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Second Page (RF Control of Skinny)

Third Page (IR Sensors on Skinny)

What Happens When Your Test Stand Gets Out of Control

A More Sophisticated Robot (a *little* more sophisticated). This is a series of web pages about Skinny. Motor Control, Sensors, and RF Control are discussed.


This is the basic frame


This is Skinny on his birthday. Skinny was built to explore navigation and PID control using a robot. Skinny has ended up being four robots (or more), each of which have different motor control implementations and different control schemes. Look through these pages and the links to these pages to see how Skinny grows. These pages were generated from about August '99 to present and were made mostly because of a collaboration with Bill Ruehl. The two of us decided to make a PID motor controller. After we got the controller half way working, we needed a robot to put it on. I went the simpler route, and Bill went a much more sophisticated route. See some of Bill's robots at Bill Ruehl's Web page 

The Skinny robots use a plywood octagonal base (1/8") with aluminum angles for reinforcement and for mounting heavy components. The wheels are turned on a lathe from 1/4" plexiglas and the 'tires' are the O rings for a Eureka vacuum (series 1100). The hubs for the wheels are brass and also turned on a lathe. The tail wheel is adapted from a model airplane tail wheel (about $2 in a hobby shop) for a .60 wire axle. The battery in this picture is a normal 7.2 volt NiCad RC battery for RC cars. Various versions of Skinny use this battery or a lead acid Gel Cell. The cost for the batteries are about the same - but a Gel Cell will get you 12 volts which is a bit heftier for some motors. The motors keep changing on the different models and I will mention them as we go along.



This is the frame with motor controller


The second picture is a little fuzzy (my last digital camera sucked with shots like this - it did macros well, but in-between shots were rarely in good focus).

The motors are running (which is why the pattern is a bit more blurry than usual) and you can just make out the Duty Cycle in the LCD.

The 16C73A is in the lower part of the picture in a 40 pin ZIF on a protoboard. The connector by the wheel on the right side is for a ribbon cable to run to the second deck of the 'bot when it becomes one. All the wiring going to the controller, etc will be headed off there. The encoder sensors are mounted, but not hooked up right now. The circuitry for them will go on the blank board in the front. There are two possible motor sensors. The QRB1114QT-ND (3.5 mm focal length) which is the one in the picture and the SY124 which is a 1 mm focal length thingy that Bill used in his flexor sensors. I have a hard time with the little rascals and prefer the QRB sensor.


Skinny's new nerve system


Here is skinny with a redesigned motor controller. Notice the difference in the quality of the photo? My new camera is much better (Sony Mavica - kewl!). Anyway, back to the 'bot: All the experimentation with the previous design came up with this. You can set Skinny's PID, endpoints, speed, direction and most of his important parameters through the PC (or through a serial connection with most MCUs). The board is a standard Radio Shack protoboard with a 16C73A (PIC chip), L293D (H bridge chip), 74HC04 (inverter), 74HCT14 (Schmitt trigger for shaping the encoder waveform). Wouldn't it be nice if someone made all this in one package? 


Skinny at Tiffany's


Skinny trying on his second deck with a BasicX module on top. Just for show - lots to do yet before we get this far. However, I did stick a Homebrew Stamp on Skinny - hooked it to the motor controller umbilical and did a few turns. See the video below.

NEW! Real Movie of Skinny

Skinny is doing a four turn 20' run and returning in the above movie. His previous video was off by six inches. He is a lot closer here. Improvements included a higher encoder density (90 stripes or segments), locked anti-phase PWM, and discovering that the left wheel was .025" smaller than the right wheel (made several inches difference over a 20' course!).


Skinny Gets an Evil Sister Sarah #1 (SS1)


Bill asked me if I would like to make the mockup mobile so I made a second platform for the mockup electronics. The following picture is of the encoder pickup that Bill made. 

Bill's Flexor Encoder Design Using an SY124 (one of first prototypes after I had bent it up a bit!) 

Because the Pittman motors were a bit bigger than the Hsiang motors I used for Skinny, I put them on the bottom. I also used a 12 volt Gel Cell for power - got a couple of them from BG Micro for a good price. The Pittman motors are faster than the Hsiang motors so I dropped the wheel size down to 4" - makes the whole 'bot look smaller, but it really isn't. Sarah is shown here with her umbilical running off to a PC somewhere. She has a little problem right now with her encoder pattern so it may be a while before she is running as smoothly as Skinny. In any case, here's a video of her taking a P (the course is a P shaped course). The video starts out a bit late - Sarah actually starts at my feet in the video, so when she comes back, she really lands on the same square that she started from. I also managed to cut the video off before she gets fully turned around for her next run. In the video, note the dog bowls (empty) and chew toys on the floor. These are natural obstacles left by our retrievers. One of whom is watching the 'bot from behind me while I'm shooting this video. She doesn't quite know what to make of the robots in her kitchen.

SS1 Takes a Turn (REAL Movie)

Second Page (RF Control of Skinny)

Third Page (IR Sensors on Skinny)