feat(pid_longitudinal_controller): re-organize diff limit structure (#1052)

* rearange params

Signed-off-by: Yuki Takagi <yuki.takagi@tier4.jp>

Author: yuki-takagi-66

autoware_launch/config/control/trajectory_follower/longitudinal/pid.param.yaml

@@ -53,12 +53,11 @@
 
     # stopped state
     stopped_vel: 0.0
-    stopped_acc: -3.4
-    stopped_jerk: -5.0
+    stopped_acc: -3.4 # denotes pedal position
 
     # emergency state
     emergency_vel: 0.0
-    emergency_acc: -5.0
+    emergency_acc: -5.0 # denotes acceleration
     emergency_jerk: -3.0
 
     # acceleration limit
@@ -68,6 +67,7 @@
     # jerk limit
     max_jerk: 2.0
     min_jerk: -5.0
+    max_acc_cmd_diff: 50.0 # [m/s^2 * s^-1]
 
     # slope compensation
     lpf_pitch_gain: 0.95