Ram HD: locked Steering Ratio (#156)

* Ram HD: locked SR

* gate to only ram hd

* attribute error

* gotta init first

* define type

selfdrive/car/chrysler/interface.py

@@ -82,6 +82,7 @@ class CarInterface(CarInterfaceBase):
       ret.mass = 3405. + STD_CARGO_KG
       ret.minSteerSpeed = 16
       CarInterfaceBase.configure_torque_tune(candidate, ret.lateralTuning, 1.0, False)
+      ret.flags |= ChryslerFlags.SP_RAM_HD_FIXED_STEERING_RATIO.value
 
     else:
       raise ValueError(f"Unsupported car: {candidate}")

selfdrive/car/chrysler/values.py

@@ -14,6 +14,8 @@ Ecu = car.CarParams.Ecu
 class ChryslerFlags(IntFlag):
   HIGHER_MIN_STEERING_SPEED = 1
 
+  SP_RAM_HD_FIXED_STEERING_RATIO = 2
+
 
 class CAR:
   # Chrysler

selfdrive/controls/controlsd.py

@@ -606,7 +606,7 @@ class Controls:
     lp = self.sm['liveParameters']
     x = max(lp.stiffnessFactor, 0.1)
     sr = max(lp.steerRatio, 0.1)
-    self.VM.update_params(x, sr)
+    self.VM.update_params(x, sr, self.CP)
 
     # Update Torque Params
     if self.CP.lateralTuning.which() == 'torque':

selfdrive/controls/lib/vehicle_model.py

@@ -19,6 +19,8 @@ from numpy.linalg import solve
 
 from cereal import car
 
+from selfdrive.car.chrysler.values import ChryslerFlags
+
 ACCELERATION_DUE_TO_GRAVITY = 9.8
 
 
@@ -38,13 +40,14 @@ class VehicleModel:
 
     self.cF_orig: float = CP.tireStiffnessFront
     self.cR_orig: float = CP.tireStiffnessRear
-    self.update_params(1.0, CP.steerRatio)
+    self.chrysler_ram_hd: bool = (CP.carName == "chrysler") and CP.flags & ChryslerFlags.SP_RAM_HD_FIXED_STEERING_RATIO.value
+    self.update_params(1.0, CP.steerRatio, CP)
 
-  def update_params(self, stiffness_factor: float, steer_ratio: float) -> None:
+  def update_params(self, stiffness_factor: float, steer_ratio: float, CP: car.CarParams) -> None:
     """Update the vehicle model with a new stiffness factor and steer ratio"""
     self.cF: float = stiffness_factor * self.cF_orig
     self.cR: float = stiffness_factor * self.cR_orig
-    self.sR: float = steer_ratio
+    self.sR: float = CP.steerRatio if self.chrysler_ram_hd else steer_ratio
 
   def steady_state_sol(self, sa: float, u: float, roll: float) -> np.ndarray:
     """Returns the steady state solution.