Introduction to FRC Robot Inspections Presented at CT FIRST University Day Mike Betts 9/19/2010

Disclaimers The information in this presentation is based on previous competitions. FIRST changes the rules of the game every year. Your mileage may vary… Some opinions are those of the author and may not reflect those of FIRST or other Robot Inspectors.

Links to Monitor Bill’s Blog: http://frcdirector.blogspot.com/ FIRST Forum: http://forums.usfirst.org/ Chiefdelphi Forum: http://www.chiefdelphi.com/forums/index.php Game Manual: http://usfirst.org/roboticsprograms/frc/content.aspx?id=452 Team Updates: http://usfirst.org/roboticsprograms/frc/content.aspx?id=450 FRC Email Blasts: http://www.usfirst.org/roboticsprograms/frc/emailblastarchive.aspx

The Role of Robot Inspectors To help teams get to the playing field in a safe and equitable manner.

Robot Inspections

Robot Pre-Inspection (Voluntary) Any team may ask for a quick safety inspection before going to the practice field. Is the Battery secure? Is the 120A Circuit breaker in an easily accessible location? For robots using pneumatics: Is the PRV present and the vent valve easily accessible? For robots using stored energy devices that are “charged” before the match: Is there some sort of safety interlock device preventing accidental discharge or firing? This inspection should last less than two or three minutes.

Robot Pre-Inspection (Voluntary) There It is not anticipated that there will be any mandatory safety inspection requirement this year. However, any field, pit or event official may request a robot safety inspection if he or she believes that a robot presents a potential hazard to others. The FTA may decide to make this inspection mandatory for any robot at his or her discretion.

Network and Encryption Inspection There is usually a dedicated kiosk for this inspection. This kiosk is usually self-serve and not staffed. A robot will not function on the field if it does not have: The correct cRIO firmware. The correct Driver’s Station software installed. The correct network addresses. The correct encryption key. It is usually a team responsibility to utilize the kiosk and insure compliance before their first practice match.

Robot Inspections Your team should try and begin your robot inspection as soon as possible on Thursday. This is critically important for rookie teams. The sooner you begin inspection, the sooner you will know what needs to be done in order to compete. Also, this allows inspectors to flag teams who need additional assistance and get them the help they need.

Why Start Inspections Early? The event planners will usually have quite a few inspectors volunteering on Thursday and only a skeleton crew for Friday and Saturday. Teams who have waited until Friday morning to complete their inspections can become very anxious as their first match is approaching and there are no available inspectors to look to their robot. Many of the inspectors are also team mentors. They will appreciate being able to rejoin their teams as soon as possible. Lastly, there will always be a few stragglers (usually rookies). If the majority of teams have passed inspection, the inspectors are able to concentrate on the needs of the few remaining and allocate the resources they require in a more focused manner.

There is Nothing Special About Thursday… After you have completed inspection, you are encouraged to continue working on your robots through the end of the competition on Saturday. Merely come up for re-inspection. Tell the inspector what you changed. In most cases, no other action is necessary.

The BOM The number one reason why teams do not pass inspection on Thursday has constantly been not having a Bill of Material. While your team is uncrating the robot, please send one team member up to the inspection desk with a thumb drive containing your Bill of Material (BOM). Your file will be copied into a common directory and renamed FRCxxxx_Hartford.xls (where xxxx is your team number) IAW Team Update 11 (2010).

The Inspection Checklist Teams should download and review the Inspection Checklist before their event. A good exercise is to have one or two students play the role of inspectors and go through the list in a mock inspection. Two or three students should play the role of the Pit Crew and answer the questions posed by the inspectors. You will be amazed how effective this can be. This should be done before you ship your robot.

The Inspection Process Submit your Bill of Material (BOM). When ready, bring the robot up to the inspection station. Your robot’s bumpers should be removed and carried (along with all fastening hardware) separately. Your 12V battery should be removed and left in the pit. Your operator's station can be left in the pit. At the Inspection station: If required: Safety check as per <R97>. Size check (size box). Weight check (scale). Both the robot and the bumpers will be weighed separately and both weights recorded. Frame perimeter check (level). Return to your pit. Reinstall your Battery and Bumpers You will soon be visited by two inspectors.

