1. The System: Software/Electronics/Control/Navigation Steve McPhail Miles Pebody, James Perrett l The system is Physically Modular: 15 nodes (sub-systems) l Truly Distributed: No sub-system is overly complicated l Uses a small subset of simple hardware (2 types mostly) l The hardware is easy to programme l The Interfaces / Data flows are well defined l System Data logging is straightforward >>

2. Autosub Distributed System Architecture EMERGENCY ABORT MISSION CONTROL DEPTH CONTROL POSITION CONTROL MOTOR + SPEED CONTROL ROUTER / RADIO MODEM DATA LOGGER ACOUSTIC COMS ORBCOMM SAT. COMSADCP ATTITUDE SENSOR GPS NAVIGATION FWD ECHO SOUNDER DEPTH SENSOR(S) LINE DEPLOY SYSTEM LonWorks Network POWER SYSTEM 100V 24V 48V Distributed Power Harness END ARGOS LIGHTS HF TRANSPONDER LF TRANSPONDER >>

3. Emergency Abort System l EAS Abort System Drops the Ballast weight and stops the motor IFF: Vehicle has dived too deep(max depth)Vehicle has dived too deep(max depth) Mission Has been continuing for too long(mission timeout)Mission Has been continuing for too long(mission timeout) Vehicle has been submerged for too long (dive timeout)Vehicle has been submerged for too long (dive timeout) Leak of one of the 6 main pressure casesLeak of one of the 6 main pressure cases Battery over temperatureBattery over temperature Communications Failure with pressure sensors or Mission Control nodes;Communications Failure with pressure sensors or Mission Control nodes; Command from Acoustic Command system (either HF or LF)Command from Acoustic Command system (either HF or LF) Failure of power (as Solenoid is held on with Electromagnet).Failure of power (as Solenoid is held on with Electromagnet). l EAS also periodically and actively enables propulsion motor so that system fails safe (motor is disabled) l EAS also periodically and actively enables propulsion motor so that system fails safe (motor is disabled) >>

4. MISSION CONTROL Mission Control Node Mission Script (Via Radio) START, STOP, ABORT TIMEOUT GOT GPS FIX REACHED XY POS. REACHED DEPTH DIVED SURFACED POSITION Demands DEPTH Demands MTR POWER Demands Events trigger execution of next line in Mission Script : - demands are sent out to Control nodes

5. Example of 1 line of Mission Script. WHEN(GotGPSfix)// When GPS fix acquired ……… MotorPower(400), // Set Motor Power to 400 Watts. TimeOut(5000),// Set timeout of 5000 seconds. Depth(10),// Dive to 10 metres. TrackP(N:56:27.586, W:5:29.477); // Follow to end of track // Next line, when reached end of the track …… WHEN(GotPosition)// When Got there (OR timeout) WHEN(GotPosition)// When Got there (OR timeout) >> ……… ……… // When satisfactory GPS fix has been acquired dive and track follow: // Set timeout to 5000 seconds.

6. Autosub Systems: Propulsion and Actuators Direct drive DC motor. No gear box or shaft seal ~ 70% efficiency Specially designed propeller. 250 N thrust ~ 70% efficiency Actuators pressure balanced: no shaft seal

7. Position (Rudder), Depth (Stern Plane), Speed (Motor) Control Nodes. Motor Control Position Control Depth Control

8. Motor Power Control l TWO MODES : Torque (only used for Test); + POWER CONTROL ALSO : RPM, TORQUE, VOLTAGE, CURRENT, FAULT made available to NW for logging and diagnostics. Motor Controller Prop Motor Lonworks Network D to A RPM Torque Demand Power Demand Enable (from EAS) A to D Dig. Out EN

9. Position Control l CONTROL MODES: RUDDERRUDDER (Only Useful during set-up and test) HEADINGHEADING (Sometimes useful, And needed for compass calibration) POSITIONPOSITION (Line Of Sight).. Head directly towards Way Point. TRACK FOLLOW :TRACK FOLLOW : (Follow Straight line track between WP n, WP n+1 … The most useful..) >>

10. Position Cascade Control Position Heading Lonworks Network ALSO : Rudder Position, Range to Go, Fault, and Intermediates made available to NW for logging & Diagnostics. |L| |P p | |P h, D h Scale+Offset| Track Demand Track Follower Position Controller Heading Controller Position Demand Heading Demand Rudder Demand ADC Servo Motor Control Rudder Motor Pot 48 V

