2022bot

Source code for the ESHS Robotics 2022 FRC Rapid React competition robot.

The robot's tentative name is TATR (The Articulated Turret Robot.)

This file contains motor and port assignments, the robot's control scheme, and technical discussion about its various subsystems.

Control scheme

Note: for field-oriented swerve to work, the robot must start the match with its front side facing away from the driver.

• XBox controller:
  1. Left joystick: Field-oriented strafing Regardless of the orientation of the robot, pushing the left joystick away from you will cause it to drive away from you; moving the joystick to the left will cause the robot to move leftward, and so on.
  2. Right joystick:
     1. Horizontal channel: Rotation Moving the right joystick to the right turns the robot clockwise; moving it to the left turns the robot counterclockwise.
     2. Vertical channel: Unused
  3. Right Trigger: Manual Shoot Pressing the button will release a ball from the indexer to the shooter manually.

Motor and port assignments

Motor distribution is as follows:

CAN bus IDs

• Drive subsystem:
  • Speed motors:
    1. Front left speed motor (Brushless NEO @ Spark MAX)
    2. Back left speed motor (Brushless NEO @ Spark MAX)
    3. Back right speed motor (Brushless NEO @ Spark MAX)
    4. Front right speed motor (Brushless NEO @ Spark MAX)
  • Pivot motors: 5. Front left pivot motor (Brushless NEO @ Spark MAX) 6. Back left pivot motor (Brushless NEO @ Spark MAX) 7. Back right pivot motor (Brushless NEO @ Spark MAX) 8. Front right pivot motor (Brushless NEO @ Spark MAX)
• Shooter subsystem: 9. Turret turntable motor (Brushless NEO 550 @ Spark MAX) - This doesn't need a CAN ID because it will not require a CANEncoder SparkMaxAlternateEncoder -- since we can get the set point from the vision subsystem, we can put this on PWM if we want. 11. Left shooter flywheel (Brushless NEO @ Spark MAX) 12. Right shooter flywheel (Brushless NEO @ Spark MAX)
• Intake/uptake subsystem: 13. Indexer roller left (Brushless NEO 550 @ Spark MAX) 10. Indexer roller right (Brushless NEO 550 @ Spark MAX)

PWM ports

• Climber subsystem:
  • (PWM port number?) (name/purpose) motor (Brushless NEO @ Spark MAX)
    • Is this going to be PWM or CAN?
  • (PWM port number?) (name/purpose) motor (CIM @ Spark)
• Intake/uptake subsystem: 0. Intake axle motor (Mini-CIM @ Spark)
  1. Uptake belt motor (Mini-CIM @ Spark)
• Shooter subsystem::
  • (PWM port numbers?) 2x hood motors (Linear servo @ Rev servo Hub)

Subsystems

Drive

As the team did for the 2019-2020 and 2020-2021 seasons, this year's robot will employ a swerve drive using MK3 modules from Swerve Drive Specialties. Eight brushless NEO motors control the swerve modules; their Spark MAX motor controllers are daisy-chained in a CAN bus, allowingh us to use the CANSparkMAX SparkMaxRelativeEncoder or SparkMaxAlternateEncoder classes to access the default and alternate encoders for the pivot wheels' motor controllers.

Shooter

The shooter's purpose is to sink balls into the circular goal. The goal is ringed with reflective tape, and the center of that formation of reflective quadrilaterals represents a vision solution that we can target with the Limelight vision camera.

Shooter components

1. Limelight. The Limelight is a versatile and easy-to-configure camera with built-in LED headlights designed to quickly identify reflective tape targets. Once identified, it asynchronously calculates five parameters and returns them to the rest of the robot code via NetworkTables:

   • tv: Whether the Limelight has any valid targets; 0 or 1.
   • tx: Horizontal offset from crosshair to target; ranges from -27.0° to 27.0°.
   • ty: Vertical offset from crosshair to target; ranges from -20.5° to 20.5°.
   • ta: Target area in terms of percentage of the image. Ranges from 0.0 to 1.0.
   • ts: Target skew or rotation. Ranges from -90.0° to 0.0°.

   From these values, we can use trigonometry to obtain the solution distance, and then feed that parameter into the shooting algorithm.

2. Flywheels and hood. The shooter consists of a circular opening with a bottom flywheel adjacent to it. A hood behind the opening can be adjusted to fine-tune the trajectory of the parabolic arc the launched cargo will travel in.

   The goal in the competition field contains a rotating agitator in the center. If you are thinking of the agitators that you would see in washing machines, you are not far off the mark (except this one is larger and allows balls to slip through.) The agitator seems specifically designed to thwart attempts to sink cargo in using high parabolic arcs with a lot of topspin, which is typical for flywheel-based shooters.

   In response, we added a second, rear flywheel to the design on 2022-01-19 to reduce the topspin of the ball.

Shooting algorithm

• Independent variables (inputs). There is one under consideration and a few others that we are ignoring:

  1. Distance (d): The diagonal distance from the Limelight camera to the center of the vision target. The units don't actually matter.

  2. Height: The distance from the Limelight camera to the ground plane.

     Always assumed to be constant.

  3. Azimuth: The horizontal deviation in degrees from the center of the target.

     Because the shooter subsystem is always supposed to aim at the center of the vision solution, we can assume that this is a constant with a value of 0.0.

• Dependent variables (outputs). These variables must be expressed as functions of the independent variables, and are directly related to the ball trajectory. We have two variables under consideration and one that we are ignoring.

  1. Bottom flywheel speed (s): The voltage to apply to the bottom flywheel.

     This controls the strength of the shot, and is achieved by compressing the cargo within the shooter.

  2. Hood angle (θ): The amount by which the hood curls over the ball.

     This controls the steepness of the shot's trajectory.

