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Pololu Sample Project: Simple Hexapod Walker Manual

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Sample Project: Simple Hexapod Walker
Sample Project: Simple
Hexapod Walker
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Materials and Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Sequencing the Hexapod Gait . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5. Using a Script for Obstacle Avoidance . . . . . . . . . . . . . . . . . . . . . . . . .
6. Suggested Modifications and Improvements . . . . . . . . . . . . . . . . . . . . . .
7. Conclusion and Community . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
© 2001-2010 Pololu Corporation
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Summary of Contents for Pololu Sample Project: Simple Hexapod Walker

  • Page 1: Table Of Contents

    Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Sample Project: Simple Hexapod Walker 1. Introduction ........2 2.

  • Page 2: Introduction

    The 2"-high hexapod is capable of walking forward and backward, and can turn left and right. Two forward- looking distance sensors provide obstacle avoidance. The brain of the hexapod is the Pololu Micro Maestro , a 6-servo controller that can read [http://www.pololu.com/catalog/product/1351]...

  • Page 3: Materials And Tools

    Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation 2. Materials and Tools Parts list: Parts you will need to build the hexapod robot. Quantity Part # Part Notes Pololu Micro Get the kit version so that you can solder in your...
  • Page 4 Most of these parts are available in the Tools section [http://www.pololu.com/catalog/category/5] of the Pololu web site. A hot glue gun is available at most craft stores for a few dollars. Update: The case for sub-micro servo 3.7g generic [http://www.pololu.com/catalog/ has changed slightly since this sample project was written. Versions...

  • Page 5: Construction

    Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation 3. Construction Step 1: Attach the battery connector. Using a pair of pliers, flip the leads on the battery connector to the other side. Bending the leads on the battery connector to the other side.
  • Page 6 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Self power and a battery connector on the Micro Maestro. Step 3: Verify that the Maestro and servos are functioning. The Maestro Control Center is used for configuration and control of the Micro Maestro, for testing, debugging, scripting, and more.
  • Page 7 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Step 4: Construct the body by gluing the servos together. Remove the mounting tabs from all three servos with diagonal cutters. The tabs are not needed for this project and can interfere with the motion of the servos.
  • Page 8 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Continue, soldering the right servo to channel 0 and the left servo to channel 2, so that the servos are arranged in the same relative positions as the ports. Connecting the servos to ports 0, 1, and 2 on the Micro Maestro.
  • Page 9 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Soldering the sensor cable on to the Maestro. You now have a complete electrical assembly. Plug in the batteries, and the sensors should become active, turning on their red LEDs whenever they detect an object within 10 cm. With the Maestro control center, you should be able to see the input value change from 255, when no object is present, to a low value of 40 or so, when an object is detected.
  • Page 10 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation The front and back legs of the hexapod. The segments at the end should be 1.5” in length. Fold the third piece into an M shape, with sections of length 1.25", 1.75", 1.75", and 1.25", like this: The middle legs of the hexapod.
  • Page 11 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Gluing the hexapod legs to servo horns. With battery power connected, so that the servos hold their neutral positions, put the horns onto the servos so that the legs are as close as possible to neutral positions, as shown in the picture.
  • Page 12 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Important: Never apply torque to the legs with your hands, attempt to prevent them from moving, or backdrive them. Servo gears can be easily broken, so they should only ever move under their own power. Use the Maestro Control Center to experiment with different positions, instead of forcing the servos.
  • Page 13 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation The assembled hexapod, top view. Step 8: Final touches. Use the Maestro Control Center to find the neutral positions (where the legs are as symmetrically arranged as possible) as well as their safe minimums and maximums. Set the neutral positions as the “Go to”...
  • Page 14 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation The assembled hexapod, side view. One final, optional thing that you might want to do is to add a dab of hot glue to each foot, so that the metal is less likely to scratch up your work surface. Your hexapod is now ready to be programmed! 3.

  • Page 15: Sequencing The Hexapod Gait

    Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation 4. Sequencing the Hexapod Gait Gaits Now that you have constructed your hexapod, it is time to make it walk. A method of walking forward with legs is called a gait, and animals or robots with many degrees of freedom have a variety of gaits available –...
  • Page 16 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Frame 0 right front & back, left middle legs touching the ground Frame 1 down legs move back, front legs move forward Frame 2 weight shifted to the other tripod 4. Sequencing the Hexapod Gait...
  • Page 17 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation Frame 3 down legs move back, front legs move forward In the screenshots of the Maestro Control Center, you can see that the servos are always either at their minimum or maximum values, which you should have configured to be safe values that do not cause the servo to strain.

  • Page 18: Using A Script For Obstacle Avoidance

    Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation 5. Using a Script for Obstacle Avoidance The Micro Maestro has an internal scripting language that can store sequences, read sensors, and link everything together to form intelligent behaviors, making your hexapod truly autonomous.
  • Page 19 Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation 100 6528 frame_1 # Frame 2 150 7168 5056 frame_0_2 # Frame 3 return # right sub right 100 4992 5312 6976 frame_0_1_2 # Frame 1 120 7168 5056 frame_0_2 # Frame 2...

  • Page 20: Suggested Modifications And Improvements

    Sample Project: Simple Hexapod Walker © 2001–2010 Pololu Corporation 6. Suggested Modifications and Improvements Here are some ideas for improvements or modifications that could be made to the hexapod design: • More complicated scripted behaviors – help your hexapod get out of stuck situations more reliably.

  • Page 21: Conclusion And Community

    ShC v1 (Simple hexapod Clone version 1) [http://letsmakerobots.com/node/15458] This is a simple hexapod built by a letsmakerobots.com user who was inspired by the Pololu Simple Hexapod Walker. 7. Conclusion and Community...