Utils

There are a number of support functions and classes included in progpy.utils. These utilities are used throughout the package, but are also available for use in your own code.

Trajectory

class progpy.utils.traj_gen.Trajectory(lat, lon, alt, takeoff_time=None, etas=None, **kwargs)

Trajectory class.

This class generates a trajectory object that is used to create a smooth profile including position, velocity, acceleration, Euler’s angles, and attitude rates. The profiles are used to generate the desired state of a vehicle that needs to be followed to complete the trajectory.

Parameters

• lat (np.ndarray) – rad, n x 1 array, doubles, latitude coordinates of waypoints

• lon (np.ndarray) – rad, n x 1 array, doubles, longitude coordinates of waypoints

• alt (np.ndarray) – m, n x 1 array, doubles, altitude coordinates of waypoints

• takeoff_time (float, optional) – take off time of the trajectory. Default is None (starting at current time).

• etas (list[float], optional) – ETAs of each waypoints. Default is None. In that case, the ETAs are calculated based on the desired speed between waypoints.

kwargs:

gravity (float, optional):

Magnitude of force of gravity. Default 9.81 m/s^2

max_phi (float, optional):

Maximum Euler’s angle (rad). Default 45/180.0*np.pi

max_theta (float, optional):

maximum Euler’s angle (rad). Default 45/180.0*np.pi

max_iter (int, optional):

maximum number of iterations to adjust the trajectory according to the maximum average jerk. Default: 10

max_avgjerk (float, optional):

maximum average Jerk allowed (m/s^3), if the generated trajectory has a higher value, new, more forgiving ETAs are generated to satisfy this constraint. Default: 20

nurbs_order (int, optional):

order of the NURBS used to generate the position profile. Default: 4

waypoint_weight (int, optional):

default weight value associated to all the waypoints. Default: 20

weight_vector (np.ndarray, optional):

Waypoint weight vector. Default is None (all waypoints will have same value from ‘waypoint_weight’). If passed, the user can define different weight for each waypoints, such that some waypoints will be approached more closely and some will be approached more smoothly.

nurbs_basis_length (int, optional):

default length of basis function used to generate the position profile with the NURBS.Default: 1000

cruise_speed (float, optional):

desired cruise speed between waypoints (m/s). If ETAs are provided, this value is ignored. Default = 6.0.

ascent_speed (float, optional):

desired ascent speed (m/s) between waypoints. If ETAs are provided, this value is ignored. Defualt: 3

descent_speed (float, optional):

desired descent speed (m/s) between waypoints. If ETAs are provided, this value is ignored. Default: 3

landing_speed (float, optional):

desired landing speed (m/s) between waypoints. This speed is used when the vehicle’s altitude is lower than ‘landing_altitude’ parameter. If ETAs are provided, this value is ignored. Default: 1.5

landing_altitude (float, optional):

landing altitude (m) below which the vehicle is supposed to move at ‘landing_speed’. Default: 10.5

generate(dt, **kwargs)

Generate trajectory given the waypoints and desired velocity or ETAs. The function requires the time step size dt, in seconds, used to interpolate the waypoints and generate the trajectory.

Parameters

dt – s, scalar, time step size used to interpolate the waypoints and generate the trajectory

Returns

dictionary of state variables describing the trajectory as a function of time