Pathfinder API¶
-
class
pathfinder.
Segment
¶ -
property
acceleration
¶
-
property
dt
¶
-
property
heading
¶
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property
jerk
¶
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property
position
¶
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property
velocity
¶
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property
x
¶
-
property
y
¶
-
property
-
class
pathfinder.
TrajectoryInfo
¶ -
property
dt
¶
-
property
filter1
¶
-
property
filter2
¶
-
property
impulse
¶
-
property
length
¶
-
property
u
¶
-
property
v
¶
-
property
-
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
()¶ Convert angle x from degrees to radians.
-
pathfinder.
r2d
()¶ Convert angle x from radians to 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 defaultkv (
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 controllerska (
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
-
-
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 trackticks_per_revolution (
int
) – How many ticks per revolution the encoder haswheel_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 defaultkv (
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 controllerska (
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
-
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
]
-
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 drivebasewheelbase_depth (
float
) – The width (in meters) between the individual front-back sides of the drivebase
- Return type
- 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
]
-
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.
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