Mission monitor sequencer

Revision as of 17:44, 31 October 2008

Introduction

This plug-in implements a a language that is a mixture of a rule-based and a sequential based language. The idea is that a number of situations need permanent - or semi permanent - monitoring to get a good situation awareness for the root, and at the same time a large number of the robot tasks are better described by a sequential language.

This implementation attempts to cover this gab.

Language

An example function could look like this:

<?xml version="1.0" ?>
<plan name="CrossRoad">
   <init>
       odoPose.tripB = 0
       nearRoad = false // define local variable
       <plan name="maxOdoDist" if="odoPose.tripB > 250">
           // this is a rule to moditor distance traveled since trip-counter were reset
           print("Driven too far on odo " odoPose.tripB "m") // print message
           break CrossRoad // failed to cross road - could trigger a relocalization
       </plan>
       <plan name="closeToRoad" if="hypot(utmPose.poseY - 6174307, utmPose.poseX - 707873) < 15" >
           // this is a rule that monitors the distance to an UTM point
           print("Cose to road slowing down) // print message
           smr.speed=0.5  // set the desired maximum speed in mrc interface module
           nearRoad = true  // set flag
           disable  // disable this rule
       </plan>
       <plan name="turn">
           <parameter angle="pi" dist=1.0/>
           // this is a plan 
           <commands to="smr.send">
             # construct commands to MRC using the smr.send command
             'drive @v ' smr.speed ' : ($drivendist > ' dist ')'
             'turn ' angle
             'drive : ($drivendist > ' dist ')'
           </commands>
       </plan>
   </init>
   print("started")
   roaddrive.right(0.75) : nearRoad // follow road 75cm from edge until near road
   // more stuff missing here to detect traffic etc.
   ...
   turn() // turn back - using a call to a plan
   success=true
   <post>
       print("finsihed crossRoad - success=" success)
   </post>
</plan>

A number of these plans can be started (enabled) simultaniously, an can in principle be total independant. I.e.one can control the robot arm while another controls the navigation.

Language keywords

Enable/Disable

This will make a plan active - if not already, or stop or prohibit a plan from getting active, e.g.

enable foo

Will make the plan "foo" active, that is start running the code as if it was a rule. If there is a rule condition, then the code will not run until this is satisfied.

If the plan is active already, either it is an active rule or the plan is waiting at a control statement, the statement will have no effect.

The disable command:

disable foo

Will disable the plan "foo", if the plan is a rule, then the rule condition will no longer be evaluated. If the plan is waiting at a control statement, then this will be interrupted, and any post-lines will be executed, before the plan is disabled. If the plan is not a rule and is not waiting at a control statement, then the statement will have no effect.

A rule can disable itself with the statement:

disable

(a plan can not enable itself)

Language definition

The language definition is:

Plan

planBlock ::= planOpenTag planBody planCloseTag

planOpenTag ::= '<plan' 'name=' planName [runAttribute] [ruleCondition] '>\n'

planName ::= '"' symbol '"'

runAttribute ::= 'run="default"' (there may come more values later)

ruleCondition ::= 'if="' expression '"' (this expression may be split into more lines)

planCloseTag ::= '</plan>\n'

planBody ::= [parameters] [description] [planInitBlock] planMainBlock [planPostBlock]

parameters ::= '<parameters ' [symbol '="' [paramDefaultValue] '"']* '/>\n'

paramDefaultValue ::= constantValue

description ::= '<description>\n' xmlText '</description>\n'

xmlText ::= any 7-bit characters except '\0', '&' and '<', the last two must be coded as & and <

planInitBlock ::= '<init>\n' [declarationStatement]* '</init>\n'

declarationStatement ::= planBlock | executableStatement

planMainBlock ::= [statement]*

planPostBlock ::= '<post>\n' [statement]* '</post>\n'

Statements

statement ::= executableStatement | controlStatement

executableStatement ::= assignment | procedureCall | blockStatement | breakStatement | enableStatement | ifStatement | emptyStatement

controlStatement ::= proceureCall ':' expression [remark] '\n'

assignment ::= [symbol.]* symbol '=' expression [remark] '\n'

procedureCall ::= [symbol.]* symbol '(' [expression [',' expression]* ')' [remark] '\n'

blockStatement ::= '<block>\n' [statement]* '</block>\n'

breakStatement ::= ('break' [symbol] | 'continue' ) [remark] '\n'

enableStatement ::= ('enable' | 'disable') [symbol] [remark] '\n'

ifStatement ::= 'if (' expression ')' [remark] '\n' statement [remark] '\n' [elseStatement]

elseStatement ::= 'else' [remark] '\n' statement [remark] '\n'

emptyStatement ::= [remark] '\n'

remark ::= ('#' | ';' | '//') xmlText except '\n'