Inertial Sensor#

Introducción#

The inertial class is used to control and access data from the IQ (2nd gen) Brain’s built-in Inertial Sensor. This sensor measures how the Brain is moving and turning.

The Inertial Sensor uses two parts to do this. The gyroscope measures turning, such as heading, rotation, gyro rate, and orientation. The accelerometer measures changes in motion, such as speeding up or slowing down along the x-, y-, and z-axes.

Class Constructors#

inertial(
  turnType dir = turnType::right );

Class Destructor#

Destroys the inertial object and releases associated resources.

~inertial();

Parámetros#

Parámetro

Type

Descripción

dir

turnType

Optional. The direction that returns positive values:

  • right (default) — Right turns return positive values.
  • left — Left turns return positive values.

Examples#

// Create the inertial instance
inertial myInertial = inertial(
    right);     // dir

Member Functions#

The inertial class includes the following member functions:

  • heading — Returns the direction the sensor is facing.

  • rotation — Returns how far the sensor has turned.

  • setHeading — Sets the sensor’s current heading to a new heading value.

  • setRotation — Sets the sensor’s current rotation to a new rotation value.

  • calibrate — Calibrates the Inertial Sensor.

  • resetHeading — Resets the sensor’s current heading to 0 degrees.

  • resetRotation — Resets the sensor’s current rotation to 0 degrees.

  • isCalibrating — Returns whether the Inertial Sensor is currently calibrating.

  • changed — Registers a callback function that runs when the heading changes.

  • installed — Returns whether the Inertial Sensor is installed.

  • acceleration — Returns how quickly the sensor is speeding up or slowing down on the selected axis.

  • gyroRate — Returns how fast the sensor is rotating on the selected axis.

  • orientation — Returns the Inertial Sensor’s roll, pitch, or yaw angle.

  • collision — Registers a callback function that runs when a collision is detected.

  • setTurnType — Sets which turn direction returns positive heading values.

  • getTurnType — Returns which turn direction produces positive values.

Before calling any inertial member functions, an inertial instance must be created, as shown below:

/* This constructor is required when using VS Code.
Inertial Sensor configuration is generated automatically
in VEXcode with the IQ (2nd gen) Brain. Replace the values
as needed. */

// Create the inertial instance
inertial myInertial = inertial();

heading#

A heading is the direction the sensor is facing, measured in degrees from 0 to 359.99. This function returns the sensor’s current heading.

The starting heading is 0 degrees. If the sensor turns past 359.99 degrees, the heading wraps back to 0 degrees.

Available Functions 
double heading( rotationUnits units = degrees );
Parameters

Parámetro

Type

Descripción

units

rotationUnits

The heading unit:

  • deg / degrees (default) — degrees
  • turns / rev — revolutions
Return Values

Returns a double representing the current heading of the sensor in the specified units.

Notes

  • The heading value is wrapped between 0 and 359.99 degrees. Use rotation to access the continuous rotation value.

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

rotation#

Returns the current rotation of the Inertial Sensor.

Rotation is how much the sensor has turned. Unlike heading, rotation can increase past 359.99 degrees or decrease below 0 degrees. For example, making two full turns to the right returns a rotation of 720 degrees. Turning one full turn to the left from 0 degrees returns a rotation of -360 degrees.

Available Functions 
double rotation( rotationUnits units = degrees );
Parameters

Parámetro

Type

Descripción

units

rotationUnits

The rotation unit:

  • deg / degrees (default) — degrees
  • turns / rev — revolutions
Return Values

Returns a double representing the current rotation in the specified units.

Notes

  • The rotation value is continuous and does not wrap between 0 and 359.99 degrees. Use heading to access the wrapped heading value.

Examples 
// Turn, then show the current rotation
Drivetrain.turnFor(right, 450, degrees);
Brain.Screen.print("%f", myInertial.rotation(degrees));

setHeading#

A heading is the direction the sensor is facing, measured in degrees from 0 to 359.99. This function changes the Inertial Sensor’s current heading to a new heading value.

