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Functions of Autonomous Motion Subsystem I/O Data of Autonomous Motion Subsystem   I/O Data of Autonomous Motion Subsystem’s AI Modules
Reference Architecture of Autonomous Motion Subsystem Functions of Autonomous Motion Subsystem’s AI Modules

8.1        Functions of Autonomous Motion Subsystem

The typical series of operations carried out by the Autonomous Motion Subsystem (AMS) is described below. Note that the sequential description does not imply that an operations can only be carried out after the preceding one has been completed.

  • Human-CAV Interaction requests Autonomous Motion Subsystem to plan and move the CAV to the human-selected destination. A dialogue between AMS-HCI-human may follow.
  • Computes the Route satisfying the human’s request.
  • Receives the current Basic Environment Representation from Environment Sensing Subsystem.
  • While moving, the CAV:
    • Broadcasts a subset of the Basic Environment Representation and other data to CAVs in range.
    • Receives subsets of Basic Environment Representations and other data from other CAVs.
    • Produces the Full Environment Representation by fusing its own Basic Environment Representation with those from other CAVs in range.
    • Plans a Path connecting Poses.
    • Selects behaviour and motion to reach the next Pose acting on information about the Poses other CAVs in range intend to reach and the Objects between the current Pose and the next Pose.
    • Defines a Trajectory that:
      • Complies with general traffic regulations and local traffic rules.
      • Preserves passengers’ comfort.
    • Refines Trajectory to avoid obstacles.
    • Sends Commands to the Motion Actuation Subsystem to take the CAV to the next Pose.
  • Stores the data resulting from a decision (Route Planner, Path Planner etc.)

The AMS should consider that different levels of autonomy, e.g., those indicated by SAE International [5.2] are possible depending on the amount and level of available func­tionalities.

8.2        Reference Architecture of Autonomous Motion Subsystem

Figure 7 gives the Autonomous Motion Subsystem Reference Model.

Figure 7 – Autonomous Motion Subsystem Reference Model


This is the operation according to the Reference Model:

  1. A human requests the Human-CAV Interaction to the CAV transports them to a destination.
  2. HCI interprets request and passes interpretation to the AMS.
  3. The AMS activates the Route Planner to generate a set of Waypoints starting from the current Pose, obtained from the Full Environment Representation, up to the destination.
  4. The Waypoints enter the Path Planner which generates a set of Poses to reach the next Waypoint.
  5. For each Path, the Motion Planner generates a Trajectory to reach the next Pose.
  6. The Obstacle Avoider AIM receives the Trajectory and checks if there is a last-minute change, detected from Alert.
  7. If an Alert was received, the Obstacle Avoider AIM checks whether the implementation of the Trajectory creates a collision, especially with the Object creating the Alert.
    1. If a collision is indeed detected, the Obstacle Avoider AIM requests a new Trajectory from the Motion Planner.
    2. If no collision is detected, Obstacle Avoider AIM issues a Command to the Motion Actuation Subsystem.
  8. The Motion Actuation Subsystem sends Feedback about the execution of the Command.
  9. The AMS, based on the MAS-AMS Responses received and the potential discovery of changes in the Environment, can decide to discontinue the execution of the earlier Command and issue another AMS-MAS Command instead.
  10. The decision of each element of the said chain may be recorded.

8.3        I/O Data of Autonomous Motion Subsystem

Table 9 gives the input/output data of Autonomous Motion Subsystem.


Table 10 – I/O data of Autonomous Motion Subsystem


Input data From Comment
Basic Environment Representation Environment Sensing Subsystem CAV’s Environment representation.
HCI-AMS Command Human-CAV Interaction Human commands, e.g., “take me home”
Environment Representation Other CAVs Other CAVs and vehicles, and roadside units.
MAS-AMS Response Motion Actuation Subsystem CAV’s response to AMS-MAS Command.
Output data To Comment
AMS-HCI Response Human-CAV Interaction MAS’s response to AMS-MAS Command
AMS-MAS Command Motion Actuation Subsystem Macro-instructions, e.g., “in 5s assume a given State”.
Environment Representation Other CAVs For information to other CAVs

8.4       Functions of Autonomous Motion Subsystem’s AI Modules

Table 10 gives the AI Modules of the Autonomous Motion Subsystem.


Table 11 – Functions of Autonomous Motion Subsystem’s AI Modules


AIM Function
Full Environment Representation Fusion Creates an internal representation of the Environment by fusing infor­mation from itself, CAVs in range and other transmitting units.
Route Planner
Path Planner Generates a set of Paths, considering:

1.      Route.

2.      Spatial Attitude.

3.      Full Environment Representation.

4.      Traffic Rules.

Motion Planner Defines a Goal and a Trajectory to reach the Goal using the Spatial Attitude satisfying the CAV’s kinematic and dynamic constraints and considering passengers’ comfort.
Obstacle Avoider Checks that the Trajectory is compatible with any Alert information. If it is, it passes the Trajectory to the Command Issuer. If it is not, it requests a new Trajectory. If Command Issuer informs Obstacle Avoider that there is an anomalous situation, Obstacle Avoider may issue a “discontinue previous Command” and forward to the next appropriate upstream AIM, possibly including the Route Planner. This may decide to communicate the Road State to the Human-CAV Interaction Subsystem.
Command Issuer Instructs the MAS to execute the Trajectory considering the Environment conditions and receives MAS-AMS Responses about the execution.

8.5        I/O Data of Autonomous Motion Subsystem’s AI Modules

Table 11 gives, for each AIM (1st column), the input data (2nd column) and the output data (3rd column) of Autonomous Motion Subsystem.


Table 12 – CAV Autonomous Motion Subsystem data


CAV/AIM Input Output
Environment Representation Fusion Alert

Basic Environment Representations

Environment Representations from other CAVs

Other data from other CAVs

Full Environment Representation
Route Planner Full Environment Representation Offline maps Route

Estimated time

Path Planner Route

Full Environment Representation

Offline maps

Set of Paths
Motion planner Path

Full Environment Representation

Obstacle Avoider Trajectory

Full Environment Representation


Route State

Command to AMS Trajectory

Environment Data




The AMS may harvest available bandwidth and utilise it to send a version of the Full Environment Representation that is compatible with the available mobile bandwidth.

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