Presented By: Lynbrook Robotics, Team 846 John Chai, David Liu, Aashish Sreenharan, Michael Wachenschwanz, and Toshi Tochibana Available online at lynbrookrobotics.comlynbrookrobotics.com Tech > 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) ‏ Spikes Controller

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 Delivery Control Signal

David Liu presents…

Pulse Width Modulation  Two types Power 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 3.5V 3 K Ω 7 K Ω Acts as a Voltage Divider +5V GND Output Simplest type: Slider Slider is connected to output. 3.3V 4.2V 10 K Ω 0.5V 9 K Ω 1 K Ω

Reading the Value  Analog voltage level  Analog-to-Digital Converter (ADC) Converts to number for 10-bit ADC

Pots: Uses  Sense position: e.g. lift  How to sense the lift position? Travel length is 6 feet No linear pot long enough  Rotary Pots

Pots  Multi-turn pot: Screw with wiper resting on threads Usually 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 Travelled Count pulses Example: ○ Given: Encoder stripes = 128 ○ Given: Wheel diameter = 6” ○ Given: counted 85 pulses = inches

Optical Encoders  Determining Speed A. Count pulses per interval ○ Example: in 1 second, 256 pulses. Speed = 2 revolutions/second ○ Inaccurate and slow ○ Analogy: On a bicycle Mark the wheel Count passes in a minute

Optical Encoders  Determining Speed B. Measure time between pulses ○ Example: time between two pulses = 3.9ms ○ Only requires observing two consecutive pulses

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.comlynbrookrobotics.com Tech > Resources > “WRRF Presentations”