<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">%=====================================================================
\section{The CutRange Behavior}
%=====================================================================
\wikisec{grp=bhvmulti}
\wikisec{file=BehaviorCutRange, short=CutRange Behavior}
\label{bhv_cutrange}
\index{IvP Behaviors Implemented!\var{BHV\_CutRange}}
\index{CutRange Behavior}

The CutRange behavior will drive ownship to reduce the range between
itself and another specified vehicle (nearly the opposite of the
BHV\_AvoidCollision behavior).


%=====================================================================
\subsection{The Patience Parameter}
\label{sec_cutr_patience}

The behavior reasons about candidate ownship maneuvers and will use a
combination of immediate-rate-of-closure (IROC) and expected closest
point of approach (CPA) distance, to evaluate candidate
maneuvers. Using solely IROC is regarded as having zero patience, and
using solely CPA is regarded as having maximal patience. The idea is
conveyed in Figure \ref{fig_cutrange} below. The former method may be
preferred for a contact with frequent heading changes, while the
latter may be preferred for contacts on a trajectory that rarely
changes.

\vspace{0.15in}
\begin{figure}[H]
  \centering 
  \includegraphics[width=0.5\textwidth]{figs_bhvs/bhv_cutrange_basic.png}
  \caption{The {\em CutRange} behavior will either drive ownship
    directly toward the current contact position (zero patience
    setting) or drive ownship to be on the fastest intercept course
    based on the contact current position, heading and speed (maximal
    patience setting).}
    \label{fig_cutrange}
\end{figure}
\vspace{0.15in}

%=====================================================================
\subsection{Automatic Priority Weight Variation Based on Range}
\label{sec_cutr_variable_pwt}

The CutRange behavior may optionally be configured to automatically
decrease its priority weight down to zero as it closes range to the
contact. This can be used to ensure ownship does not collide with the
contact or to transition the helm to a different mode of operation as
it closes range to the contact. The idea is shown in Figure
\ref{fig_cutrange_pwt}

\vspace{0.15in}
\begin{figure}[H]
  \centering
  \includegraphics[width=0.65\textwidth]{figs_bhvs/bhv_cutrange_pwt.png}
  \caption{When ownship is at the outer range
    (\bvar{pwt\_outer\_range}), the priority is at its maximal
    value. When ownship is at the inner most range
    (\bvar{pwt\_inner\_range}), the priority weight drops to zero. The
    priority weight decreases linearly as the range is closed.  If the
    overall configured priority weight for the behavior were set to 80
    instead of 100, the outer weight would 80, and 40 at the
    intermediate range.}
    \label{fig_cutrange_pwt}
\end{figure}
\vspace{0.15in}

\noindent
When the contact is at a range at or beyond \bvar{pwt\_outer\_dist},
the priority weight will be 100 percent of the behavior's configured
priorty weight. When the contact is at or closer than the range given
by \bvar{pwt\_inner\_dist} the priorty weight will be zero. At contact
ranges between these two values the priority weight will linearly
decrease in value. In the situation depicted in Figure
\ref{fig_cutrange_pwt}, the vehicle transistion to a dominant Shadow
behavior as the range is closed. When the range decreases to
\bvar{pwt\_inner\_dist}, the Shadow behavior is solely determining
ownship heading and speed to match the contact's current heading
and speed.

%=======================================================================
\subsection{Initiating and Abandoning Pursuit}
\label{sec_cutr_giveup}

The \bvar{giveup\_dist} parameter sets a contact range beyond which
the behavior will assign, a zero priority weight, essentially giving
up pursuit and becoming an inactive behavior. The parameter is
typically set to be a bit higher than the \bvar{pwt\_outer\_dist}
parameter, but any non-zero configured value will be respected. A
\bvar{giveup\_dist} of zero is the default, and disables this feature.

