Brick is our third robot and build for the 2015 Recycle Rush season. Unlike the previous robots we didn't name our third robot after something related to de Dutch painter Rembrandt van Rijn. At the start of the 2015 building season we received some sad news. Our hearts were filled with sorrow on hearing the news about Ben Poole passing. Ben has meant a lot for us when he was a mentor for team 122 - NASA Knights. Without him even knowing, he made Team Rembrandts what it currently is.
“My teachers were some of the greatest influences in my life. By challenging and trusting me. These mentors got me to understand, that I could do anything I put my mind to!"
Ben was one of our first teachers, and one of the best we ever had! With his knowledge, experience, tranquility and integrity he was one of the most inspiring people we’ve known. By his friends he was also know als Ben "Brick" Poole. So, in honor of him we named our robot "Brick". With Brick we competed at the Virginia Regional in Richmond and the FIRST Championship 2015 in St. Louis. At the start of the Virginia Regional 1 front plate was still missing on the robot. This front plate had a special text on it, "Ter nagedachtenis aan Ben "Brick" Poole" which translates too "In memory of Ben "Brick" Poole". To make it even more special that the father of Ben Poole (also mentor of team 122 - NASA Knights) was given the honor to place the front plate on the robot. During the Virginia Regional we managed to get into the finals and eventually we got the Finalist Award and the Engineering Inspiration Award. After the regional, the front plate was removed from the robot and given to the father of Ben Poole. With a special design holder the father could give the front plate a special place. Thanks to the Engineering Inspiration Award we got qualified for the FIRST Championship 2015. Here we won the Team Spirit Award sponsored by Chrysler in the Tesla Division.
We came quickly to 3 type of robots that we could build for the Recycle Rush game:
- A stacker robot
- A recycling container specialist
- A Hydride (Stacker robot and recycling container specialist together)
After some discussions and considerations we decided to build a stacker robot. But if the stacker robot is complete finished. So mechanical, electrical and programming are finished then we may try to make an extra sub unit which will make the stacker robot into a hybrid. This will only happening if the robot is below the maximum weight. We decided that we do nothing with the litters.
Further we divided the strategy into autonomous and teleop.
For autonomous we decided to go for the STACKED TOTE set. To accomplish this the robot starts in front of the left yellow tote. When the autonomous period starts the robot will pick up the FIRST yellow tote then the recycle container will be pushed away. Then the robot picks up the second yellow tote and again push the recycle container away. Finally the robot will pick up the third yellow tote and drives to the auto zone. With this we want to score 20 points.
For teleop there were multiply strategies. 1 of the strategies is to pick up the STACKED TOTE set from autonomous period and place it on the step or on 1 yellow tote that is placed on the step by the other alliance. Another strategy is that the robot must stack totes from the landfill and the feeder station. Where in the feeder station is the most important of the two. The final strategy is that separate from the lift system at the front of the robot, there must also be a system to drag totes on the scoring platform. This is useful when the 2 feeder stations are occupied and to get the tote from the landfill. It is also a backup system for when the lift system is broken. By all strategies the lift system must carry minimal 3 totes supported and the system to drag the totes from the landfill must be able to drag 2 totes simultaneously.
This is our smallest, most compatible and innovative modular electrobox since 2013. A combination of 3D printing, laser cutting of Acrylic and the new control system made this happen. Having mechanical, electrical and software students working parallel on the robot has never been so easy. Thanks to FIRST and their suppliers, some components were changed. So, was this the FIRST year that the FRC teams were going to use the RoboRIO, the Power Distribution Panel (PDP) got smaller and new motor controllers (The Victor SP) were introduced. This all made it possible to design a very small, compatible and innovative modular electrobox.
