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| The Launch
Lexi Stefanatos
Only the bravest and most courageous superheroes can attempt Vexoic – it's a mission of sheer determination passion and ingenuity. The mission consists of launching tennis balls into a series of plexiglass garages to obtain as many points as possible. The superheroes collaborate with three other teams to load tennis balls onto our robots, drive to the garages, open some of the closed garage doors and launch the tennis balls inside. On October 24th, 2008 – all the teams gathered together to discuss the difficult mission ahead of us. We The build of January 9th consisted mainly of getting our ideas straight and setting goals. We had the intention of finishing the base for our robot in this meeting but we ended up further discussing all our ideas for the design of our robot. We felt that it was a better idea to make sure we had the design completely figured out before we began building parts of the robot – therefore we wouldn’t have to rebuild anything.
The first discussion that we had in our meeting was about the base itself. We decided to build it entirely of materials from the Vex Kit. The big theme that we were talking about is four-wheel drive. We needed to look at whether we wanted four wheel-drive or not and if yes, how would we achieve that. Last year when we participated in Port-O-Toss we had a rubber band that circled both our wheels, which simulated four-wheel drive. We were considering doing the same thing this year when we realized we now have new possibilities with the Vex Kit. We are now able to make a gear system, which allows us to have four-wheel drive with one motor on each side of the robot. were briefed on the rules of the mission and saw the great game board that our mission will be carried out on. Once the briefing was over, we split up into two groups – one measuring the game board and one attending a meeting about the engineering aspect. In the engineering meeting, rules tips and tricks were given out to help our superhero team win this grueling mission. While we face a dangerous journey ahead of us – we’re up for the challenge. |
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Programming Workshops
Jane Panangaden
During the last two weeks we have had a three programming workshops with Prof. Laurie Hendren who teaches computer science at McGill University. So far we have learned the basics of programming in C using the Apple C programming environment called XCode. We have learned about variables, functions, different libraries, “if, then, else” statements, while loops, arrays, binary expressions and the difference between “and”, “or” and “not”.
See the full session notes. |
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We built one of the Vex standard robots called Squarebot in order to experiment with RobotC and test out some programs. We have decided that we want to be able to drive the robot using the remote and only want to use programming for a few functions. Is it possible to map certain functions to parts of the controller? Does it have buttons or do we have to use the joysticks?
Possible uses for programming:
1. Using a light sensor on the part of he robot that sticks out the most, we could prevent the wheels from turning forwards if it senses the line. The line is bright yellow on a black surface so there is a lot of contrast. This would help us avoid penalties since the driver must stay in their chair and may not be able to see.
2. Program how much tension to put on the spring or cord depending on the distance from the crease. We need to be able to shoot from 10 feet for the skills competition and from four feet during game play.
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Initial Design
Jenna Ditto
During our first engineering meeting, we focused on coming up with a design for our robot. We started our meeting by brainstorming, and we came up with several interesting ideas. First, we made a list of all the tasks we could think of that the robot has to perform. When we eventually complete our robot, we will go back to this list and make sure that our robot can indeed do everything it needs to do.
1. drive
2. turn
3. stop
4. store balls (both pre-loaded and from the loader)
5. push and hold the button on the loader
6. open the garage doors
7. pick up balls from the ground?
8. Shoot balls into garages with different amounts of force (so we can shoot from far – 10 feet, and close up – 4 feet)
9. Stop at the crease (possible use for pragramming?)
10. sort balls by colour
After the creation of the above list, in terms of strategy for this year’s robotics competition, we concluded that the robot MUST be able to both open the garage doors and shoot, but that it would be impossible to do both of these actions at once, since the fact that we cannot enter the airspace above the crease makes this extremely difficult. So, because our robot cannot shoot and open the doors at the same time, we must coordinate with the other teams in our heat so that we can work with them: 2 out of the 4 teams will hold the doors open and the other 2 teams will shoot the balls into the garages.
In terms of the design of our robot, one aspect that we all easily came to a consensus on was the use of four-wheel drive. Four-wheel drive will allow us to better control the movement of our robot, and will allow us to turn it quickly and with precision.
We realized that we need to be able to control the amount of force that we shoot the tennis balls with, because we will need to be able to shoot from various distances. If we are only able to shoot the ball with a large amount of power, we would be able to successfully shoot the ball from a distance of 10 feet from the garages, but shooting from the crease would be a disaster because the balls would have too much power and might bounce out of the garages. We must be able to adjust the amount of force that we shoot the ball with for better control of our shots at closer distances.
We also realized that we must be able to SEE the colour of the balls in our shooting device, so we must build the main body of our robot and the shooter in a clear material (possibly plexiglass). We discussed how exactly we would build our shooter, and agreed that we should use a spring system. We also decided to build the shooter out of a tennis ball container, since it would fit the tennis balls perfectly.
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After taking into account all the points that were brought up during our initial discussion, we were able to come up with a working design for our robot. A tray will extend from the main body of the robot. This tray will be used to collect tennis balls from the loader. We will use the main body of the robot to push the button on the loader and to open the garage doors, meaning that all we will have to do is drive the robot into the button and door to be able to open them. This will reduce the number of motors that we will need for our robot to function.
