feat(rl): add bus-control primitives and smooth move functionality for leader intervention

src/lerobot/teleoperators/so_leader/so_leader_follower.py

@@ -36,6 +36,12 @@ intact (so :func:`get_action` returns ``{"<motor>.pos": float}``) while adding:
   toggled on, leader torque is disabled so the user can move it freely.
 * Lower position-loop gains on :func:`connect` (``P=16, I=0, D=16``) so the
   haptic follow does not jerk the user's hand when grabbing the leader.
+* Bus-control primitives (:func:`enable_torque`, :func:`disable_torque`,
+  :func:`write_goal_positions`) and a :func:`smooth_move_to` helper. These
+  satisfy the ``teleop_has_motor_control`` capability gate in
+  ``examples/hil/hil_utils.py``, so the BC-style HIL data collector
+  (``examples/hil/hil_data_collection.py``) can drive an SO leader the same way
+  it drives the OpenArm Mini -- pause / smooth-mirror to follower / take over.
 
 The joint-to-EE-delta conversion does **not** happen here; it is performed by
 :class:`LeaderArmInterventionStep` in the action processor pipeline so the
@@ -48,6 +54,7 @@ import contextlib
 import logging
 import os
 import sys
+import time
 from typing import Any
 
 import numpy as np
@@ -170,16 +177,101 @@ class SOLeaderFollower(SOLeader):
         self._listener.daemon = True
         self._listener.start()
 
+    def enable_torque(self) -> None:
+        """Enable position-loop torque on every motor.
+
+        Exposed alongside :func:`disable_torque` and :func:`write_goal_positions`
+        so this teleop satisfies the ``teleop_has_motor_control`` gate used by
+        ``examples/hil/hil_data_collection.py`` (mirrors the OpenArm Mini API).
+        Errors are logged and swallowed -- the loop must keep ticking even if a
+        single haptic update fails.
+        """
+        if not self.is_connected:
+            return
+        try:
+            self.bus.sync_write("Torque_Enable", 1)
+            self._leader_torque_enabled = True
+        except Exception as e:  # pragma: no cover - hardware path
+            logger.warning(f"[SOLeaderFollower] could not enable leader torque: {e}")
+
+    def disable_torque(self) -> None:
+        """Disable position-loop torque so the user can move the leader freely."""
+        if not self.is_connected:
+            return
+        try:
+            self.bus.sync_write("Torque_Enable", 0)
+            self._leader_torque_enabled = False
+        except Exception as e:  # pragma: no cover - hardware path
+            logger.warning(f"[SOLeaderFollower] could not disable leader torque: {e}")
+
+    def write_goal_positions(self, positions: dict[str, float]) -> None:
+        """Push goal positions to the leader bus (no torque toggling).
+
+        Accepts dataset-style keys ``{"<motor>.pos": deg}`` (matches what
+        :func:`get_action` produces and what :func:`smooth_move_to` and
+        :func:`send_action` consume) -- bare motor names are also tolerated
+        for parity with :class:`OpenArmMini.write_goal_positions`.
+        """
+        if not self.is_connected:
+            return
+        goal_pos: dict[str, float] = {}
+        for motor in self.bus.motors:
+            if f"{motor}.pos" in positions:
+                goal_pos[motor] = float(positions[f"{motor}.pos"])
+            elif motor in positions:
+                goal_pos[motor] = float(positions[motor])
+        if not goal_pos:
+            return
+        try:
+            self.bus.sync_write("Goal_Position", goal_pos)
+        except Exception as e:  # pragma: no cover - hardware path
+            logger.warning(f"[SOLeaderFollower] could not push goal position to leader: {e}")
+
+    def smooth_move_to(
+        self,
+        target_pos: dict[str, float],
+        duration_s: float = 2.0,
+        fps: int = 50,
+    ) -> None:
+        """Linearly ramp the leader from its current pose to ``target_pos``.
+
+        Mirrors the ``teleop_smooth_move_to`` helper from
+        ``examples/hil/hil_utils.py`` so the leader can be safely re-engaged
+        without yanking the user's hand -- typical use is right after
+        :func:`connect` (or whenever the leader and follower drift apart, e.g.
+        on episode reset). Blocks for ``duration_s`` seconds.
+        """
+        if not self.is_connected:
+            return
+
+        steps = max(int(duration_s * fps), 1)
+        try:
+            current = self.get_action()
+        except Exception as e:  # pragma: no cover - hardware path
+            logger.warning(f"[SOLeaderFollower] smooth_move_to could not read current pose: {e}")
+            return
+
+        self.enable_torque()
+        if not self._leader_torque_enabled:
+            return
+
+        for step in range(steps + 1):
+            t = step / steps
+            interp = {}
+            for key, current_val in current.items():
+                if key in target_pos:
+                    interp[key] = current_val * (1.0 - t) + float(target_pos[key]) * t
+                else:
+                    interp[key] = current_val
+            self.write_goal_positions(interp)
+            time.sleep(1.0 / fps)
+
     @check_if_not_connected
     def get_action(self) -> RobotAction:
         # When the user has just toggled into intervention, make sure leader
         # torque is OFF so they can move it without fighting the position loop.
         if self._is_intervention and self._leader_torque_enabled:
-            try:
-                self.bus.sync_write("Torque_Enable", 0)
-                self._leader_torque_enabled = False
-            except Exception as e:  # pragma: no cover - hardware path
-                logger.warning(f"[SOLeaderFollower] could not disable leader torque: {e}")
+            self.disable_torque()
         return super().get_action()
 
     def send_action(self, action: dict[str, float]) -> None:  # type: ignore[override]
@@ -193,9 +285,6 @@ class SOLeaderFollower(SOLeader):
         as the user toggles intervention on (SPACE), torque is dropped in
         :func:`get_action` so the human can move the leader freely.
 
-        Errors talking to the bus are logged and swallowed -- the policy /
-        learner loop must keep ticking even if a single haptic update fails.
-
         Args:
             action: Dictionary of follower motor positions, ``{motor.pos: deg}``.
         """
@@ -215,20 +304,11 @@ class SOLeaderFollower(SOLeader):
             return
 
         if not self._leader_torque_enabled:
-            try:
-                self.bus.sync_write("Torque_Enable", 1)
-                self._leader_torque_enabled = True
-            except Exception as e:  # pragma: no cover - hardware path
-                logger.warning(f"[SOLeaderFollower] could not enable leader torque: {e}")
+            self.enable_torque()
+            if not self._leader_torque_enabled:
                 return
 
-        goal_pos = {m: float(action[f"{m}.pos"]) for m in self.bus.motors if f"{m}.pos" in action}
-        if not goal_pos:
-            return
-        try:
-            self.bus.sync_write("Goal_Position", goal_pos)
-        except Exception as e:  # pragma: no cover - hardware path
-            logger.warning(f"[SOLeaderFollower] could not push goal position to leader: {e}")
+        self.write_goal_positions(action)
 
     def get_teleop_events(self) -> dict[TeleopEvents, bool]:
         events = {