Designing a radio frequency controlled robot platform

Introduction:

Presents, wireless communicating engineering has been spread outing quickly. It is important part to human being as the distance between each other become shorter because of these radio engineerings, such as Radio Frequency, Microwave, Bluetooth, LAN and WIFI engineerings. Wireless communicating devices are indispensable to human being lives as people use to pass on with other by utilizing cordless phones and other radio devices. Besides that, wireless frequence devices are being applied in infirmary or a nursing place for monitoring of patients, and besides the radio mouse, keyboards for computing machine countries and robotics every bit good.

Since the radio communicating engineering is important and indispensable to human lives, so the wireless frequence technique has been chosen as the robot remote control in order to look into and use this engineering. The wireless frequence technique uses on this undertaking but non other radio engineerings because it has the suited transmittal scope and more dependable than other techniques. For illustration, infrared technique requires signal transmit in line with unobstructed between the sender and receiving system.

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Radio frequence technique applies on this undertaking for conveying the signal sent by user from sender to robot 's receiving system in order to command the going waies of automaton, such as move frontward, rearward, left or right. The scope between RF sender and receiving system is based on the frequence of its faculty. Higher frequence RF faculty will hold farther transmittal scope and RF range from 100 kilohertzs to 1 GHz. It is propagating along the land or contemplation from the ionosphere so reaches the receiving system.

The wireless frequence controlled robot platform motions non merely command by RF remote control, but besides obstacle sensors. Two supersonic detectors are installed on the forepart and dorsum of automaton to move as obstruction sensors to avoid obstruction in the class set by the accountant. Furthermore, a PIC ( Peripheral Interface Controller ) is used to command the turning way of motors which the automaton wheels by determines RF and supersonic detector signals. When there is an obstruction in the class set of automaton, automaton will halt, so LED on automaton platform will illume on and the doorbell will makes a warning sound to bespeak accountant to alter the going way of automaton.

Aim:

The purpose of the undertaking is to plan a RF ( Radio Frequency ) Controlled Robot Platform which the going way of automaton is controlled by RF remote control within a peculiar scope without the usage of electrical music directors. Besides that, detectors will be installed to move as an obstruction sensor of this automaton to do certain it can avoid obstructions in the class set by the accountant. Furthermore, a micro accountant will be used to command and to implements the operation by analysis the signal receives from distant control and detectors. For this undertaking, it involves larning to utilize detectors, Peripheral Interface Controllers and larning its scheduling every bit good.

Background literature:

A PIC microcontroller is use to move as a control Centre of the automaton as it has computation, memory and I/O maps. By utilizing PIC, C scheduling or assembly linguistic communications accomplishments are required as microcontroller operations are based on the package programming to implement the undertakings. The PIC16F76  has been chosen as the microcontroller of this undertaking as it has several particular pins and characteristics that suits for this undertaking demands such as:

O PIC16F76 has a entire figure of 28 pins. It is made up of three I/O ports ( Port A, B and C ) which has a 22 I/O pins in sum.

O In I/O port A, there are five input channels of 8-bit Analog-to-Digital Module which allows transition of an parallel input signal to a corresponding 8-bit digital figure that is helpful in analysis the signal transmits from RF receiving system.

O Two PWM ( Pulse Width Modulation ) Capture/Compare pins those are good in control the velocity and on/off of the DC motor by puting PWM responsibility rhythm.

O SCL and SDA pins can pass on with supersonic straight.

An supersonic is a type of detector that uses to bring forth high frequence ( above 20 KHz ) sound wave pulsations and detects an object by construing the reverberations signal from its sound moving ridge pulsation. The sound moving ridge pulsations are going in one way, when it detects an object, the echoed signal will be reflected back to the transducer of the supersonic detector. The scope from detector to object is able to find by ciphering the continuance of clip between the minute the sound wave pulse detects the object and clip for the echoed signal to return back to detector. When detector detects an object, it will trip a signal and sends it to PIC.

Supersonic detector is good in observing liquids, seeable objects and irregularly molded objects. Therefore, it has been chosen to move as an obstruction sensor of this undertaking instead than other detectors. Besides that, supersonic detector has a higher sensing scope and the reflected signal does non affected by the surface and colour of objects. The supersonic detector SRF08  is a high public presentation supersonic scope finder with a scope from 3cm to 6m. The communicating between SRF08 with microcontroller is via I2C coach. The I2C coach consists of 2 active wires and a land. Bi-directional SDA and SCL are the active coachs. SDA is Serial Data line and SCL is Consecutive Clock line, both of them have a pull-up resistance to +5v someplace on I2C coach. SRF08 is ever a slave ne'er a coach maestro.

