docs: update vehicle interface with some samples (autowarefoundation#453

)

* init vehicle interface

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

* add table formatting

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

* update differential drive doc

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

* update structure, add missing example

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

---------

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

docs/how-to-guides/integrating-autoware/creating-vehicle-interface-package/.pages

@@ -1,3 +1,5 @@
 nav:
-  - Creating a vehicle interface for an Ackermann kinematic model: creating-a-vehicle-interface-for-an-ackermann-kinematic-model.md
+  - Vehicle interface overview: vehicle-interface.md
+  - creating-vehicle-interface.md
+  - ackermann-kinematic-model.md
   - customizing-for-differential-drive-model.md

docs/how-to-guides/integrating-autoware/creating-vehicle-interface-package/ackermann-kinematic-model.md

@@ -0,0 +1,67 @@
+# Ackermann kinematic model
+
+Autoware now supports control inputs for vehicles based on an Ackermann kinematic model.  
+This section introduces you a brief concept of the Ackermann kinematic model
+and explains how Autoware controls it.
+Please remember,
+Autoware control output (/control/command/control_cmd)
+publishes lateral and longitudinal commands according to the Ackermann kinematic model.
+
+- If your vehicle does not suit the Ackermann kinematic model, you have to modify the control commands. [Another document gives you an example how to convert your Ackermann kinematic model control inputs into a differential drive model.](https://autowarefoundation.github.io/autoware-documentation/main/how-to-guides/integrating-autoware/creating-vehicle-interface-package/customizing-for-differential-drive-model/)
+
+## Geometry
+
+The basic style of the Ackermann kinematic model has four wheels with an Ackermann link on the front,
+and it is powered by the rear wheels.  
+The key point of Ackermann kinematic model is
+that the axes of all wheels intersect at the same point,
+which means
+all wheels will trace a circular trajectory with a different radii but a common center point
+(See the figure below).  
+Therefore,
+this model has a great advantage that it minimizes the slippage of the wheels
+and prevents tires from getting worn soon.
+
+In general,
+the Ackermann kinematic model accepts the longitudinal speed $v$ and the steering angle $\phi$ as inputs.
+In autoware, $\phi$ is positive if it is steered counterclockwise,
+so the steering angle in the figure below is actually negative.
+
+<figure markdown>
+  ![ackermann_link](images/Ackermann_WB.png){ align=center }
+  <figcaption>
+    The basic style of an Ackermann kinematic model. The left figure shows a vehicle facing straight forward, while the right figure shows a vehicle steering to the right.
+  </figcaption>
+</figure>
+
+### Control
+
+Autoware publishes a ROS 2 topic named `control_cmd` from several types of publishers.  
+A `control_cmd` topic is a [`AckermannControlCommand`](https://gitlab.com/autowarefoundation/autoware.auto/autoware_auto_msgs/-/blob/master/autoware_auto_control_msgs/msg/AckermannControlCommand.idl) type message that contains
+
+```bash title="AckermannControlCommand"
+  builtin_interfaces/Time stamp
+  autoware_auto_control_msgs/AckermannLateralCommand lateral
+  autoware_auto_control_msgs/LongitudinalCommand longitudinal
+```
+
+where,
+
+```bash title="AckermannLateralCommand"
+  builtin_interfaces/Time stamp
+  float32 steering_tire_angle
+  float32 steering_tire_rotation_rate
+```
+
+```bash title="LongitudinalCommand"
+  builtin_interfaces/Time stamp
+  float32 speed
+  float32 accelaration
+  float32 jerk
+```
+
+See the [AckermannLateralCommand.idl](https://gitlab.com/autowarefoundation/autoware.auto/autoware_auto_msgs/-/blob/master/autoware_auto_control_msgs/msg/AckermannLateralCommand.idl) and [LongitudinalCommand.idl](https://gitlab.com/autowarefoundation/autoware.auto/autoware_auto_msgs/-/blob/master/autoware_auto_control_msgs/msg/LongitudinalCommand.idl) for details.
+
+The vehicle interface should realize these control commands through your vehicle's control device.
+
+Moreover, Autoware also provides brake commands, light commands, and more (see [vehicle interface design](https://autowarefoundation.github.io/autoware-documentation/main/design/autoware-interfaces/components/vehicle-interface/)), so the vehicle interface module should be applicable to these commands as long as there are devices available to handle them.