This page is updated as the project progresses. Check back for updates.Your comments are welcome.
Last updated 1/15/2011.
This page maintained by DKDeckmann@HiTekGizmos.com
Phase B - Hardware Enhancement will deal with the addition of a basic sensor package and refinement of the power distribution system.Click to go to Phase B - Hardware Enhancement page.
Phase A - Electromechanical Prototype - complete 4/30/2005. Basic platform proven to be a viable self-propeled unit capable of hauling a significant payload. The remainder of this page is dedicated to the fabrication, assembly, and simple programming as well as an outline for further expansion.
Wilby Walker is a Hexapod robotic development platform.
Wilby Walker's mission is to facilitate my development of robotic devices
and programming. Wilby Walker's primary purpose is to aid me in the development of:
A walking machine to evaluate the practicality of designing ind implementing a walking platform versus conventional wheeled platforms.
Evaluating the OOPic microcontroller for use in such projects versus other controllers such as Basic Stamp, PICs, Rabbits, 68HC11, BASICX, etc.
Evaluate remote vision and telemetry systems using CCD and similar cameras, ATV transmitters and video overlay circuits.
Evaluate sheet acrylic as a construction media.
Evaluate hobby type servos as a means of control and locomotion.
Evaluate various sersor devices such as Polaroid SONAR, infarad proximity detectors, bump switches, feelers, etc. as they may be employeed in such robotic devices.
Acrylic seems to machine better with higher feed pressures and lower speeds. Too fast tool movement seems to result in meltdown. A table saw with a carbide blade seems to cut it nicely as does a Dremel Scroll Saw. Keep your blade sharp and your cut free of shavings or it will get hot and sticky. A Delta 1 inch belt / 5 inch disk sander does a fine job smoothing but tends to melt it a little. I speed control might be the answer. A Unimat lathe was used for most of the drilling operations.
The project is controlled by a standard OOPIC with several i/o pins left over. Each leg carries its own 4 AA cell battery for its two servos. This design lets half of the battery weight rest on the ground at all times raising its payload accordingly. The OOPIC is mounted in the hexapod's butt making it difficult to not name it after someone I know, instead it is named after one of my dogs, Wilber.Click to visit the OOPIC web site to find out more about this controller.
Unfortunately the ooPIC is no longer available (as of December 2008 or so). The interpreter code is claimed to be open sourced but no one knows where to find it and the author has disappeared from the face of the earth as far as I can tell. I suppose this means I will be looking at different controllers.
The DB-25 connector on the top, not shown in the drawings, serves two purposes; fitted with a jumpered plug it serves as an emergency STOP by pulling the plug power is removed from all servos, and it provides seperate connection to each of the six batteries for charging.
In its current form Wilby walks under the control of a gutted IBM/Apple joystick, looking at the two pots via 2 of the 4 OOPICs a/d converters. This a/d value is then scaled down and used to control the swing of each side when taking a step.
The two serial communication lines are currently unused. I plan to use the serial lines to control the video overlay generator.
I plan to use a video overlay generator from Intuitive Circuits to display telemetry and whatever other information I desire over a blank screem or over onboard camera video.Click to visit the Intuitive Circuits site to find out more about this and other pic based video overlay generators.
A video camera will be installed on a pan/tilt head. Infared sensitivity is desirable. An IR illuminator panel should also be afixed to this "head". Image capture and recognition is well beyond the capabilities of the current OOPIC processor. The CMU cam might be explored further.
An ATV transmitter from PC Electronics will be fitted to transmit the camera and or overlay video from the platform to the monitoring station.Click to visit the PC Electronics site to find out more about this and other ATV transmitters and equipment.
Polaroid SONAR modules are available new and may also be salvaged from their auto-focus cameras. The modules from the cameras require some support interface hardware such as a way to trigger them and the controller must then precisely measure the time between the ping and return echo. Range values from about 1 foot to 15 or more feet are accurately. easily, and reliably measurable. The OOPIC has been successfully used in this application by others. Mounted on the pan/tilt "head" the range data could produce a 3-D map.
