Pathfinder API¶

class pathfinder.Segment¶

acceleration¶

dt¶

heading¶

jerk¶

position¶

velocity¶

x¶

y¶

class pathfinder.Waypoint¶

angle¶

x¶

y¶

class pathfinder.TrajectoryInfo¶

dt¶

filter1¶

filter2¶

impulse¶

length¶

u¶

v¶

pathfinder.generate()¶

pathfinder_generate(path: List[pathfinder._pathfinder.Waypoint], fit: capsule, sample_count: int, dt: float, max_velocity: float, max_acceleration: float, max_jerk: float) -> Tuple[pathfinder._pathfinder.TrajectoryInfo, List[pathfinder._pathfinder.Segment]]

Generate a motion profile trajectory using the given waypoints and configuration.

Parameters:	path – A list of waypoints (setpoints) for the trajectory path to intersect fit – A fit function; use FIT_HERMITE_CUBIC or FIT_HERMITE_QUINTIC sample_count – dt – max_velocity – max_acceleration – max_jerk –
Returns:	A tuple of TrajectoryInfo, and a generated trajectory (a list of segments)

pathfinder.d2r()¶

radians(x)

Convert angle x from degrees to radians.

pathfinder.r2d()¶

degrees(x)

Convert angle x from radians to degrees.

pathfinder.boundHalfDegrees(degrees)[source]¶: Bound an angle (in degrees) to -180 to 180 degrees.

Followers¶

class pathfinder.followers.DistanceFollower(trajectory)[source]¶

The DistanceFollower is an object designed to follow a trajectory based on distance covered input. This class can be used for Tank or Swerve drive implementations.

calculate(distance_covered)[source]¶

Calculate the desired output for the motors, based on the distance the robot has covered. This does not account for heading of the robot. To account for heading, add some extra terms in your control loop for realignment based on gyroscope input and the desired heading given by this object.

Parameters:	distance_covered (`float`) – The distance covered in meters
Return type:	`float`
Returns:	The desired output for your motor controller

configurePIDVA(kp, ki, kd, kv, ka)[source]¶

Configure the PID/VA Variables for the Follower

Parameters:

kp (float) – The proportional term. This is usually quite high (0.8 - 1.0 are common values)
ki (float) – The integral term. Currently unused.
kd (float) – The derivative term. Adjust this if you are unhappy with the tracking of the follower. 0.0 is the default
kv (float) – The velocity ratio. This should be 1 over your maximum velocity @ 100% throttle. This converts m/s given by the algorithm to a scale of -1..1 to be used by your motor controllers
ka (float) – The acceleration term. Adjust this if you want to reach higher or lower speeds faster. 0.0 is the default

Return type:

None

getHeading()[source]¶

Return type:	`float`
Returns:	the desired heading of the current point in the trajectory

getSegment()[source]¶

Return type:	`Segment`
Returns:	the current segment being operated on

isFinished()[source]¶

Return type:	`bool`
Returns:	whether we have finished tracking this trajectory or not.

reset()[source]¶

Reset the follower to start again. Encoders must be reconfigured.

Return type:	None

setTrajectory(trajectory)[source]¶

Set a new trajectory to follow, and reset the cumulative errors and segment counts

Return type:	None

class pathfinder.followers.EncoderFollower(trajectory)[source]¶

The EncoderFollower is an object designed to follow a trajectory based on encoder input. This class can be used for Tank or Swerve drive implementations.

calculate(encoder_tick)[source]¶

Calculate the desired output for the motors, based on the amount of ticks the encoder has gone through. This does not account for heading of the robot. To account for heading, add some extra terms in your control loop for realignment based on gyroscope input and the desired heading given by this object.

Parameters:	encoder_tick (`int`) – The amount of ticks the encoder has currently measured.
Return type:	`float`
Returns:	The desired output for your motor controller

configureEncoder(initial_position, ticks_per_revolution, wheel_diameter)[source]¶

Configure the Encoders being used in the follower.

