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FRC Robot Framework

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FRC Robot Framework Add and Use a Sensor & Autonomous For FIRST Robotics * * * * * Sensors Adding Intelligence and Enabling Automation Types of sensors: Limit ... – PowerPoint PPT presentation

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Title: FRC Robot Framework


1
FRC Robot Framework
  • Add and Use a Sensor
  • Autonomous
  • For FIRST Robotics

2
Sensors Adding Intelligence and Enabling
Automation
  • Types of sensors
  • Limit Switches on/off
  • Gyro - provides Robot rotation angle position
  • Potentiometer like a volume control can be
    used to control arm rotation
  • Encoder - measures shaft rotation robot
    distance, lift height
  • Light sensors detect object breaking beam
  • Infrared - detect presence of object nearby
  • Ultrasonic - detects distance to object such as
    wall
  • Camera (Vision) - Direct feed to dashboard,
    Targeting with vision processing
  • Kinect (Camera Infrared) For Driver Station
    or on board robot?
  • not used .. yet

3
Session Objectives
  • Discuss principles and applications for Gyro
    sensor.
  • Bicycle wheel demo
  • Incorporate Gyro into Autonomous code
    Control Robot to drive in straight line
  • Open Gyro in Begin.vi
  • Get Gyro Angle Tele-op.vi display on Front Panel
  • Next use Gyro reading as Feedback to tell if
    robot is driving straight (at angle specified)
  • PID control

4
FRC Project
  • Browse to find your last code
  • (or open new)
  • Navigate to the Robot Main block diagram
  • Then select Begin
  • Go to Block Diagram

5
Begin .vi Updated for adding Gyro
  • Edit vi Add an accessory motor
  • Open function palette and select WPI Robotics
    Library / Sensors / Gyro
  • Add Open Gyro .vi
  • Identify where plugged in
  • Add Refnum Set.vi
  • Give it a name

6
Open the Autonomous VI
  • Remove diagram disable
  • Put cursor on edge of disabled structure, right
    click and select Remove Diagram Disable
    Structure
  • Delete the last 2 while loops
  • After noting what the default code is intended to
    do
  • A method of sequencing operations in autonomous
    that we may return to

7
Set up a While Loop in Autonomous
  • In remaining While Loop
  • Enlarge, create space to add Gyro and PID
    functions
  • Change length of time to 5 seconds
  • Each loop is 50 ms, 100 loops 5 secs.
  • Change motor inputs to 0
  • For now

8
Modify Autonomous.VI to Read Gyro
  • From WPI Robotics Library/ Sensors/ Gyro palette
  • Bring the Refnum Get and provide name it was
    given in the Begin.vi
  • Bring Gyro Get Output vi and connect them
  • Put cursor on angle output, right click,
    select, create indicator
  • Indicator shows up on Front Panel
  • Digital indicator is default but can be replaced
    with a Dial or Linear Indicator

9
Modify Front Panel Indicatorfor Gyro reading
  • Put Cursor on indicator, right click and select
    Replace, then Gauge
  • Enlarge gauge by dragging diagonally
  • Click on the 10 and change to 180
  • Click on the 0 and make it -180
  • Hover on the 180 until you see the rotation
    arrows then drag the 180 around to the -180.

10
Test the CodeSee if in Autonomous the Gyro is
being read
  • Next Lets use it for an Autonomous code
  • With Feed-back control

11
Feed-Back Control
  • Open Loop
  • Examples
  • In an (older) car turn heater knob to high
  • Heater turns on and stays on until the driver
    gets too hot and manually turns it down
  • Robot Harvester(2012) Operator holds button to
    turn harvester motor, watches until sees ball
    move up and then releases which stops motor

Controller
Robot
12
Feed-Back Control
  • Closed Loop
  • Examples
  • In a (newer) car turn heater knob to 70oF
  • Heater goes on until the thermostat (sensor)
    reads that it is 70oF , then automatically turns
    it off until it gets too cool, then back on, etc.
  • Robot Harvester Operator presses button to
    start harvester motor
  • Motor goes until on board light sensor sees
    ball sends signal back to cRio
  • Labview program then directs motor to stop

Controller
Robot
Sensor
Generally using it to see if a process is
complete, then stabilize
13
PID Control
  • PID stands for Proportional-Integral-Derivative
  • A method of closed loop feedback control
  • A way of using what you know from your sensors to
    compute an intelligent motor output.
  • Proportional P looks at difference between
    desired position and actual and sets motor speed
    to close gap proportional to that gap
  • Incorporates the idea that you need to slow down
    as you get close so you dont overshoot the
    target.

14
The PID Function Block
  • Set-point
  • Desired value to get to
  • Process variable
  • Actual value as measured by a sensor
  • Output determined by magnitude of difference
    (error) between setpoint and process variable
  • PID Gains adjust sensitivity

15
Add Read Gyro And PID Control Of Steering
Correction
  • Get Gyro Refnum, Get Gyro Angle
  • Add PID function block
  • Setpoint set to 0 to drive straight forward
  • Connect Gyro output as Process variable input to
    PID
  • Limit output range
  • Set PID gains
  • Connect output to X input to arcade drive
    (Steering)

16
Suggested method for determining PID gains
  • Method for Setting Values
  • ? Start with CP small and CI, CD both zero.
  • ? Raise CP until the robot is oscillating
  • consistently around the target.
  • ? Once this is accomplished, start increasing
  • CD until the robot stops oscillating.
  • ? Then add CI until the robot stops within a
  • desired range of the target.

Often we have only used the P, or PD
17
Next we will see if our code works!
18
Homework Challenge Slides
  • Learn how to modify the Dashboard
  • Make an autonomous Drive Sequence
  • Drive a square pattern
  • Learn to use the examples and be able to code a
    variety of sensors including encoder

19
Modifying the Dashboard Gyro Indicator
  • Open Dashboard Project, Modify to display Gyro
    angle on a gage
  • (follow Labview tutorial number 7)
  • Modify Robot code Tele-op to send data to
    dashboard (also part of Labview tutorial)

DashboardMain.vi
Front Panel
20
Incorporating Sensors Gyro
  • Open Dashboard Project, Modify to display Gyro
    angle on a gage (follow Labview tutorial)
  • Modify Robot code Tele-op to send data to
    dashboard (also part of Labview tutorial)
  • Follow Tutorials 4-7
  • Adds Gyro
  • Opens Dashboard Project

21
Homework / Challenge 2
  • Update the Autonomous code
  • Add 3 sequential While loops (like in default
    disabled structure)
  • Have robot go straight, turn 90 degrees,
  • Repeat 3 times to drive in a square.

22
Homework / Challenge 3
  • Add variety of sensors to Begin and Tele-op
  • Use Examples as source to copy correct formats

23
Begin.VI - Open and name sensors
24
Tele-op.VI - Get values and display
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