2023:Acquisition

Introduction:

Our Subteam, the acquisition team, is part of the larger subteam called Game Piece, in which our team, lift, and robot controls work together to acquire and score both game pieces. Since acquisition is the first mechanism that touches the game piece during an actual match, we decided to get a rough idea of what the acquisition mechanism would look like before beginning the other mechanisms. We ran through the mechanical constraints and robot restriction manuals, and took extensive notes (see below).

Mechanical Constraints

-Although not all of these pertain to acquisition, it was important for every student to understand the limitations of the robot design.

5.8 Game Pieces -

• Cone 1’ and 13/16” (33 cm) tall, 8 and 3/8” ± 1/8” (21 cm) wide, bottom hole is 6 and 5/8” (17 cm) circumference, top hole is 1 ¾” (45 mm) circumference
• - Cube is 9.5” ± ¼” on all sides

5.4 Charging station

• -Charging station: 8ft. ¼ in. (~247 cm) wide, 6ft. 4 1/8 in. (~193 cm) deep structure
• -Main pivoting surface is 8 ft. (~244 cm) wide and 4 ft. (~122 cm) deep. Pivots +/- 15° about the long axis
• -the center of the charging station is 8 ft. 2 5/8 in. (~251 cm) away from the far edge of the GRID’s tape line and centered in the width of the Community

7.1 Robot Restrictions

• - Bumpers need to be low and fully below 7.5” above the ground
• - Bumpers may not fall apart in a way that exposes corners or makes the team number or alliance color undistinguishable
• - Robots can’t intentionally detach or leave parts on the field

• -Start 4’6”
• -Robots can’t be taller than 6’6”
• -Robot maximum frame perimeter is 120 in.
• -Robots can’t extend more than 48” outside of the frame perimeter
• -The robot cannot extend over a curved frame perimeter
• -nothing dedicated to destroying robots or game piece
• --no purpose alliance only in our community zone
• -robots are allowed to grab, grasp, attach to, and deform the game piece (vacuum suction is allowed)
• -robot cannot interfere with field sensors
• -1 game piece can be held at a time

• -Can launch game pieces in community zone

9.2 ROBOT safety and damage prevention

• R201: Do not damage the rugs.
• ITEMS NOT PERMITED:
• Most is common sense but ones that stick out are written below
• -Shields/materials designed or used to obstruct or limit the vision of the drive team and their ability to drive the robot safely
• -Exposed lasers other than class one  
• -No EMP jamming devices or devices that can interfere with remote sensing capabilities and no physical objects that can mess with a robot's sensors ex: retro reflective tape
• - “exposed, untreated hazardous materials (e.g., lead weights) used on the ROBOT. These materials may be permitted if painted, encapsulated, or otherwise sealed to prevent contact. These materials may not be machined in any way at an event.”
• - “High intensity light sources used on the ROBOT (e.g., super bright LED sources marketed as ‘military grade’ or ‘self-defense’) may only be illuminated for a brief time while targeting and may need to be shrouded to prevent any exposure to participants. Complaints about the use of such light sources will be followed by re-inspection and possible disablement of the device”

9.3 Budget Constraints and Fabrication:

• - No individual non-KOP item or software should have a Fair Market Value of over $600, but components bought in bulk can cost over $600, if one item doesn’t cost over $600.    
• - Fabricated parts made before kickoff are not allowed, but some exceptions are bumpers, fabricated items containing one COTS electrical device, and operator console.    
• -During an event the team can only work on their robot or robot elements while the pits are open, unless it is for software development or charging batteries.  
• - Create new designs and software, unless they’re available publicly prior to Kickoff

9.4 Bumper Rules:

• -Bumpers should protect all outside corners of the frame perimeter  
• - Bumpers must extend at least 6 inches from frame (side cannot be shorter than 6 inches)
• - no more than a .25-inch gap between inside of bumper and outside of frame perimeter- if side is shorter than 12 inches, must be fully covered in bumper
• -Bumpers should stay low, contained within the area from the ground with a volume of 7 ½ in
• -Bumpers should not be able to move, and bumpers should be able to be removed from the robot
• -Bumpers indicate alliance color and team number (number MUST be consisting of white Arabic numerals ONLY, at least 4 in. high, at least ½ in. in stroke width, cannot wrap around corners less than 160 degrees)
• -Bumpers cannot weigh more than 15 lbs. (including any fasteners/things that attach bumpers to robot.)
• -Must be backed by ¾ in. thick plywood, OSB, or solid wood, with the allowance of small mounting holes.
• -Hard bumper parts cannot extend more than 1 in. beyond frame perimeter
• -Pool noodles must be used as a cushion material, and must be covered by a “rugged, smooth cloth)

