Chassis

How to interact with the robot

Constructor

Chassis(mik::motor_group left_drive, mik::motor_group right_drive, int inertial_port,
        double inertial_scale, bool force_calibrate_inertial, double wheel_diameter,
        double drivetrain_rpm, int forward_tracker_port, double forward_tracker_diameter,
        double forward_tracker_center_distance, int sideways_tracker_port,
        double sideways_tracker_diameter, double sideways_tracker_center_distance,
        mik::distance_reset reset_sensors);

Parameter	Description
left_drive / right_drive	Motor groups for each side of the robot.
inertial_port	Inertial sensor port (1-21).
inertial_scale	Scale factor applied to raw gyro angles to correct drift.
force_calibrate_inertial	If true, keeps calibrating until drift is within threshold for 1 second.
wheel_diameter	Drivetrain wheel diameter, in inches.
drivetrain_rpm	RPM of the drivetrain output (after gearing).
forward_tracker_port	Forward tracker rotation sensor port (1-21). Use PORT0 for motor encoders.
forward_tracker_diameter	Forward tracking-wheel diameter, in inches.
forward_tracker_center_distance	Distance from chassis center to the forward tracker, in inches.
sideways_tracker_port	Sideways tracker rotation sensor port (1-21).
sideways_tracker_diameter	Sideways tracking-wheel diameter, in inches.
sideways_tracker_center_distance	Distance from chassis center to the sideways tracker, in inches.
reset_sensors	Distance sensors parallel to a robot face that can reset odometry axes.

Motion algorithms

Each motion blocks until it finishes by default (wait = true). It also can take multiple individual constants passed as struct (documented on the Constants page), so you override only what you need:

chassis.drive_distance(24);                      // all defaults
chassis.turn_to_angle(90, {.max_voltage = 6});   // override max voltage

drive_with_voltage

void drive_with_voltage(float left_voltage, float right_voltage);

Drives each side of the chassis at the specified voltage (-12 to 12; negative drives that side backward).

Reset of motions are documented here

Async control

Use these to chain or interrupt motions when running them non-blocking ({.wait = false}).

Method	Description
void wait()	Yields until the current motion finishes.
void wait_until(float units)	Yields until the motion has traveled units (inches for drives, degrees for turns).
void wait_until(float units, vex::percentUnits)	Same, where units is 0-100 percent of the motion.
void wait_until_within(float units)	Yields until the motion is within units of the target.
bool is_in_motion()	Returns true if the robot is in motion.
void cancel_motion()	Cancels the current motion, leaving drive voltage at min_voltage so the next motion starts without stopping.

Odometry

Method	Description
void set_coordinates(float X_position, float Y_position, float orientation_deg)	Sets the robot's position and heading, and also starts the odometry task
void set_heading(float orientation_deg)	Sets just the robot's heading.
float get_X_position() / float get_Y_position()	The robot's x / y position in inches.
void position_track()	Runs one iteration of the odometry update loop.
static int position_track_task()	VEX task entry point that continuously calls position_track(). Pass to vex::task.

Distance Resets

important

Distance resets only work if you use the absolute positioning system. Where 0, 0 is at the center of the field. Using path.jerryio is recommended.

important

This simulator is how distance resets work in mikLib

reset_axis

bool reset_axis(mik::distance_position sensor_pos, float max_reset_distance, int reset_attempts = 1);
bool reset_axis(mik::distance_position sensor_pos, mik::wall_position wall_pos,
                float max_reset_distance, int reset_attempts = 1);

Resets an X or Y odometry axis using a distance sensor facing a wall. The wall is detected automatically from the robot's pose, or you can specify it with wall_pos. Returns true if the axis was reset successfully.

Parameter	Description
sensor_pos	The side of the robot the distance sensor is mounted on.
wall_pos	The wall to reset against, overriding automatic detection.
max_reset_distance	Maximum distance (inches) an axis is allowed to change.
reset_attempts	Number of readings to average before applying the reset.

Driver control

Call one drive mode every loop in the usercontrol task, or use control() to dispatch by the selected mode.

Method	Description
void split_arcade()	Left stick throttle (Axis3), right stick turn (Axis1), with deadband.
void split_arcade_curved()	Split arcade with an exponential response curve; desaturates combined output.
void tank()	Left stick controls the left side (Axis3), right stick the right (Axis2).
void tank_curved()	Tank with an exponential curve per stick.
void field_centric_holonomic()	Field-centric holonomic control (inputs rotated by heading).
void split_arcade_holonomic()	Robot-centric holonomic split arcade: Axis3 throttle, Axis1 turn, Axis4 strafe.
void control(mik::drive_mode dm)	Dispatches joystick input based on the given drive mode.
void enable_control() / void disable_control()	Enable/disable joystick control of the drivetrain.

Setters

These override the global tuning Constants at runtime.

