we have 3 weeks for our group to build a robot that can pick up blocks and tenis balls
The tinnis balls have to be dumped into a container 8.25 in high and 2.75 in wide
The blocks are 2in by 2in by 2in and made of wood
and the Blocks also need to be able to be stacked
we only have 3 minuts to do all this
and we can only use the parts that come with the VEX Classroom Lab Kit
we have had a few idias but theve all fallen short
please help
i would try to make a claw. if the claw had 4 pressure points like sticking out your middle and index fingers on both hands then it could grab the balls rather easily and i’m not sure the diameter of a tennis ball but my guess is it is close enough that the blocks could be grabbed this way too. if the claw were on an arm then you could raise and lower it. the claw could be driven by a servo and a wrist would be good to make the gripper parallel to the floor to stack blocks. i believe the classroom kits come with an extra servo the you could use for this.
2 motor drive
1 servo gripper
1 servo wrist
1 motor arm lifter (elbow or shoulder)
so 3 motors an 2 servos would do the job
thanks this could help a lot
but the idia we are working on noe is pretty much the same exept insted of a claw we are using tank treds
you have treads in your kit ok. well unless the diameter of the tennis balls is 2 inches you are going to have trouble making a zippy style robot with the conveyor belts. i would still go with the the claw because it is simple. i will get on the diameter of a tennis ball.
tennis balls have a diameter of between 2-1/2 and 2-5/8 inches just bigger than the cubes.
that being said you could actually go with a conveyor system if that is what you have your heart set on. it would be kinda complicated though. you would have to use rubber bands to always apply pressure pushing the conveyor belts towards each other. then the bot could pick up and stack the blocks. when the belts hit a ball and suck it in the conveyors will spread apart stretching the rubber bands apart which would hold the ball in. the tricky part is mounting the reads in a way that they can slide freely closer and farther apart at least 1/2 an inch.
thanks
we dont know what tennis balls there using we didnt even know that the bloks were 2 in and wood untill today
i think any tennis ball is that size the small difference is due to varying conditions of possibly heat, ball usage and other factors I’m sure.
how many 90 degree gussets do you have? i am thinking those could work as the sliders.
also take a look at the picture below although this bot used pneumatics you could do something similar using a servo. you would want 2 fixed “fingers” in the back and probobly just 1 finger that is doing to be driven by the servo. this way when you go to grab the balls they won’t slip.
thanks
but right now were trying the tank tred idia
if any one has any idias plese post them
You might want to check out the ideas in this thread:
https://vexforum.com/t/my-slippery-slope-vex-home-challenge/15246/1
Items could be delivered from the top, rather than the bottom, which would be more useful for a container over 8" high.
and like i said before you could use rubber bands to pull the conveyor belts (tank treads) together and when a ball is sucked in the treads would separate but still apply pressure to suck in the ball. does this make sense?
kinda like on this robot (below) but instead of having the treads on the arm mounted at a fixed distance apart they could be mounted on one of the pieces with a long slot in it so that they can move away and apart from each other when you push them gently and then with rubber bands like i said before they would stretch apart when a ball is sucked in and go back to their original position when the ball is expelled allowing you to lift balls and cubes of different diameter / width with one system.
i would also like to point out that if you are looking for somebody to give you all the answers you are probably out of luck. in the majority of these types of threads when somebody asks for help with a school project people give fairly vague ways of getting the job done and leave quite a bit to the person who was given the assignment. ya know? it is good to realize when you need help and ask for it when you do but the whole idea of vex is to kinda learn as you go and I’m sure your teacher will take effort and concept of design into consideration. i know in my robotics class many people can never make a robot that performs the task but they have good ideas in theory and work hard and usually get like a 90%
In every case I’ve seen, the “elevator” style robots always work better. A claw robot can complete the task, but an elevator/collector can do it faster. Speed is key in a timed competition.
you might get away with the treads being fairly far apart and using A LOT of zip ties attached to the tread links. This is how we pick up blocks and it will suck up balls if we tried.
That picture is actually where we got our insperation from