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VEX V5 system
Lots of good promises.  Programming promises look interesting. 
Pushing "2x power of 393 motor" through an RJ11 connector is hard to believe;  its not your grandma's RJ11 phone extension cord.
It looks exciting for Vex. 

I don't know how it will affect BEST.
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game design
BEST Game design usually includes small points for dozer robots, just to get off of zero points.
It was possible for Crossfire, but you needed at least a static hook or a magnet to drag manny backwards.
Game for 2018 is being developed now.  I'll voice your concerns to them.
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Can Someone Help!!!
The problem with the line with red X is, the last parameter should be a deadband threshold, typical value 4 to 10, rather than the name of a joystick channel.

So change  Ch4 
to just  4
and that error should go away.

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game design
  I agree field was visually appealing,  but lack of planned disassembly made the field center painful to move between Kickoff,Demo,Game,Demo,Game,Regional.
Throwing projectiles was new as far as I know, and cool idea;  not too many shot out of the field.
The design team consists of former BEST competitors, now mostly engineers in aerospace, and they think they know how rules should be written to be clear;  they also did PayDirt.

Contrasting opinions: 
   I disagree about the importance fast manny:  There are only a few top teams that can even clear the field at all, so it is only those teams that fast manny is the distinction between them.   And of those,  reliably picking up manny the first time is more important than shaving a few seconds of drive speed.  What does it mean that a robot can completely clear their field in half the time?  not hard enough?  opportunity for cooperation to other teams?

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Friction Tape
My name "Summer BEST" has some official name about nationally branded BEST training intended for teachers.  It usually gives Continuing Education credits, lasts 4 ish days.  There are some grant funds available for public school teachers, and I hear next year for all teachers. It has been going a couple years at UT Dallas, but I hear they are trying to expand to three locations this summer.

re Large. small:  The usual minimum width of a BEST robot is constrained by having motors back to back.  How can you get narrower?
- use belts or some other non-direct transfer of motors to wheels, so the motors can be mounted differently.
- mount motors non co-linear side by side in horizontal plane, so that the wheel centers are not directly across from each other; how does that affect steering in each direction?
- mount motors non co-linear top/bottom in the vertical plane, so that the wheels centers are parallel in the vertical plane, but not in horizontal plane
-- When top/bottom mounted, the wheels have to be different sizes to avoid tilting.  Might as well make the larger wheel to be 2x larger, and use the large motor. 

Learning Technical stuff:  I dont have a good answer.   There is a lot of stuff on BEST website, team resources. 
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Friction Tape
So cans over wheels in back, and manikin over skids in front?
The other issue with 20" wheels is that they narrow the mounting location to the center.
If I could come up with a decent belt material, like metal pipe hanging tape, I'd like to try larger motors with 4" pulley belt drive to 10" wheels with 2" pulley. 
Another interesting idea that allows very narrow (<6"?) robots is large motor with large wheel on top of small motor with small wheel.  Summer BEST training generated a protobot with that motor/wheel combination, and it drove ok.  That also allows a small and large motor for mechanisms, if needed.

More drive control:  Yes, half speed feature and non-linear joystick conversion can make robot easier to drive.  In 1987, ElectroGlass brand semiconductor wafer probers had an X,Y,theta joystick that twisted to switch between 3 modes:  scan (fast), Jog (repeated small steps), and single step.  That would be interesting to try as drive mode.   When aiming a pea shooter, you get more resolution if the exit point is centered between the drive wheels.
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Friction Tape
Why didn't you have the drive wheels in the front, next to the manny/can lift, instead of at the back?

Wow, 10" wheels on small motors, that's fast! That is eqv of 20" wheels on large motors, which I have not seen lately, only up to 14" or so.
I'll have to check the compliance form survey to see what largest wheels were in Texas.

Balancing weight over wheels is always an important issue, and even more so when picking up relatively heavy loads, to avoid your kind of traction issues.
Good balance without low CG and slew control also leads to jerky robots, and often requires wheelie bars in both sides of drive wheels,  which can then lead to high-centering the robot on game objects. 
  Wheel notches are fast to make with a band-saw.  I'm against hex heads as wheel treads, because they tear up the field, and leave sawdust on plywood ramps.
  Castors are surprisingly easy to make from 1/4" threaded rod with 2-4 bends, 7 nuts, and 0-2 base plate bearings.  I thought for hours about how to make a jig to get the bend angles and places exactly correct; I finally just bent the rod by hand to see how the jig should be made, and it was so easy, I never made the jig. 
  If you want two castors, a second wheel can be made with a hole saw, and 0-2 wheel bearings.

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Winning scores at hub competitions
Texas BEST REGIONAL results are available now
Regional Finals scores, out of 3x600=1800 (average rescue time) :
1761 (13), 1700 (33?), 1554, 1462
Winner averaged 587 points per match for 3 matches, and usually done in < 2 minutes.
I've not yet seen a video of a sub 10 sec rescue time, as mentioned in the rules.

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Friction Tape
Always good advice to use real spec kit materials. 
If you ran out of tape because you used some failed other attempts, getting more is fine.
If you need more than one roll on the robot at one time, you shouldn't be using extra.

Friction tape has two sides, one is stickier.  I hope that was not your problem.
If you are using friction tape as a tire on the wheel, there are other things that work too.
  - string wrap as treads,
  - Bike inner tube provided, cut into strips.
  - rubber bands
  - rubber core from the bungee cord.
or even 
  - one Team Custom Part per wheel, using some kind of flat rubber strip from McMaster, and you have an extra that you can roll up into a 2x4x4 block to show that you pass compliance.

With the other materials, the challenge is to keep it on the wheel.
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Servo Programming
In the real world on a robot, the loop time might be < 1ms, the signal to the servo might be updated 13-40ms apart, and the servo might take 300ms to travel end to end.  If we want to slow the end to end transition time from 300ms to 1 second, and the ends are 254 units apart, we would put in a sample time of 1/254 = 0.04 or about 40ms, and use smaller rate times to get faster transitions.  In the real world, the block has access to the real world timer, so the random servo update time of 13-40ms has no effect, and the loop time of 1ms or 1us or 10ms has no effect.  Is that right?
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Servo Programming
This is Simulink forum so we should assume that.

Is there an easy way to implement slew control in Simulink?  ie gradually decrease or increase servo when down or up button is pressed, respectively.

I just replaced a broken gear servo for a team that is banging heavy claw open and shut without slew control, but you can't do that during a match.
  However, I have untested pseudo C code to show some ideas for implementing slew control posted below.

This is pseudo code,  you'll have to figure  out real code yourself.  
 test each step as you go.

level 0:  joystick digital to servo like you have now.
level1: (similar to  C code from DGauntt)

   declare    int : var1, var2;
    var1 = get joystick (button);    var2 = get joystick (button2);
   if (conditional based on vars )then { setmotor this} 
   if (conditional based on vars)then {setmotor that }

level2:  add slew control, but may not be effective if loop time is very fast.
  declare more vars for servostep, timestep,  prevtime, nowservo, wantservo
  initialize as 1,5,0,0,0
    var1 = get joystick (button);    var2 = get joystick (button2);
   if ( conditional based on vars )then  // move positive
       { nowmotor=min(127,nowmotor+servostep) }
   if ( conditional based on vars )then  // move negative
        { nowmotor=max(-127,nowmotor-servostep)  }

 setmotor( now motor) // doit

Level3; Add 1ms wait time in the loop,  adjust slew speed by changing wait time vs servostep size to get what you want.
Level4; How do you avoid adding wait time?  have to keep track of last time you updated nowmotor, and don't update it again until timestep has passed.

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Problem losing connection
You are Welcome, and thanks for the new and tested hypothesis.
(In hindsight), it should be expected.   
 The flat cortex was improved to the 'turbo bump' cortex, because even a half-inch of extra distance between the X MHz CPU stuff and the 2.4MHz wifi key makes a noticeable difference.  Maybe the underside of the top-case is coated with conductor shield as well.  It is even possible that a change in the robot code you are running on the Cortex could change the interference noise pattern.  

That also suggests that wrapping your on-robot gopro or phone-cam in conductor may reduce interference as well.

I'll forward this to the other Regionals.  Thanks again.

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Servo Programming
Servos only move +-45 degrees, but you can call that -90 to zero degrees if you want.
There is no button called gain, just buttons 5 through 8, with various up down left right adders.
Look at the other thread something like "help for rookie team".
I helped them work out a similar problem.  Maybe that type of solution you can adapt to your problem
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How to improve responsiveness of program
Thanks for writing back to close the loop on what worked for you. 
That will be helpful for future teams reading the forum with the same problem.
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How to improve responsiveness of program
I haven’t compared Simulink to others.
There is some delay in Cortex because your program runs on slave cpu, which has serial link to master, which sends 10ms base Pwm to motor port where mc29 interprets it as 1ms Pwm to dc motor. As a result, there is a random 12-30ms delay between command and motor change.
If you have more than this there might be something in your program. Can you post your program?
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