Important Field Dimensions

• -From edge of Grid to edge of Charging Station: 60.69 in.
• -From edge of Charging Station to Barrier: 59.39 in.
• -From edge of Charging Station to Wall: 59.39 in.
• -Charge Station Platform: 4ft x 8ft
• -Charge Station with ramps: 6ft 4 1/8 in x 8ft 1 ¼ in
• -Height of second level platform: 1ft 11 ½ in
• -Height of second level Cone Node: 2ft 10in
• -Height of third level platform: 2ft 11 ½ in
• -Height of third level Cone Node: 3 ft 10 in
• -Horizontal distance to front edge of second level platform: 1ft 2 ¼ in
• -Horizontal distance to second level cone node: 1ft 10 ¾ in
• -Horizontal distance to front edge of third level platform: 2ft 7 5/8 in
• -Horizontal distance to third level cone node: 3 ft 3 ¾ in

Legacy Research!

-We started by defining the constraints to our mechanisms (ex: frame perimeter, field dimensions, weight limit, etc) to help us evaluate what we can and cannot do. Then, we split into groups, and each designed our own robot. We came up with what we each wanted to see, especially in terms of mechanism concepts. Then, we all met and discussed each mechanism and ranked them on highest interest. After that, we evaluated their practicality and then we used that information to help us decide what ideas to focus on. Next, we did legacy research. We looked at 2011 robots, due to the inflatable game piece, 2015 and 2019, because of the general intake/lift mechanisms and similar movements, and we looked at 2018 robots due to the cubes and the lifts. Next, we looked at VEX 2018 (cones) and FTC 2022 (cones). By the end of our research, we were able to identify the dimensions that we would be operating on the drive base with (11.75 x 10 inch cutout)

After researching, we were able to identify some constraints:

• we can and should fit into our bumper cutout
• We do not need to be larger than our cutout mechanically
• need a strong connection to the lift
• need to keep the weight of the gripper near the back
• try to keep the CoG centered to limit twisting
• pistons are great for this kind of actuation.

Sunday 1/8/23

We started off strong with a small-group brainstorming session, then presenting our ideas to the whole group. We decided on what feature(s) we were sure we wanted on the robot, which would up being swerve. Then, we tested the properties of our game pieces to see how well then could be pushed around and how easily the cone could be flipped. To do this, we used our 2022 robot to simulate our soon-to-be 2023 robot, as they will both have swerve drive bases, as well as a similar bumper height. The Mechanical group also did some conceptual prototyping for the gripper to see what would work best with both the cone and the cube. We decided that our best bet would be to have one gripper for both game pieces so that we didn’t have to worry about switching between two intakes.

Tuesday/Wednesday 1/10/23 - 1/11/23

Over the last two days, we have been heavily focused on prototyping. We have determined the following:

• Green 3" compliance wheels work best for our allocated space
• Ideal cone compression: 4.5 to intake, as tight as possible to pick up cone
• both cones and cubes are best to pickup at 3 inches off the ground
• worked with drive base team to ensure that we have the a mechanism that firs

Thursday 1/12/23

• Our intake prototype is now mounted on a wooden beam, and we experimented with different widths between the wheels of the intake to see what would grab the cone best.
• We found a different type of slider that will most likely be more robust and less wobbly than our current slider, so we may be switching over to that shortly. We also did some calculations and found that 2.75” would be the ideal stroke length for our gripper’s pistons, and we also discovered that the distance between the slide and the wheels needs to be increased significantly (to about 8.5”)
• . We discussed whether it would make more sense to consistently flip the cone no matter what so that the program can stay simpler.

Saturday 1/14/23

Problem Discovered: Our prototype slide was not stable. Had a lot of give in the vertical direction. We dived into the possible causes and discovered the following:

• Our original prototype used drawer slides. Draw slides were not made to handle torque, and considering the weight of the prototype, the force on the end of the mechanism was not easily supported by drawer slides.
• by reinforcing from the back, we gave ourselves only one direction of attachment points.

Some of our solutions included:

• Changing out the drawer slide for linear rails (must purchase)
• For prototyping purposes, adding a channel of 80-20 to replace the drawer slide is more stable
• On the final, attaching to the top and bottom, so that attachment points are in two different directions with two different normal forces acting upon the gripper brackets, we can eliminate some of the wiggle

We began making these adjustments to the prototype, had integration, and then did research into other types of linear rails.

Sunday 1/15/23

We finished the prototype and made the necessary adjustments. We then dived into the testing for the majority of the day. Our results allowed us to learn some critical points.

