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  1. 1. IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE)e-ISSN: 2278-1676 Volume 4, Issue 4 (Jan. - Feb. 2013), PP 30-37www.iosrjournals.org Solar Energy Based Optimal Battery Charging Mechanism in Robotic Vehicle by Using Smart Host Microcontroller S.Menakambal1, A.Satheesh2 1 PG Scholar, 2Professor 1 M.E (Embedded System Technologies) 1,2 Department of EEE, Nandha Engineering College, ErodeAbstract: The PENTRON robotic platform-an autonomous unmanned exploration vehicle specialized inrecognition. The robotic vehicle having pack of two rechargeable batteries each performing charging anddischarging operation independently. The two pack of battery charging system can be controlled by means oftracked single tiltable solar PV panels for improving PENTRON’s power regardless of its mobility. The designconcept of robotic vehicle is based on a PIC16F877 microcontroller and the efficient wireless camera,temperature sensor, humidity sensor, light sensor, voltage sensors are attached in the robotic vehicle. The Zig-Bee wireless technology provides adequate information about the environmental conditions in nearby PC. Theaim of this paper is to reduce the weight of the robotic vehicle by means of reducing the usage ofmicrocontrollers and to increase the power of the robotic vehicle by the help of solar PV Panels. On the otherhand, the switching time taken by two pack of batteries can be reduced.Keywords: Wireless camera, Li–Po battery, mechatronic system, photovoltaic (PV), robotic vehicle, solartracker, Sensors, Zig-Bee transceiver, PIC Microcontroller I. Introduction SOLAR power systems in autonomous robotic vehicles have been often used for some years. A realexample is the VANTER robotic platform uses huge number of microcontrollers and 3 solar PV Panels. This inturn improves weight of the vehicle and power consumption [1]. The main drawback behind existing system isthat the robotic vehicle having four-wheel-drive (4WD) and the individual control of each wheel allow differenttypes of movement; including Ackerman configuration, the crabbing maneuver or the rotation with inner inertialcentre. The DC motor is fixed in all the four wheels, each wheel consumes 12V supply and 60mA from thebattery. This leads to huge power consumption. Solar tracker prototypes built in mobile robots have proven thatorientation of PV systems leads to increased energy efficiency relative to systems with fixed solar panels (20–50% per collector)[2]. In Proposed model, the PENTRON robotic exploration vehicle aims to improve variousaspects of the aforementioned rovers with scientific and academic purposes. The rover was developed to beguided and has 2 wheels coupled to a plane chassis that can rotate independently. The 2-wheel-drive (2WD) isplaced at one end and the tracking ball is placed at the other end for the movement of robotic vehicle. The twowheels in PENTRON are sustained by means of independent passive suspension of double aluminium fork toabsorb terrain vibrations shown in (see Fig.1).Each wheel consists of two motors, one for rotation and another for driving. The forward movement is producedby means of dc motors (12 V and 60 mA) that provides 120r/min with a torque of 8.87 kg/cm. On the otherhand, the rotation motor provides a speed of 152r/min. The reduction huge microcontroller to singlemicrocontroller and four wheels to two wheels in the proposed model improves the rover capacity and reducespower consumption. The robotic vehicle having single tiltable Solar PV Panels it can be controlled by means ofsolar tracked panels. The robotic system programming is divided into three main code levels and its hardwarewas designed with a hierarchical control structure based on modular microcontrollers. The top level program,carried out in LabVIEW it is executed in a remote PC and offers a Zig-Bee technology to monitor and controlthe whole robotic vehicle. The second code level, programmed in C language, runs autonomously on a masterPIC16F877 microcontroller aboard PENTRON. www.iosrjournals.org 30 | Page
  2. 2. Solar Energy Based Optimal Battery Charging Mechanism in Robotic Vehicle by Using Smart Host Microcontroller Fig 1: PENTRON: A solar-powered robotic vehicle II. Proposed System The PENTRON rover series has a single solar panel system coupled to an assisted suspensionmechanism. This prevents the manipulator arm mounted on the middle of the rover to minimize solar panel-generated power and allows it to dust solar panel surface.2.1 Robot terminal unit The PIC16F877 microcontroller which monitors PENTRON power consumption and decisions in acomplete autonomous way. The microcontroller performs two main functions: 1) detecting environmental lightlevel and controlling the solar tracking system to obtain the highest power; and 2) interpreting operation datafrom batteries and solar panels to control the working mode of the charger accordingly (see Fig. 2). Fig 2: Block diagram of PENTRONThe robotic vehicle generally uses four different kinds of sensors: They are Temperature sensors, voltagesensors,Light sensors and Humidity sensors. The sensors that used in a robotic vehicle observes the remoteenvironmental conditions and the observed data can be measured and simulated by the help of MP LABsoftware in nearby PC. The thermistor is the temperature sensitive resistor which is used to measure bodytemperature. The thermistor resistor is varied as per the temperature. The varying resistance level is convertedinto corresponding voltage signal which is given to ADC through amplifier. The ADC is nothing but analog to www.iosrjournals.org 31 | Page
