Trackers¶

A client-side tracker mirrors franky and sends references over the conflated tracker socket:

import time

with robot.start_joint_impedance_tracker(stiffness=[10.0] * 7) as tracker:
    deadline = time.monotonic() + 10.0
    while time.monotonic() < deadline and tracker.tick() is not None:
        tracker.set_target(q, dq=dq)

Leaving the with block stops the tracker. tick() returns None when control ends.

Every control cycle, the robot produces a ~2.5 KB RobotState object. Depending on your network configuration, this might be too much information to send every control cycle. So zero_franky’s tracker.state and robot.latest_state are specialized msgpack dictionaries which only contain subsets of the full franky.RobotState values.

The default is the fast profile, which contains:

Key	Meaning
`q`, `dq`	Measured joint position and velocity.
`O_T_EE`	Measured end-effector pose.
`O_F_ext_hat_K`, `K_F_ext_hat_K`, `tau_ext_hat_filtered`	Force/torque estimates.
`O_dP_EE_est`	Estimated end-effector twist.
`time_step`	Duration of the last control cycle, in seconds.
`rel_time`	Time elapsed since the motion started, in seconds.
`abs_time`	Robot time, in seconds.
`control_signal`	Motion-specific control signal produced by `franky`.
`robot_id`	Server-assigned identifier for the robot proxy.
`in_control`	Whether the robot is still executing the motion.
`reference`	Latest reference accepted by the controller; motion-specific.

reference is JointReference, CartesianReference, or Torque, with a motion-specific payload.

Accessing Extended State Information¶

Use full to stream all 54 RobotState fields, or specify a comma-separated list of fields:

zero-franky server --state-fields full
zero-franky server --state-fields q,dq,O_T_EE

For lower latency, run the policy beside franky on the server:

policy_transport="import": the policy must be installed as a module on the server.
policy_transport="cloudpickle": the policy is serialized and sent over RPC.

A policy step returns a joint or Cartesian reference, None to hold the current reference, or False / {"stop": True} to stop.