feat(pid_longitudinal_controller): update readme

Signed-off-by: Berkay Karaman <brkay54@gmail.com>

Author: brkay54

control/pid_longitudinal_controller/README.md

@@ -55,18 +55,27 @@ For reliable stopping, the target acceleration calculated by the FeedForward sys
 
 Based on the slope information, a compensation term is added to the target acceleration.
 
-There are two sources of the slope information, which can be switched by a parameter.
+There are two sources of the slope information, both sources are used in controller with respect to state of the node.
 
-- Pitch of the estimated ego-pose (default)
+- Pitch of the estimated ego-pose
+  - Only used when `slope_source` is "raw_pitch"
   - Calculates the current slope from the pitch angle of the estimated ego-pose
   - Pros: Easily available
   - Cons: Cannot extract accurate slope information due to the influence of vehicle vibration.
+  - Cons: Can not be used in combination with delay compensation.
 - Z coordinate on the trajectory
-  - Calculates the road slope from the difference of z-coordinates between the front and rear wheel positions in the target trajectory
-  - Pros: More accurate than pitch information, if the z-coordinates of the route are properly maintained
-  - Pros: Can be used in combination with delay compensation (not yet implemented)
+  - Only used when `slope_source` is "trajectory_pitch"
+  - Calculates the road slope from the difference of z-coordinates between the front and rear wheel positions in the target trajectory.
+  - Pros: More accurate than pitch information, if the z-coordinates of the route are properly maintained.
+  - Pros: Can be used in combination with delay compensation.
   - Cons: z-coordinates of high-precision map is needed.
-  - Cons: Does not support free space planning (for now)
+  - Cons: Does not support free space planning (for now).
+- Adaptive pitch information
+  - Only used when `slope_source` is "trajectory_adaptive"
+  - It switches the slope sources with respect to velocity of the ego vehicle
+  - The trajectory_pitch is used when the vehicle's velocity is higher than `adaptive_trajectory_velocity_th` otherwise pitch of the estimated ego-pose is used for slope value.
+  - Pros: Can be used in combination with delay compensation for high speeds
+  - Cons: There might be a loss of comfort when slope source is switched
 
 **Notation:** This function works correctly only in a vehicle system that does not have acceleration feedback in the low-level control system.
 
@@ -108,23 +117,6 @@ Depending on the actuating principle of the vehicle, the mechanism that physical
 
 In this controller, the predicted ego-velocity and the target velocity after the delay time are calculated and used for the feedback to address the time delay problem.
 
-### Slope compensation
-
-Based on the slope information, a compensation term is added to the target acceleration.
-
-There are two sources of the slope information, which can be switched by a parameter.
-
-- Pitch of the estimated ego-pose (default)
-  - Calculates the current slope from the pitch angle of the estimated ego-pose
-  - Pros: Easily available
-  - Cons: Cannot extract accurate slope information due to the influence of vehicle vibration.
-- Z coordinate on the trajectory
-  - Calculates the road slope from the difference of z-coordinates between the front and rear wheel positions in the target trajectory
-  - Pros: More accurate than pitch information, if the z-coordinates of the route are properly maintained
-  - Pros: Can be used in combination with delay compensation (not yet implemented)
-  - Cons: z-coordinates of high-precision map is needed.
-  - Cons: Does not support free space planning (for now)
-
 ## Assumptions / Known limits
 
 1. Smoothed target velocity and its acceleration shall be set in the trajectory
@@ -178,7 +170,8 @@ AutonomouStuff Lexus RX 450h for under 40 km/h driving.
 | min_acc                                     | double | min value of output acceleration [m/s^2]                                                                                                                                                | -5.0          |
 | max_jerk                                    | double | max value of jerk of output acceleration [m/s^3]                                                                                                                                        | 2.0           |
 | min_jerk                                    | double | min value of jerk of output acceleration [m/s^3]                                                                                                                                        | -5.0          |
-| use_trajectory_for_pitch_calculation        | bool   | If true, the slope is estimated from trajectory z-level. Otherwise the pitch angle of the ego pose is used.                                                                             | false         |
+| slope_source                                | string | It defines the slope source for the vehicle. Available options: "raw_pitch", "trajectory_pitch" or "trajectory_adaptive"                                                                | "raw_pitch"   |
+| adaptive_trajectory_velocity_th             | double | Threshold velocity value for state transition of slope sources. Only usable when `slope_source` is "trajectory_adaptive". [m/s]                                                         | 1.0           |
 | lpf_pitch_gain                              | double | gain of low-pass filter for pitch estimation                                                                                                                                            | 0.95          |
 | max_pitch_rad                               | double | max value of estimated pitch [rad]                                                                                                                                                      | 0.1           |
 | min_pitch_rad                               | double | min value of estimated pitch [rad]                                                                                                                                                      | -0.1          |