11. Time Domain Simulation (MathCad) Response to step depth demand change of 5 m

12. Depth and Altitude Control l CONTROL MODES: SternPlaneSternPlane Useful during diving and setup/test DepthDepth Where Constant Depth Required. NB safety limits overide Altitude Altitude Where Constant Altitude required. NB safety limits overide Feedback via ADCP Altitude AND Fwd echo sounder l SAFETY LIMITS: Maximum DepthMaximum Depth Minimum AltitudeMinimum Altitude Maximum Pitch (up) eg. +60 degrees.Maximum Pitch (up) eg. +60 degrees. Minimum Pitch (down) eg. -15 degrees >>Minimum Pitch (down) eg. -15 degrees >>

13. Depth and Altitude Cascade Control Depth Pitch Lonworks Network ALSO : SternPlane Position. Fault and Intermediates Output to Netwrok for Logging and Diagnostics P p, D p Scale+Offset Altitude Demand Altitude & & Depth Controller Pitch Controller Pitch Demand SternPlane Demand ADC Servo Motor Control Stern- Plane Motor Potentio- meter 48 V P z, I z, D z Max Pitch, Min Pitch, Max Depth, Min Altitude Altitude (ADCP) FWD Range

14. Echo Sounder and ADCP Simrad Mesotech. 200kHz Effective range 180 m (Should be 300 m)

15. Autosub Navigation (Via Radio or Acoustic Modem) DGPS receiver (IDAR Capable) Navigation processor Doppler Velocity Log Attitude sensor heading salinity [temperature] depth Latitude, Longitude Depth sensor V north V east position fix (For speed of sound calculation) GPS Antenna position fix Acoustic Transponder USBL Tracking System INS

16. Inertial Navigation System (INS) for Autosub l INS unaided Position estimate performance is ultimately limited by Bias Stability of the Gyros. l Affordable Gyros for AUVs (FOG or RLG) have: Gyro Bias Stability  0.005 degrees/ hour. l INS Position Drift  60 n.m. x Gyro Bias Stability  0.3 knt. (Is 8 % of 4 knt.)  0.3 knt. (Is 8 % of 4 knt.) l Practical System must use aiding by Doppler Velocity. l In this mode INS effectively is giving high accuracy heading. l 0.1% of distance travelled is achievable. >>

17. Seatex MRU6 Attitude Sensor l Measures Roll, Pitch and Heading. l Heading based on Tri-axis flux gate compass. Crucial to dead-reckoning navigation (ADCP) + heading control. l Problems with any such compass are A) Establishing compass deviation in local area (MagneticNorth - TrueNorth ) B) Magnetic materials on Autosub causing hard iron effects. (Heading error which is sinusoidal Vs true heading, can be several degrees error) l Both are dealt with by calibration mission taking about 30 minutes. Vehicle runs N,E,S,W submerged (15 minutes) Surfaces gets GPS fix, dives and runs in constant direction for 15 minutes, then surfaces and gets GPS fix. This reduces errors to +/-0.5 degrees. l Such a calibration mission needed where significant movement of ferrous objects near Compass and/or large change in geographical location. >>

18. l LEO Satellites. Email type of service. (Also Doppler position available) l Messages sent immediately on surfacing. 90% availability l Basic Parameters Sent: (position, GPS fix, time since fix, battery state, errors, leaks, temperatures, mission line…)(position, GPS fix, time since fix, battery state, errors, leaks, temperatures, mission line…) l Messages relayed to: Mobile phone SMS serviceMobile phone SMS service 2nd Orbcomm transceiver.2nd Orbcomm transceiver. l ARGOS position messages also forwarded to the above. l 2 way coms is an option (not implemented in Autosub). >> Orbcomm Telemetry: Autosub to base.

19. Forward Collision Avoidance l !The control algorithm for Forward Collision Avoidance has proved to be not as effective as hoped (As proved by collision with cliff in Sicilian channel)! l We will be working on the problem, improving algorithm by end of 2001. l Upgrade will be free to you. >>

20. Digiquartz Pressure Sensors l Diquartz 4000m rated Vibratory quartz pressure sensors. Rated Accuracy 0.01% Fs (40 cm equivalent). Resolution is 3cm. l In practice zero offset is most important for our use, as AUV control determines whether on-surface or dived using pressure only. l Sensor has RS232 output. One of our standard interface boards connect its data to the network. Sampled at 2 Hz. l 2nd sensor added for EAS, as we found that there was a possible single point failure to abort on overdepth if one sensor failed (and read low). l We have found that performance is good & to specification >>

21. RDI ADCP 300 kHz WH l Measures Velocities and Altitudes. l Will Bottom Track to 200 m altitude (necessary for good navigation), beyond that relies on Velocity Through Water. (System can fill in short gaps in bottom track, by calculating local current when BT available, then adding this to VTW) l Is a current profiler, (but you are probably not interested in that) You will set the number of profile bins to a minimum (3), so that you can ping at maximum rate (about 1.5 seconds). l Frame of reference rotation done in ADCP, using Heading sensor input. Hence important output is Vnorth, Veast. l ! Given time I would look at possibilities of having it fire through an acoustic window, as having it poking out the bottom gives increase in drag, and it is vulnerable. >>

