Presented By: Lynbrook Robotics, Team 846 John Chai, David Liu, Aashish Sreenharan, Michael...
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Transcript of Presented By: Lynbrook Robotics, Team 846 John Chai, David Liu, Aashish Sreenharan, Michael...
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”