Parameters:	initial_position (`int`) – The initial ‘offset’ of your encoder. This should be set to the encoder value just before you start to track ticks_per_revolution (`int`) – How many ticks per revolution the encoder has wheel_diameter (`float`) – The diameter of your wheels (or pulleys for track systems) in meters
Return type:	None

configurePIDVA(kp, ki, kd, kv, ka)[source]¶

Configure the PID/VA Variables for the Follower

Parameters:

kp (float) – The proportional term. This is usually quite high (0.8 - 1.0 are common values)
ki (float) – The integral term. Currently unused.
kd (float) – The derivative term. Adjust this if you are unhappy with the tracking of the follower. 0.0 is the default
kv (float) – The velocity ratio. This should be 1 over your maximum velocity @ 100% throttle. This converts m/s given by the algorithm to a scale of -1..1 to be used by your motor controllers
ka (float) – The acceleration term. Adjust this if you want to reach higher or lower speeds faster. 0.0 is the default

Return type:

None

getHeading()[source]¶

Return type:	`float`
Returns:	the desired heading of the current point in the trajectory

getSegment()[source]¶

Return type:	`Segment`
Returns:	the current segment being operated on

isFinished()[source]¶

Return type:	`bool`
Returns:	whether we have finished tracking this trajectory or not.

reset()[source]¶

Reset the follower to start again. Encoders must be reconfigured.

Return type:	None

setTrajectory(trajectory)[source]¶

Set a new trajectory to follow, and reset the cumulative errors and segment counts

Return type:	None

Modifiers¶

class pathfinder.modifiers.SwerveModifier(source)[source]¶

The Swerve Modifier will take in a Source Trajectory and spit out 4 trajectories, 1 for each wheel on the drive. This is commonly used in robotics for robots with 4 individual wheels in a ‘swerve’ configuration, where each wheel can rotate to a specified heading while still being powered.

The Source Trajectory is measured from the centre of the drive base. The modification will not modify the central trajectory

getBackLeftTrajectory()[source]¶

Get the trajectory for the back-left wheel of the drive base

Return type:	`List`[`Segment`]

getBackRightTrajectory()[source]¶

Get the trajectory for the back-right wheel of the drive base

Return type:	`List`[`Segment`]

getFrontLeftTrajectory()[source]¶

Get the trajectory for the front-left wheel of the drive base

Return type:	`List`[`Segment`]

getFrontRightTrajectory()[source]¶

Get the trajectory for the front-right wheel of the drive base

Return type:	`List`[`Segment`]

getSourceTrajectory()[source]¶

Get the initial source trajectory

Return type:	`List`[`Segment`]

modify(wheelbase_width, wheelbase_depth)[source]¶

Generate the Trajectory Modification

Parameters:	wheelbase_width (`float`) – The width (in meters) between the individual left-right sides of the drivebase wheelbase_depth (`float`) – The width (in meters) between the individual front-back sides of the drivebase
Return type:	`SwerveModifier`
Returns:	self

class pathfinder.modifiers.TankModifier(source)[source]¶

The Tank Modifier will take in a Source Trajectory and a Wheelbase Width and spit out a Trajectory for each side of the wheelbase. This is commonly used in robotics for robots which have a drive system similar to a ‘tank’, where individual parallel sides are driven independently

The Source Trajectory is measured from the centre of the drive base. The modification will not modify the central trajectory

getLeftTrajectory()[source]¶

Get the trajectory for the left side of the drive base

Return type:	`List`[`Segment`]

getRightTrajectory()[source]¶

Get the trajectory for the right side of the drive base

Return type:	`List`[`Segment`]

getSourceTrajectory()[source]¶

Get the initial source trajectory

Return type:	`List`[`Segment`]

modify(wheelbase_width)[source]¶

Generate the Trajectory Modification

Parameters:	wheelbase_width (`float`) – The width (in meters) between the individual sides of the drivebase
Return type:	`TankModifier`
Returns:	self

Serialization¶

For serializing/deserializing in python programs, it’s probably easiest to use Python’s pickle module to directly serialize a trajectory:

import pickle

with open('fname', 'wb') as fp:
    pickle.dump(trajectory, fp)

with open('fname', 'rb') as fp:
    trajectory = pickle.load(fp)

One advantage to this approach is that you could put multiple trajectories in a data structure such as a dictionary, and serialize them all in a single file. The pathfinder compatibility serialization routines only support a single trajectory per file.

However, for compatibility with other pathfinder implementations, the following functions are made available.

pathfinder.deserialize()¶

pathfinder_deserialize(fname: str) -> List[pathfinder._pathfinder.Segment]

Read a Trajectory from a Binary (non human readable) file

pathfinder.deserialize_csv(fname)[source]¶: Read a Trajectory from a CSV File

pathfinder.serialize()¶

pathfinder_serialize(fname: str, trajectory: List[pathfinder._pathfinder.Segment]) -> bool

Write the Trajectory to a Binary (non human readable) file

pathfinder.serialize_csv()¶

pathfinder_serialize_csv(fname: str, trajectory: List[pathfinder._pathfinder.Segment]) -> bool

Write the Trajectory to a CSV File