The Complete 2DoF Hexapod Tutorial

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<td valign="top" align="left">The Complete

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2DOF Hexapod Tutorial. Updated <!--webbot bot="Timestamp"

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S-Type="EDITED" S-Format="%m/%d/%Y" startspan -->09/30/2010

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9

Notice:

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- This tutorial follows the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-2dof-hexapods/inline-hexapod-body/">2DOF

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Hexapod assembly guide</a>. Make sure all servos and other connections are

12

set up as detailed there.

Required Hardware:

- Any

Lynxmotion 2 DOF Hexapod

17

- SSC-32

18

- Bot Board / BASIC Atom Pro 28

19

- PS2 Cable

20

  - PS2 Wireless Controller (Not included

21

in combo kit)

22

- Sharp GP2D12 Sensor (Optional, see text)

23

Required Software:

24

- LynxTerm (free <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/ses-software/lynxterm/" target="_blank">download</a>)

25

- Basic Micro Studio ver 2.0.0.0

26

- Basic Atom Pro Hexapod Programs:

27

> <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-2dof-hexapods/the-complete-2-dof-hexapod-tutorial/WebHome/h2prog01.zip" target="_blank">h2prog01.zip</a> PS2.

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> <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-2dof-hexapods/the-complete-2-dof-hexapod-tutorial/WebHome/h2prog02.zip" target="_blank">h2prog02.zip</a> PS2.

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> <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-2dof-hexapods/the-complete-2-dof-hexapod-tutorial/WebHome/h2prog03.zip" target="_blank">h2prog03.zip</a> PS2.

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> <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-2dof-hexapods/the-complete-2-dof-hexapod-tutorial/WebHome/h2prog04.zip" target="_blank">h2prog04.zip</a> Autonomous!

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Resources:

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- Wiring Schematic (<a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-2dof-hexapods/the-complete-2-dof-hexapod-tutorial/WebHome/2dofsch2.gif" target="_blank">2dofsch2.gif</a>)

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Goal:

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- Install, program, and test the electronics to operate a Hexapod 2

35

remotely from a Lynxmotion wireless controller or autonomously using

sensors.

</td>

Image of Hexapod 2.

</td>

</tr>

<tr>

</tr>

<tr>

</td>

</tr>

<tr>

</tr>

<tr>

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

56

1. Establishing Communication.

57

The first thing we need to

58

do is establish a connection between your computer and the SSC-32 so that

59

we can align the servos. This is done by using a program called LynxTerm

60

on the PC with the SSC-32 connected.

61

Connect the serial data cable to the PC's serial port. This can be

62

recognized by having 9 pins

63

that stick out. Connect the other end of the serial data cable to the SSC-32's DB9 port.

64

Note, if your computer does not have a

65

native serial port, you can add one,

66

or you can also use a high quality USB to Serial adapter

67

such as one made by FTDI. If you are using an FTDI adapter cable, please install the VCP (Virtual Com Port) driver and change the "latency" property to its minimum. </td>

Figure 1.</td>

</tr>

<tr>

</td>

</tr>

<tr>

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

77

2.

78

Install and run <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/ses-software/lynxterm/"> LynxTerm</a> on your PC.

79

Plug the 9vdc battery in and notice the green LED light up on the SSC-32. Choose the COM port for your computer from the drop down menu in the upper left corner. Click in the black box, type

80

"ver" and press "enter". If everything is working correctly, you should receive a response such as "SSC32-2.03XE".

81

82

83

Note, the LED on the SSC-32 is not a power indicator but a status indicator. Its job is to light up on power up showing the SSC-32 is 95% functional. After it receives a serial command it will turn off, and from there on it will blink when it receives data. This will happen even if the data is not formatted correctly. The LED on the Bot

84

Board II is a simple power indicator.

</td>

Figure 2.</td>

</tr>

<tr>

</tr>

<tr>

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

95

3. Aligning the Servos.

96

Place the robot on top of a

97

CD spindle or other similar object to support the body and lift the legs

98

off the ground.

99

Make sure your 6v battery is connected to

100

the wiring harness and flip the power switch to the ON position to apply power to the servos.

101

Click the All=1500 button at the bottom

102

of the program and the legs should respond by quickly moving to a position

103

near centered. If the robot was constructed properly, the legs will be horizontal and perpendicular to the body.

104

If the legs are more than 15° off you may need to remove the output horn, rotate

105

it, and reinstall it. The next step is to align the servos in software to be perfectly aligned.

</td>

Figure 3.</td>

</tr>

<tr>

</td>

</tr>

<tr>

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

117

4.

118

Click on the H2 Sequencer button in the lower left corner.

119

Since

120

no servo is perfect, you will need to set offsets to center each servo.