Sharp manufactures some small, low power demand IR Ranging modules with analog output. The OOPIC supports 4 a/d channels. Mounted on the body or head these would provide enough information for simple navigation tasks such as wall following or obstacle avoidance.
The I2C bus is currently unused. The project is already starting to stretch the capability of the OOPIC. Fortunately the OOPIC supports the I2C standard bus. The I2C bus may be used to allow the OOPIC to "talk" to other devices that have an I2C interface such as thermostats, a/d converters, and even network with other OOPICS, all on the same bus. It might make sense to dedicate one OOPIC to servo control and another one to data acqusition and navigation.
You may use the following DXF files if your CAD program supports DXF. Many allow you to import DXFs and manipulate them.
Six of these are required, 3 left hand, 3 right hand. These were made from 1/4 inch thick sheet arcylic. Holes for leg links should be just big enough to pass #8 hardware without binding. Semicircular notch at bottom end as required to clear servo horn screw head. End drill bottom end to conform to your servo horn & thread for #4 sheetmetal or machine hardware End drill top to pass #4 machine hardware without binding for top pivot. Holes for wire ties 1/8 inch typical.
Twenty-four of these are required. These were made from 1/8 x 1/2 inch bar aluminium. Holes should be just big enough to pass #8 hardware without binding. Make and keep in matched pairs to prevent binding. Assemble #8-32x1-1/4 screw, washer, link, washer, leg, washer, link, washer, lock nut. Over tightening lock nut results in unacceptable binding.
Six of these are required, 3 left hand, 3 right hand, Make them the same, just flop 3 or them over! These were made from 1-1/2" x 8" x 1/4" arcylic. Notch for servo need to conform to the requirements of your servo. Holes for servo mounting screws need to conform to your servo mounting requirements. Holes for leg links should be just big enough to pass #8 hardware without binding. Holes for battery ties 1/8 inch typical. Batteries and wires are secured with standard wire ties. Holes at corners of servo notch not required but included for ease of construction, 1/8 inch.Click to download lowleg.dxf - Lower leg drawing.
Six of these required. These were made from 1/2" x 1/8" aluminium.Click to download cranknk.dxf - Link for connecting legs to servo drawing.
One of these is required. This was made from 1/4 inch thick sheet arcylic. Drill top pivot holes to just pass #4 machine hardware. Assemble top pivots, 4-40x3/4 screw, washer, upper body, washer, nut, washer.Click to download upbody.dxf - Upper body drawing.
Three of these are required. These were made from 1/2 inch thick sheet arcylic. End drill for #4 sheetmetal or machine threads.Click to download bodyspac.dxf - Spacer drawing.
One of these is required and is the hardest part of the whole project. This was made from 4" x 14" x 1/4" thick sheet arcylic. Notch for servo need to conform to the requirements of your servo. Holes for servo mounting screws need to conform to your servo mounting requirements.Click to download lowbody.dxf - Lower body drawing.
BASIC Source for the OOPic here! No attempt has been made to optimize this for speed or size. Just quick and dirty to get results ASAP for platform evaluation. Not a complete "personality", just a few routines to move the thing around. Several things can be done to make the code a little fancier including naming the legs using a for/next loop and giving them array names rather than easily decoded ones. Only 6 different outputs are really needed for this to work but some servos would have to look at the same OOPIC control lines. A nice touch would be a startup delay and setting the legs to a specific starting point. Might be nice to stop the legs from marching when no speed/direction is present. You name it. This is a starting point...Click to view joywalk1.
A modification for more inscect like movement was sent to me by Scott Savage. This makes for nice movement but It, of course, will need modification for steering, etc.Click to view bugwalk1.
See if you can get it off of the drawing board before I do. Here are a couple of drawings in DXF format for viewing or editing using your CAD program. Also a couple of drawings in JPG format for viewing directly from your browser. These are for one of my proposed project series using the same legs and control as Wilby Walker but featuring unique body style. You'll see why I named the project Daisy.
You can guess what Daisy 8 might look like... Like Daisy 6 but 8 legs...Click to download DXF drawing of Daisy 6 body part.