# HeadControl Symbols All symbols that are needed for the HeadControl state machine The formalized behavior references a variety of input and output symbols, which can stand for variables or functions of the agent's software. Constants are constant decimal values. ## Input Symbols
Name | Type | Measure | Description
position-in-walk-cycle | decimal | % | The current position of the legs in a step
ball.time-since-last-seen | decimal | ms | The time since the ball was seen last
ball.consecutive-seen-time | decimal | ms | The time for which the ball was seen consecutively
ball.time-since-last-seen-consecutively | decimal | ms | the time since the ball was seen consecutively last
ball.communicated-ball-distance | decimal | mm | The distance to the communicated ball
ball.relative-speed-x | decimal | mm-per-s | The speed of the ball relative to the robots x axis
ball.relative-speed-y | decimal | mm-per-s | The speed of the ball relative to the robots y axis
ball.speed-abs | decimal | mm-per-s | The speed of the ball absolute
ball.seen.distance | decimal | mm | disctance to the seen ball
body-PSD-detect-ball | boolean | true/ false | Body PSD detects something...
time-since-last-seen-beacon | decimal | ms | The time since the last beacon was seen
time-between-last-beacons | decimal | ms | The time difference betwen the last two seen beacons
head-control-mode | enumerated | search-auto search-for-ball catch-ball catch-ball-high look-between-feet-for-carried-ball release-caught-ball-when-turning-left release-caught-ball-when-turning-right search-for-ball-left search-for-ball-right hold-ball open-challenge none look-left look-right scan-for-obstacles search-for-landmarks search-for-landmarks-head-low look-at-blue-pink-landmark look-straight-ahead look-toward-opponent-goal look-between-feet look-to-stars snap-at-finger look-parallel-to-ground direct stay-as-forced watch-origin calibrate-head-speed look-at-most-informative-landmark directed-scan-for-obstacles real-slow-scan | Possible requested head control modes
head-is-blocked | boolean | true/ false | The head is blocked by a special action or a walk type
last-head-path-is-finished | boolean | true/ false | The last path of the head path planner is finished
set-joints-is-close-to-destination | boolean | true/ false | True if the set-joint-destination is reached
set-joints-max-pan-reached | boolean | true/ false | True if the head's pan is either max +/- to the side
next-landmark-is-within-reach | boolean | true/ false | True if the next landmark in a directed scan can be reached
## Constants
Name | Value | Measure | Description
time-after-which-is-considered-lost | 300 | ms | The time after which the a previously seen ball is considered lost