INTELLIGENT CONTROL OF MATERIAL HANDLING SYSTEMS - Environmentally Conscious Materials Handling - page 103

• The communication field solely consists of the predecessor, as it should be
notified if the agent could meet its goals.
• The action field consists of the baths of the requested type, and organization
ensures that an agent only sees one particular bath, even if the bath type
is duplicated in the system.

12.2.2 Agent Goals
An agent has two main goals:
1. Go in the right bath.
2. Stay close to the predecessor agent of its group.
When both goals are satisfied, for all agents of a group, the bar represented
by the group has a valid way to be processed by the system. Furthermore, an
agent has three constraints:
1. Keep distance to both the min and max time.
2. Help the successor to stay close.
3. Help other agents in same bath type to fulfill goals.
Constraints are added to make agents cooperate with others in fulfilling their
goals, too. When agents from two groups share interests to the same time slot
for a given bath, they have to be able to negotiate which will win the time slot.
Therefore, an extra type of agent is introduced — an observer. For each group
of agents, one observer agent monitors the movements and how satisfied agents
are in general. Information withdrawn from this observer is used when solving
conflicts.

12.3 Interactions

Agents move around in the virtual world in discrete steps. They calculate a force
vector ν as responses to input/output from the three fields. Each discrete time
step has two parts. First, all agents gets a parallel chance to decide which way
to go and at what speed. Hereafter, they get the chance to move themselves. In
this moving step, they will try to move in the direction and distance specified by
ν , within the space allowed by their action field.

12.3.1 Basic Forces
The most basic behaviors of the agents come from their primary goals and are
modeled with two forces: a spring force and a gravity force. The spring force, F s ,
represents the attraction to the predecessor, if any, and attracts the agent towards
the point where the predecessor's time slot of the previous bath ends, so the bar
can move from one bath to another, which is a criteria for a plan to be valid.
In general, a spring force is denoted: F s

=− kx ,where k is the spring con-

stant and x the distance, so in this case: F s

=− k parent (x − x p ) ,where k parent is a