121

Use the Offset tool under Servo Quick Test. Click on "Read" to

122

load any previous offset settings. Select the

123

servo on the Hexapod diagram and adjust the offset slider to fine-tune the leg alignment. Do this for all twelve servos. When completed, click

124

on "Write" to save your offsets to the SSC-32 EEPROM.

125

Refer to Figures 4-2 and 4-3 for how each

126

servo should be aligned.

</td>

Figure 4-1.</td>

</tr>

<tr>

</tr>

<tr>

Figure 4-2.</td>

Figure 4-3.</td>

</tr>

<tr>

</td>

</tr>

<tr>

Schematic.

Double check your connections against the schematic below. Be sure that red wires

151

go to positive (+) and black wires go to negative (-). Also be sure that

152

your jumpers are connected the exact same way as detailed below. Note: Your PS2 cable may not match up with Schematic 1. Refer to Schematic 2 for accurate connection information.

Schematic 1.</td>

</tr>

<tr>

</td>

</tr>

<tr>

Schematic 2.

</td>

</tr>

<tr>

<td valign="top" >Step 5.

167

Programming the Microcontroller.

168

The following steps refer to several programs that offer complete control of all aspects of the

169

hexapod gait sequence through a wireless PS2 controller. Install and run the BASIC

170

Micro Studio to allow programming the chip.

171

172

Refer to <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/view/support/basic-atom-pro-programming/">this tutorial</a> for

173

assistance on using the BASIC Micro Studio program.

<td >

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

184

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

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Default

program. </td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Tank

194

mode and single joystick mode.</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Single joystick

199

mode and pan-and-tilt on left joystick.</td>

</tr>

</tbody></table>

</div>

</td>

</tr>

<tr>

<td >

Table 5

</td>

</tr>

</tbody></table>

</center>

</div>

</td>

Figure 5.</td>

</tr>

<tr>

</tr>

<tr>

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

222

6. PS2 Control.

223

224

Controlling the motion of the hexapod is handled using a single joystick. Make sure the controller is in Analog mode.

225

control of the

226

direction of walking with the right joystick, while Left and Right on the D-Pad adjusts speed.

227

Initially, in either mode the joystick positions will allow a max of 100% XS speed. Pressing D-Pad Left lowers the max in 5% increments, and

228

D-Pad Right increases the max in 5% increments up to 200%

229

Both modes offer additional control of leg trajectory for the alternating tripod gait. This refers to the

230

vertical and horizontal motion that the foot goes through during the walking gait. Pressing /\, O (default), X, or [] changes how the

231

foot is lifted and the stride motion.

232

If the robot is driven toward an obstacle, after a threshold is reached the forward joystick position is

233

ignored. However, you can still reverse direction. The controller will also vibrate proportionally in relation to the distance from the

234

obstacle. The Sharp sensor can be enabled or disabled with the Start button.

235

You may notice that there are no commands

236

to change the height of the robot's body in the default program. In order

237

to take full advantage of the mechanical advantage legs, they need to

238

remain at their highest point.

</td>

Figure 6.</td>

</tr>

<tr>

</td>

</tr>

<tr>

<td >

<td align="center" bordercolor="#808080" bgcolor="#C0C0C0" colspan="4">PS2

Controls

Right-Joystick Mode

Applies to h2prog01.zip</td>

</tr>

<tr>

L Joy U</td>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Tilt Servo up</td>

272

273

274

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

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Tilt

281

Servo down</td>

282

283

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

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Pan

Servo left</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Pan

Servo right</td>

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

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">See

307

Figure 8</td>

308

309

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">See

Figure 8</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">See

315

Figure 8</td>

316

317

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">See

Figure 8</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Speed Limit Down</td>

323

324

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Speed Limit Up</td>

325

</tr>

326

<tr>

327

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

328

329

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Disable/Enable Crash Monitor</td>

</tr>

</tbody></table>

</div>

</td>

</tr>

<tr>

<td >

Table 6-1

</td>

</tr>

</tbody></table>

</center>

</div>

<td >

<td align="center" bordercolor="#808080" bgcolor="#C0C0C0" colspan="4" >PS2 Controls

353

Right Joystick Mode

354

Applies to h2prog03.zip</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Tilt

359

Servo up</td>

360

361

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

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Tilt

366

Servo down</td>

367

368

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

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Pan

Servo left</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Pan

380

Servo right</td>

381

<td align="center" bordercolor="#808080" bgcolor="#C0C0C0" >R Joy

382

R</td>

383

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

</tr>

<tr>

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

388

Other Commands</td>

389

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >See

Table 8-3</td>

</tr>

</tbody></table>

</div>

</td>

</tr>

<tr>

<td >

Table 6-2

</td>

</tr>

</tbody></table>

</center>

</div>

</td>

<td >

<td align="center" bordercolor="#808080" bgcolor="#C0C0C0" colspan="4" >PS2 Controls

415

Tank Mode or (Right Joystick Mode)

416

Applies to h2prog02.zip</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Left Side Forward

