BRAT Biped Autonomous Tutorial

<td valign="top" align="left">Biped BRAT Autonomous Tutorial.

Updated

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12/20/2011

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Safety first! Wear eye protection and never touch a powered robot!

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Note: This tutorial uses the Bot Board II, BASIC Atom Pro 28, a Sharp GP2D12 sensor, and a Buffered

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2-Axis Accelerometer (DE-11).

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Software:

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- BASIC Micro Studio

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/bratosf3.zip">BRAT Servo Offset Finder

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Program v3</a> (09/16/09)

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat1.zip">Autonomous Walk Code</a>

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(09/16/09)

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat2.zip">Autonomous GP2D12 Code</a>

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(09/16/09)

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-- Video: <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/avoid01.mpg">Avoiding an obstacle (mpg)</a>

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-- Video: <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/break01.mpg">Taking a break (mpg)</a>

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-- Video: <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/walkaway.mpg">Demonstrating proximity beeps (mpg)</a>

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat3.zip">Autonomous 1-Axis Accelerometer Code</a>

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(09/16/09)

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-- Video: <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/getup01.mpg">Getting up front and back (mpg)</a>

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat4.zip">Autonomous 2-Axis Accelerometer Code</a>

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(09/16/09)

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-- Video: <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/getup02.mpg">Getting up front and side (mpg)</a></td>

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Image of Biped BRAT.</td>

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<td valign="top" align="left">Step 1.

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Make sure your servos are plugged into the appropriate channels, as shown in Table 1.

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*Note, P9 is used by the speaker, so we can't plug a servo in there.</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Bot Board I/O</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Connection</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Left Ankle</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right Ankle</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right Knee</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right Hip</td>

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</tbody></table>

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Table 1.</td>

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</tbody></table>

</center></div>

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<td valign="top" align="left">Step 2.

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Make sure the Bot Board's jumpers are set according to Table 2.

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Refer to Figure 2 for help with jumper settings.

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*Note, the VS to AX0 jumper enables the program to monitor the servo battery voltage. When the battery is low,

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the robot can beep in warning.</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0" colspan="2">Bot Board II

Jumper Settings</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Enable</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">A, B, and C buttons</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">I/O Group 0-3</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">I/O Groups 4-7 and 8-11</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Enable</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">SPKEN (Speaker Enable)</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Enable</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">VS (Servo Voltage) to AX0 (P16)</td>

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</tbody></table>

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Table 2.</td>

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</center></div>

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Figure 2.

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<td valign="top" align="left">Step 3.

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Download and install the BASIC Micro Studio. Download the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/bratosf3.zip">BRAT Servo Offset Finder program</a>, and load it into the IDE.

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Program the Atom Pro, and follow these instructions to find your robot's offsets.

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<ul>

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<li>Press A to decrease the servo offset by 5us.</li>

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<li>Press C to increase the servo offset by 5us.</li>

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<li>Press B to change which servo is being manipulated, and to

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save your offsets. The order of the

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program is shown in Figure 3.</li>

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</ul>

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Note, if you have the Speaker enabled, when you press the B button you will hear a short tone. The tone will

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raise in pitch when you change from servo to servo, and will lower in pitch and be longer when you get back to Start.</td>

Figure 3.</td>

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<td valign="top" align="left">Step

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4.

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Place the robot in a position as close to neutral as possible, and turn it on. Your robot should go to and hold the neutral position, and should

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resemble figures 4-1 through 4-3. If the joints are off by more than 15° you may have made an error in assembly. To correct this, remove the

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center screw from the round servo horn, pull the servo horn off the servo, rotate until it's aligned, then reattach the servo horn.

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Use the A, B, and C buttons to straighten the BRAT as shown in Figures

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4-1, 4-2, and 4-3.

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Note, if you are building the robot with HS-422 servos, you will notice the hip servos oscillate if the robot

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is lifted off the ground. This is normal, and is due to the lower power servo. When the robot is walking, the effects are minimal. Using a

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voltage that is higher than 6vdc will make the oscillations worse. When building a robot with more powerful servos such as HS-475,

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HS-485, or HS-645, you

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will not see this effect.

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After you've cycled through the servos and adjusted them to match Figures

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4-1 through 4-3, pressing the B button again will save your servo offset

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values to the Atom Pro's EEPROM.

