Inertial

Introduction

The VEX IQ (2nd gen) Brain includes a built-in 3-axis gyroscope for measuring rotational movement and a 3-axis accelerometer for detecting changes in motion. These sensors allow the robot to track its orientation, heading, and acceleration.

For the examples below, the configured Inertial Sensors will be named BrainInertial, and will be used in all subsequent examples throughout this API documentation when referring to Inertial class methods.

Below is a list of all available methods:

Orientation - Measure rotational movement from the Inertial Sensor.

• heading – Returns the current heading.

• rotation – Returns the cumulative rotation.

• setHeading – Sets the Inertial Sensor’s heading to a specified value.

• setRotation – Sets the Inertial Sensor’s rotation value.

• calibrate – Calibrates the Inertial Sensor for stable heading tracking.

• isCalibrating – Returns whether or not the Inertial Sensor is calibrating.

• resetHeading – Sets the heading of the Inertial Sensor to 0.

• resetRotation – Sets the rotation of the Inertial Sensor to 0.

Motion – Detect changes in motion.

• acceleration – Returns the linear acceleration along the x, y, or z axis.

• gyroRate – Returns the angular velocity around the x, y, or z axis.

• orientation – Returns the roll, pitch, or yaw based on tilt and rotation.

• changed – Registers a function to call when the Inertial Sensor detects change.

Constructors – Manually initialize and configure an Inertial Sensor.

• inertial – Creates an Inertial Sensor.

Orientation

heading

heading returns the current heading of the Inertial Sensor.

Usage:
BrainInertial.heading(units)

Parameters	Description
units	Optional. The units that represent the heading: degrees (default) turns

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Turn, then show the current heading
  Drivetrain.turnFor(right, 450, degrees);
  Brain.Screen.print("%f", BrainInertial.heading(degrees));
}

rotation

rotation returns the current rotation of the Inertial Sensor.

Usage:
BrainInertial.rotation(units)

Parameters	Description
units	Optional. The units that represent the rotation: degrees (default) turns

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Turn, then show the total rotation
  Drivetrain.turnFor(right, 450, degrees);
  Brain.Screen.print("%f", BrainInertial.rotation(degrees));
}

setHeading

setHeading sets the heading of the Inertial Sensor to a specific value.

Usage:
BrainInertial.setHeading(value, units);

Parameters	Description
value	The heading value to set.
units	The unit that represents the new heading: degrees turns

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Make current facing equal to 90 degrees
  BrainInertial.setHeading(90, degrees);

  // Turn to 0 degrees using that new reference
  Drivetrain.turnToHeading(0, degrees);
}

setRotation

setRotation sets the rotation of the Inertial Sensor to a specific value.

Usage:
BrainInertial.setRotation(value, units);

Parameters	Description
value	The rotation value to set.
units	The unit that represents the new rotation: degrees turns

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Pretend we have already turned 180 degrees
  BrainInertial.setRotation(180, degrees);

  // Spin back to the 0 degree rotation
  Drivetrain.turnToRotation(0, degrees);
}

calibrate

calibrate calibrates the Inertial Sensor. All subsequent lines will wait for the calibration to complete before executing. Calibration is an internal procedure that measures and compensates for sensor noise and drift over a specified period. During this time, the Brain must remain completely still (i.e., on a stable surface without any external movement). Movement during calibration will produce inaccurate results.

VEX brains attempt to calibrate themselves automatically at the start of every project. However, if the robot is being carried or moved during project start, the sensor may fail to calibrate properly or yield incorrect calibration.

Usage:
BrainInertial.calibrate();

Parameter	Description
	This method has no parameters.

isCalibrating

isCalibrating checks if the Inertial Sensor is currently calibrating.

• 1 - The Inertial Sensor is calibrating.

• 0 - The Inertial Sensor is not calibrating.

Usage:
isCalibrating()

Parameter	Description
	This method has no parameters.

resetHeading

resetHeading resets the heading of the Inertial Sensor to 0.

Usage:
BrainInertial.resetHeading();

Parameters	Description
	This method has no parameters.

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Turn to 90, reset heading, then turn to 90 again
  Drivetrain.turnToHeading(90, degrees);
  wait(0.5, seconds);
  BrainInertial.resetHeading();
  Drivetrain.turnToHeading(90, degrees);
}

resetRotation

resetRotation resets the rotation of the Inertial Sensor to 0.

Usage:
BrainInertial.resetRotation();

Parameters	Description
	This method has no parameters.

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Turn to rotation -90, reset, then turn to -90 again
  Drivetrain.turnToRotation(-90, degrees);
  wait(0.5, seconds);
  BrainInertial.resetRotation();
  Drivetrain.turnToRotation(-90, degrees);
}

Motion

acceleration

acceleration returns the acceleration of the Inertial Sensor in terms of G (gravity).

Usage:
BrainInertial.acceleration(axis);

Parameters	Description
axis	The axis to return the acceleration from: xaxis yaxis zaxis

gyroRate

gyroRate returns the gyro rate for one axis of the Inertial Sensor.

Usage:
BrainInertial.gyroRate(axis, units);

Parameters	Description
axis	The axis to return the gyro rate from: xaxis yaxis zaxis
units	The unit used to represent the gyro rate: dps – degrees per second rpm – rotations per minute velocityUnits::pct – percent

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Turn, then display z-axis rate in degrees per second
  Drivetrain.turn(right);
  wait(1, seconds);
  Brain.Screen.print("%f", BrainInertial.gyroRate(zaxis, dps));
  Drivetrain.stop();
}

orientation

orientation returns the orientation for one axis of the Inertial Sensor.

Usage:
BrainInertial.orientation(type, units);

Parameters	Description
type	The axis to return the orientation from: pitch roll yaw
units	The unit used to represent the orientation: degrees turns

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Display the changes in orientation as the Brain
  // Tilt and rotate the Brain to see the values change
  while (true) {
    Brain.Screen.clearScreen();
    Brain.Screen.setCursor(1, 1);
    Brain.Screen.print("Roll: %f", BrainInertial.orientation(roll, degrees));
    Brain.Screen.newLine();
    Brain.Screen.print("Pitch: %f", BrainInertial.orientation(pitch, degrees));
    Brain.Screen.newLine();
    Brain.Screen.print("Yaw: %f", BrainInertial.orientation(yaw, degrees));
    wait(100, msec);
  }
}

changed

changed registers a callback function for when the Inertial Sensor’s heading changes.

Usage:
BrainInertial.changed(callback);

Parameters	Description
callback	The callback function to be called when the Inertial Sensor heading changes.

void onHeadingChange() {
  // Show a message when heading changes
  Brain.Screen.clearScreen();
  Brain.Screen.setCursor(1, 1);
  Brain.Screen.print("Heading changed!");
}

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Register callback and cause a heading change
  BrainInertial.changed(onHeadingChange);
  Drivetrain.turnFor(right, 90, degrees);
}

Constructors

inertial

inertial creates an Inertial Sensor.

Usage:
inertial BrainInertial = inertial();

Parameter	Description
	This method has no parameters.

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Create an Inertial object and read heading
  inertial BrainInertial = inertial();
}