For example, if the sensor has turned to face right, setting the heading to 0 degrees makes that right-facing position the new 0 degrees. Then the sensor can track other headings based on that new direction.

Available Functions 
void setHeading( double        value,
                 rotationUnits units );
Parameters

Parámetro

Type

Descripción

value

double

The heading value, in degrees, to set for the sensor. This can be a value from 0 to 359.99.

units

rotationUnits

The heading unit:

  • deg / degrees — degrees
  • turns / rev — revolutions
Return Values

This function does not return a value.

Examples 
// Turn the robot around
myInertial.setHeading(180, degrees);
Drivetrain.turnToHeading(0, degrees);

setRotation#

Sets the Inertial Sensor’s current rotation to a specified value.

Rotation is how much the sensor has turned. Unlike heading, rotation can increase past 359.99 degrees or decrease below 0 degrees.

Available Functions 
void setRotation( double        value,
                  rotationUnits units );
Parameters

Parámetro

Type

Descripción

value

double

The rotation value, in degrees, to set for the sensor. This can be an integer or a decimal.

units

rotationUnits

The rotation unit:

  • deg / degrees — degrees
  • turns / rev — revolutions
Return Values

This function does not return a value.

Examples 
// Turn the robot around
myInertial.setRotation(-180, degrees);
Drivetrain.turnToRotation(0, degrees);

calibrate#

Calibrates the Inertial Sensor.

Calibration helps the sensor measure turns correctly. Keep the sensor still during calibration. If the sensor moves during calibration, heading, rotation, gyro rate, and orientation values may not measure correctly.

Available Functions 
void calibrate( );
Parameters

This function does not accept any parameters.

Return Values

This function does not return a value.

Notes

  • The sensor should remain stationary while calibration is in progress.

  • Use isCalibrating to determine when calibration has completed.

resetHeading#

Resets the Inertial Sensor’s current heading to 0 degrees.

After this function is used, the sensor’s current direction becomes the new 0 degree heading.

Available Functions 
void resetHeading();
Parameters

This function does not take any parameters.

Return Values

This function does not return a value.

resetRotation#

Resets the Inertial Sensor’s current rotation to 0 degrees.

After this function is used, the sensor tracks future turns from the new 0 degree rotation value.

Available Functions 
void resetRotation();
Parameters

This function does not take any parameters.

Return Values

This function does not return a value.

isCalibrating#

Returns whether the Inertial Sensor is currently calibrating.

Available Functions 
bool isCalibrating();
Parameters

This function does not take any parameters.

Return Values

Returns a Boolean indicating whether the Inertial Sensor is calibrating:

  • true — The sensor is currently calibrating.
  • false — The sensor is not currently calibrating.

changed#

Registers a callback function that runs when the heading value of the Inertial Sensor changes.

Available Functions 
void changed( void (* callback)(void) );
Parameters

Parámetro

Type

Descripción

callback

void (*)(void)

A pointer to a function that will be called when the heading value changes. The function must take no parameters and return void.
Return Values

This function does not return a value.

Examples 
// Called when the inertial sensor's heading value changes
void onHeadingChanged() {
  Brain.Screen.clearScreen();
  Brain.Screen.setCursor(1, 1);
  Brain.Screen.print("Heading: %.2f", myInertial.heading());
}

myInertial.changed(onHeadingChanged);

installed#

Returns whether the Inertial Sensor is installed and connected.

Available Functions 
bool installed();
Parameters

This function does not take any parameters.

Return Values

Returns a Boolean indicating whether the Inertial Sensor is installed and connected:

  • true — The sensor is connected and responding.
  • false — The sensor is not connected or not detected.

acceleration#

Acceleration is how quickly the sensor is speeding up or slowing down. This function returns the acceleration of the Inertial Sensor on the selected axis, from -4.0 G to 4.0 G.

