Rapid Development of a Multi-Gaited Hexapodal Robot

[TylerBAdams]

Rapid Development of a Multi-Gaited Hexapodal Robot

Contact Information: Tylerbadams@gmail.com
            Phone: (619)249-2617

University and Department: UC Berkeley, Mechanical Engineering
Team Members: Tyler Adams, Ben Blasdell, David Lander
Faculty Advisors: George Anwar
Primary Email Address: Tylerbadams@gmail.com

Products Used:
SbRIO 9632, Labview 2009, Labview Robotics

The Challenge:

Develop a 3 degree-of-freedom (DOF) hexapodal robot with both 4 and 6 legged gaits.  The front two legs will be clawed and independently manipulated.  The presentability of the project is very important and time/man-power is very limited.

“The robot “Hexaquad” would be used as a robotic dog in a post-apocolyptic hunting party where terrain is difficult to navigate, food is scarce, and bandits are a’plenty!”

The Solution:

By using lean production methods, CNC machining, and proper planning, we are able to create the largest 3 DOF hexapod(Figure 1) in existence.

“We got our bot fast! Good thing too since our camp’s been gettin’ hammered by wild dogs at night.  Its really good at standing watch when we’re sleeping and is perfect for collecting our kill when hunting.  Its aluminum frame makes it so easy to carry that we fight over it.  Everyone else is a pack mule for the gear.”

Body Text:

The robot(Figure 2)  is powered by 2 6 v, 10 AH NiMH packs; a 22.4 v LiIon pack, and a 9 v battery.  It occupies a 4-foot diameter circle (3.5 feet when walking). The front two legs are clawed and are used for grasping objects.  There are 4 modes of locomotion (4-legged walk, 4-legged trot, 6-legged walk, and 6-legged trot).  In addition to these gaits, there is claw mode where the claws can be controlled independently of one another.  There is an on-board router so any computer with the control software will be able to use the robot.

Control of the robot was designed to be as intuitive as possible.  We utilize two wii remotes, and a display.  The display shows live video feed from the robots head, look angles, walking speeds, pack life, and results from the tracking systems/sensors.  In walking modes, one wii remote is used to control the camera look direction (which also controls turning), while the other is in control of the locomotion type, and speed.  In clawed mode, each wii remote controls a clawed leg independently.

Because the project was given a 4 month time-frame, modularity was very important to increase the efficiency by allowing multiple areas of work to be done concurrently.  In our system, the SbRIO 9632 acts as the brain.  It is in control of coordination and communication with both the outside world (sensors) and the host which the user is operating.  We use a Lynxmotion SSC-32(powered by an atmega168) for motor control.  This circuit is connected to the SbRIO via serial and is directly in charge of manipulating the limbs.  The host is used for control of the system and user interfacing with the robot.

“We were really excited to get the Hexaquad.  Our last scout, the Bandsaw, was builky and slow.  That thing was a pain-in-the-ass to maintain!   It always locked up when on patrol and we’d have to wait until morning for a pick up.  We have found the claws more useful anyhow.  Those things are TOUGH!  We tested those suckers on a rabbit carcass before hooking em up to the bot’s body and man those things are strong!  It shattered three of the ribs and broke the spine.  We tried pulling that little fella out of them pincers, but damn near ripped the guy in two.  We had to build the whole system up to get it out.

Maintenance –wise, this bot is great!  All the legs are hot swappable and supposedly they’ll have shields and interchangeable legs on the market soon.  The need for replacement parts is always on our minds.  Ever since old Bandsaw was crushed by a rock, David has been using one of its damaged legs as a tent stake….kind of menacing…”

Images:

http://img27.imageshack.us/i/figure1a.jpg/

http://img193.imageshack.us/i/figure2q.jpg/

Video Links:
http://www.youtube.com/watch?v=5ReoMRYK_zg
http://www.youtube.com/watch?v=8MttSo6f8WI
http://www.youtube.com/watch?v=yQOYpomB-EY
http://www.youtube.com/watch?v=LFpE7KvXYBo