latcontrol_torque: refactor low speed factor into pid controller

selfdrive/controls/lib/latcontrol_torque.py

@@ -6,7 +6,6 @@
 from opendbc.car.lateral import FRICTION_THRESHOLD, get_friction
 from openpilot.common.constants import ACCELERATION_DUE_TO_GRAVITY
 from openpilot.common.filter_simple import FirstOrderFilter
-from openpilot.selfdrive.controls.lib.drive_helpers import MIN_SPEED
 from openpilot.selfdrive.controls.lib.latcontrol import LatControl
 from openpilot.common.pid import PIDController
 
@@ -16,16 +15,16 @@
 # wheel slip, or to speed.
 
 # This controller applies torque to achieve desired lateral
-# accelerations. To compensate for the low speed effects we
-# use a LOW_SPEED_FACTOR in the error. Additionally, there is
-# friction in the steering wheel that needs to be overcome to
-# move it at all, this is compensated for too.
+# accelerations. To compensate for the low speed effects the
+# proportional gain is increased at low speeds by the PID controller.
+# Additionally, there is friction in the steering wheel that needs
+# to be overcome to move it at all, this is compensated for too.
 
-LOW_SPEED_X = [0, 10, 20, 30]
-LOW_SPEED_Y = [15, 13, 10, 5]
 KP = 1.0
 KI = 0.3
 KD = 0.0
+INTERP_SPEEDS = [1, 1.5, 2.0, 3.0, 5, 7.5, 10, 15, 30]
+KP_INTERP = [250, 120, 65, 30, 11.5, 5.5, 3.5, 2.0, KP]
 
 LP_FILTER_CUTOFF_HZ = 1.2
 LAT_ACCEL_REQUEST_BUFFER_SECONDS = 1.0
@@ -37,7 +36,7 @@ def __init__(self, CP, CI, dt):
     self.torque_params = CP.lateralTuning.torque.as_builder()
     self.torque_from_lateral_accel = CI.torque_from_lateral_accel()
     self.lateral_accel_from_torque = CI.lateral_accel_from_torque()
-    self.pid = PIDController(KP, KI, KD, rate=1/self.dt)
+    self.pid = PIDController([INTERP_SPEEDS, KP_INTERP], KI, KD, rate=1/self.dt)
     self.update_limits()
     self.steering_angle_deadzone_deg = self.torque_params.steeringAngleDeadzoneDeg
     self.lat_accel_request_buffer_len = int(LAT_ACCEL_REQUEST_BUFFER_SECONDS / self.dt)
@@ -79,13 +78,11 @@ def update(self, active, CS, VM, params, steer_limited_by_safety, desired_curvat
       measurement_rate = self.measurement_rate_filter.update((measurement - self.previous_measurement) / self.dt)
       self.previous_measurement = measurement
 
-      low_speed_factor = (np.interp(CS.vEgo, LOW_SPEED_X, LOW_SPEED_Y) / max(CS.vEgo, MIN_SPEED)) ** 2
       setpoint = lat_delay * desired_lateral_jerk + expected_lateral_accel
       error = setpoint - measurement
-      error_lsf = error + low_speed_factor / KP * error
 
       # do error correction in lateral acceleration space, convert at end to handle non-linear torque responses correctly
-      pid_log.error = float(error_lsf)
+      pid_log.error = float(error)
       ff = gravity_adjusted_future_lateral_accel
       # latAccelOffset corrects roll compensation bias from device roll misalignment relative to car roll
       ff -= self.torque_params.latAccelOffset
@@ -105,10 +102,10 @@ def update(self, active, CS, VM, params, steer_limited_by_safety, desired_curvat
       pid_log.i = float(self.pid.i)
       pid_log.d = float(self.pid.d)
       pid_log.f = float(self.pid.f)
-      pid_log.output = float(-output_torque)  # TODO: log lat accel?
+      pid_log.output = float(-output_torque) # TODO: log lat accel?
       pid_log.actualLateralAccel = float(measurement)
       pid_log.desiredLateralAccel = float(setpoint)
-      pid_log.desiredLateralJerk= float(desired_lateral_jerk)
+      pid_log.desiredLateralJerk = float(desired_lateral_jerk)
       pid_log.saturated = bool(self._check_saturation(self.steer_max - abs(output_torque) < 1e-3, CS, steer_limited_by_safety, curvature_limited))
 
     # TODO left is positive in this convention

selfdrive/test/process_replay/ref_commit

@@ -1 +1 @@
-1841c3c365689310f7f337a2aa6966d79bc4a60c
+b508f43fb0481bce0859c9b6ab4f45ee690b8dab