Line Follow Task¶

Summary¶

This task converts the measured line centroid into left and right wheel speed commands. It acts as the outer line-following controller, while the two motor tasks act as the inner wheel-speed controllers.

Important class¶

task_line_follow(enable, base_speed, Kp_line, Ki_line, centroid, setpoint_L, setpoint_R, center=7.0, delta_limit=0.10, line_seen_share=None): Generator-based line-following task that computes steering corrections from centroid error.

Important methods¶

run(): Reads the centroid, computes error from the centerline, applies PI control, clamps the steering correction, and updates the left and right wheel setpoints.

Important state constants¶

S0_INIT: Initialization state.
S1_RUN: Main control state.

Important variables¶

self._enable: Share that enables or disables the line-following controller.
self._base: Share holding the base forward speed.
self._kp / self._ki: PI gains for the line-following controller.
self._centroid: Share containing the current centroid estimate from the line-sensor task.
self._spL / self._spR: Shares that publish the left and right wheel setpoints.
self._center: Desired centroid value corresponding to the middle of the sensor array.
self._limit: Maximum steering correction magnitude applied to the base speed.
self._I: Integral term for the line-following controller.
self._last_t: Previous timestamp used to compute dt.
self._line_seen: Optional share passed into the task. In the current implementation it is stored but not used directly inside run().

Control behavior¶

When enabled, the task computes:

err = centroid - center
delta = Kp_line * err + Ki_line * integral

The steering correction delta is then clamped to ±delta_limit. Finally, wheel setpoints are generated as:

left = base + delta
right = base - delta

Both commands are limited to the range 0.0 to 0.35 meters per second. When the task is disabled, the integral term is cleared and the time base is reset.