  3. 3. Solar Energy Based Optimal Battery Charging Mechanism in Robotic Vehicle by Using Smart Host Microcontrollerdigital converter which converts the input analog signal to corresponding digital signal. The converted digitalsignal is given to microcontroller. The LM 324 thermistor consist of four independent high gains internalfrequency compensated operational amplifier which were designed specifically to operate from a single powersupply over a wide voltage range. The voltage sensors are generally used for observing the voltage level of theLi-Po batteries placed inside the robotic vehicle. A photo resistor or LDR is an electronic component whoseresistance decreases with increasing incident light intensity. The light sensors generally observes the intensity oflight that coming from sun. The light sensors attached in the robotic vehicle predicts the environmental lightintensity and sends it to microcontroller. The robotic vehicle uses humidity sensors for observing the moisturecontent of the atmosphere. The wireless camera fixed infront of the robotic vehicle captures the image of theenvironment and the captured image can be monitored in our nearby PC through Zig-Bee wireless technology(see Fig.3). Fig 3: Architecture of Robot terminal unit2.2 System terminal unit Zig-Bee is a low-cost, low-power, wireless mesh network standard. The low cost allows the technologyto be widely deployed in wireless control and monitoring applications. The wired serial communication is usedto transfer the data between microcontroller and PC through Zig-Bee communication. PC side is the transmitterend and Microcontroller is the receiving end. To Interface the micro controller to PC we need level converterwhich current TTL compatible voltage level to RS232 voltage level using wireless Zig-Bee. The PC is used todrive the robot. The robot side captures the image and captured picture is displayed in the PC. Fig 4: Architecture of System Terminal UnitThe commands send from the PC side is recieved by the Microcontroller as a signals and activates the DriverCircuit. Driver Circuit consists of Transistor which acts as switch to turn ON and turn OFF the relay. The relayoutput is given to motors which are attached in the robot. To drive the robot in the forward directioncorresponding information is transmitted from PC side and received in robot side using Zig-Bee transceiver (seeFig .4) www.iosrjournals.org 32 | Page
  4. 4. Solar Energy Based Optimal Battery Charging Mechanism in Robotic Vehicle by Using Smart Host Microcontroller Fig 5: Mechanical design of the solar tracking system of PENTRON: (a) upper solar panel, (b) mobile solar panels,(c) aluminium chassis,(d) methacrylate chassis,(e)methacrylate support,(f)pan and tilt unit,(g)pitch servometer, and(h)yaw servomotor.Fig. 5. shows the mechanical solar tracking system. This comprises(a) a fixed solar panel mounted horizontallyon PENTRON and (b) Single panels with symmetrical movements. The mechanical structure is mounted on (c)an aluminium chassis on which the electronics were mounted. On top of this platform (d) a methacrylate panelwith (e) two side supports has been assembled. The solar panel are mounted on (f) pan and tilt units formedDYS0213MGs metal gear servos. Each pair of digital servomotors allow soft rotations with an amplitude of180◦in (g) azimuth and (h) elevation, so that the solar panel can be oriented toward any part of the space.2.3 Li-Po batteries switching operation The switching system consists of two MAX1538EVKIT selectors with break-before-make operationlogic. Their function is connecting electrically the charge and discharge paths between the batteries, the chargermodule, and the load system (see Fig.6) that is, selector 1 is inserted between the charger and the dual-batterypack. Its function is routing the current from the PV panels to the input of the charger and, from there, to thebattery selected in each moment. Selector 2 is used to connect the selected battery to the load system. Therefore,the dynamic connections of the electric circuit are carried out according to the PIC16F877-defined logicaloperation mode. This is based on the voltage thresholds programmed into the control algorithm. Now, these twopack of Li-Po batteries performs their charging and discharging operation independently. In the first row,selector 1 was programmed to charge battery 1 while selector 2 is preset to discharge battery 2. Charge currentobtained from the PV panels is routed to the charger through selector 1 and, from the charger, to the selectedbattery. Likewise, the discharge current of battery 2 is routed to the load system through selector 2. The mainadvantage of the dual selector system is that it allows hot swapping of separated power supplies. In addition, incase both batteries were fully discharged, a working mode was programmed in selector 1 to supply the loadsystem directly from the PV panels. TABLE I. Logical operation mode of the battery selectors C= Closed, O= Open, X= Not Connected www.iosrjournals.org 33 | Page