\vspace{0.1in}
\noindent
As ownship range to the contact increases and crosses the
\bvar{giveup\_dist} threshold, the behavior may be configure to post
one or more messages, using the \bvar{giveupflag}
parameter. Similarly, when ownship range to contact decreases below
the giveup range, the behavior may be configure to post one or more
messages, using the \bvar{pursueflag} parameter. For example:

\prevblue
\begin{verbatim}
  pursueflag = PURSUIT=true
  giveupflag = PURSUIT=false
\end{verbatim}
\postverb

\vspace{0.1in}
\noindent
In the above case, the two flags could be used to transition the helm
out of its present mission mode and back again based on the status
of closing range to the contact.


%=======================================================================
\subsection{Configuration Parameters}
\label{sec_bhv_cutrng_params}

\input{includes/bhv_all_properties}

\input{includes/bhv_contact_properties}

\vspace{0.15in}
\begin{listing}{Configuration Parameters for the CutRange Behavior}
\label{lst_bhv_cutrange}
\small
\renewcommand{\arraystretch}{1.15}
\begin{longtable}{rp{0.76\textwidth}} 

  {\bf Parameter} &amp; {\bf Description} \\  

  \bvar{giveup\_dist}: &amp; Range to contact, in meters, outside which
  the behavior will give up (become inactive). Default is zero.
  Section \ref{sec_cutr_giveup}. \\
  
  \bvar{giveupflag}: &amp; Optional MOOS variable-value pairs posted when
  ownship range to contact increases above
  \bvar{giveup\_dist}. Section \ref{sec_cutr_giveup}. \\

  \bvar{patience}: &amp; Linear scale choice between preferring heading
  directly to the contact (\bsvar{patience=0}) or heading on the
  lowest closest point of approach (\bsvar{patience=100}). Section
  \ref{sec_cutr_patience}. \\

  \bvar{pursueflag}: &amp; Optional MOOS variable-value pairs posted when
  ownship range to contact drops below \bvar{giveup\_dist}. Section
  \ref{sec_cutr_giveup}. \\

  \bvar{pwt\_outer\_dist}: &amp; Range to contact outside which the 
  behavior has maximum priority. Section \ref{sec_cutr_variable_pwt}. \\ 

  \bvar{pwt\_inner\_dist}: &amp; Range to contact within which the 
  behavior has zero priority. Section \ref{sec_cutr_variable_pwt}. \\ 
  
\end{longtable}
\end{listing}
\normalsize

\vspace{0.15in}
\begin{listing}{Example Configuration Block}
\label{lst_bhv_cutrange_ex}

\begin{fileverb}
Behavior = BHV_CutRange
{
  // General Behavior Parameters
  // ---------------------------
  name         = cutrange_                         // example
  pwt          = 200                               // example
  condition    = AVOID = true                      // example
  updates      = CONTACT_INFO                      // example
  endflag      = CONTACT_RESOLVED = $[CONTACT]     // example
  templating   = spawn                             // example


  // General Contact Behavior Parameters
  // -----------------------------------
      bearing_lines = white:0, green:0.65, yellow:0.8, red:1.0   // example

            contact = henry            // example
              decay = 15,30            // default (seconds)
        extrapolate = true             // default
   on_no_contact_ok = true             // default
        time_on_leg = 60               // default (seconds)


  // Parameters specific to this behavior
  // ------------------------------------
        giveup_dist = 225              // Meters. Default is 0, disabled
           patience = 45               // [0,100]. Default 0 
     pwt_inner_dist = 50               // Meters. Default is 0. 
     pwt_outer_dist = 200              // Meters. Default is 0.
         pursueflag = PURSUIT=true
         giveupflag = PURSUIT=false
}
\end{fileverb}
\end{listing}

%=======================================================================
\subsection{Variables Published}

The below MOOS variables will be published by the behavior during
normal operation, in addition to any configured flags. A variable
published by any behavior may be supressed or changed to a different
variable name using the \var{post\_mapping} configuration parameter
described in Section \ref{sec_bhv_post_mapping}.

\begin{packed_itemize}[2]

\item \mvar{VIEW\_SEGLIST}: A bearing line between ownship and the contact
  if configured for rendering. 
  
\item Any variables involved in the \bvar{giveupflag} or \bvar{pursueflag}
  configurations, or other general behavior flags. 
  
\end{packed_itemize}


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