update readme

Signed-off-by: yoshiri <[email protected]>

perception/map_based_prediction/README.md

@@ -109,6 +109,21 @@ For the additional information, here we show how we calculate lateral velocity.
 
 Currently, we use the upper method with a low-pass filter to calculate lateral velocity.
 
+### Path generation
+
+Path generation is generated on the frenet frame. The path is generated by the following steps:
+
+1. Get the frenet frame of the reference path.
+2. Generate the frenet frame of the current position of the object and the finite position of the object.
+3. Optimize the path in each longitudinal and lateral coordinate of the frenet frame. (Use the quintic polynomial to fit start and end conditions.)
+4. Convert the path to the global coordinate.
+
+See paper [2] for more details.
+
+#### Tuning lateral path shape
+
+`lateral_control_time_horizon` parameter supports the tuning of the lateral path shape. This parameter is used to calculate the time to reach the reference path. The smaller the value, the more the path will be generated to reach the reference path quickly. (Mostly the center of the lane.)
+
 ### Path prediction for crosswalk users
 
 This module treats **Pedestrians** and **Bicycles** as objects using the crosswalk, and outputs prediction path based on map and estimated object's velocity, assuming the object has intention to cross the crosswalk, if the objects satisfies at least one of the following conditions:
@@ -155,6 +170,7 @@ If the target object is inside the road or crosswalk, this module outputs one or
 | ---------------------------------------------------------------- | ----- | ------ | ------------------------------------------------------------------------------------------------------------------------------------- |
 | `enable_delay_compensation`                                      | [-]   | bool   | flag to enable the time delay compensation for the position of the object                                                             |
 | `prediction_time_horizon`                                        | [s]   | double | predict time duration for predicted path                                                                                              |
+| `lateral_control_time_horizon`                                   | [s]   | double | time duration for predicted path will reach the reference path (mostly center of the lane)                                            |
 | `prediction_sampling_delta_time`                                 | [s]   | double | sampling time for points in predicted path                                                                                            |
 | `min_velocity_for_map_based_prediction`                          | [m/s] | double | apply map-based prediction to the objects with higher velocity than this value                                                        |
 | `min_crosswalk_user_velocity`                                    | [m/s] | double | minimum velocity used when crosswalk user's velocity is calculated                                                                    |