Module pyastrobee.config.astrobee_motion

Astrobee constants associated with motion planning and control

Note: The nominal operating mode is good for most operations. Astrobee is in general very slow, so it is sometimes interesting to use the higher limits on velocity and acceleration. But, Astrobee is also pretty limited in the amount of force/torque it can provide, so if we're operating in a faster mode, this can lead to some highly dynamic motions that are hard to recover from.

Sourced from: - astrobee/gds_configs/AllOperatingLimitsConfig.json - A Brief Guide to Astrobee

View Source

"""Astrobee constants associated with motion planning and control

Note: The nominal operating mode is good for most operations. Astrobee is in general very slow, so it is sometimes

interesting to use the higher limits on velocity and acceleration. But, Astrobee is also pretty limited in the amount

of force/torque it can provide, so if we're operating in a faster mode, this can lead to some highly dynamic motions

that are hard to recover from.

Sourced from:

- astrobee/gds_configs/AllOperatingLimitsConfig.json

- A Brief Guide to Astrobee

"""

# TODO make flight mode an input somewhere, rather than a hardcoded variable here?

# TODO improve force/torque magnitude handling

from enum import Enum

import numpy as np

class FlightModes(Enum):

    # Standard flight modes specified in the NASA codebase

    QUIET = 0

    DIFFICULT = 1

    NOMINAL = 2

    LOMO = 3  # (not entirely sure what this mode means. locomotion?)

    # Custom flight modes

    MAXED_OUT = -1

# TODO: Update this parameter if testing a different mode

FLIGHT_MODE = FlightModes.NOMINAL

if FLIGHT_MODE == FlightModes.QUIET:

    LINEAR_SPEED_LIMIT = 0.02  # m/s

    LINEAR_ACCEL_LIMIT = 0.002  # m/s^2

    ANGULAR_SPEED_LIMIT = 0.0174  # rad/s

    ANGULAR_ACCEL_LIMIT = 0.0174  # rad/s^2

elif FLIGHT_MODE == FlightModes.DIFFICULT:

    LINEAR_SPEED_LIMIT = 0.4  # m/s

    LINEAR_ACCEL_LIMIT = 0.02  # m/s^2

    ANGULAR_SPEED_LIMIT = 0.5236  # rad/s

    ANGULAR_ACCEL_LIMIT = 0.2500  # rad/s^2

elif FLIGHT_MODE == FlightModes.NOMINAL:

    LINEAR_SPEED_LIMIT = 0.2  # m/s

    LINEAR_ACCEL_LIMIT = 0.0175  # m/s^2

    ANGULAR_SPEED_LIMIT = 0.1745  # rad/s

    ANGULAR_ACCEL_LIMIT = 0.1745  # rad/s^2

elif FLIGHT_MODE == FlightModes.LOMO:

    LINEAR_SPEED_LIMIT = 0.15  # m/s

    LINEAR_ACCEL_LIMIT = 0.0175  # m/s^2

    ANGULAR_SPEED_LIMIT = 0.0873  # rad/s

    ANGULAR_ACCEL_LIMIT = 0.1745  # rad/s^2

elif FLIGHT_MODE == FlightModes.MAXED_OUT:

    # Use the absolute maximum values that our actuators can provide

    # Acceleration limits are calculated using standard rigid body dynamics (F=ma, t=Ia)

    # with the Astrobee's mass and inertia properties

    # Speed limits are left the same as the ISS_DIFFICULT profile

    LINEAR_SPEED_LIMIT = 0.4  # m/s

    LINEAR_ACCEL_LIMIT = 0.042  # m/s^2

    ANGULAR_SPEED_LIMIT = 0.5236  # rad/s

    ANGULAR_ACCEL_LIMIT = 0.2840  # rad/s^2

else:

    raise NotImplementedError("Flight mode has not been implemented")

# For forces/torques, assume we can operate at up to the max motor speed in RPM

# See the Astrobee guide for more values if this is not the case

MAX_FORCE = np.array([0.849, 0.406, 0.486])  # Max force applied in local xyz axes

MAX_TORQUE = MAX_FORCE / 10  # Max torques about local xyz axes

# NOTE: The torque values are an approximation. See guide for reasoning

# Slightly hacky force/torque magnitude values... In theory the world-frame force values depend on the orientation

# of Astrobee, but we'll ignore this for now

MAX_FORCE_MAGNITUDE = 0.849

MAX_TORQUE_MAGNITUDE = 0.849 / 10

Variables

ANGULAR_ACCEL_LIMIT

ANGULAR_SPEED_LIMIT

FLIGHT_MODE

LINEAR_ACCEL_LIMIT

LINEAR_SPEED_LIMIT

MAX_FORCE

MAX_FORCE_MAGNITUDE

MAX_TORQUE

MAX_TORQUE_MAGNITUDE

Classes

FlightModes

class FlightModes(
    /,
    *args,
    **kwargs
)

An enumeration.

View Source

class FlightModes(Enum):

    # Standard flight modes specified in the NASA codebase

    QUIET = 0

    DIFFICULT = 1

    NOMINAL = 2

    LOMO = 3  # (not entirely sure what this mode means. locomotion?)

    # Custom flight modes

    MAXED_OUT = -1

---

Ancestors (in MRO)

• enum.Enum

Class variables

DIFFICULT

LOMO

MAXED_OUT

NOMINAL

QUIET

name

value