22. Power System l Integrates + fuses power from 4 battery tubes. l Separate “Fuse Pot”, externally plugged in to pressure case, for convenience is designed to blow before internal fuses. l Provides 24 volt (450 Watt), 48 volt (300 Watt) and raw battery volts (15 Amp max from 120 to 60 volt). l Measures battery,and converter currents and voltages. l Also measures temperatures in the battery tubes, and can detect a leak in any tube. >>

23. Line Deployment System (Jack in the box) l Small float attached to string held on with electromagnet; released by radio command at end of mission. Spring helps release. l Float is grappled for, recovered and string pulled in. l String attached to thicker recovery lines (for and aft) which are attached to recovery winches, and then vehicle recovered. l Electromagnet is same design as EAS abort weight solenoid. l Control hardware is a “standard interface pot” (which is shared with the LF acoustics interface). >>

24. Standard Interface POT Power and LonWorks 15, 24, 48 volt isolated RS232 AUTOSUB SYSTEM Power isolate/protect. LonWorks interface 300 mm 115 mm Was useful in coping with rapid changes in science sensors One is used for LF Acoustics and Jack-in Box (combined) 24 volt to solenoid To SeaPam

25. Acoustic Communications l Since 1997 have used simple Applied Acoustic Engineering HF (around 30 kHz) system giving: Pulse delay telemetry (altitude, depth, heading); Command to AUV (GO, STOP, ABORT, SURFACE, CENTRE) Tracking Using ORE LXT system, with on screen plotting (IPS) ! System has worked well. Only notable problem is on Command giving false command (notably tends to abort (drops weight when we want to stop) Also tracking range ( 2 km), is not adequate for deep diving missions l New all digital LF (~12 kHz) ordered in January 1999 from AAE. Two way digital coms at ~100 baud to 5km, as well as transponder mode, and pulse delay telemetry. Our Vehicle And Top End software for command, telemetry, acoustic navigation fix is done but: ! There have been many problems with AAE ‘SeaPam / DeckPam’. Digital coms never really worked beyond 500 m. Pulse delay telemetry is little better. However they say that their upgrade using DSP technology is going well. (April 2001)… >>

26. Router / Radio Modem l Allows remote Transparent access to the LonWorks Network. l Only 4800 baud link; but adequate for mission uploads, and browsing the vehicle network sub-systems, and for ship utilities (starting / stopping / checking systems) l Uses Multitone transciever ~ 450 MHz. Range about 1km at best. l Router is our own HW based on standard Echelon module. Needed to avoid congestion of low bit rate radio modem. l Aerial of own design (made by PDM Ltd), identical to the ARGOS antennae. l Identical hardware at ship end completes link. >>

27. Data Logger and Radio Ethernet l PC104 486 DOS based data logger l Selectively Timestamps and records messages off the LonWorks Network l 10 Mbit/s Radio Ethernet allows data download remotely (up to 500 m range) l Currently 2 Gbyte hard-disk. More requires 32bit FAT (not tried yet). l ! Could be modified to log Ethernet data as well ? >>

28. l Go and Return on Twisted pairs so that External (wet) Harnesses can be daisy chained together, giving flexibility on number of nodes (sub-systems) in system. l Each Harness has 4 male and one female connector. >>

29. Relocation l Satellite: 2 independent ARGOS beacons. (2 month duration). On surface ARGOS Transmits every 120 seconds for approximately 1 second. Satellite locates mobile by Doppler shift.On surface ARGOS Transmits every 120 seconds for approximately 1 second. Satellite locates mobile by Doppler shift. Position Fixes available by Telnet/Email/Fax/ (by subscription).Position Fixes available by Telnet/Email/Fax/ (by subscription). Passes are approximately every hour at this latitude.(Better higher latitude)Passes are approximately every hour at this latitude.(Better higher latitude) We also use a direction finder (GONIO) to locate.... Useful.We also use a direction finder (GONIO) to locate.... Useful. ! Hardware transmitters we use are old... possibly obsolete, (but plenty of alternatives)! Hardware transmitters we use are old... possibly obsolete, (but plenty of alternatives) Orbcomm also useful for relocationOrbcomm also useful for relocation l Acoustic Tracking. Have ~30 kHz, and ~12 kHz stand alone transponders as well as telemetry transponders (total of four). Used for tracking underwater, up to 6km (LF), 2km (HF). Use ORE LXT and Trackpoint II systems. l Flashing lights. (Makes dark location easier than day) >>