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Extending autopilot related paths 2020

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AdrianP edited this page May 9, 2022 · 24 revisions

This doc is a draft for extending Signal K autopilot related paths to improve integration with different autopilots.

Autopilot paths:

List of relevant paths, proposed extensions in italic

  • autopilot/state
    • enum: enabled disabled error
  • autopilot/mode
    • current mode: e.g. compass
  • autopilot/availableModes
    • array of modes supported by the Auto-pilot e.g. [compass, gps, windApparent, windTrue]
  • autopilot/target/windAngleApparent
  • autopilot/target/windAngleTrue
  • autopilot/target/headingTrue
  • autopilot/target/headingMagnetic
  • autopilot/target/courseTrue
  • autopilot/target/courseMagnetic (not really relevant?)
  • autopilot/deadZone
  • autopilot/backlash
  • autopilot/gain
    • what subkeys should we have here?
  • autopilot/maxDriveCurrent
  • autopilot/maxDriveRate
  • autopilot/portLock
  • autopilot/starboardLock
  • _ slew speeds ??_

Course paths:

V1 specification:

  • navigation/courseGreatCircle/crossTrackError
  • navigation/courseGreatCircle/bearingTrackTrue
  • navigation/courseGreatCircle/bearingTrackMagnetic
  • navigation/courseGreatCircle/activeRoute
  • navigation/courseGreatCircle/activeRoute/estimatedTimeOfArrival
  • navigation/courseGreatCircle/activeRoute/startTime
  • navigation/courseGreatCircle/nextPoint {type + href}
  • navigation/courseGreatCircle/nextPoint/distance (tkurki: no idea why these are missing)
  • navigation/courseGreatCircle/nextPoint/position
  • navigation/courseGreatCircle/nextPoint/arrivalCircle (size in m)
  • navigation/courseGreatCircle/previousPoint {type + href}
  • navigation/courseGreatCircle/previousPoint/distance
  • navigation/courseGreatCircle/previousPoint/position

V2 specification:

  • navigation/course/calcValues/calcMethod {great circle | rhumbline}
  • navigation/course/calcValues/crossTrackError
  • navigation/course/calcValues/bearingTrackTrue
  • navigation/course/calcValues/bearingTrackMagnetic
  • navigation/course/calcValues/estimatedTimeOfArrival
  • navigation/course/calcValues/distance
  • navigation/course/calcValues/bearingTrue
  • navigation/course/calcValues/bearingMagnetic
  • navigation/course/calcValues/velocityMadeGood
  • navigation/course/calcValues/timeToGo

Autopilot API:

Implementation of an Autopilot API to perform common operations and provide a consistent way to populate the relevant steering/autopilot paths (similar to Course and Resources APIs).

Examples:

  • GET /steering/autopilot (retrieve autopilot status)

  • GET /steering/autopilot/modes (retrieve available autopilot modes)

  • PUT /steering/autopilot/mode { "value": "compass"}` (set autopilot mode to compass)

  • PUT /steering/autopilot/enable (set autopilot to active i.e. steer a course)

  • PUT /steering/autopilot/disable (stop autopilot from steering a course)

  • PUT /steering/autopilot/tack/port (perform a port tack)

  • PUT /steering/autopilot/tack/starboard (perform a starboard tack)

  • PUT /steering/autopilot/adjust { value: 10 } (increment heading / wind angle) value by 10)

Todo

  • Dodging - what does it mean in real life?
  • More than one autopilot? Marking as active / standby? _Example: Path for each autopilot device with reference to path of active device.
/steering/autopilot/
                   href: "pypilot"
                   ...
                   pypilot/
                          ...
                   raymarine/
                            ...
  • Tacking
  • +/- adjustments
  • Internal autopilot operation values (gain, deadZone, backLash, etc.) in designated path? e.g. autopilot/internal/deadZone, autopilot/internal/backlash, autopilot/gain
  • What well defined notification/* paths should there be?

Control vs informing about a state

In Signal K control/command is usually separate from "sensor data", eg. data about the current value of something. Control messages are HTTP PUTs or (ws) messages with put syntax: https://github.com/SignalK/specification/blob/master/gitbook-docs/put.md

SK Server Network Plugin CAN / serial Autopilot
/stream <------------ status ----------------------
steering.autopilot.state
steering.autopilot.mode 		N2K to SK <------
/stream <------------ target details ------------
autopilot.target.courseTrue
autopilot.target.headingMagnetic
autopilot.target.windAngleTrue
etc. 		N2K to SK <------
/stream --------------- course data ------------>
navigation.course.nextPoint
navigation.course.calcValues 		SK to 0183
(TCP 10110) 		---------->
RMB, APB, XTE
/stream --------------- course data ------------>
navigation.course.nextPoint
navigation.course.calcValues 		SK to N2K ---------->
PGN 129283
PGN 129284
HTTP GET <---------------- options -------------------
steering.autopilot.availableModes 		AP Plugin <------
HTTP PUT --------------- set state ------------>
PUT steering.autopilot.state {value: string}		 AP Plugin ------>
HTTP PUT --------------- set mode ------------>
PUT steering.autopilot.mode {value: string}		 AP Plugin ------>
HTTP PUT --------------- set target ------------>
PUT steering.autopilot.target {value: number}		 AP Plugin ------>

Operation / Usage:

Assumption: Autopilot is a standalone device operating autonomously. It can accept commands and course settings via:

  • Direct input on the device / built-in UI
  • NMEA0183, NMEA200, SeaTalk messages
  • Signal K delta messages

Signal K Course API: signalk-server PR #1381 implements a course API that provides operations for setting an active route or destination point and facilitates the setting of navigation.course path values.

Assumption: navigation.courseGreatCircle and/or navigation.courseRhumbline (v1 specification), navigation.course.calculations (v2 specification) path values are populated through the use of a course data provider plugin.

Action Signal K aware Autopilot Plugin/Provider
1. SK Server startup Send status in steering/autopilot/mode path(s) to server. Connect to autopilot and retrieve status. Send steering/autopilotdeltas with retrieved values.
2. Autopilot engaged (autopilot UI) Send deltas containing updated autopilot path values. Detect change in autopilot status, retrieve status from autopilot, send deltas containing updated autopilot path values.
3. Changes to Autopilot status (autopilot UI) Send deltas containing updated autopilot path values. Detect change in autopilot status, retrieve status from autopilot, send deltas containing updated autopilot path values.
4. Destination set via Signal K Course API Receives course/nextPoint, course/calcValues deltas and uses values to set course to steer. Receives course/nextPoint, course/calcValues deltas and sends values to autopilot to set course to steer.
5. Send command to autopilot via Signal K Autopilot API Receives steering/autopilot deltas and adjusts operation based on received values. Receives steering/autopilot deltas and sends values to autopilot to adjust operation based on values supplied.

Real World setups

How about describing some real world setups to get context and depth.

A start point would be current NMEA0183 and N2K systems and OpenCpn & pypilot, then we could construct a "pure" Signal K system.

Related resources:

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