Gripper routine help (Gripper Kit #28202)

aprtunedgti

I have a Boe-Bot with a gripper kit, and I need to program a simple task to pick up a golf ball, proceed to a station, and drop the golf ball on a target. Any suggestions? Time is a limitation, thus I am turning to the experts on here.

Martin_H

Use line following sensors under the Boe-bot to lead it to the golf ball. Use a T junction to indicate the grab point and follow a line to the drop off point.

aprtunedgti

Thanks Martin. That's a nice simple approach. What's the best way to combine QTI and Gripper programs? While it's refreshing to follow the lines, how can I make sure the bot doesn't drop the golfball?

Martin_H wrote: »

Use line following sensors under the Boe-bot to lead it to the golf ball. Use a T junction to indicate the grab point and follow a line to the drop off point.

erco

Sounds like a school assignment, or maybe a contest?

WRT dropping the golfball, might I humbly suggest preloading the gripper with a spring or rubber band so it grips the ball even with the servo turned off? That way, you can just focus on reading sensors and driving instead of refreshing your gripper servo. It will work the servo harder when opening up, but that's ok.

aprtunedgti

Just an assignment. We were introduced to the Boe-Bot and had to figure everything out on our own. I have quite a bit of experience so my learning curve was a little bit higher than the rest of my class, so it basically turned into me teaching 18 people everything as I figured it out. Almost my entire class in made up of future Civil Engineers and no one had even a basic understanding of electronics... It's been fun. My programing experience is so minimal it's not even funny, but I've slowly but surely figured out Basic Stamp in a 1 month time frame.

The issue with rigging up a rubberband is that that will help keep the gripper arms closed, but the servo will still drop and the item will just be dragged on the ground. I understand that I can just make sure the servo keeps reseting in every function of the code, it's just that I'm not sure if there is an easier way than just putting:

FOR
PULSOUT 14, 900 (14 is my servo pin, 900 is the value of close)
PAUSE 20
NEXT

...in every function in my coding.

erco wrote: »

Sounds like a school assignment, or maybe a contest?

WRT dropping the golfball, might I hjmnly suggest preloading the gripper with a spring or rubber band so it grips the ball even with the servo turned off? That way, you can just focus on reading sensors and driving instead of refreshing your gripper servo. It will work the servo harder when opening up, but that's ok.

erco

OK, so how about adding another rubber band to the lift servo to keep it (and the golf ball) raised with power off?

aprtunedgti

I guess because I just want to use the potential of the Bot and learn out to incorporate code functions into each other...

erco wrote: »

OK, so how about adding another rubber band to the lift servo to keep it (and the golf ball) raised with power off?

erco

Well, you can definitely tough it out and write code to manage 4 servos while reading the QTI sensors to follow the line, or you could offload some processor overhead and servo management by adding a ServoPal or two. Each ServoPal can continuously manage 2 servos with a single command: http://www.parallax.com/product/28824

Or, add 2 rubber bands.

Martin_H

What I do is keep pulsing the gripper servo to maintain grip on the object. The parallax gripper is designed to elevate when gripping but still maintain tension. It's a bit tricky to pulse three servos and poll the QTI sensors, but tight Pbasic can do it.