A G is a unit used to measure acceleration. 1 G is about the acceleration you feel from gravity while sitting still. The value can be positive or negative depending on the direction of acceleration on the selected axis.

Available Functions 
double acceleration( axisType axis );
Parameters

Parámetro

Type

Descripción

axis

axisType

The axis to measure acceleration on:

  • xaxis
  • yaxis
  • zaxis
Return Values

Returns a double representing the acceleration along the specified axis in G (gravitational units).

Notes

  • Acceleration values are reported in units of G.

gyroRate#

Gyro rate is how fast the Inertial Sensor is rotating. This function returns the current rotation speed of the Inertial Sensor on the selected axis.

The value can be positive or negative depending on the direction the sensor is rotating on that axis.

Available Functions 
double gyroRate( axisType      axis,
                 velocityUnits units );
Parameters

Parámetro

Type

Descripción

axis

axisType

The axis to return the gyro rate from:

  • xaxis
  • yaxis
  • zaxis

units

velocityUnits

The gyro rate unit:

  • dps — degrees per second
  • rpm — revolutions per minute
Return Values

Returns a double representing the current rotation speed along the specified axis in the selected units.

Examples 
// Display the rate of change of rotation while turning in dps
Drivetrain.turn(right);
wait(1, seconds);

Brain.Screen.print(myInertial.gyroRate(zaxis, dps));

Drivetrain.stop();

orientation#

Orientation is the Inertial Sensor’s current angle on a selected turning axis. This function returns the current orientation of the Inertial Sensor for the specified axis.

Roll, pitch, and yaw describe different ways the sensor can tilt or turn.

Available Functions 
double orientation(
  orientationType type,
  rotationUnits   units );
Parameters

Parámetro

Type

Descripción

type

orientationType

The orientation angle to return:

  • pitch
  • roll
  • yaw

units

rotationUnits

The orientation unit:

  • deg / degrees — degrees
  • turns / rev — revolutions
Return Values

Returns a double representing the selected orientation angle in the specified units.

Examples 
while (true) {
  Brain.Screen.clearScreen();
  Brain.Screen.setCursor(1,1);
  // Show the Inertial Sensor's orientation value
  // for roll in degrees
  double orient = myInertial.orientation(roll, deg);
  Brain.Screen.print("%f", orient);
  wait(0.1, seconds);
}

collision#

Registers a callback function that runs when the Inertial Sensor detects a sudden impact or collision.

Available Functions 
void collision( void (* callback)(axisType, double, double, double) );
Parameters

Parámetro

Type

Descripción

callback

void (*)(axisType, double, double, double)

A pointer to a function that will be called when a collision is detected. The callback function must accept the following parameters:

  • axisType — The axis on which the collision was detected.
  • Acceleration values at the time of impact, in order:
    • double — Acceleration along the x-axis (in G).
    • double — Acceleration along the y-axis (in G).
    • double — Acceleration along the z-axis (in G).
The function must return void.
Return Values

This function does not return a value.

Examples 
// Called when the Inertial Sensor detects a collision
void onCollision(axisType axis, double x, double y, double z) {
  Brain.Screen.print("Collision detected!");
}

// Firmly move the robot by hand briefly to simulate
// a collision and call the onCollision function
myInertial.collision(onCollision);

setTurnType#

Sets which turn direction returns positive values.

Available Functions 
void setTurnType( turnType dir );
Parameters

Parámetro

Type

Descripción

dir

turnType

The direction that returns positive values:

  • right
  • left
Return Values

This function does not return a value.

Notes

getTurnType#

Returns which turn direction produces positive values.

Available Functions 
turnType getTurnType();
Parameters

This function does not take any parameters.

Return Values

Returns a turnType indicating which direction produces positive values:

  • right — Clockwise rotation returns positive values.
  • left — Counterclockwise rotation returns positive values.
Notes
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