  5. 5. Solar Energy Based Optimal Battery Charging Mechanism in Robotic Vehicle by Using Smart Host Microcontroller Fig 6: Overall connection diagram for batteries selectors. III. Experiment Results3.1 Measuring parameters The three parameters like (Temperature, humidity, Battery voltage) are predicted by the sensorsattached in the robotic vehicle and also plot graph depends on parameters. Parameter value received frommicrocontroller kit through RS232 port (serial communication) in 9600 baud rate, parity bit is none and data bitis 8. Proteus7.2 simulation software is used to run and simulate the total process. The software code is written inMP LAB software with high tech c compiler. The embedded C language is used for program compilation and itis converted into hex file.3.1.1 Input Parameter Measuring Fig 7: Input Parameter Measuring3.1.2 Waveform of Input Parameters Fig 8: Characteristics of Temperature www.iosrjournals.org 34 | Page
  6. 6. Solar Energy Based Optimal Battery Charging Mechanism in Robotic Vehicle by Using Smart Host Microcontroller Fig 9: Characteristics of Humidity Fig 10: Characteristics of Battery Voltage3.1.3 Rotating Direction The rotating direction of robotic vehicle depends upon the key press from PC (LabVIEW software)and also we can send the command from pc to microcontroller through RS232 port Key. TABLE II. Working Principle of Robot Rotating Direction Key Press Command send LED from PC to UC Glowing Forward F 1010 Reverse R 0101 Left L 0110 Right G 1001 Stop S 0000If the robotic vehicle needs to move in the forward direction corresponding information is transmitted from PCto microcontroller in the form of signals using Zig-Bee transceiver. In Receiver section, the microcontrollerdrives the robot in forward direction as per the appropriate command given by PC. Likewise, the robotic vehiclecan be moved in reverse, left and right direction. The direction of the robotic vehicle can be indicated by LED. Fig 11: Robot rotating direction www.iosrjournals.org 35 | Page
  7. 7. Solar Energy Based Optimal Battery Charging Mechanism in Robotic Vehicle by Using Smart Host Microcontroller Fig 12: Characteristics of the charge voltage measured in the cells battery Fig 13: Characteristics of the discharge voltage measured in the cells battery IV. Conclusion SOLAR power systems in autonomous robotic vehicles have been often used for some years. In realexample most of the supplied energy is generated by a reduced size photovoltaic (PV) panel. It includes theconstruction of a robotic vehicle which we designed is to move robot in forward and reverse with right and leftturns using dual battery. The robot controlling is done with the help of microcontroller which brings the robot onmovement. The proposal includes that the monitoring actions of rover are simulated using LabVIEW software. References[1] Justo E. Gonzalez Ramos.,and Tomas de J. Mateo Sanguino 2012 ―Smart Host Microcontroller for Optimal Battery Charging in a Solar-Powered Robotic Vehicle,‖ IEEE/ASME Trans Mechatronics.[2] Afarulrazi, A.B., Liew, K.L., Utomo,W.M., and Zafari,M. 2011―Solar tracker Srobot using microcontroller,‖ in Proc. Int. Conf. Bus., Eng. Ind. Appl.,pp. 47–50.[3] Chiang, C.M., Chou, P.C., Lee, C.Y., and Lin, C.F. 2009 ―Sun tracking systems A review,‖ Sensors, vol. 9, pp. 3875–3890.[4] Bajracharya,M., Helmick, D., and Maimone, M.W.,2008 ―Autonomy for mars rovers Past, present, and future,‖ Computer, vol. 41, no. 12, pp. 44–50.[5] Kubota, T., Kunii, Y., Kuroda, Y., and Otsuki,M.2008 ―Japanese rover test- bed for lunar exploration,‖ in Proc. Int. Symp. Artif. Intell., Robot. Automat. Space, no.77.[6] Lamon,P. 2008 ―The solero rover. 3D-position tracking &control for all-terrain robots,‖ Adv. Robot., vol. 43, pp. 7–19.[7] Arunrungrasmi, S., Jinayim, T., Mungkung, N., Tanitteerapan, T. 2007 ―Highly efficient low power consumption tracking solar cells for white-LED based lighting system,‖ World Acad. Sci., Eng. Technol., vol. 28,pp. 291–296.[8] Lever, J.H., Price, A.D., Ray, L.E., and Streeter, A.D. 2007 ―Design and power management of a solar-powered cool robot for polar instrument networks,‖ J. Field Robot., vol. 24, no. 7, pp. 581–599.[9] Smith, N., 2006 ―Dynamic power path management simplifies battery charging from solar panels,‖ Texas Instruments, Dallas, TX, Tech. Rep. SLUA394.[10] Lever, J. H., Ray, L. R., Streeter, A. and Price, A. 2006 ―Solar power for an antarctic rover,‖ Hydrol. Process, vol. 20, pp. 629–644.[11] Pharoah, J. G., Surgenor, B.W and Wilhelm, A. N. 2006, ―Design and Evaluation of a micro-fuel-cell-based power system for a mobile robot,‖ IEEE/ASME Trans. Mechatronics, vol. 11, no. 4, pp. 471–476[12] Baskaran,V., Cabrol,N., Calderon,F., Heys,S., . Jonak, D., Luders, A.,Wettergreen, D., Pane, D., Smith,T.,Teza,J.,Tompkins,P.,Villa,D., Wagner, M., and Williams,C.,. ―Second experiment in the robotic investigation of life in the Atacama Desert of Chile,‖ presented at the 8th Int. Symp. Artificial Intelligence, Robotics and Automation in Space, Munich, Germany,2005. www.iosrjournals.org 36 | Page
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