Robotics

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Robotics

• Overview of NXT-G
• Actuators in Mindstorms.
• Touch sensor
• Labwork CATCH-UP measurement, circle stool
• Explore Move versus Motor
• Move mini motor mini. Motor.
• Add bumper and program move to (gentle) stop.
• Homework Postings. Talk about nxtasy next class

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Mechanics readings

• What did you learn?

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Catch-up lab

• I'm missing timing for going around stool for
  many groups and measurements for some groups
• Circle stool
• What approach is best? How to define 'best'?
• Quickest performance
• Development time / ease of development
• Robustness ?
• Do this first, then build bumper, experiment with
  mini-blocks, sound.

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Mindstorms terms

• NXT-G refers to iconic language
• NXT-G programs are compiled (translated) into
  what is termed byte code and downloaded to
• NXT Brick, which holds
• a 32-bit microprocessor (little computer)
• 32 bit refers to size of data handled by
  microprocessor
• memory for programs system routines sound
  startup/demo programs

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Actuators

• Multiple blocks for connecting to motors
• Motor vs Move differ as to what the programmer
  does versus built-in controls
• Motor, etc. used for other motors, sensors,
  etc., including hardware from older Lego products
• Legacy
• mini blocks later addition
• Produces smaller code
• Some reduction in function

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Note

• Up to you (robot builder) how the motor is
  attached
• What port
• And what the motor is attached to
• Wheel
• Grabber
• ?
• And direction

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Move block

• Set synchronized movement of 1 to 3 motors
  (usually 2)
• Forward, backward, or specified degree of turning
• Units can be
• time (in seconds)
• Rotations or degrees
• Unlimited
• Something else, a subsequent block, puts on the
  brakes
• Set to brake or coast (if not unlimited)
• Move will make sure to go exactly the rotations
  specified by control of motor.
• Contrast with the motor blocks in which you the
  programmer specify ramping.

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Defaults

• Note for all blocks default settings
• Which port for motors (default B and C)
• Specific ports for each sensors
• Default rotation versus others
• Default power
• Default brake versus coast
• other

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Move block data links can set values and/or
transmit values to subsequent blocks

• Left motor (port)
• Right motor (port)
• Other motor (port)
• Direction (forward/backward)
• Steering
• Power
• Duration
• Next action

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Move mini block

• Must use exactly 2 motors
• Otherwise, reportedly produces smaller programs
  on the NXT brick.
• NOTE reports that using different blocks
  produces larger code
• Souse just move mini, not move mini, move and
  motor, if possible
• Worry about this only if you need to

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Motor block

• Specify movement of one motor
• Power
• Duration
• Action constant or ramp up to set speed or ramp
  down to stop
• Specify wait for completion or go on to next
  block
• Brake or coast

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Changed settings
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Motor mini block

• Appears to be identical functionality
• Claimed to produce smaller code

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Wait blocks
Wait for something to happen In programming
language event driven or event based
programming NXT-G program will wait for the
indicated condition.
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Default assumption is port 1. You can change this.
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Basic bumper exercise

• Use directions to build a bumper a flexible
  piece that when it hits something, the touch
  sensor is pressed
• coupled

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Program move until bumper hits

• Move block (forward, unlimited)
• Wait until touch block (press)
• Move block (stop)

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Exercises

• Replace move blocks with move mini blocks.
  Download new program (different name)
• With the robot connected, check size of the two
  programs.

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Exercises

• Using base robot (two wheels), write program
  moving just one motor a set number of rotations
• this will cause the robot to turn.
• Experiment to make robot turn to the left. This
  will not be a sharp turn, but an arc to the left.
• NOTE this isnt degrees 90!
• Do this using the move mini block and using the
  motor mini block
• Compare.

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Homework

• complete exercises
• Invent small application involving touch
  sensor, perhaps multiple uses, moving forward,
  backward, turning, stopping, etc.
• Postings