For the wireless frequence remote control, the wireless wave signal can go through around or through the object, such as wood, glass, walls and other stuffs. The advantages of utilizing wireless frequence remote control are, signal transmits range farther than infrared distant control and signal does non necessitate to be transmitted in line to receiver. The disadvantage of utilizing wireless moving ridges to convey signal is, signal will be affected by the presence electromagnetic intervention in the environment. A RF faculty [ 3 ] ( TWS-434 and RWS-434 ) has transmitter frequence 433.92 MHz when it end product is 8mW with a scope of about 200 pes for indoors and 400 pes for out-of-doorss. It is ability to accept both digital and additive inputs. Operating electromotive force is 1.5 to 12 volts-DC. For the RWS-434 receiving system, it is besides operates at the same frequence which is 433.92 MHz and a sensitiveness of 3uV. The receiving system has both additive and digital end products and runing electromotive force from 4.5 to 5.5 volts-DC supply.

Two DC Gear motors are installed on the automaton platform as the motor thrusts ( wheels of automaton ) . The EMG30motor is a DC motor with encoder. Encoder is used to tracking the figure of revolutions and the place of motor. The rated electromotive force of this motor is 12v. These are the characteristics of EMG30 DC motor:

• No burden velocity: 216 revolutions per minute
• No load current: 150 ma
• Rated torsion: 1.5 kg/cm
• Rated current: 530 m
• Rated velocity: 170 revolutions per minute
• Rated end product: 4.22 W

The motor shaft can be rotated in two waies that clockwise or counter-clockwise way. Therefore, the automaton moves frontward or rearward merely inversing the mutual opposition of the power supply of the DC motor. The turning operation makes by holding two wheels turning in different waies at the same time. This motor has Hall detectors every bit good. A hall detector varies its end product electromotive force in response to alterations in magnetic field, it used for placement and velocity sensing applications of this undertaking.

An H-bridge is a four shift elements device which enables a electromotive force to be applied across the motor or burden in merely one way. It is utilizing to move as a motor control circuit that allow DC motor to run forwards and backwards by providing the electromotive force to different switches. An H-bridge is built with four switches. When the switches S1 and S4 are closed, S2 and S3 are unfastened a positive electromotive force will be applied across the motor. The electromotive force will be in the reversed way by opening S1 and S4 switches, shuting S2 and S3 switches. The H-bridge is by and large used to change by reversal the mutual opposition of the motor, but it can be besides used to halt the motor or to allow the motor run freely. Switches S1 and S2 or S3 and S4 should non be closed at the same clip as it will do a short circuit on the input electromotive force. L298  is a high electromotive force and high current double full-bridge driver. The chief intent of L298 is to move as a motor accountant to command the rotate way of DC motor harmonizing to the end product electromotive force from PIC.

It is taken from mention of ''H-bridges: Theory and Practice '' , available from: hypertext transfer protocol: //www.mcmanis.com/chuck/robotics/tutorial/h-bridge/

Work done

In the past few hebdomads, a batch of consideration and research undertakings have been done. For illustration, the extension rule of wireless frequence, and besides the working rule of H-bridge motor control and PWM. Some tutorials that helpful and related to the PIC scheduling have been read as good. On the other manus, all the constituents of this undertaking have been decided after reading the datasheets of each constituent. At the same clip, automaton platform has been designed and sent to the mechanical 's workshop in order to cut metal home base into the designed form. Furthermore, the pin connexions between the PIC, detectors and motors have been decided after reading datasheets of constituents and PIC. So far, the advancement of this undertaking is on the measure of circuit conventional designing and larning the package scheduling of PIC undertakings.

