We’ve been working on our claw-bot for a month now and are ready to do a sneak peak.
4 Motor Speed Tank Drive with 4" wheels
6 Motor Single bar lift
2 Motor Claw
In the video below we are running our robot for 5 minutes straight, switching batteries and then continuing for another five minutes. We believe that if our robot can withstand this stress, it will be able to come straight off the competition match, run a skills match, and then be placed back in the following match with only battery changes in between.
Our robot can score cubes and stars, both in the near and far zone. The claw has a capacity of 4 stars, 1 cube, or 1 cube and a star. We have a 3 point autonomous and a 12 point autonomous.
We tested our robot on 11/5/16 at the West Jay Starstruck HS/MS Qualifier. We went 5-1 in qualifying and found out, during a rematch, that motor PTC’s can ruin a match. Our base stalled and it caused us to fail the rest of the day. We had a very good alliance that carried us to semifinals after converting the claw into a blocking mechanism due to weight. A major thanks to teams 121X and 9116.
After competition we decided to utilize slew rate code and use both joysticks. This created a robot that now wouldn’t fail under stress or bad driving, and it also greatly increased our efficiency. We are now at a place where we can score a cube every 7 seconds.
We will be testing this design again with a few improvements this Saturday at the Iron Pride Starstruck Blended Fall Qualifier. We will post an official reveal at a later date.
why did you chose a motor over a pneumatic design? what are the benefits, and does the ablilty to stall your motors really outweigh the benifit of not losing air pressure, my team has a pneumatic claw, and has never had the problem of running out of air
We designed our claw to operate using 2 #64 elastics to create a constant force when closing. A potentiometer tells the motors to stop moving when they get to a determined value. I apologize for the range the video was taken, this is clearer up close. We will be releasing HD footage of some practice soon and competition film very soon.
As for the reason for deciding against pneumatics, we simply don’t have the funds available. We may have some plans for fundraising to buy some pneumatics. It will allow us to create a lift we are designing.
Honestly, if I had the choice between pneumatics or motor power, I would choose motor power. I currently have 37 inches of horizontal reach when the claw is extended. Which allows clearing the fence with ease. I can also grab stars that I would otherwise not reach. I would however choose the pneumatic option overall and eliminate two lift motors with a system similar to 4194A in their skyrise bot. They used pneumatics to aid in the lifting of their arm.
I’m not sure on an exact time from open to close and vis versa, but it is geared 1:5. We ultimately split the controls between two joysticks to greater advance the efficiency and scoring. It still opens fast enough to throw cubes into the far zone with ease. We actually have developed an issue with stars bouncing out of the fence during our last competition.
The flex in the single bar was a worry during the planning and building phase. However, after extensive testing, driving, and a competition we found that the arms flex allows for error. Instead of the arm being solid and then forcing the robots base to bully objects out of the way, the arm can flex an inch and a half to allow the driver to maneuver better and find easier routes. This was in no means planned, but it turns out to be a blessing. It helps to not stall the base, which was one problem we overcame.
My advice as with any robot is do the math and calculations first. Trial and error works, but the fastest route to a working robot is precise planning. When building a claw-bot I would build the lift first. It is easier to build a drivetrain later. One of the most important things to a claw-bot are the sensors onboard. Build a robot around sensors, then make them capable of correcting driver error. Utilize potentiometers and limit switches to create efficient movements. Drive using shaft encoders or IME’s. Sensors are your friend, learn them and they will help you with the robot.
I was noticing that while your driving, your claw is rarely ever in between being open and closed. Are you running a sensor so you can only have the claw open or closed? If the range of motion wasn’t so large and relatively slow, I would have thought maybe it was pneumatic…
Yes, we are utilizing a potentiometer. The arm has a starting position (Folded all the way back), a open position, and a closed position. The closed position is set so that the motors will not burn out. The rubber bands then take over.