Robot Preparation for the VEX World Championship/ US Open. Lessons learned over the past 6 years by David Kelly 2013 VWC, Teacher of the Year

Transcription

1 Robot Preparation for the VEX World Championship/ US Open Lessons learned over the past 6 years by David Kelly 2013 VWC, Teacher of the Year

2 Re-designing Re-designing your robot to a new concept yields about a 10% chance (random estimate) that your new design will perform better than the design you took apart. Even if the concept might be better - you will not have time to perfect it to be more competitive than the concept which qualified you for the big event. Re-designing practically eliminates all your driving practice you have gained throughout the year and takes away most of the practice time you will have. Re-designing practically eliminates all your programming you have gained throughout the year and takes away most of the programming time you will have. It may seem like you have a long time between the time you qualify and the Big competition, but it is less than 1/10th the time you have had to get to this point.

3 Use your time for PREP P- Programming R - Repairs E - Engineering Notebook P - Practice

4 Programming For most of us programming is the most tedious part of the robot design. How many times have you gone to a competition and said - I wish I had more time to program, but I just finished my robot? If you stay away from re-designing - you have a robot ready to program - it may be tedious, BUT: There is a reason they call it the Autonomous Bonus - because it is a bonus - the opponent alliance can not take those points away from you. Many matches are won or lost because of the autonomous bonus.

5 Repairs The worst feeling is spending huge resources and time to get to the BIG venue and your robot does not move while you are being watched on a Webcast throughout the universe. The two most common causes of robots not moving are: Motors Connections

6 Repairs - Motors Motors stop most often because of overheated PTC s ( Thermo-resistors) This heat comes from pushing too high of a gear ratio or friction, look for: Misalignment of bearings, bent frames, bent arms, bent drive shafts, bearings in which the holes are too tight from the molding Chain on sprockets too tight- binding drive shafts or spacers/shaft collars putting too much pressure on the structural metal Drive shafts without bearings or only 1 point of support Any structural element should be aligned, braced, and secured with nylock nuts to prevent binding

7 Repairs - Motors (continued) If you have checked whatever the motor is actuating by disconnecting the motor and competing the motion (spinning the wheel, lifting the arm, etc.) by hand and everything seem to move with very little resistance and the motor still times out. It maybe the PTC on the motor has reset too many times and it is time to replace the motor. Or, it may be time to think about the gear ratio you have. Any clicking motor is NOT good. Be sure to check all the internal gears for broken teeth and replace any gears which you can - or replace the motor

8 Repair- Motors (continued) Also remember motor ports 1-5 are on one PTC in the cortex and motor ports 6-10 are on another, so if you have a system with a lot of current draw split the motors between the 2 PTCs

9 Repairs - Connections Check all wires for breaks in the insulation. A very small break can yield a huge issue, from melting a power expander to a smoking cortex. Secure all wire connections with zip ties or VEX extension wire retaining clips P/N: Label both ends of every wire and label motors with their motor port. Use battery extension cables- it is much easier to replace an extension cable than replace a cortex or a power expander. P/N: Check all pivot points that wire extensions are not pinched or stretched.

10 Repairs - Connections To insure good connections re-look the placement of your cortex: Is the cortex orientated so neither gravity nor the action/reaction of a hard stop in either the forward or reverse direction will cause the VEXnet key to come out of the cortex? If not, re-orientate your cortex or use an USB Extension. j. A USB extension cable may be used for the sole purpose of remote mounting of a VEXnet key. The key must be mounted in the following manner. i. The VEXnet key must be mounted such that no metal is touching the key above the VEXnet logo. ii. We highly recommend that no metal may be within 2 of the top of the VEXnet key. Are any of your wire connections stretched to reach their port in your cortex? Is your on/off switch easily accessible, so if something starts smoking on your robot it can be turned off?

11 Repairs - Connections Batteries Be sure to secure your battery well. There is nothing more scary than seeing your robot drag its battery around on the ground during a match - knowing at best it can come out - at worse it could snap the battery port in the cortex. The new battery clips P/N: work well, the linear motion gear box P/N: works well with non-slip matting and a ziptie to secure the battery in place and the old battery straps P/N: are marginal

12 Repairs - Connections The most common cause of a failed field communications is a battery issue, either batteries with low voltage in the joystick, or low battery voltage for the cortex. All teams at minimum should have a multimeter/battery voltage meter to test their batteries. (also check all your battery wires and connection clips) Even better, purchase a battery capacity tester similar to the Battery Beak at Field control connection issues are rarely the field control, if you have been having random disconnects during the season, it may be a faulty competition port connection on your joystick and it could be worth investing in a new joystick before your competition

13 Engineering notebook It is very easy to ignore your engineering notebook after you have qualified for the Big event. But at the large events judges use the engineering notebook to determine who they are going to interview. Use this time you are not frantic building a robot to develop goals and objectives and reflect in your notebook. DO NOT neglect your engineering notebook. The US Open requires a video to be submitted in order to be judged - be sure to check the information on their event page. Helpful hints for the engineering notebook

14 Practice Practice, Practice, Practice It sounds simple, but it is the number one thing teams have a tendency to overlook. I can not tell you in my 20+ years in competitive robotics how many times I have seen an amazingly engineered robot look completely silly when faced off with a mediocre robot with a talented drive team and a great game strategy. Have the coaches practice with the drivers, so instructions are clear and easy to follow. Have coaches practice watching the things the driver is NOT watching. When practicing try to simulate actual match conditions as close as possible, but in any case - practice, practice, practice until you become one with you robot!

15 Checklists My last piece of advice is develop 3 checklists: - Things to bring to the competition - Things you need when you are leaving for your match from the pits (you could be a LONG way from your playing field) - Things you need to check on your robot when you place it on the playing field* *Some teams even print off these lists on decals and stick them on their robot. Be sure to include on your checklist - HAVE FUN AND ENJOY THE EXPERIENCE!!