© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT...

© 2006 Carnegie Mellon Robotics AcademyDesigned for use with the LEGO MINDSTORMS® Education NXT Software and Base Set #9797

Tree SurveyingExisting Design

See Teacher Guide for printing instructions


Opening ActivityFind something to replace the wheel.

Your idea must be:

• Cheap

• Easy to manufacture

• Easy to use

• Durable

• Energy-efficient in use

• Scalable to many sizes, large and small

• Able to do something the wheel can’t


Opening Activity

• Legs are difficult to manufacture and operate

• Treads are more expensive and less energy-efficient than wheels (and they use wheels inside them anyway)

• Flying is very energy-inefficient, expensive, and hard to do

• Hovercraft are also energy-inefficient

• Crawling like a slug is slow and expensive

• A ball is basically a 3D wheel, but has trouble moving in a straight line

Replace the wheel.


Opening Activity

WHY???

• “Reinventing the wheel” means wasting effort on trying to develop a new solution when a perfectly good one already exists

• Don’t reinvent the wheel! Use it!

• Side note: “Reinventing the square wheel” is a related idiom that means wasting effort on trying to develop a new solution when a perfectly good one already exists… and coming up with something even worse

Replace the wheel.


Auto-Caliper• A measuring tool that takes

and displays measurements of tree size already exists

– Instead of inventing a new one, build and improve on the existing design

– How does it work?– Build and analyze one

• The proverbial “wheel”?

– Probably not, but good enough for us

Existing Tree Caliper DesignThis measuring device already exists,

why spend time building a different one?


Existing Design:Technical Review

Data Hubs & WiresDisplay Block


Data Hubs & WiresMany blocks have data hubs which can be opened by clicking the notch in the lower-left corner of the block.

A data hub contains many data plugs, which allow information to flow in and out of the block.

Data wires control the flow of data between blocks.

Output plugs typically send out a sensor value, or the result of a computation.

Such information usually goes into another block’s input plug, allowing the reading or result to be used as a value inside the block.

Speed Controlled by SensorUltrasonic Sensor distance output plug controls

the value of the Move Block’s power setting


Display Block: NumberThe Display Block displays images or text on the NXT’s LCD display.

The Display Block does not have built-in support for displaying Numbers. In order to display a Number, you must first convert it to Text using the Number to Text Block.

The Display Block must also be configured to display Text, or it will ignore the wired-in value.

Display Ultrasonic Sensor ValueUltrasonic Sensor reading is converted to Text

then displayed on the NXT’s LCD screen


• It’s inefficient to reinvent solutions that already exist and work

• Instead, build and adapt existing solutions to meet your new needs

Summary

• You will study an existing caliper measuring device to understand how it works

• You will build the device

• You will write the default program

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT...

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Transcript of © 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT...