Exceptions

Exception hierarchy for error handling in pylibfranka.

Exception Hierarchy

All pylibfranka exceptions inherit from FrankaException:

FrankaException (base)
├── CommandException
├── NetworkException
├── ControlException
├── InvalidOperationException
└── RealtimeException

Exception Classes

FrankaException

exception pylibfranka.FrankaException

Bases: Exception

Base exception for all Franka-related errors.

All exceptions in pylibfranka inherit from this base class, allowing you to catch all library-specific exceptions with a single except clause.

Example:

import pylibfranka

try:
    robot = pylibfranka.Robot("172.16.0.2")
    control = robot.start_torque_control()
    # ... control code ...
except pylibfranka.FrankaException as e:
    print(f"Franka error occurred: {e}")

CommandException

exception pylibfranka.CommandException

Bases: RuntimeError

Thrown if an error occurs during command execution.

This exception is raised when:

• A robot command (e.g., Robot.set_collision_behavior()) fails

• Configuration changes are rejected by the robot

• Commands contain invalid parameters

NetworkException

exception pylibfranka.NetworkException

Bases: RuntimeError

Thrown if a connection to the robot cannot be established, or when a timeout occurs.

This exception is raised when:

• Initial connection to the robot fails

• Network connection is lost during operation

• Communication timeout occurs

• Robot is not reachable on the network

Handling in control loop:

import pylibfranka

robot = pylibfranka.Robot("172.16.0.2")

try:
    state = robot.read_once()
except pylibfranka.NetworkException as e:
    print(f"Lost connection: {e}")
    # Attempt reconnection...

ControlException

exception pylibfranka.ControlException

Bases: RuntimeError

Thrown if an error occurs during motion generation or torque control.

This exception is raised when:

• Motion generator detects discontinuities

• Joint limits are violated

• Cartesian limits are exceeded

• Safety thresholds are triggered

• Commanded values cause instability

Common causes:

• Velocity discontinuities in commands

• Acceleration discontinuities

• Torque discontinuities

• Collision detected

• Position limits exceeded

InvalidOperationException

exception pylibfranka.InvalidOperationException

Bases: RuntimeError

Thrown if an operation cannot be performed.

This exception is raised when:

• Attempting to start a control loop while one is already running

• Calling methods in an invalid state

• Conflicting operations are requested

RealtimeException

exception pylibfranka.RealtimeException

Bases: RuntimeError

Thrown if real-time scheduling requirements cannot be met.

This exception is raised when:

• Real-time scheduling cannot be enabled (Linux RT kernel required)

• Real-time priority cannot be set

• RealtimeConfig.kEnforce is used without proper permissions

See Also

• Robot – Robot control interface that may raise exceptions

• RobotState – Use current_errors and last_motion_errors attributes

• Errors – Detailed error information