PID constants

void set_drive_constants(float drive_max_voltage, float drive_kp, float drive_ki, float drive_kd, float drive_starti, float drive_slew);
void set_heading_constants(float heading_max_voltage, float heading_kp, float heading_ki, float heading_kd, float heading_starti, float heading_slew);
void set_turn_constants(float turn_max_voltage, float turn_kp, float turn_ki, float turn_kd, float turn_starti, float turn_slew);
void set_swing_constants(float swing_max_voltage, float swing_kp, float swing_ki, float swing_kd, float swing_starti, float swing_slew);

Each setter resets the default constants for one PID controller.

Parameter	Description
max_voltage	Max voltage out of 12.
kp	Proportional constant.
ki	Integral constant.
kd	Derivative constant.
starti	Minimum error before the integral term begins accumulating (degrees for turn/heading/swing, inches for drive).
slew	Slew rate, in volts per 10 ms.

Controller	Affects
drive	drive_distance(), drive_to_point(), drive_to_pose(), holonomic_to_pose(), strafe_distance()
heading	Keeps the robot facing the target during every drive motion.
turn	turn_to_angle(), turn_to_point()
swing	left_swing_to_angle(), right_swing_to_angle(), left_swing_to_point(), right_swing_to_point()

Exit conditions

void set_drive_exit_conditions(float drive_settle_error, float drive_settle_time, float drive_timeout);
void set_turn_exit_conditions(float turn_settle_error, float turn_settle_time, float turn_timeout);
void set_swing_exit_conditions(float swing_settle_error, float swing_settle_time, float swing_timeout);

A motion exits once error stays below settle_error for settle_time, or once timeout elapses.

Parameter	Description
settle_error	Error to be considered settled (inches for drive, degrees for turn/swing).
settle_time	Time within settle_error before settling, in milliseconds.
timeout	Time before quitting and moving on, in milliseconds.

Driver control constants

void set_control_constants(float control_throttle_deadband, float control_throttle_min_output, float control_throttle_curve_gain, float control_turn_deadband, float control_turn_min_output, float control_turn_curve_gain, float control_desaturate_bias);

Resets the joystick deadbands and expo curves for throttle and turn. Tune it visually in Desmos.

Parameter	Description
control_throttle_deadband	Deadband percent for the throttle axis.
control_throttle_min_output	Minimum throttle output percent after deadband.
control_throttle_curve_gain	Expo gain for the throttle axis (1 linear, 1.06 very curvy).
control_turn_deadband	Deadband percent for the turn axis.
control_turn_min_output	Minimum turn output percent after deadband.
control_turn_curve_gain	Expo gain for the turn axis.
control_desaturate_bias	Desaturation bias when throttle + turn exceeds 100 (0 = prioritize turn, 1 = prioritize throttle, default 0.5).

Tracking offsets

void set_tracking_offsets(float forward_tracker_center_distance, float sideways_tracker_center_distance);

Updates the tracker offsets when the robot's center of rotation changes (e.g. clamping onto a large game object).

Parameter	Description
forward_tracker_center_distance	Distance from the chassis center to the forward tracker, in inches.
sideways_tracker_center_distance	Distance from the chassis center to the sideways tracker, in inches.

Brake type

void set_brake_type(vex::brakeType brake);

Globally sets the brake mode (coast, brake, hold) for both drive motor groups. Defaults to coast.

Other utilities

Method	Description
void stop_drive(vex::brakeType brake = undefined)	Stops both sides of the drivetrain.
void calibrate_inertial()	Calibrates the inertial sensor (until within threshold for 1s if force-calibrating).
float get_rotation()	Inertial rotation scaled by inertial_scale, in degrees.
float get_absolute_heading()	Field-relative heading (0-360°).
float get_motor_encoder_position()	Average of the left/right drive encoders, in inches.
float get_left_drive_position(int index = -1) / get_right_drive_position(int index = -1)	Side drive position in inches; -1 averages the side.
float get_forward_tracker_position() / get_sideways_tracker_position()	Tracker positions in inches.
void mirror_all_auton_x_pos() / mirror_all_auton_y_pos()	Mirror all subsequent coordinates/angles across the X / Y axis (for the opposite field side).
void disable_mirroring()	Disables all mirroring.
bool x_pos_mirrored() / bool y_pos_mirrored()	Whether X / Y coordinates are currently mirrored.

Public members

Member	Description
mik::tracker_mode tracker_mode	Tracking mode used for odometry.
vex::brakeType stop_behavior	How the robot stops after a motion. A min_voltage > 0 skips this.
bool sideways_tracker_used	True if a sideways tracker is configured.
mik::drive_mode selected_drive_mode	The drive mode used by control().
float percent_traveled	Progress through the current motion, 0-100.
bool position_tracking	True while the odometry task is running.
bool control_disabled	True when joystick control is disabled.
desired_angle, desired_distance, desired_heading, desired_X_position, desired_Y_position, desired_angle_offset	Current motion setpoints (useful for graphing or cross-task access).