  3. Top flywheel speed: The voltage to apply to the top flywheel.

     Reduces topspin. We plan to always make this a multiple of the bottom flywheel's speed, so it does not need to be considered in our model.

So our goal is to determine the two equations F and G so that

    s = F(d)
    θ = G(d)

will correctly launch the ball into the target from the given shooting distance d.

Gathering data

To gather enough data to solve the unknown equations for the dependent variables, we need to position the robot (really, position the Limelight) at fixed distances and heights and then attempt to find a flywheel speed and hood angle that will reliably sink the shot. The indexer should only release the ball to the shooter once the flywheel has accelerated to the correct speed.

At the time of writing, we do not know what the relationship between the distance and the independent variables is, other than that we predict that the functions will monotonically increase as the distance increases.

Intake

The intake subsystem is divided into three parts:

1. The intake, which consists of:
   • Intake rollers that use 3D-printed miniature Mecanum wheels to direct any cargo placed beneath them to the maw of the chassis; and
   • A downward-facing intake color sensor positioned at the top of the intake that ascertains whether a ball of the wrong color is positioned beneath the intake;
2. The uptake, which consists of:
   • Uptake rollers, which move balls up from the intake to the indexer; and
   • The uptake sensor, which tells us if a ball is detected within the uptake (i.e., it has passed the intake and it has not reached the indexer.)
3. The indexer, which consists of:
   • Indexer belts, which use encoders to offer precise control over when ball is released into the shooter; and
   • The indexer sensor, which tells if a ball is caught in the indexer.

For the intake rollers to work properly, cargo must be trapped in front of the robot and pressed beneath the rollers so that they roll along the front bumpers toward the front center.

Algorithm

The subsystem is controlled by a state machine. The overarching goal is to immediately transfer any ball that was not rejected by the intake into the indexer, where it waits to be shot.

1. Start

   Initial state.

   Next states:

   • Deploy (unconditionally.)

2. Deploy

   In this state, the subsystem uses pneumatics to deploy the intake rollers to a down position. The private intakeAndUptakeEnabled variable is set to true and the private indexerReleased variable is set to false.

   Next states:

   • Deploy (as long as the intake rollers are not down; this can be a simple timer.)
   • Intake/Uptake On (otherwise.)

3. Intake enabled branch:

   1. Intake/Uptake On

      In this state, the subsystem performs nominal ball intake. In other words:

      • The intake rollers, uptake rollers, and intake belts are activated, bringing balls in and up.
      • If a ball of the wrong color is detected by the intake color sensor, then the intake rollers will reverse until the sensor is clear.

      Next states:

      • Intake/Uptake Off (if the intakeAndUptakeEnabled private variable is set to false; this can happen if a human driver command or the climber subsystem calls the intake subsystem's public intakeDisable() method.)
      • Intake/Uptake On + Ball in Index (if the indexer sensor detects the presence of a ball and the intake/uptake rollers are spun up -- the spin-up can use a simple timer.)
      • Intake/Uptake On (otherwise.)

   2. Intake/Uptake On + Ball in Index

      In this state, the system is ready to release a ball to the shooter.

      • The indexer belts are deactivated.
      • The intake rollers and uptake rollers remain enabled.

      Next states:

      • Intake/Uptake Off (if the intakeAndUptakeEnabled private variable is set to false; this can happen if a human driver command or the climber subsystem calls the subsystem's public intakeDisable() method.)
      • Intake/Uptake On + Firing (if the indexerReleased private variable is set to true; this can happen if a human driver command or the vision subsystem has called the intake subsystem's public releaseToShooter() method.)
      • Intake/Uptake On + Ball in Index (otherwise.)

   3. Intake/Uptake On + Firing

      In this state, the indexer belts and uptake rollers release balls into the shooter until the uptake and indexer are empty. When this is done, indexerReleased is set back to false.

      Next states:

      • Intake/Uptake On (if a minimum amount of time has passed and the indexer sensor does not detect a ball.)
      • Intake/Uptake On + Firing (otherwise.)

4. Intake disabled branch:

   1. Intake/Uptake Off

      In this state, the intake rollers, uptake rollers, and intake belts spin down and performs no intake or uptake.

      Next states:

      • Intake/Uptake On (if the intakeAndUptakeEnabled private variable is set to true; this can happen if a human driver command or autonomous calls the intake subsystem's public intakeEnable() method.)
      • Intake/Uptake Off + Ball in Index (if the indexer sensor detects the presence of a ball and the intake/uptake rollers are spun down -- the spin-down can use a simple timer.)
      • Intake/Uptake Off (otherwise.)

   2. Intake/Uptake Off + Ball in Index

      In this state, the system is ready to release a ball to the shooter. The indexer belts, intake rollers, and uptake rollers are deactivated.

      Next states:

      • Intake/Uptake On (if the intakeAndUptakeEnabled private variable is set to true; this can happen if a human driver command or autonomous calls the intake subsystem's public intakeEnable() method.)
      • Intake/Uptake Off + Firing (if the indexerReleased private variable is set to true; this can happen if a human driver command or the vision subsystem has called the intake subsystem's public releaseToShooter() method.)
      • Intake/Uptake Off + Ball in Index (otherwise.)

   3. Intake/Uptake Off + Firing

      In this state, the indexer belts and uptake rollers release balls into the shooter until the uptake and indexer are empty. When this is done, indexerReleased is set back to false.

      Next states:

      • Intake/Uptake Off (if a minimum amount of time has passed and the indexer sensor does not detect a ball.)
      • Intake/Uptake Off + Firing (otherwise.)

Absolute alignment values

• Front left: ~166.0 degrees
• Back left: ~17.8 degrees
• Back right: ~255.0 degrees
• Front right: ~202.0 degrees