Last active 5 weeks ago

  1. 5 weeks ago
    Mon Dec 10 23:33:12 2018
    A Alex241N posted in BATTERY FIX.

    This really isn't good advice to be giving in a forum composed mostly of Young adults- especially with the lack of safety warnings or clear and proper notation of procedure.

    Plugging LiPo batteries directly into each other can produce a mild explosion and flame.

    You should be supervised, an in an area lacking in flammable materials, you should be wearing gloves and safety glasses.

    The method can work, no disputing that. Just make sure that you know why the battery doesn't work before you try this fix.

  2. 3 months ago
    Wed Oct 10 20:40:37 2018

    @Anomaly If nobody responds the first time, you probably shouldn't be posting it a second time.

    There exist polite ways to decline an offer for work.

  3. Wed Oct 10 20:39:55 2018

    @DarinSelby I would like to hire an experienced robotic engineer for a few hours, ($100hr?), more if necessary, paid via W.U., to go through the VexRobotics catalog and structural support system, and intuitively suggest some ideas and concepts for building a 4ft. 'Windswimmer', as I'm calling it.
    I've narrowed down what I am needing to these two sources. Though, I am open to other sources for parts as well.

    1. IGUS catalog:
    2. VexRobotics with the VersaFrame System:

    If a 'shopping list' of parts could be dialed-in of what I need to order here, that would be a great beginning. It doesn't have to be precise, just your best educated guess. And, if it doesn't work out, I will buy different structural parts/bearings until it does.
    Okay, what exactly is a 'Windswimmer', anyway? Click here for the animation:

    Why have I designed this? I believe that if this device were to be scaled up to a 'windfarm turbine' size, local flying wildlife would be more protected. The reciprocating airfoils move much slower than spinning turbine blades, though the specific torque is 3X greater. Yes, the reciprocating airfoil is mathematically rated at 3X the power output. See here for more details on that:
    This animation^ only shows how it all works together. The final 4 ft. prototype design does not need to look like everything's been 3D-printed. Just 'erector set' operational, and all built around the Igus bearings that are chosen, functional for wind tunnel testing purposes.
    The only part that will need to be 3D-printed are the 'Savonius Rotor Blades', at the very top of the device. This is my own design to make the curves match that of the Nautilus shell. More for aesthetics purposes than efficiency.
    Here are the different bearings needed for the 4ft Windswimmer prototype:
    (4) roller bearings for main drive shaft
    (4) roller bearings for both airfoils
    (2) cross 'universal' bearing assemblies
    (4) roller/thrust bearings for the crank arms
    (1) main 360* thrust bearing, for complete rotation of the mast into the direction of the wind.
    Your engineering thoughts and robotics expertise are welcome on how to improve upon this design, and the best way to integrate the Igus bearings to be used

    My U.S. Provisional Patent:
    STEP file for 3D printing a 4ft Windswimmer is included in the above link.
    A free online STEP file viewer: http://viewer.autodesk.com/ [/url]
    When you open the .zip file^, 'AssemblyA4.stp' is the main one to view.
    Thank you for your consideration.
    Best regards,
    Darin Selby

    Thank you for posting this opportunity here. You might want to contact one of the Vex U teams directly, as they are University students, often with coursework related to robotics.

  4. 4 months ago
    Fri Sep 14 16:04:23 2018

    @jpearman Well, the final numbers are still being determined, what was put in there for the V1.0 release was somewhat temporary and is probably too high. It will most likely be revised for the VCS October release. So I would rather not say right now. Same applies to the motor temperature reading.

    If I may ask, why as a percentage? Doesn't this make user code written now volatile, if programmers aren't aware of the max temperature change?

  5. Wed Aug 29 13:31:23 2018
    A Alex241N posted in Launcher Ideas.

    If you're going to focus on flags, you'll need to be flexible. It should be hard to prevent you from scoring, or to slow you down.

    If you're using a catapult, you can have at most two shooting positions for the same flag- either while the ball is going up on the arc, or coming down. Making it difficult for you to use one or both of those positions would suffice to slow down your field effectiveness.

    If you're using a flywheel, you can shoot from virtually anywhere on the field. This makes it more difficult to counter strategize against your robot.

    Looking at shooting speed, this year, your rate of fire is virtually unimportant- so long as you're primed to launch the moment you enter your shooting position. As both the flywheel and catapult are capable of this, this is a null point.

    As for launching multiple balls at once, I doubt this tactic will find much success later in the year, as flags will change so quickly and randomly that the added complexity and weight of a dual launcher system would be non- advantageous.

  6. 5 months ago
    Mon Aug 13 07:36:21 2018
    A Alex241N posted in P-Loop programming.

    @tabor473 Exactly. It's a unit conversion from encoder units to motor units. The example you gave I find is the best way to get everything to click.

    I'll add one more point to this. Yes, Kp is a unit conversion. However, it's important to remember that there may be various desirable values of Kp, depending on preferred behavior: fast convergence, less oscillation, less jerk.

  7. Sun Aug 12 14:33:41 2018
    A Alex241N posted in P-Loop programming.

    @alanchan Hello,

    Can someone please explain to me what P loops and PID loops are, and what difference exists between them? Any help will be appreciated.

    A P Loop is a programmed Proportional controller. It uses the error between a desired and current value to modify a parameter through the mutiplication with a constant 'Kp' that is then added to the parameter to help reach that value. In the case of a fly wheel, you try to reach a certain angular velocity, by modifying the 'power' the motors get.

    An I controller is an integral controller. It takes the previous integral sum from the last loop iteration and adds it to the current loops (error times time passed since the last loop iteration) (dt). A constant 'Ki' is then used to modify the controlling parameter through mutiplication with the total error and then added to the parameter.

    A D controller is a differential controller, that takes the previous error Minus the current error, divided by the time passed between those two errors to derive the rate of change. The controlling parameter is than changed by multiplying a constant 'Kd' to the rate of change and that product to the parameter.

    Think of K as a parameter that converts the answer from each controller into a value in the order of magnitude of the controlling variable.

    A P Loop is therefore simply a PID loop without an I or D controller.

  8. Mon Jul 23 19:17:29 2018
    A Alex241N posted in VEX U.

    @tabor473 https://www.vexforum.com/index.php/27203-wpi1-reveal/0

    I apologize. It's been a while since I've competed!

    Pretty neat stuff.

  9. Sat Jul 21 22:10:13 2018
    A Alex241N posted in VEX U.

    This entire year is exceeding my expectations. The possibilities these changes open up towards robot design and pure sensor processing power is insane. With processing of sensor information now allowed outside of the V5 brain, you could conceivably allow a micro controller determine the exact position the robot has on the field, and then relay that information via a single connection back to the cortex. That would allow the micro-controller to handle a vision sensor, multiple sonars, etc. all in one...

    Not to mention hardware filtering...

  10. Sat Jul 21 19:06:36 2018
    A Alex241N started the conversation VEX U.

    There's been a lot of disgruntled posts regarding changes to the competition structure.

    Let's talk about something I'm sure we can all agree on: the new VEX U changes allowing unlimited machined, printed, punched, etc. parts is amazing!

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