network, mainly, is not , since we expect the effect of

the zero to be insignificant. For systems with PD

compensators, a prefilter is used to eliminate any

undesired effects of the term s + z introduced in the

closed-loop transfer function, the required prefilter transfer

function is given by:

Pr _ Pr( ) , , ( )O PD

efilter PI efilter

O PD

Z ZG s G s

s Z s Z

(10)

Lead compensator Lead compensator is a soft

approximation of PD-controller, PD controller transfer

function is given by GPD(s) = KP + KDs , The PD controller

is not physically implementable, since it is not proper, and

it would differentiate high frequency noise, thereby

producing large swings in output. To avoid this, PD-

controller is approximated to lead controller of the

following form:

( )Lead C

s ZG s K

s P

Where : Zo < Po , The larger the value of P, the better the

lead controller approximates PD control,

5.4 Sub-systems and overall system simulation, testing,

analysis and optimization .

5.4.1 Electric motor sub-system simulation in

MATLAB/Simulink

Simulation of one DOF solar tracker open loop system is

shown in Figure 7, where in Figure 7(a) is shown, the

actuator sub-system inner sub-model, that to be used to

built the actuator sub-system model function block shown

in Figure 7(b), this model can give designer different

readings including; speed, angle, current and torque, to

evaluate and verify actuator sub-system performance, the

same model is used for other direction in case of two DOF

systems

5.4.2 Electronics and interfaces simulation and testing:

To test and evaluate the selection and integration of

electronic circuit design, microcontroller programming

and interface components, simulation using ISIS-

Professional Proteus is used. as noted, there are three types

of trackers; Passive tracker, Chronological tracker and

active tracker, shown in Figure 8, different control circuits

can be used to control the motion of solar tracker,

including using timers (Figure 8(a)) to generate pulse to

control motor motion. For smart solar tracker, the control

program is written in C language, with the help of MikroC

program is converted to Hex.File that is downloaded on

the simulated solar system including PIC-microcontroller

and circuit, the simulation of solar tracker is shown in

Figure 8(d), simplified algorithm can be as follows:

unsigned int LDR1, LDR2,error ;

void main(solarpanel) {

Ansel=0x06;

TRISC=0;

TRISB=0;

while(1){

//dealy(1500)

LDR1=ADC_Read(1);

LDR2=ADC_Read(2);

error= LDR1- LDR2;

error=abs(error);

if(error == 0){ PORTB.F1=0;

} if(error > 0){ PORTB.F1=1;

} } }

5.4.3 Overall system simulation, testing and analysis.

The simulink model of closed loop solar tracker system is

shown in Figure 9 (a), including electric motor, sensor,

input altitude angle and two controllers PID, PD with

prefilter sub-systems.


760

5.5 Overall system testing and results

With a set of PD controller gains; KP, KD ,the response of

the proposed model is shown in Figure 9 (b). Response

curves show the system reaches desired output position in

0.2 seconds with zero steady state error, but with

overshoot.

Applying PD controller with deadbeat response, and

calculating desired values of gains, we find Kp =

23.8893525618918 and KD= 0.767435051920526, PD

zero Z0 = Kp/ KD =31.1288.Applying PD controller with

deadbeat response, will result in response curves shown in

Figure 9(c), Response curves show response proceeds

rapidly to the desired level and holds at that level with

minimal overshoot and steady state error.

To further test our design, by using signal builder to

generate signal that mimic angular input similar to sun

altitude angle, will result in response curves shown in

Figure 9 (d) , the output smoothly follows the output .

Applying PID controller will result in response curves

shown in Figure 9 (e)

Applying variable angular position to the system, will

result in system responses shown in Figure 10 (f), the

system stands such variable values. To test the proposed

model, for actual input signal values, based on derived

equations given supposed by Ashraf Balabel,2013, altitude

angle is calculated, for Taif city, western of Saudi Arabia,

the altitude angle, which is the angle between the solar

radiation and the solar panel surface, is evaluated in the

day specified, plotting the calculated altitude angle versus

time, is shown in Figure 10(a). The altitude angle is

changed regularly, based on this, the readings of two

LDRs are changed, and the sequenced altitude angle

change can be considered as the difference (error) between

the readings of two LDR sensors that is used by control

system to drive the electric motor. Generally, the sun

altitude angle change can be simulated assuming, the sun

is shining exactly 12 hours, from sunrise at 6 am to

sunset at 6 pm, in these 12 hours the sun is to travel from

the 0 degree to maximum 180 degrees, correspondingly,

the solar panel, in 12 hours will rotate 180 degrees, sun

angle changes per hour can be calculated by dividing

maximum degree over number of hours; or minutes or

seconds; 180/(12) = 0.004166=15 degrees per hour or,

18/(12*60*60 ) = 0.004166 degrees per second, with the

initial altitude angle is at 30 degrees, and maximum angle

limit to be 90 degrees, the simulation shown in Figure

9(g) is proposed.

