Roundup Mentor Bot: Programming Challenge

Well, I set up a 2 tile programming challenge in my living room.  I built a little A frame mockup that has the 14 degree tilt and the dimensions of the actual roundup ladder face.

See video of the  25 step programming challenge here:

A very simple  autonomous script which is embedded in the RobotC code causes the robot to move forward while holding heading, pick up 4 tubes and head toward the movable base goal.  It is allowed to bump into the goal since a special space bar is deployed by servo to keep the robot from over running the goal and maintain the exact spacing needed for a drop.  A timer expires and the drop begins.   The plunger or spike has a grip that is servo controlled to three positions: HOLD, DROP ALL, DROP ONE.  The DROP ONE is done twice and the DROP ALL  is performed last to let the remaining two tubes score.  The robot then backs up a little  and lowers the lift for a line tracking function that continues until it backs into the A frame.  This is signaled by a bumper switch.   The robot then does a 180 deg turn and raises the lift to clear the pick up mechanism from striking the 6 in high crossbar on the bottom of the A frame.

Ready for the finale:  The robot must tilt 14 degs in order to grab the A frame.  This is done using the robots momentum.  A full speed burst forward followed by a sudden full speed reversal does the trick.   The robot tilts against the A frame and then extends higher to allow the grippers to reach around the sides of the A frame.  The lift is then lowered until the grippers grab the sides of the A frame and then the bottom is raised above 6 inches.

The lifts have a 36 tooth drive gear connected to the Vex 2 wire 393 motors.  This allows quick movement of the lifts and yet retains enough torque to lift the full weight of the robot.   Special lift geometry allows the lifts to travel over 19 inches so it can do the 18 in above ground high hang in theory.

More Roundup Mentor Bot:

Complete RobotC code in case you missed it.

Posted pictures on the vex site:

High Hang??

Low Hang.

More blog stuff:


3 Responses to Roundup Mentor Bot: Programming Challenge

  1. RLee says:

    Hey there!

    That’s a really cool robot.
    Would it be possible to upload pictures of the dual-sliding mechanism? I found that really interesting.
    I noticed on your mentor bot post that you say the robot has a plunger and a pincher. Yet right below it in the update you say it was removed. Do you still have any drawings of it because I don’t see how a pincher could remove the rings from the poles.

    Thanks in advance for any infomation,


  2. vamfun says:

    Hi Roger,
    I might post some better pictures after everyone has some time to noodle about the mechanism. The design issues are extension constraints with the standard slide motor brackets, slide speed vs torque, slide orientation to facilitate gripper/tube collectors , wire routing so that nothing gets tangles up, slide friction, limit switch placement and left/right motor synchronization. It took a while to optimize a design even though the concept is simple.

    I used no drawings with this robot. I did spend a lot of time making the pincher which also had a built in geared base spacer that would deploy when you wanted to score above the white base. Unfortunately , the pincher had to be on the lower slide so it could only displace two tubes from a goal.

    When I first envisioned this concept, I had a claw gripper in mind which could attach to the upper lift and then also be used for de-scoring even the upper wall goals. This is really the way to go if you want to play defense.

    The conveyer lifts could also be attached to the bobcat with ease I think.

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