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Figure 4-1.</td>

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Figure 4-2.

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Figure 4-3.</td>

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</td>

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<td valign="top" align="left" colspan="2">Step

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5.

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Now download the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat1.zip">BRAT Autonomous Walk Code</a>, load it into the

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IDE, and program your BRAT.

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Congratulations, your BRAT will now be able to walk around! The autonomous walk program will make the BRAT

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follow this sequence: walk, walk, walk, turn, long-stride, long-stride, kick, turn, stop.

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To change the behavior of your robot, you can modify the code below the label "main" and above the

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label "move". You can also create sequences following the format shown in the code below the label "move". We will provide

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several more code examples including common sensors.</td>

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<td valign="top" align="left">Step

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6.

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Use double-sided tape to attach the GP2D12 sensor to the BRAT's head area. The exact position doesn't matter too much, as long as the sensor is

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facing toward the front of the robot.

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Plug the sensor in to the channel shown in the following table.

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Bot Board I/O</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Connection</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">GP2D12 Sensor</td>

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</tbody></table>

</div></td>

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Table 6.</td>

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</tbody></table>

</center></div>

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Figure 6.</td>

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<td valign="top" align="left" colspan="2">Step

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7.

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Now download the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat2.zip">BRAT Autonomous GP2D12 Code</a>, load it into the

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IDE, and program your BRAT.

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Congratulations, your BRAT will now be able to roam without bumping into anything! We also added a

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"behavior" looping counter so the robot will periodically go into a resting position. You can edit the pauses to change how long it

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rests and you can change the value of the looping counter to change how often it rests. The GP2D12 sensor is read before each step when the

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robot is walking forward. You will hear a short low beep if nothing is detected. If an object is detected, the beep raises in pitch depending on

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how close the object is. When the object is about 8" away, the robot will back up one step, turn left two steps, then continue forward. The

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code also illuminates LEDs depending on which command is being processed.

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Check out these videos:

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/avoid01.mpg">Avoiding an obstacle (mpg)</a>

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/break01.mpg">Taking a break (mpg)</a>

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/walkaway.mpg">Demonstrating proximity beeps (mpg)</a></td>

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<td valign="top" align="left">Step

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8.

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Use double-sided tape to attach the accelerometer sensor to the BRAT's head area. With the accelerometer, the sensor's physical position

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isn't as important as the axis orientation. Make sure you follow the orientation shown in Figure

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8.

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Plug the sensor in to the channel shown in the following table.

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Bot Board I/O</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Connection</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Accelerometer Sensor - Y Axis

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(Used for Front-to-back tilt)</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Accelerometer Sensor - X Axis

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(Used for Side-to-side tilt)</td>

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</tbody></table>

</div></td>

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Table 8.</td>

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</tbody></table>

</center></div>

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Figure 8.</td>

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<td valign="top" align="left" colspan="2">Step

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9.

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Now download the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat3.zip">BRAT Autonomous 1-Axis Accelerometer Code</a>, load it into the

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IDE, and program your BRAT.

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For this program, we are only using the values from the Y Axis. The Y Axis measures the

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front-to-back tilt, so the BRAT can tell when it has fallen onto its back or front. We will incorporate the X Axis in a later program.

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Congratulations, your BRAT will now be able to roam without bumping into anything, and get back up if it falls!

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Check out this video:

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/getup01.mpg">Getting up front and back (mpg)</a></td>

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<td valign="top" align="left" colspan="2">Step

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10.

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Now download the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/abrat4.zip">BRAT Autonomous 2-Axis Accelerometer Code</a>, load it into the

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IDE, and program your BRAT.

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For this program, we have added the accelerometer's X Axis to measure side-to-side tilt. Now if the BRAT falls

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onto its side, it will know to roll over in order to get back up. We have also incorporated a more advanced "get up from back"

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routine, which will enable robots with lots of cabling or weight in the back to stand one foot at a time. Additionally, we've added a

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"startled" behavior. If the BRAT is in resting mode and something is suddenly detected by the GP2D12 sensor, the BRAT will be

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startled, lean back, and beep.

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Congratulations, your BRAT will now be able to roam without bumping into anything, and get back up if it falls!

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Check out this video:

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-autonomous/WebHome/getup02.mpg">Getting up front and side (mpg)</a></td>

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Wiki source code of BRAT Biped Autonomous Tutorial