421

(N/A)</td>

422

423

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Right Side Forward

(Forward)</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Left Side Backward

429

(N/A)</td>

430

431

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Right Side Backward

(Backward)</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >N/A

(Left)</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >N/A

(Right)</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Raise body height</td>

451

452

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Increase leg lift</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Lower body height</td>

457

458

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Decrease leg lift</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Switch control mode</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Raise body height</td>

469

470

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >See

Figure 8</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Lower body height</td>

476

477

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >See

Figure 8</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Speed Limit Down</td>

483

484

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >See

Figure 8</td>

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Speed Limit Up</td>

490

491

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >See

Figure 8</td>

</tr>

<tr>

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

496

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF" >Disable/Enable Crash Monitor</td>

497

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

</tr>

</tbody></table>

</div>

</td>

</tr>

<tr>

<td >

Table 6-3

</td>

</tr>

</tbody></table>

</center>

</div> </td>

</tr>

<tr>

</tr>

<tr>

<td valign="top" >Step 7.

518

Autonomous Control.

519

The following autonomous-behavior program requires the addition of three Sharp GP2D12 sensors, connected as follows:

520

521

A to D channel 0 sensor: on front left side, facing right.

522

A to D channel 1 sensor: on front right side, facing left.

523

A to D channel 2 sensor: on rear, facing behind the robot.

524

The exact angle of the sensors isn't

525

critical, but will affect the robot's behavior. Experimentation is

encouraged.

<td >

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

536

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

</tr>

<tr>

<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Autonomous using two Sharp

541

GP2D12 sensors and one on the rear.</td>

</tr>

</tbody></table>

</div>

</td>

</tr>

<tr>

<td >

Table 7

</td>

</tr>

</tbody></table>

</center>

</div>

</td>

Figure 7.</td>

</tr>

<tr>

</td>

</tr>

<tr>

<td valign="top" >Step 8.

565

Additional Information.

566

The Hexapod Sequencer can be used to test the hexapod without a microcontroller. Simply connect the SSC-32 to the serial port as if you were going to align the servos, then follow along.

567

The values for the L* and R* textboxes will control the positions the legs are moved to in the

568

sequence. You can fine-tune these values to your mechanical leg arrangement with the same Servo Quick Test. Just adjust the position slider

569

instead of the offset slider.

<td >

<td align="center" bordercolor="#808080" bgcolor="#C0C0C0" colspan="4">Tripod Leg

580

Movement Sequence</td>

</tr>

<tr>

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

585

586

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

</tr>

<tr>

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

591

592

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

</tr>

<tr>

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

597

598

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

</tr>

<tr>

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

603

604

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

</tr>

<tr>

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

609

610

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

</tr>

</tbody></table>

</div>

</td>

</tr>

<tr>

<td >

Table 8

</td>

</tr>

</tbody></table>

</center>

</div>

</td>

Figure 8.</td>

</tr>

<tr>

</tr>

<tr>

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

633

9.

634

Now to make the robot walk forward. Adjust the XL and XR sliders to 100%. Note that HT=1500uS (1.5 seconds). Set the XS slider to ~50% and

635

notice that the stride takes 3 seconds. Adjust the HT slider to 1000 and notice that the stride now takes 2 seconds.

636

You have complete control over all aspects of the tripod gait. Adjust either XL or XR lower to do gradual

637

turns. Setting XL and XR to opposite directions will cause the robot to turn in place. Reverse values of XL and XR will cause the robot to walk

638

backwards. Moving a slider is the same as typing from the terminal or sending the command from a microcontroller. For example, moving XS to 50%

639

is the same as sending "XS50". Once the commands are sent, the robot will continue to walk until it receives XS = 0. If you are using

640

a host microcontroller to send commands, it will be free to do any timing-intensive tasks without worrying about any of the walking process.

</td>

Figure 9.</td>

</tr>

<tr>

</tr>

<tr>

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

651

10.

652

For the do-it-yourselfers, the program to the right will set up and initiate walking on the robot. To change

653

speed and direction just alter the XL, XR, XS values. The robot will immediately begin walking in the speed and direction commanded.</td>

<td bordercolor="#000000">XL var sbyte

XR var sbyte

XS var byte

XL = 100

XR = 100

XS = 100

start:

serout p15,i38400,["LF1700 RF1300 LR1300",13]

669

serout p15,i38400,["RR1700 LH1000 LM1700",13]

670

serout p15,i38400,["LL1800 RH2000 RM1300",13]

671

serout p15,i38400,["RL1200 VS3000 HT1500",13]

672

serout p15,i38400,["XL",SDEC XL,"XR",SDEC XR,13]

673

serout p15,i38400,["XS",DEC XS,13]

loop:

goto loop</td>

</tr>

<tr>

Table 10.</td>

</tr>

</tbody></table>

</center>

</div>

</td>

</tr>

</tbody></table>

</body>

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