Presented By:Lynbrook Robotics, Team 846

John Chai, David Liu, Aashish Sreenharan,Michael Wachenschwanz, and Toshi Tochibana

Available online at lynbrookrobotics.comTech > Resources > “WRRF Presentations”

Talk Outline

Pneumatics Sensors and Electronics Electrical Components Robot Drive Train Design

Michael Wachenschwanz and Toshi Tachibana present…

Pneumatics

Can you feel the pressure Pneumatics is the use of

pressurized air to achieve mechanical movement.

Air tends to move from high pressure to low pressure

Important note: There is no such thing as a negative pressure

Compressor

Where it all starts The compressor

takes air from the surrounding atmosphere and compacts it via pistons.

Comes with a release valve attached to it

Pressure Switch

Better safe than sorry

Safety Mechanism Turns the

compressor off at 120 psi and turn it back on at 115 psi

Tubing and Fittings

Keeping connected

Tank

The more the merrier

Tanks allows more air in the system.

When air is lost, psi drop is mitigated by larger tanks

Plug Valves Done for the day Releases all the

compressed air in the system.

Must be release manually

Be sure to release the stored air when done with the system

Regulator Stay in control Regulators regulate

the pressure. Uses air from input

to maintain the pressure of the output

Usually kept at 60 psi for FIRST competitions

Electric Valves Handling the pressure Single and double

solenoid valves are used

Controlled by the control board via electricity

Double solenoids exposes one port to pressure and the other to the surrounding atmosphere

Actuators

Use the force Actuators convert the difference in

air pressure to mechanical motion Linear actuators, or cylinders, are

the more common actuators. For the competition, they come in 3 bore sizes: ¾, 1 ½, and 2 inches

Rotary actuators are also allowed

Notes on Actuators

Force = Pressure x Area Area= pi x squared radius radius = diameter (bore) / 2

Retracting force is less than extending force

Flow Rate Valve

Control the flow Simply a fitting that widen or

narrows the flow path of the air Used to slow the air movement,

thus slowing mechanical movement

Does not take away from the net force.

Must be adjusted manually

Aashish Sreendharan presents…

Motors - CIM

Used to drive robot

Motors – Van Door

Powers doors on mini-vans

Motors – Fisher Price Motors

Used on Fisher Price Toys

Made by Johnson Electric or Mabuchi.

Power Distribution Diagram

Power Distribution Explained Battery (12V, Lead-Acid Battery) Main Circuit Breaker Power Distribution Block Components:

Victors (ESC)SpikesController

Power Distribution Picture

Spikes Relays Control direction. Two single pole,

double throw relays. Forward = 12V to

M+ and M- grounded.

Reverse = 12V to M- and M+ grounded.

Neutral = M+ and M- grounded, or 12V applied.

H-Bridge.

H - Bridge

4 Switches. Combination of

switches on to drive motor.

Electronic Speed Controllers

Known as: Victors.

Use Victor 884's. Control speed

and direction. Uses PWM.

Pulse Width Modulation

Two Types: Power DeliveryControl Signal

David Liu presents…

Pulse Width Modulation

Two typesPower transfer○ Between speed controller and motor

Signaling○ Between controller and speed controller

Potentiometers (Pots)

Sensor for measuring position:Rotation, distance, etc.

Potentiometers

+5V

GND

5V

2.5V

0V

+5V

GND

3.5V3 KΩ

7 KΩ

Acts as aVoltage Divider

+5V

GND

Output

Simplest type:Slider

Slider is connected to output.

3.3V4.2V

10 KΩ

0.5V9 KΩ

1 KΩ

Reading the Value

Analog voltage level Analog-to-Digital Converter (ADC)

Converts to number0-1023 for 10-bit ADC

Pots: Uses Sense position: e.g.

lift How to sense the lift

position?Travel length is 6 feetNo linear pot long

enough Rotary Pots

Pots

Multi-turn pot:Screw with wiper resting on threadsUsually 3, 5, or 10 turns

Alignment is important!Continuous rotation: use encoder

Optical Encoders

Optical

Sensor

to controller

Optical Sensor

to controller

Optical Encoders

Optical

Sensor

to controller

Optical Sensor to

controller

Optical Encoders

Determining Distance TravelledCount pulsesExample:○ Given: Encoder stripes = 128○ Given: Wheel diameter = 6”○ Given: counted 85 pulses

= 12.52 inches

1 revolution 6 inches85 pulses

128 pulses 1 revolution

Optical Encoders

Determining SpeedA. Count pulses per interval○ Example: in 1 second, 256 pulses.

Speed = 2 revolutions/second

○ Inaccurate and slow

○ Analogy: On a bicycleMark the wheelCount passes in a minute

Optical Encoders

Determining SpeedB. Measure time between pulses○ Example: time between two pulses =

3.9ms

○ Only requires observing two consecutive pulses

1 pulse

3.9 ms

1 revolution

128 pulses

1000 ms 2 rev/sec

1 sec

Ultrasonic Sensors

Determine distance Send pulse of sound Measure time until echo

Johnathan Chai presents…

Required Capabilities

Speed Point-to-point Movement Turning in place Controllable

Skid/Tank Steering

Power left and right sides independently

Joystick control

Ackerman Steering

Limited turning due to geometry

Team 34’s Design on Chief Delphi

4 Wheels Fast but slides on ground when turning Wide vs. Long base

6 Wheels

Center wheels dropped about a quarter inch

“Rock” on center when turning

Swerve Drive Maneuverability Time costs

Craig Hickman’s Design on Chief Delphi

Wheels

Rubber Roughtop Mecanum Omni-wheels Tank Treads

AndyMark Wheels

Conclusion

Covered major components of FIRST robots

Slides available at lynbrookrobotics.comTech > Resources > “WRRF

Presentations”