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Anthony DiVirgilio

Rear wheel drive vs. front wheel drive. Which is better? - 8 views

  • fwd holds an advantage in slippery conditions such as ice or snow as more weight is over the drive wheels reducing slip during acceleration
    • Anthony DiVirgilio
       
      rear wheel drive only has advantages where steering is envloved
    • Bryan Kelleher
       
      AGREED, BUT ARE WE GOING FOR PURE STEERING? OR POWER?!
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    this could be useful
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    its really opinion but it does seem like a good idea to put it in the front
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    This could be very helpful for gear changing
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    these are real cars not NXTs
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    thanks for pointing that out, i didnt want to say anything
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    it doesn't matter the theory is sound
Declan Coen

PID Controller For Lego Mindstorms Robots - 7 views

  • light sensor "sees white" then we know it is left of the line's edge (and the line). If it "sees black" then we know it is to the right of the line's edge (and on the line). This is called a "left hand line follower" since it is following the line's left edge
  • We need to know what values the light sensor returns when it "sees white" and when it "sees black". A typical uncalibrated sensor might give a "white" reading of 50 and a "black" reading of 40 (uncalibrated, on a 0 to 100 scale). It is convenient to draw the values on a simple number line to help visualize how we convert light sensor values into changes in the robot's movement.
  • Below are our made up light values for white and black.
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  • We'll just divide the range into two equal pieces and say that if the light level is less than 45 we want the robot to turn left. If it is greater than 45 we want to turn right. I won't go into how exactly the turns should be done. I'll just say that gentle turns work well for a fairly straight line
  • line with lots of curves usually needs to be making sharper turns. For gentle turns you might use Power levels of 50% on the fast wheel and 20% on the slow wheel. For sharper turns on a curvy line you might need to use 30% power for the fast wheel and coast or brake the slow wheel. Whatever power levels you use the numbers will be the same for the two turns, you just switch which motor gets the big number and which get the smaller number (or a stop command).
  • This type of a line follower will follow a line but it isn't very pretty. It looks OK on a straight line with with the motors programmed for gentle turns. But if the line has any curves then you have tell the robot to use sharper turns to follow line. That makes the robot swing back and forth across the line. The robot only "knows" how to do two things; turn left and turn right. This approach can be made to work but it is not very fast or accurate and looks terrible.
  • In the above approach the robot never drives straight, even if it is perfectly aligned with line's edge and the line is straight. That doesn't seem very efficient does it? Lets try to fix that. Instead of dividing our light value number line into two regions lets divide it into three.
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    seems useful for following a line effectively
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    this is a really good technique
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    the top of this article explains how it would be easier to follow the edge of the line rather than the center of the line. As it detects the white it will turn back to the black and as it detects the black it will turn back to the white.
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    i found the edge thing on another site too
Joshua Wilkinson

http://www.teamhassenplug.org/NXT/Gears/ - 16 views

  • This motor shaft will make 3 rotations, in the same time the output shaft makes 5 Gears used: 20 tooth on motor, 12 tooth on output Gear Ratio: 3:5 Power: 3/5x motor Speed: 5/3x motor (faster)
  • This motor shaft will make 1 rotations, in the same time the output shaft makes 3 Gears used: 24 tooth on motor, 8 tooth on output Gear Ratio: 1:3 Power: 1/3x motor Speed: 3x motor (faster)
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    great ideas for gear ratios
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    very helpful gear ratio chart
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    the bottom two charts are good. It does make it go considerably faster
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    It looks like a smart idea for designing the wheels maybe it would be possible to adjust it and make it stronger
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    This is probably the best for speed and power(torque). The robot would be front wheel drive based on that if the nxt is on the back with the wheels the robot would flip or slide down due to the weight on the downhill side of the robot not the uphill side(assuming the track is at 22.5 degress
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    I agree wit Josh this is what we need for the project
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    this has some good ideas
Bryan Kelleher

bumper tech - 8 views

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    ^ this show an idea we can use for backing up when objects contact our nxt
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    this would help our robot detect things from different angle. also, it is more efficient than using a touch sensor with no attachments.
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    this works if its driving with the castor wheel in back not the front, it looks like a good idea though
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    its actually a pretty nice setup if we found space for the other sensors, but id stick with the back wheel we have now, it also shows how to make it very nicely
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    HEY
Anthony DiVirgilio

Gear and Wheels Part 1 - YouTube - 6 views

    • Anthony DiVirgilio
       
      really good demonstration of gear ratios at work
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