Individual Controlled Lift
The lift is individually driven by one RS-550 motor on each side. The height is actuated by a PI controller with a first or second order reference signal. For the arms we started of with 2mm Aluminum sheet metal and Perspex clips. After testing we found out that the Aluminum sheet metal wasn't stiff enough when we were lifting 4 totes. So after the robot was send to Richmond for the competition we worked on a solution. We choose to switch from 2mm Aluminum sheet metal to 7mm carbon fibre. But because full carbon fibre was pretty heavy and not necessary, we went for a carbon sandwich (1mm carbon on each side with 6mm foam in between). This made the arms light and strong enough. Next to that we changed the Perspex clips, because after a few rounds of stacking the totes the clips broke or were damaged. So we replaced them with springsteel clips, we tested two kind of thickness 0,5mm and 1mm. After testing we found out that the 0,5mm clips did't have enough strength to hold the 6 tote stack when driving. Through the high torsion, the plates will fold when driving the totes around the field. This is because the moment of inertia isn’t big enough to hold this much weight. With the 1mm plate the moment of inertia is increased and the plates where strong enough to hold the 6 tote stack when driving.
After a few matches we saw that the PI controller of the lift was constant correcting the lift while driving. So we programmed the 2 pneumatic brakes that were on the lift, so that as soon the lift started to drive the brakes were active and the RS-550 motors of the lift system weren't constantly powered.
Besides picking totes up of the field, it is also possible to get totes at two sides of the game field by the human player. The team strategy decided that the human feeder station is used to feed totes and stack them fast and easily. But there was a problem with the feeder stations, if the totes are sliding down and fall on the ground they can tip over and stand in the vertical position instead of the horizontal position. So, we decided to make a tote guide for the human feeder station. With this we could simply drive our robot with the back against the feeder station and the totes slide very easily in the lift mechanisme.
This was the first time designing our robot completely out of sheet metal. Implementing whatever we wanted in our robot in a way that was unique, aesthetically and metric compatible has never been so easy. Eventually being able to anodize our robot orange & black was the cherry on top. The drivetrain is the base of the robot and it must be able to carry everything we place on top of it. We made some calculations and did some testing to see what works the best. The placement of the tote relative to the drivetrain is important because of the tipping. The conclusion is that 66% outside the drivetrain is the best solution. When it’s 66% outside the totes can be easily placed on the step without pushing. The point of gravity will be closer to the drivetrain so the chance of tipping over is smaller than when it’s 100% out the drivetrain. 50% is not enough because then a mechanism is needed to push the totes out the robot. By testing these three possibilities we could see the behavior of the totes while braking, and verify our assumptions. For the wheels we did not chose to use Omni/mecanum wheels because we expected that this would make driving accurate in autonomous difficult. Colson wheels have a lot of friction, but weren’t easy to order for us and we wouldn’t have them delivered on time. The friction of Plaction and Performance on HDPE has been tested and Performance wheels had a little bit more friction. There has been chosen to use Performance wheels, because these were less expensive and more wear resistant. The wheel will be powered 4 CIMS total. 2 CIMS on each side of the robot.
We placed 2 intake arms on the front of the drivetrain. With these intake arms we could make sure the tote is in the center of the lift. Thanks to the wheels on the intake arms we can take a tote into the robot without driving against the tote or take a tote out of the robot. After some testing of the feeder of our robot we noticed that the first tote slides outside the lift mechanisme and with the intake arms we can take it back into the robot. During the autonomous period we use the intake arms to take in the yellow totes faster but also to spin the recycle container out of the way of our robot. Thanks to this we were able to stack 3 yellow totes in autonomous period.
We decided to use 2 hook systems on the backside of the robot. This was our back-up system incase our lift broke down during the match. The hook system is used to take one or two totes. The hook systems can grab a single tote per hook, and by this the robot can drag them onto the scoring platform. Because our robot was already over the weight limit without the hook system installed on the robot we decided not to use them. In the end we borrowed our hook system to team 3361 - Governators. Because of a blizzard they weren't able to build there robot. So, we helped them build a robot during the practice day. Together we were able to get their robot working.