• Pin 1: Seriess connected with a 10kI© resistance to +5v DC supply.
• Pins 2 & A ; 3: End product ports for LEDs.
• Pins 5 & A ; 7: to move as inputs from shaft encodes of motor.
• Pin 8: Connect to land.
• Pin 9 & A ; 10: Connect to a parallel crystal 4 MHz and two series 33 pF capacitances with land.
• Pins 12 & A ; 13: PWM outputs connect to the H-bridge.
• Pins 14 & A ; 15: I/O ports of I2C lines connect to the supersonic detectors.
• Pin 18: End product port for doorbell.
• Pins 25 & A ; 26: End product signals connect to H-bridge.
• Pins 21, 22, 23 and 24: Act as input ports from RF receiving system.

Advancement AND Plan:

Now, it is on the measure of larning package scheduling and circuit conventional designing undertakings, but it is a small spot delayed due to the clip disbursement on the undertaking less than undertaking program for past few hebdomads, since I was busy in making other faculty 's assignments and could non make up one's mind the constituents on clip.

On the following semester, the clip disbursement on this undertaking will be more than the novice program in order to catch up the advancement that has been planned as undertaking program. These are the major undertakings that will transport out consequently on the undermentioned semester:

1. RF faculty proving.
2. Supersonic faculty testing.
3. DC motor testing.
4. PCB circuit design.
5. PCB etching and soldering of constituents.
6. Prototype theoretical account building.
7. Trial and seek run the automaton system to modify the scheduling of PIC.
8. Troubleshooting and debugging.
9. Test overall functionality.

On the undermentioned semester, the clip disbursement on making this undertaking will be 18 hours per hebdomad.

The item agenda of this undertaking has been shown on the Gantt chart.

References

1. DEVENDRA K. MISRA, `` Radio-Frequency and Microwave Communication Circuits '' , Printed in the United States of America, By John Wiley & A ; Sons, Inc, 2001.
2. Newton C. Braga, `` Roboticss, Mechatronics, and Artificial Intelligence, Experimental Circuit Blocks for Designers '' , Printed in the United States of America, By Newnes Boston Oxford Auckland Johannesburg Melbourne New Delhi, 2002.
3. Richard J. Valentine, `` Motor Control Electronics Handbook '' , Printed in the United States of America, The McGraw-Hill Companies, Inc. , accessed by 30th October 2009, E-book, available from:
4. hypertext transfer protocol: //books.google.com/books? id=kLZL5hTsVIYC & A ; printsec=frontcover & A ; source=gbs_navlinks_s # v=onepage & A ; q= & A ; f=false
5. Jim Brown, `` Brief H-BRIDGE THEORY OF OPERATION '' , Written at April 1998, accessed by 1st November 2009, available from: hypertext transfer protocol: //www.dprg.org/tutorials/1998-04a/
6. Chuck McManis, `` H-bridges: Theory and Practice '' , accessed by 1st November 2009, available from: hypertext transfer protocol: //www.mcmanis.com/chuck/robotics/tutorial/h-bridge/
7. Milan Verle, `` PIC Microcontrollers '' , mikroElektronika ; 1st edition, Written at 2008, accessed by 25th November 2009, available from: hypertext transfer protocol: //www.mikroe.com/en/books/picmcubook/ch5/
8. Nebojsa Matic, `` Programing PIC Microcontroller in BASIC '' , mikroElektronika, Chapter 6 PWM Module, accessed by 1st December 2009, available from: hypertext transfer protocol: //www.mikroe.com/en/books/picbasicbook/06.htm # 6.5
9. Chuck McManis, `` H-bridges: Theory and Practice '' , accessed by 1st November 2009, available from: hypertext transfer protocol: //www.mcmanis.com/chuck/robotics/tutorial/h-bridge/
10. PIC16F7X Data Sheet28/40-Pin, 8-bit CMOS FLASH Microcontroller, By Microchip Technology, Inc. , 2002.hypertext transfer protocol: //ww1.microchip.com/downloads/en/DeviceDoc/30325b.pdf
11. SRF08 High Performance Ultrasonic Range Finder, By Acroname, Inc. , 1994-2009.hypertext transfer protocol: //www.acroname.com/robotics/parts/R145-SRF08.htmlhypertext transfer protocol: //www.robot-electronics.co.uk/htm/srf08tech.shtml
12. Radio Frequency Module ( TWS-434 and RWS-434 ) Data Sheet, By Rentron Electronic.hypertext transfer protocol: //www.rentron.com/Files/rf.pdf
13. DC Gear motor ( EMG 30 ) Data Sheet, By technonots.co.uk.

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