Basic Robot

WHAT'S called a robot?

Robot should have the ability to think - make decisions.

it has an on-board brain and it can still accept instructions

from an operator and be called a robot


Building Your Robot

Four step for building

• Design mobility
  
  
• Design Gripper
  
  
• Design Circuit , Senser
  
  
• Programing
  

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Mobility

Type of mobility depends on the job they have to do

and the environment they operate in.

• - Wheels
  
  
• - Tracks
  
  
• - Legs
  

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Wheels

Type of wheel mobility

1. The two wheeled drive

The two wheel drive system is simple

to build because one motor drives one

wheel and another drives the second

wheel. When both motors are going

forward the robot moves forward.

When you reverse one of the motors, the robot turns

2. 4 wheel system is a two wheel drive with two wheel steering

This is a similar system to what is seen on

automobiles thay has a large turning radius

but thay relatively easy to drive

3. 4 wheel system driven

4 wheel system driven by either one or

two motors and the wheels on the other

side are set up in the same fashion the

wheels must skid or slide when the robot is

turning. This means using more battery power and

additional stresses on the drive system and motors

4. omni

The omni wheel is unique because it rolls

freely in two directions. In one direction,

it rolls like a normal wheel. It can also roll

laterally because of the smaller wheels

spread about its circumference. it in any direction. By changing

the speeds and directions of the motors the robot can drive in

any direction without needing to turn. This makes it very useful

for navigating around the house. It works on anyindoor surface

or outdoors in short grass, pavement, concrete, etc

Size of wheels

Wheel size depends on how fast and how heavy.

If your robots move at approximately 15 feet per second.

Of course rams and wedges tend to move faster where as

vicious shell spinners can move slower. To calculate how fast

your robot will move with a specified wheel is simple.

First measure the diameter of the wheel and calculate

the circumference.

Wheel diameter in feet x 3.14 = Circumference

(distance around the wheel)

0.8" x 3.14 = 2.512"


Second, calculate the speed

RPM of the wheel x Circumference = number of feet per minute

230 RPM x 2.512 = 577.76 feet per minute


Forth, convert to feet per second

feet per minute / 60 (seconds in a minute) = feet per second

481.4 / 60 = 8.02 feet per second


The speed here is reasonable if you are building a smaller bot,

such as a feather weight or light weight or even if your building

a heavy weight with a strong weapon. Its a bit on the slow side

for a heavy weight wedge or ram.


How heavy the robot is an important factor in wheel size.

You should try to have about 2 pounds of torque for every

pound of robot. Again, a simple bit of math is required.


Simply divide the torque by the radius

of the wheel (1/2 of the diameter).

480 inch pounds of torque / 4 inch radius = 120 pounds of

torque. The torque is good if your were building light weight.

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Tracks

Tracks provide good traction in

loose soil, low ground pressure

and increased surface area.

This increases the capability of

the vehicle to operate in areas

where traction is limited, but leads to inefficiencies on hard

smooth surfaces and may be inadequate in highly cluttered

environments. With tracks attached locomotion is accomplished

via skid steer. Due to the dual drive system, the tracks can be

driven by either of the two motors. Using the walking drive, the

tracks have increased torque, but a lower top speed. Using

the track drive, the tracks have a higher maximum speed, but

lower torque


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Legs

Legs provide better mobility in

highly cluttered environments.

However, legs are less efficient

and more difficult to control

precisely. Legs may also have more difficulty navigating steep

slopes than wheels or tracks. In the legged configuration the

vehicle maneuvers via quadrupedal motion by coordinating the

movements of all four legs simultaneously. Turning is accomplished

by slowing the rate of movement on a side

(similar to skid steer movement). This leads to large turns

(increased turning radius) that may be slow to effect. Stepping

over obstacles can be accomplished by rotating one leg

independently of the others and then continuing with coordinated motion.


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