We decided that we indeed want to minimize the number of motors that we use for the robot, since the batteries that we are allowed to use this year are far less powerful than they were last year, and may drain quickly.
There will be a platform inside the robot that is slanted towards the front and curved, with its lowest part being the middle. The tennis balls that fall into this inner platform will then roll to the lowest point: the front and middle. At the lowest point, there will be a hole that acts as the opening to the cylindrical shooting device. On top of this tube, there will be a disk that is controlled by a |
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motor, that can open and close the opening to the shooter, therefore controlling the number of balls that fall into the shooter. The tube of the shooting device will be slanted in the opposite direction of the inner platform so that the balls inside it will roll back and sit on the top of another small platform that is attached to the spring system. This small platform rests right on top of the spring itself. A cord will be attached to this platform, and will then run through the spring, and finally be attached to a spool, located below the spring. The spool will be on an axle. A gear is also attached to this axle (it cannot rotate: it is in a fixed position), along with a motor. When the motor turns, the axle turns, and consequently, so does the spool and the gear (they all turn as one unit). This tightens the cord, and pulls the platform on top of the spring towards the spool, therefore compressing the spring. When the power to this motor is cut, the spool will be free to turn. The cord that wrapped around the spool will extend, and the spring will be released. When the spring is released, the platform on top of the spring will be pushed out towards the opening of the shooting device. This motion will be what pushes the tennis ball out of the shooter’s barrel and towards a garage.
During this meeting, we discussed eliminating the inner platform from our design, and having the tennis balls go directly from the tennis ball tray to the shooting device. We decided against this idea, since this design would make it extremely difficult to control the balls falling into the shooting device.
Now that we have a working design, we are almost ready for our first build!!!
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Gameboard Build
Sam Walsh
It is now January 4th; two days before the end of winter break. Though it may still be considered holiday vacation, our team of superwomen and supermentors gather in a St. Leonard warehouse that belongs to a team member’s parent despite the freezing cold and harsh winds.
Both our media and engineering teams came together to help build our miniature game board. Why build a mini model? Well, we thought that the best thing we could do to prepare ourselves for the competition would be practicing on a life-size game board that we could build ourselves.
Using the sketches and measurements that we took during the launch, we previously set off to the hardware store to purchase our materials. In order to reduce as much waste as possible, we decided to build only what was necessary. The essentials included one garage compartment complete with a door and lever along with a mock loader for the balls.
We were mostly prepared, equipped with cameras, laptops, screwdrivers, measuring tapes and much more. Sure we hit a few bumps along the way- we had to search around for quite a bit of time (because even superheroes need safety glasses) and we also dug around for a hinge that would fit our garage door but all in all, we were right on the ball.
There were a few moments when the team collectively goofed off. Both riding a conveyor belt in the warehouse and snapping silly candid shots. But it did us good and relieved us from the stress of the nearing competition. Besides, technically it still was our vacation.
We had allotted a total of 5 hours for the entire building process including figuring out how to build it and the tweaking process. Despite all of our distractions that we had created for ourselves by the time the 4th hour rolled around we realized that our game board was ready to go! Not wanting to waste the opportunity of having the whole team together, the meeting shifted over from engineering to media as we discussed our soundtrack and our HeroEcs names.
Though we all knew that return of school from winter holidays was around the bend, the entire team couldn’t help leaving with a smile knowing that we had accomplished a lot in those short few hours. |
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Planning
Lexi Stefanatos
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The build of January 9th consisted mainly of getting our ideas straight and setting goals. We had the intention of finishing the base for our robot in this meeting but we ended up further discussing all our ideas for the design of our robot. We felt that it was a better idea to make sure we had the design completely figured out before we began building parts of the robot – therefore we wouldn’t have to rebuild anything.
The first discussion that we had in our meeting was about the base itself. We decided to build it entirely of materials from the Vex Kit. The big theme that we were talking about is four-wheel drive. We needed to look at whether we wanted four wheel-drive or not and if yes, how would we achieve that. Last year when we participated in Port-O-Toss we had a rubber band that circled both our wheels, which simulated four-wheel drive. We were considering doing the same thing this year when we realized we now have new possibilities with the Vex Kit. We are now able to make a gear system, which allows us to have four-wheel drive with one motor on each side of the robot.
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The next issue we discussed was our idea for a launcher – the device that will launch the tennis balls into the garages. We had several different views on how this should be done. We all agreed that the launcher itself should be something clear so that we can see the color of the tennis balls – the first idea that came to mind was the container you buy tennis balls in – this met all our requirements. Once that decision was made we thought about how we would get the tennis balls into the tube. We all agreed we would need to have a tray of some kind extending past the robot to catch the balls. Now is when the many different ideas came in to play. We needed to decide how we would get the balls into the launcher tube one at a time so that they could be launched out. After careful discussion we decided that we would build a platform that is on an angle coming from the tray to the launcher. The balls will role down from the tray towards the launcher but will be stopped by a door which allows only one ball to roll all the way down to the launcher at a time. We thought this was the best idea because it allowed the mechanics of the launcher to be simplified – without too much clutter from many things happening in the same place at the same time. |
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Building the Drive System
Mimi Warshaw
Today in our robotics meeting, we concentrated on our drive system. We decided to use a smaller driver gear and larger follower gears for the wheels so that our robot was not unbelievably slow and also had enough strength to open the door. We figured that you could get to the door as fast as you want, but if you cant open it, what is the point. After some small flimsy mistakes, we were able to have our robot up and running, literally. We tried her out and she drove smoothly through the school. |
The Shooting Mechanism
Jenna Ditto
An ECS Ped Day means nothing to us engineers! The school was very quiet on Friday, the day of our last build, so we took the opportunity to escape to our building lair (it really is a lair…no one else dares to approach it because it is in such remote location in our school!) to further construct our robot. The first thing that we did during out meeting was attach one motor to each wheel, instead of having one motor control the front and back wheels of each side of the robot (this was our original set up). Even though this required the addition of two motors to our robot, it gave our robot more agility and zip, which will definitely help us during the competition. When we went to test the new drive system of our robot, we initially had quite a bit of trouble with the configuration of our controller. At first, when we pushed the joystick on the controller forwards, our robot would turn, and when we would push it diagonally, the robot would move forwards or backwards. But, after switching around a few of the motor’s connectors, we were able to set them up so that moving the joystick forwards would result in the forward motion of our robot. It was a relief to see that our robot was indeed not “possessed” and that it was finally moving in the right direction!
After much discussion earlier in the week, we finally came up with a detailed plan for our shooting system, and were able to figure out a way to solve the problem that we had been anticipating since we first began thinking about the tasks our robot would need to perform: how we would be able to release the plunger attached to the bungee cords fast enough, with a motor that does not allow the axle attached to it to spin freely when power is cut from the motor.
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Our idea for our shooting mechanism involves using gears. We planned to attach a medium-sized gear to an axle, which will then be attached to a motor. This gear bites onto a larger gear, which is on a second axle. This second axle will be parallel to the first axle, where the motor is attached, and will have a second large gear on it, placed beside the first large gear. The second large gear will have some of its teeth cut out of it, and where it does have teeth, it will mesh with the teeth of a much smaller gear, located on a third axle, which will once again be parallel to the first two axles. This third axle will be where the string, which is attached to the plunger, and that will pull back the bungee cords, will be coiled. When the axle attached to the small gear rotates, the string will wrap around it. When the small gear’s teeth reach the point in the large gear where the teeth were cut out, the small gear and its axle will be able to rotate freely, since it’s teeth will not be biting into anything. When this occurs, the bungee cords will snap forwards and they will bring the plunger with them, therefore shooting the tennis ball, and the string that was coiling on the third axle will unwind rapidly. |
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With this idea finalized, on Friday, we began building our shooting mechanism. We used stand-offs to raise the axles holding the gears above the level of the base of the robot. After attaching the gears and positioning and aligning them correctly, we noticed that the axle attached to the smallest gear was bending slightly, because of the force that the large gear on the second axle was applying to the smallest gear. To correct this, we tightened a tie wrap around the legs of the stand-offs to prevent them from moving slightly and allowing the axles resting on them to bend.
Once we had our four gears aligned, we tied a piece of string to the third axle (the farthest one from the motor), and plugged in the motor, as well as attached a battery to the robot to see if the gears would turn in the direction we wanted them to and to see if they would be able to coil the string and stretch a bungee cord. We definitely underestimated the power of the motors that we were supplied with, because they were more than strong enough to stretch one of our stronger and thicker bungee cords!
Now that we have been assured that our shooting mechanism will work, we must cut out the appropriate number of teeth out from the large gear that meshes with the smallest gear on the third axle, so that we can see our quick release system in action! This is our plan for our next meeting. |
Shooting Mechanism Continued
Jane Panangaden
This week we continued working on the shooting mechanism. We added to the gear system by cutting out the teeth of the large gear (2b in the above diagram). Next we worked on the front part of the shooting mechanism. We took a cylindrical plastic container and cut about two thirds of it off and then attached it lengthwise to the robot. This serves as a trough for the ball to roll in. Then we built two metal guides running parallel on either side of this trough. A thin metal bar was inserted between these two guides. It moves forward and backwards. The string that is being coiled was then attached to the bar. As the string coils, the bar moves towards the back of the robot. Then, we attached a bungee cord to either end of the metal bar, so that as the bar moves backwards it puts tension on the two bungees.
When the gear is released (as explained in the last entry), the axel can turn freely and the bungees snap forwards, pulling the bar with them. The bar hits the tennis ball and shoots it along the trough and out of the robot. By the end of the week we had a robot that could shoot! Our next goal is to build the top part of the robot, which will collect tennis balls from the loader and drop them into the shooter. |
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