The Inspection Process After your team has returned to the pit, your inspectors will review your BOM and then visit your pit. The inspectors will want to communicate directly with the students. Mentors can help by stepping back and give the team room to work. If the inspectors wish to talk to the mentors, they will ask the students to invite them over. The inspection will roughly follow the “2010 Inspection Checklist”. The students will feel more comfortable if a mentor has taken them through a dry run before coming to the competition. After completion of the check list, the students should call their mentors back to the pit and explain what needs to be done (if anything). The inspectors will stand by to answer questions. After all parties have a clear understanding as to what needs to be done, the inspectors will return and begin this process with another team.

The Inspection Process After your team has corrected or addressed the issues, send a student to the inspection station and let us know that you are ready. As soon as an inspection team becomes available, they will come to your pit and re-inspect the outstanding items. Note that the inspection team need not be the same as you started with. Sometimes this process takes more than one iteration.

The Inspection Process Review the inspection checklist with the students, mentors and inspectors. The lead student and lead mentor both sign the checklist where indicated. The final inspector signs the checklist where indicated. The inspector gives the team a sticker for their robot and initials it. The color dot is usually reserved for Saturday re-inspection.

The Re-Inspection Process (Random) The FTA and/or Head Referee can request a re-inspection at any time. This is usually the inspection of a specific component or mechanism and is handled on a case by case basis. If at any time during the contest you modify your robot, a team should request a re-inspection. Let the inspector know what you modified. Re-inspection after modification may require a robot to be re-weighed or re-sized at the discretion of the inspector.

The Re-Inspection Process (Saturday) On Saturday, at the end of your last qualification match, please bring your robot directly to the inspection station for re-inspection. Do NOT visit your pit. Do NOT remove your bumpers. Do NOT remove your battery. Please DO bring your operator's station with you. At the Inspection station your robot will be reweighed. Since your bumpers were weighed at the Thursday inspection and we have a good idea how much a battery weighs, this check gives us a good insight if any uninspected modifications have been made. One of our more experienced inspectors (usually the LRI) will briefly look over your robot and may ask one or two random questions. In the event that the weight check and or visual indicates that uninspected modifications have been made, your team may be taken aside for a more detailed re-inspection, After passing re-inspection, you will get a colored sticker to place on your robot. Return to your pit and prepare for alliance selections. And Good Luck!

These Next Topics May Not Be Inspection Issues Although we try to help teams as much as possible, your inspectors will only require that your creations are safe and adhere to the rules put forth by FIRST. These next few subjects contain good advice but may not be enforceable by your inspectors. A safe robot is not necessarily a working robot…

Build a Robust Robot Question: What is the only common property possessed by every competition champion robot since FIRST was started in 1991? Answer: At the end of the competition, the robot was still working!

Battery Restraint Strength (Going Turtle)

Battery Restraint Strength (Going Turtle) Consider this free body diagram. The angular speed of a 44 inch uniform rod after falling 90 degrees at 1g is: radians per second

Battery Restraint Strength (Going Turtle) This means that the linear velocity at the end of the robot is 5.73 m/sec. The deceleration if effect on the battery will be dependant on robot design and battery placement. Somewhere between 30g and 130g (or more) Velcro will very likely fail.

Bumper Strength One way to determine how good your bumper connection needs to be is to do a little math. A robot being driven with CIM motors via an AndyMark Toughbox transmission (12.75 gear ratio) can achieve speeds of 11 ft/sec. This is the speed at which a robot could hit a wall or another robot (traveling at the same speed, bumper to bumper contact).

Bumper Strength The equation for the velocity, v, of a falling object after it has fallen a certain distance, h, under a uniform acceleration (gravity), g, is: v = sqrt (2gh) Solving for h we get h = (v**2) / 2g So, for v = 11 ft/sec we get h = 1.9 ft

Bumper Strength A drop from 1.9 feet is the abuse that your robot’s bumpers must absorb many times in each match! Consider also that, due to your robot being hit while an the bump, this force need not be orthogonal…

This method of analysis applies to more than just bumpers! 140 lbs @ 11 FPS + Motor Torque and Reflected Inertia Reaction Force On Arm The rotational torque on this shoulder mechanism will be considerable!

