Constants

Tuning constants in mikLib

• The global Constants struct, which holds every motion constant used in Chassis.
• The PID structs (drive_constants, etc.).
• The motion parameter structs (turn_to_angle_params, etc.) passed to each motion.

Constants struct

A single global instance, constants, stores the defaults applied to every motion. Set these once at startup (or via the Chassis setters).

Drive constants

Used while driving. Heading constants keep the robot facing the target while it drives.

Field	Description
drive_min_voltage	Minimum voltage on the drive, used for chaining movements.
drive_max_voltage	Max voltage out of 12.
drive_kp / drive_ki / drive_kd	Proportional / integral / derivative constants.
drive_starti	Minimum distance (inches) for integral to begin.
drive_slew	Limits drive acceleration in volts per 10 ms.
drive_exit_error	Error (inches) at which the drive motion exits.
drive_settle_error	Error (inches) to be considered settled.
drive_settle_time	Time (ms) to be considered settled.
drive_timeout	Time (ms) before quitting and moving on.
heading_max_voltage	Max heading-correction voltage out of 12.
heading_kp / heading_ki / heading_kd	Heading PID constants.
heading_starti	Minimum distance (degrees) for integral to begin.
heading_slew	Limits heading-correction acceleration in volts per 10 ms.

Turn constants

Field	Description
turn_min_voltage	Minimum voltage for turning out of 12.
turn_max_voltage	Max voltage out of 12.
turn_kp / turn_ki / turn_kd	Turn PID constants.
turn_starti	Minimum angle (degrees) for integral to begin.
turn_slew	Limits turning acceleration in volts per 10 ms.
turn_exit_error	Error at which the turn motion exits.
turn_settle_error	Error (degrees) to be considered settled.
turn_settle_time	Time (ms) to be considered settled.
turn_timeout	Time (ms) before quitting and moving on.

Swing constants

Swinging turns the robot using one side of the drivetrain.

Field	Description
swing_min_voltage	Minimum voltage for swinging out of 12.
swing_opposite_voltage	Voltage on the opposite (non-swung) side out of 12.
swing_max_voltage	Max voltage out of 12.
swing_kp / swing_ki / swing_kd	Swing PID constants.
swing_starti	Minimum distance (degrees) for integral to begin.
swing_slew	Limits swinging acceleration in volts per 10 ms.
swing_exit_error	Error at which the swing motion exits.
swing_settle_error	Error (degrees) to be considered settled.
swing_settle_time	Time (ms) to be considered settled.
swing_timeout	Time (ms) before quitting and moving on.

Boomerang, control, and slew cutoffs

Field	Description
boomerang_lead	Scale factor for how far away the carrot point is.
boomerang_drift	Lower values give slower speeds while turning. Use higher (~8) for traction drives.
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 throttle (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 for split_arcade_curved (0 = prioritize turn, 1 = prioritize throttle).
turn_cutoff	Degrees within which slew stops being applied.
drive_cutoff	Inches within which slew stops and heading correction stops.

PID structs

Each motion's k (or drive_k / heading_k) field takes one of these. Their fields default to the matching values in constants, so you only override what you need:

// Sets the only the drive PID kP
drive_constants k = { .p = 2.0 };

struct drive_constants   { float p, i, d, starti, slew; };
struct heading_constants { float p, i, d, starti, slew; };
struct turn_constants    { float p, i, d, starti, slew; };
struct swing_constants   { float p, i, d, starti, slew; };

Field	Description
p	Proportional constant.
i	Integral constant.
d	Derivative constant.
starti	Minimum error for the integral term to begin.
slew	Limits acceleration in volts per 10 ms.

Motion parameter structs

Every Chassis motion takes an optional params struct as its last argument. All fields default to the global constants, so you override only what you need with designated initializers:

chassis.turn_to_angle(90, {.max_voltage = 6, .direction = mik::turn_direction::cw});

turn_to_angle_params / turn_to_point_params

Field	Description
direction	The way the robot should turn (ccw, cw, or shortest path).
angle_offset	(point only) Angle turned past the desired heading, in degrees.
min_voltage	Minimum voltage on the drive, used for chaining movements.
max_voltage	Max voltage on the drive out of 12.
exit_error	Distance from target (degrees) within which the motion exits.
settle_error	Error (degrees) to be considered settled.
settle_time	Time (ms) to be considered settled.
timeout	Time (ms) before quitting and moving on.
wait	Yields the program until the motion finishes (default true).
k	A turn_constants override.

swing_to_angle_params / swing_to_point_params

Same as the turn params above, plus:

Field	Description
opposite_voltage	Voltage on the opposite side of the drivetrain out of 12.
k	A swing_constants override.

drive_distance_params / strafe_distance_params

Field	Description
heading	Desired heading in degrees. Defaults to the current heading.
min_voltage	Minimum voltage on the drive, used for chaining movements.
max_voltage	Max voltage on the drive out of 12.
heading_max_voltage	Max voltage for getting to heading out of 12.
exit_error	Distance from target (inches) within which the motion exits.
settle_error	Error (inches) to be considered settled.
settle_time	Time (ms) to be considered settled.
timeout	Time (ms) before quitting and moving on.
wait	Yields the program until the motion finishes (default true).
drive_k / heading_k	drive_constants / heading_constants overrides.

drive_to_point_params / drive_to_pose_params

The drive params above, plus:

Field	Description
direction	Force a forward or reverse approach. Defaults to choosing automatically.
lead	(pose only) Scale factor for how far away the carrot point is.
drift	(pose only) Limits speed while turning; higher values increase lateral speed out of 10.

holonomic_to_pose_params

The drive params above, plus separate turn settling:

Field	Description
turn_settle_error	Turn error (degrees) to be considered settled.
turn_settle_time	Turn time (ms) to be considered settled.