1. When you intake the cone, the cone MUST be lifted off the ground due to the kinetic friction between the cone and the carpet.
2. With the cone, we need two positions: first position for a wider grip, allowing less driver precision, and one position to squeeze the cone as tight as we can.
3. moving the robot into the cone makes the cone much more likely to tip towards the robot when picking up (solution: add a physical hard stop to stop the rotation of the cone?)

Made necessary changes to the prototype and made a plan to finish the design by Saturday at the latest.

There was a lot of discussion about switching from piston actuation to Lead Screw to give us more variability.

Tuesday/Wednesday 1/17/23 - 1/18/23

Having thought about it more, we think it would probably not be as good of an approach to go with a lead screw design in the gripper. Here were our thoughts.

• It adds more complexity for controls and design, which based on the rest of the complexity of the robot, could stress our ability to pull off the design well.
• It is something that we would not be able to prototype for some time. We would have to source lead screws and that could take some time.
• I think if we went with a cylinder based approach, we could have a functioning gripper much sooner and could iterate on the design faster.

There were also some other gripper prototype configurations that we think would be good to try out to collect more information.

• Try using two wheels per axel to improve gripping on the cone.
• Try a second set of larger diameter wheels in the back of the gripper to increase gripping force as the cone moves farther into the gripper.
• Try the gripper at an angle to the ground to remove the issue of the cone dragging on the ground as the drive base moves forward.

We also had a concept for a prototype that could help with the acquisition of game pieces that might otherwise hit our bumper and bounce off.

• Try over the bumper belts to try to center the cone into the gripper, that are not part of the gripper design.

Testing/Prototyping Reflection:

• The wheels can definitely be sped up and will help things        -Right now the one set of wheels is acting like a fulcrum for the cone and spinning under the frame as it contacts the carpet. Two immediate thoughts to solve this are: a second set of harder durometer wheels above the current ones to keep the nose of the cone upright, a rod or “backboard” underneath the gripper to act as a hardstop, or a combination of the two.        -If we add a second set of wheels, dropping this first set lower to the carpet will help as well.        -Interested to see if bumpers on either side help funnel the game pieces in or cause them to bounce astray        -Once we have a gripper frame, we can route the belting so it doesn’t interfere. CNC and an intermediate axle this weekend?
• the 4" wheels gripped the cone better, however they do not fit within our allocated space, so we are going to sacrifice grip in order to properly fit.
• At the end of the night Wednesday, we popped two cubes. It seems as though the cubes got snagged on the back piece of metal and when it got shot out, it ripped.

Thursday 1/19/23

We had our biggest push in detailed design tonight. First, we separated our subteam into three groups!

1. Detailed Design

• We finished a basic CAD Design
• Decided to put active wheels at the front of the drive base to allow for us to have a wider reach and a lighter gripper!
• Began adding details, bolts bearings etc
• Communicated with drive and determined the best way to place our intake within the bounds
• communicated with lift subteam to create an attachment plan

1. Research for Linear Rails

• we found three linear rails that we liked
• https://www.vevor.com/linear-guide-rail-c_10531/sbr16-1000mm-2-x-linear-rail-4-x-bearing-blocks-cnc-router-bearing-sbr-16uu-p_010694903166?adp=gmc&utm_source=google&utm_campaign=18873377992&utm_term=&gclid=EAIaIQobChMIl_nFjoPV_AIVQhbUAR3YrgpHEAQYASABEgIcevD_BwE&v_tag=ac1582a0-98ca-11ed-9549-6d0614acde99.1
• https://www.amazon.com/OUYZGIA-MGN12H-Printer-Machine-Carriage/dp/B0B1LBV3M3/ref=sr_1_6?crid=35VD3603ZPJ0Z&keywords=linear%2Brail&qid=1674178962&sprefix=linear%2Brail%2Caps%2C85&sr=8-6&th=1
• https://www.amazon.com/GUWANJI-SBR16-1200mm-SBR16UU-Bearing-1200mm/dp/B08BFXBB46/ref=sr_1_3?crid=D8U2S7T4KRUG&keywords=guwanji%2B16mm%2Blinear%2Brail&qid=1674179939&sprefix=guwanji%2B16mm%2Blinear%2Brail%2Caps%2C73&sr=8-3&th=1
• After we met with the entire team, and weighed out the pros and cons, we decided on the second design because it worked better for our parameters of weight, size, and support.

1. Prototyping

• We did various prototypes throughout the night. The first one solved the cube popping issue. The second one tested different intake angles to allow for us to lift the cone off the ground so it doesn't drag on the carpet. The last one tested the gripper within the bumper cutout (roughly) to validate that our mechanism fits and functions within context.