Physics Lesson: In less than 2 seconds, this robot will hit the wall and break 11 welds. Game Over…

Some Inspection Items That Always Cause Heartburn <R16> Bumpers Batteries Pneumatics Safety Miscellany

Protrusions outside the Frame Perimeter (<R16>) Not OK OK OK Not OK

Bumpers From “Bill’s Blog”, August 30, 2010: [for the 2011 season] “Robots will be required to have bumpers, so buy your pool noodles now while they are still in season.” This implies that bumper requirements will be largely unchanged from 2010. See <R07> from 2010 FRC Game Manual.

Bumpers protect both robots and the field… Not Legal As Shown

What FIRST Wants

C Channel Bracket Mounting A C channel mount requires additional fill to meet <R07> part M: The entire length of the BUMPER backing must be supported by the structure/frame of the ROBOT. i.e. the backing material must not be in “free space” between or beyond attachment points.

C Channel Close Up 1

C Channel Close Up 2 Note that this backing redefines the FRAME PERIMETER.

Angle Bracket Mounting The angle brackets allow easy disassembly and a flush mount to the frame. This design also allows for quick release fasteners:

What not to do… This example is not legal on at least two points. The “hard parts” of the bumpers overlap. The “soft parts” of the bumpers do not totally cover the corner.

What FIRST Wants Keep the “hard parts” out of the corners Cover the corner completely with “soft parts”

Is this gap allowed?

Is This Legal?

Good protection of the corner.

A pretty good idea…

Know the Game Specific Rules! (this example is from 2010)

Robot Signal Light (RSL) Solid ON = Autonomous Enabled Solid ON, but blinks OFF every 1.5s = Teleoperated Enabled Slow Blink (900ms on/ 900ms off) = System Disabled; caused by system watchdog, user watchdog or Driver's Station set to disabled Fast-Slow Blink (200ms on/900ms off) = Low Battery (<12V) or no user code AND system disabled either by system watchdog, user watchdog, or Driver;s station set to disabled Fast Blink (200ms on/200ms off) = System error: No driver's station communication, bad cRIO Image, bad team ID, extensive comm. error Jumper Pins 1 and 3

Stored Energy One of the most frequently misused stored energy devices is latex surgical tube.

Think You Know Better? Early in January, you will study the game and decide on a strategy. Just as “form follows function”, you will design a robot to achieve that strategy. In most cases, you and your team will have been reading, eating and breathing the Game Manual for over six weeks prior to your competition. You will have read every update to see how it affects your design. You will have posted questions to the official Q&A forum and waited in anticipation of the response.

You DO know better! Some of our robot inspectors are FRC mentors and some are not. Regardless of their background, they will not have studied those rules pertaining to your robot design as carefully as you have. It is very likely that you will know the rules better than the person inspecting your robot!

What to Do If You Disagree Show us the rule in the 2010 Game Manual. Show us the Update. Show us the Q&A post. Show us the FIRST web page or associated document. Show us the FRC Blog entry. Invoke <R94>

<R94> If a ROBOT is rejected by inspectors due to a safety issue or concern related to the team’s method of storing energy (see Rule <R01>), the concerned items must be disabled or removed from the ROBOT before it can compete in a MATCH. The team bears the burden of proof that such a rejection is not valid. Teams should be prepared to provide justifiable test data or calculations during inspection to support their design.

What NOT to do… Do not get angry with your inspectors if you do not agree with a rule. In many cases, we will dislike the rule just as much as you. Remember that you had the power to control your team’s destiny.

Postscript: Team Communications The Main Contact is NOT an honorary position! From “Bill’s Blog”, August 25, 2010: A brief word about Main and Alternate Contacts:  From FRC’s point of view, the Main and Alternate Contacts are our primary communication link with teams. Main and Alternate contacts receive regular emails that we expect them to share with all team members.  We send them questions to answer on behalf of your team, they are the gatekeepers for team information and they sign your team up for events.   We want teams to give the title Main Contact to the adult on your team who is the best communicator. If you have someone who is the best mentor, or the most valuable resource, or the person you most want to honor for their participation, please feel free to create your own title for them (Supreme Commander is always good), but assign the job of Main Contact to the adult who is most likely to check their email and forward information to everyone who needs to know what FRC sent your team.