Robot Abstract

Project Features: •

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ATMega16 Microcontroller The ATMega16 monitors all robot sensors and controls motor drive functions. In system programming is available. Microcode was developed using the MCS Bascom AVR compiler. Obstacle avoidance The robot maneuvers around obstacles while seeking for a black line to track. Obstacles cause direction reversal when the robot is in line tracking mode. The obstacle sensor is a Sharp GP2D15 sensor connected to INT0 of the ATMega16.

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Line tracking The robot is designed to search for a black line on the terrain. Once the line is found, the robot tracks the line from end to end and reverses direction when it encounters an obstacle in the path of the line. Three infrared sensors mounted under the robot and connected to port D of the Mega16 do line sensing.

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Differential Drive Two DC motors provide mechanical propulsion through friction drive of the drive wheels. The motors are electrically driven by two Allegro 3953 full bridge motor drivers connected to port A of the ATMega16.

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Drive Wheel Synchronization Infrared wheel encoders and a microcode routine provide wheel synchronization. This allows for straight-line travel without guidance.

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Rechargeable Battery Pack Power is provided by a rechargeable 9.6 Volt NiCad battery pack. There is a 5 Volt on-board regulator for logic power.

Project Number A3743 Autonomous Robot With obstacle avoidance, drive wheel synchronization and line tracking capability

Abstract

Figure 1 - AUTONOMOUS ROBOT

2004 AVR DESIGN CONTEST PROJECT NUMBER A3743 / AUTONOMOUS RO BOT BRIEF DESCRIPTION

This project is an autonomous robot that is capable of obstacle avoidance, drive wheel synchronization and line tracking. The robot initializes in seek mode, where it avoids obstacles and searches for a black line to track. Wheel synchronization, during seek mode, allows the robot to travel in a straight line without guidance. Once a black line is found, the robot tracks the line and reverses direction when an obstacle is encountered on the line. The electronic control assembly consists of an Atmel ATMega16 MCU operating at 8Mhz with an internal clock. Two Allegro 3953 full-bridge motor drivers are used for motor control. Microcode for the project was written using the MCS Basic-AVR compiler. Microcode can be updated using the on-board ISP connector. The Mechanical assembly uses a differential drive system made from two small DC motors, a friction drive system and two 78mm wheels. There are six on-board sensors that allow the robot to avoid obstacles, synchronize wheel rotation and track lines. Power is provided by a rechargeable 9.6V NiCad battery pack.

Figure 2 – Side View of Robot

2004 AVR DESIGN CONTEST PROJECT NUMBER A3743 / AUTONOMOUS ROBOT BLOCK DIAGRAM

PORT D

INT0 PORT A

2004 AVR DESIGN CONTEST PROJECT NUMBER A3743 / AUTONOMOUS ROBOT CODE SAMPLE Microcode for this project was written with the MCS Basic-AVR compiler. This code sample shows the “Seek_line” routine and drive wheel synchronization method. The robot initializes into the Seek_line routine, where it roams about looking for a black line to track. The robot must synchronize the two differential drive wheel rotations, in order to travel in a straight line, when in seek mode. Calling the “Poll_wheels” routine, where the encoder counters are updated at each wheel encoder pulse and then comparing the left and right wheel counters does this. The wheel drive is altered if there is a difference of 2 or more between “Leftc” and “Rightc”. '* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Seek_line: 'Roam around, avoid obstacles, seek the black line Leftc = 0 'Initialize wheel counters Rightc = 0 Motor = Forth 'Go forward Seek_line1: Op_mode = "seek" Gosub Poll_wheels If Csense = 1 Then 'Center line sensor found black line Motor = Brake 'Stop Waitms 300 'pause Goto Track 'Goto track mode End If Motor = Forth 'Give both motors a forward pulse Gp2 = Rightc + 2 'General Purpose reg = right counter + 2 If Leftc > Gp2 Then 'Is the left wheel 2 pulses ahead of the right wheel? Motor = Turnl 'Adjust End If Gp2 = Leftc + 2 'General Purpose reg = left counter + 2 If Rightc > Gp2 Then 'Is the right wheel 2 pulses ahead of the left wheel? Motor = Turnr 'Adjust End If If Leftc > 130 Then 'Clear the wheel counters after 10 wheel revolutions Rightc = 0 Leftc = 0 End If Goto Seek_line1 '* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 'Returns (Leftc) the left wheel encoder count and (Rightc) the Right wheel encoder count. Poll_wheels: 'Polls the wheel encoder sensors and counts pulses. If Lwheel = 0 Then 'If left wheel encoder is uncovered If Left_flag = 1 Then 'Do this once each encoder sensor transition Incr Leftc 'Increment the wheel counter Reset Left_flag End If End If If Lwheel = 1 Then Set Left_flag 'Set the flag when the sensor is covered If Rwheel = 0 Then 'If right wheel encoder is uncovered If Right_flag = 1 Then 'Do this once each encoder sensor transition Incr Rightc 'Increment the wheel counter Reset Right_flag End If End If If Rwheel = 1 Then Set Right_flag 'Set the flag when the sensor is covered Return