Applying the calculated altitude angle, for Taif city, as

the input data ( error) for the designed control system,

will result in corresponding panel angle, plotting both

input angle and output panel angle in the same graph

window, will result in response curve shown in Figure

10(b). These response curves show that, the input and

output angles curves are allmostly identical, with small

error, by soft tuning of control system, the input can match

the output without error, comparison show that the solar

panel tracks the sun, resulting in optimal operational

efficiency of solar energy photovoltaic module

0 0.2 0.4 0.6 0.80

5

10

15

Time (seconds)

Rad

Angle VS time

0 0.2 0.4 0.6 0.8-100

0

100

200

Time (seconds)

Rad/s

Speed/time

0 0.2 0.4 0.6 0.8-1

0

1

2x 10

4

Time (seconds)

Am

p

Current/time

0 0.2 0.4 0.6 0.8-200

0

200

400

Time (seconds)

Nm

Torque/time

Figure 9 (b) angle/time, speed/time, current/time,

torque/time response curves applying PD controller.

0 0.5 1-5

0

5

10

15

Time (seconds)

Rad

Angle VS time

0 0.5 1-50

0

50

100

150

Time (seconds)

Rad/s

Speed/time

0 0.5 1-2000

0

2000

4000

Time (seconds)

Am

p

Current/time

0 0.5 1-50

0

50

100

Time (seconds)

Nm

Torque/time

0 0.5 1-5

0

5

10

15

Time (seconds)

Rad

Angle VS time

0 0.5 1-50

0

50

100

150

Time (seconds)

Rad/s

Speed/time

0 0.5 1-2000

0

2000

4000

Time (seconds)

Am

p

Current/time

0 0.5 1-50

0

50

100

Time (seconds)

Nm

Torque/time

Figure 9 (c) angle/time, speed/time, current/time,

torque/time response curves applying PD with deadbeat

response.

0 2 4 6-1

0

1

2

3

Time (seconds)

Rad

Angle VS time

0 2 4 6-2

0

2

4

Time (seconds)

Rad/s

Speed/time

0 2 4 6-10

-5

0

5

10

Time (seconds)

Am

p

Current/time

0 2 4 6-0.2

-0.1

0

0.1

0.2

Time (seconds)

Nm

Torque/time

0 2 4 6

-10

-5

0

5

10

Time (seconds)

Control signal

0 0.2 0.4 0.6 0.8-5

0

5

10

15

Time (seconds)

Error signal

0 2 4 6-10

-5

0

5

10

Time (seconds)

Control signal

0 0.2 0.4 0.6 0.8-5

0

5

10

15

Time (seconds)

Error signal

Figure 9 (d) Applying PID controller response curves.


761

0 1 2 3 4-2

0

2

4

Time (seconds)

Rad

Angle VS time

0 1 2 3 4-20

-10

0

10

Time (seconds)R

ad/s

Speed/time

0 1 2 3 4-400

-200

0

200

Time (seconds)

Am

p

Current/time

0 1 2 3 4-10

-5

0

5

Time (seconds)

Nm

Torque/time

Figure 9 (e) Applying PD controllers with deadbeat

response.

0 500 1000 1500-10

0

10

20

30

40

50

60

70

80

90

Time (sec)

Deg

ree

Change of Altitude angle with time for 21st August

Sun rise Sunset

max. angle 80.83

Figure 10(a) the calculated altitude angle versus time (the

input angle change) ( Ashraf Balabel et al, 2013)

0

10

20

30

40

50

60

70

80

90

0 500 1000 1500

Angle

Time (Min)

Altitude angle

Panel angle

Figure 10(b) calculated altitude angle for Taif city, as

input and resulted panel angle as system response

time

36

start angle

Switch1

Switch

Scope1

Scope

Product2

Product1Product

12:34

Digital Clock

90

Constant1

-1

Constant

.004167

15deg/hour

Figure 10 (c) Proposed models for calculating angle

change

0 0.5 1 1.5 2 2.5 3-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Time (Sec)

Ang

le

Variable input angle

Output angle

Step input

Figure 10 (d) Responses applying variable input angle

6. Prototyping, testing, evaluation and optimization.

There is no single model which can ever flawlessly

reproduce reality, there will always be errors called as

unmodeled errors between behavior of a product model

and the actual product. In order to take into account the

unmodeled errors and enhance precision, performance in

the design process, the mechatronics design approach

includes prototyping phase. Prototyping development may

be carried out in the following two forms; Virtual

Prototype and Physical Prototype, in this paper, only

virtual prototype in MATLAB and Proteus environment is

built, shown in Figure 9(d) and Figure 8(d)

7. Conclusion & Future work

This paper proposes the conception and development of

solar tracking system based on mechatronics design

approach, where realization of design is achieved applying

concurrent design approach and considerations. A

complete system and components' selection, design and

integration as well as, modeling, simulation, and analysis

are presented. Also, a new control method was proposed

for achieving smooth fast response without overshoot. The

obtained simulation results are quite encouraging; they

show the efficiency and the simplicity of the proposed

design. The proposed mechatronics design and models are

intended for research purposes, as well as, for application

in educational process.

As a future work, both one and two DOF physical

prototypes of the proposed design to be built tested,

compared with current design and optimized.

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Farhan Atallah Salem AbuMahfouz: B.Sc., M.Sc and Ph.D., in

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Interests; Design, modeling and analysis of primary

Mechatronics Machines, Control selection, design and analysis

for Mechatronics systems. Rotor Dynamics and Design for

Mechatronics applications.

mechatronics design of solar tracking system · tracking system moves the solar panel to the...

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