.:/ Hardware /:.

 

In order to complete our project, we needed a motor, two links, optical encoders, and all the supporting miscellaneous hardware to get it all working together. Through our research, we were able to determine what we thought were ideal components for each requirement.

 

 

Motor

This is our little engine that would - a Pittman 14207S008 brush-commutated DC motor. While only 2.125" in diameter, our motor was still able to output 410 oz-in of peak torque at 24 VDC. The S008 denotes a built in 500 point optical encoder. Click Automation.com provided this motor free of charge as a generous donation.

Encoders

We used US Digital's S2-1000-B encoders. These encoders are 1000 point, 5 Volt optical encoders with a rated shaft torque of 1 lb. It turns out that the 1 lb. shaft torque rating was fairly accurate, if a little conservative.

Interface Boards & Amplifier

To interface the computer to the motor we used an break-out board to connect to the ServerToGo board. The STG board gave us all the digital and analog input and output ports that we needed to read the encoders and output to the linear amplifier.

50V Linear Amplifier

This amplifier took our +5 V source from the STG board and amplified it to match our motor's max of 24V. During testing this amplifier would become very hot and some sort of thermal protection took over, causing the amplifier to cut off. This hindered our testing, but we managed to work around it.

Links

First Set of Links

These are the first set of links that we were going to use, however after consideration we realized that we did not need strength, but speed in our Pendubot. We thought that using the lightest possible links would give us the greatest advantage.

Our secret Weapon

We thought we had a trade secret when we came up with the idea of using aluminum arrow shafts as our links. These shafts are incredibully light, while fairly rigid. In order to connect the two links together, we had to use AutoCad to make custom hardware.

Specially made pieces to attach our arrow links

We had a lot of trouble getting the light aluminum links to balance in stability. We tested repeatedly for days without any good results. In an act of desparation, we tried using new aluminum links.

Third set of links

These links were also tested and tested and tested. These links were a little more rigid than the arrows, but we still could not achieve stability. After so much testing, the aluminum pieces took too much of a beating, and the link connecting our motor to our first link broke on the day before Bonus Day.

Broken Pieces (shown with arrow link)

This piece broke around 5 PM on the day before Bonus Day. We needed pieces in a hurry, and Ty was able to convince T&S Machine Shop to work late to make us a new set of links. Our fourth set of links no longer used the inserts, eliminating a weak point in our links.

Final Links (shown with encoder and golf ball)

Initially these links did not work either. However, we decided to add some weight to link2 in the form of a piece of attached steel. This allowed us to find the stability point, and afterwards we were able to remove the steel and still had stability.

Our final hardware design:

Complete setup (shown with Tim's leg)