TEACH SIM_DEMO_DESIGN                            Aaron Sloman April 1996
Last updated  9 Jun 1996


These are design notes for the program in TEACH * SIM_DEMO


         CONTENTS - (Use <ENTER> g to access required sections)

 -- Objective of demo
 -- Ontology of scenario
 -- Design of a captain.
 -- Design of a mover
 -- Design of terrain objects
 -- Algorithm for obstacle detection

-- Objective of demo --------------------------------------------------

Show how to use the toolkit to develop a scenario involving groups of
agents that move around on terrain to achieve goals, avoid obstacles,
communicating to ask for help when necessary.


-- Ontology of scenario -----------------------------------------------

    team_agents
        captains
            give orders, receive information, make plans
        movers
            receive orders, act on orders, move around to
            achieve goals, report observed terrain_objects
            avoid bumping into one another and to static objects

    terrain_object
        has location, maybe diameter

There are two teams, the blue team and the red team. Each has a captain
and two or more movers. Each is given a goal location, which the captain
transmits to the movers.

All members of both teams have to move to their target locations without
collisions, even when the two teams pass throught each other.

It might be possible later to give them different strategies and allow
some sort of competition.


-- Design of a captain. -----------------------------------------------

Currently does not move. Merely sends and receives messages.
When receiving a message about object blocking line of sight to
target location, sends instructions to turn left or right.
(Details in teach file).

-- Design of a mover --------------------------------------------------
Acknowledges all messages from captain.

Initially does nothing till goal received from captain.

Once goal given, starts moving towards the goal.

If goal reached  stops and informs captain.

If object blocks line of sight to target location, takes evasive
    action, depending on distance of object and angle between current
    heading and line of sight to obstacle.

-- Design of terrain objects ------------------------------------------

These are merely objects with a location, shown as squares or circles.
They do nothing. They exist only to be detected by movers.

-- Algorithm for obstacle avoidance -----------------------------------

Object A wishes to get to target location T, and finds another object O
which is a potential obstacle, either static or moving

    Compute heading from A to T                 HT
    (used as current heading by default)
    Compute distance from A to O                DO
    Compute heading from A to O                 HO
    Compute angle between HT and HO             Ang

    Find object for which DO is smallest

    If DO > DT then ignore it.

    Compute new temporary heading which depends on DO and Ang
        If DO is above a threshold continue with HT
        Otherwise use DO and Ang to determine new temporary heading
        (for one step), by determining a "veer" angle to add to
        HT. Veer should be bigger if DO is smaller. Veer should be
        bigger if Ang is smaller (obstacle more directly in front).
        Direction of veer should be the same as the direction of Ang.
            (I.e. if line of sight to target is to left of line of
            sight of obstacle veer left and vice versa)

[This file may be extended]

--- $poplocal/local/sim/teach/sim_demo_design
--- Copyright University of Birmingham 1996. All rights reserved. ------