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View Full Version : [FTC]: Team 35's Servo Test


wilsonmw04
10-25-2008, 03:24 PM
We were a bit skeptical about using the servos for anything serious, articulating arm joints for example. After our first 5 hour meeting, we are VERY excited about this new kit. We brainstormed, and then prototyped 3 different ways of articulating joint for our arm. One powered by servos, one powered by 2 Lego motors and another powered by one of the larger FTC motors.

I'm posting a Video of the servo test. We attached the bracket to the frame of last years VEX 'bot for this test. The programming was a tad off for this video (we couldn't keep the arm at any angle we wanted). It was fixed later on, but i didn't get my lens on it.

http://www.flickr.com/photos/wilsonmw04/2971763225/in/set-72157608365268449/

ttldomination
10-25-2008, 04:38 PM
how heavy is ur chassis approximately???

dickswan
10-25-2008, 11:52 PM
[QUOTE=wilsonmw04;772030]The programming was a tad off for this video (we couldn't keep the arm at any angle we wanted). It was fixed later on, but i didn't get my lens on it.
QUOTE]
If you're using ROBOTC, it has a really nice PC window that allows you to manually set the position of any of the six servos by simply entering the value into one of six text boxes. This makes it really easy to determine the 'min' and 'max' values for a servo movement.

wilsonmw04
10-27-2008, 10:30 AM
with the servos and stock attached: 4.676 lbs.

it's not lifting the whole weight so that's a tad deceiving.

ttldomination
10-27-2008, 07:35 PM
That's still pretty nice.

ttldomination
10-27-2008, 07:37 PM
Well, sorry bout the double post, but 35 rings are about 6.5 pounds. With a couple o' gear reductions...:D. I see potential.

jbbjjbt
10-28-2008, 10:15 AM
Well, sorry bout the double post, but 35 rings are about 6.5 pounds. With a couple o' gear reductions...:D. I see potential.

Remember with a gear reduction of two the servo only goes +/- 45 degrees. with a ger reduction of three that would be +/- 30 degrees.

ttldomination
10-28-2008, 12:24 PM
Touche, well, there are other ways to get the mechanism up without even gearing the servo. Heck, if you wanted, you could gear the servos for speed. :D.

wilsonmw04
11-03-2008, 10:10 AM
http://www.flickr.com/photos/wilsonmw04/2999799454/in/set-72157608365268449/

A quick test of a 4-bar linkage with the new 2008 FTC kit. The programing is a tad off, but it does give you an idea of the power of the servos and the possibilities of the new kit. The arm was made with two 16" C-channel and a 6" short member. Our final arm will be shorter, but will look a lot like this.

We are now working on programing that does not relate stick position with servo position. We would like to have the servos act more like a motor, so that when we take our hands off the stick the arm stays where we want it rather than returning to the neutral position.

ttldomination
11-03-2008, 05:04 PM
Interesting, very nicely built. A few quick questions.

1. was the tower attached or were you or someone holding it in place?

2. More of a suggestion, you could have the joy stick value *add* to the position of the encoder instead of setting the joystick value to the value of the servo.

For example:

servovalue = servovalue + joystick value;
Servo[a] = servovalue;

Where the joystick no longer equals the position of the servo. Simply changes the position.

wilsonmw04
11-03-2008, 07:07 PM
It was attached to the front of the frame straight to the C-channel. This was not intended to be permanent, just a proof of concept. The Kids are working on a working mount as I type.

ttldomination
11-03-2008, 08:47 PM
It looks REALLY good and powerful. :d.