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| Some of these models were created just for looks, like the Space Navigator or the LAR Trailer. I have taken varying degrees of care to make them photo-realistic. Some models were always destined for creation, like RC Baja, and The Claw. I did not spend as much time making them photo-realistic, instead the intent was to create parts that would be fabricated and assembled. | Fabricated parts were either turned out on a manual lathe, or cut out using a CNC waterjet. For manually lathed parts, drawings were prepared. For CNC parts, Solidworks parts were prepared to be easily imported to the OMax software. A professional shop was used for some lathe work and all CNC waterjetting. Most of the finish work on these parts was done by me using a manual mill, lathe, drill press, tapping rig, band saw, sanders and buffers. My trusty calipers and a center tap are never far from me in the shop! |
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If you want to view Solidworks 3D models without using your browser, install the Solidworks eDrawings viewer (11Mb). Then download the 3D models using the link below each picture. |
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The 2009 ASME SDC was inspired by the Mars Lander. The concept is a robot that will deploy from the landing vehicle to collect rocks and deliver them. The challenge was to build a robot that would collect rocks, deliver them to a target area, and return to the start position. This robot would have to traverse over 4x4's on the course.
The Claw was slightly back heavy. It climbed the 4x4's, but took careful maneuvering to tilt forward on top of the obstacle..
There were three main mechanisms in the robot
Claw |
Hopper |
Drive Mechanism |
Two servos (connected to one channel) on the claw arm controlled the opening and closing of the claw. The exact shape of the claw went through many iterations. We did not want to have to aim for a rock exactly. With the claw open, in the down position, the robot just had to run into a rock, and the closing mechanism of the claw would center the rock as it closed. The claw arm then lifted the rock up and then down over the hopper. Then opening the claw slightly would drop the rock into the hopper. Electronics was the only challenge here. I blew a few servo circuits before figuring out how to rewire one of the servos to mirror the other. Both servos worked off the same channel, but had to do the mechanical "mirror" of eachother. The secret was reversing the motor wires, and the potentiometer wires inside the servo control circuit. In a microservo this took a steady hand. |
The hopper was at a slight angle. When the rocks dropped into the back of the hopper they rolled towards the front. In this way, the rocks stayed in the hopper in the order they were collected, and there was always an open spot in the back of the hopper where new rocks would enter. To drop the rocks over the target, the two hopper halves separated. This dropped the rocks gently to the ground keeping the orientation they had in the hopper. Then The Claw simply rolled backwards leaving the rocks on the target. Same servo electronics trick as with the claw. |
A RoboteQ AX500 motor controller board was used. This is an awesome piece of electronics. It can control two motors, via variable resistor (used as a voltage divider) or PWM input. As we were using a standard RC remote control, we took advantage of the PWM input. The board was made to work well as tank drive control. The board also has a computer interface. We programmed it to work in "mixed" mode. This means that on a dual channel gimbal (joystick with two channels - horizontal and vertical) forward moves both motors forward. Left or right moves one forward, one back. This offers a little less control than a two-stick tank control method. However, since we could only have one person controlling the beast, we used the "mixed" feature. This isolated the drive control to one hand, while the other hand controlled the claw. The electronics worked perfectly. The motors were high speed and small, with a 100:1 metal gear head. We reduced it 2:1 again in the connection from gear head to axel. If we could get the traction, this thing would climb straight up a wall. This drive mechanism was simultaneously The Claw's greatest stength and weakness. We were eliminated from the competition because the rubber tracks were derailed instantly on the business-carpet course. It had only been tested on cement and wood flooring. All rubber tracked entries suffered the same fate. A plastic tracked vehicle won the competition. |
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Click to enlarge.
The premade parts had to be modelled first, and the rest designed around them. |
The fabricated parts are shown here. |
I didn't spend too much time making this render up pretty, but here it is anyway.
Here's the real thing. I hate the ugly peice of steal zip-tied near the front to move the center of gravity. Also, a few switches weren't in the original design, but shown here. The wiring to the four servos up front is nice and tidy, but wiring in the back could be nicer.
