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Pololu Corporation Simple Hexapod Walker, Manual

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Pololu Corporation Simple Hexapod Walker Manual Download Page 16

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

Sample Project: Simple Hexapod Walker

© 2001–2010 Pololu Corporation

4. Sequencing the Hexapod Gait

Page 16 of 21

Summary of Contents for Simple Hexapod Walker

Page 1: ...als and Tools 3 3 Construction 5 4 Sequencing the Hexapod Gait 15 5 Using a Script for Obstacle Avoidance 18 6 Suggested Modifications and Improvements 20 7 Conclusion and Community 21 Sample Project Simple Hexapod Walker 2001 2010 Pololu Corporation Page 1 of 21 ...

Page 2: ...s 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 http www pololu com catalog product 1351 a 6 servo controller that can read inputs and play motion sequences in a stored script See the Micro Maestro User s Guide http www pololu com docs 0J4...

Page 3: ... as the Power HD sub micro servo HD 1440A to customize the design 2 1134 Pololu Carrier with Sharp GP2Y0D810Z0F Digital Distance Sensor 10cm This is a tiny distance sensor with a long enough range to keep your hexapod out of trouble 1 2251 Battery Pack 4 8 V 200 mAh This battery pack will provide enough power at about 5 V to power the hexapod for five or ten minutes 3 Jumbo paper clip Used to form...

Page 4: ...Tools http www pololu com catalog category 5 section of the Pololu web site A hot glue gun is available at most craft stores for a few dollars Sample Project Simple Hexapod Walker 2001 2010 Pololu Corporation 2 Materials and Tools Page 4 of 21 ...

Page 5: ...ep 2 Set up the Maestro for self power With your battery disconnected attach a wire red from the positive terminal of the male header to VIN Take care not to short or damage any of the components on the board Now with the battery plugged in your Maestro should be powered up and slowly flashing its yellow LED indicating that it is waiting to detect the baud rate on the serial communication You will...

Page 6: ...eader included with the Maestro temporarily connect a servo to port 0 Make sure to connect the wires correctly with the brown or black wire connected to ground You should hear a short high pitched whine as the servo activates moving to and holding a position in the middle of its range After a fraction of a second when the servo has reached its position it should be silent Move the slider from 1000...

Page 7: ...are A second pair of hands could be very useful Use solder to tin the leads of the servos so that they can be connected initially without additional solder Looking at the pictures below for reference place the Maestro on the back side of the body and place the middle wires over the front of the Maestro and into the holes for channel 1 Holding the wires in these holes pull the Maestro away from the...

Page 8: ...an but you can use whatever wire you have available Look ahead in the instructions to see where the sensors are going to go and make sure that you have a long enough cable Think about how to keep the wires close to the body and out of the way of the legs and servos Soldering the sensors to a four pin cable Solder the sensor power and ground to 5V and ground on the Maestro and connect the outputs o...

Page 9: ...on you probably forgot to set the ports to inputs in Step 3 Step 6 Construct the legs Unfold the paper clips into straight pieces of wire Pliers make ugly dents in the metal so try to use your fingers and the edge of a table to do this Straighten the paper clips as much as possible The wires should be six inches long To make the front and back legs fold two of them into 1 5 sections with 90 angles...

Page 10: ...exapod 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 Fix them in place with the included screws holding the legs as you tighten them so that you do not apply torque to the fragile servo gears Glue the Maestro to the back side of the...

Page 11: ...t with different positions instead of forcing the servos Step 7 Attaching the battery and sensors Glue the battery to the front of the hexapod flush with the bottom so that there will be as much clearance as possible Make sure that the middle legs have plenty of room to turn left and right without hitting the battery Glue the sensors to the top of the battery angled to the left and right Sample Pr...

Page 12: ...ng does interfere with the motion of the middle legs You might want to route yours differently Use small drops of hot glue as necessary to hold the wires in place Sample Project Simple Hexapod Walker 2001 2010 Pololu Corporation 3 Construction Page 12 of 21 ...

Page 13: ...ums and maximums Set the neutral positions as the Go to values for each servo and set Min and Max values so that your hexapod will never destroy itself Adjust the angles of the wires so that all six feet touch the ground in the neutral position probably by bending the front and back legs to more than 90 Sample Project Simple Hexapod Walker 2001 2010 Pololu Corporation 3 Construction Page 13 of 21 ...

Page 14: ...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 Sample Project Simple Hexapod Walker 2001 2010 Pololu Corporation 3 Construction Page 14 of 21 ...

Page 15: ...achieves forward motion by pushing those feet backwards against the ground while the other feet move forward through the air Then the hexapod shifts its weight to the other three feet and moves forward in the same way By continuously shifting its weight using the middle legs then moving the raised feet forward it walks forward Walking forward with the Maestro Control Center You can easily assemble...

Page 16: ...ddle legs touching the ground Frame 1 down legs move back front legs move forward Frame 2 weight shifted to the other tripod Sample Project Simple Hexapod Walker 2001 2010 Pololu Corporation 4 Sequencing the Hexapod Gait Page 16 of 21 ...

Page 17: ... select the Run script on startup option on the Script tab and apply settings your hexapod will automatically start to walk You can now disconnect it from USB and allow it to walk on its own Reconnect USB and click Stop Script or disable the Run script on startup option to get it to stop walking Backwards and turning gaits On the status tab start again with Frame 0 but go through the sequence of m...

Page 18: ...this to get the behavior you want start back up if both sensors see an object left_sensor right_sensor logical_and if back back back goto start endif back up and turn right if the left sensor sees an object left_sensor if back right right right goto start endif back up and turn left if the right sensor sees an object right_sensor if back left left left goto start endif otherwise if there is nothin...

Page 19: ...Frame 2 100 6528 frame_1 Frame 3 120 4992 6976 frame_0_2 Frame 0 return sub frame_0_1_2 2 servo 1 servo 0 servo delay return sub frame_0_2 2 servo 0 servo delay return sub frame_1 1 servo delay return Sample Project Simple Hexapod Walker 2001 2010 Pololu Corporation 5 Using a Script for Obstacle Avoidance Page 19 of 21 ...

Page 20: ...t and detect obstacles sooner Alternative servos the entire design could be scaled up A power switch so that the battery does not have to be unplugged over and over Boost regulation http www pololu com catalog product 791 for consistent power from a more compact lithium battery QTR sensors http www pololu com catalog product 958 for line following or table edge detection Light sensors for light se...

Page 21: ...obots com node 19050 A hexapod built by letsmakerobots com user AndyGadget using a PICAXE 08M This design has the batteries underneath and the servos in front and it uses small beads as feet Hexapod clone my first bot http letsmakerobots com node 16683 A hexapod built by letsmakerobots com user Bruud using the Micro Maestro and HD 1440a servos He used the assembled version of the Micro Maestro plu...

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