Autopilot Troubleshooting

Connection and Configuration (NMEA0183)

TimeZero can send NMEA0183 Navigation information to the autopilot via a COM port or via a USB to Serial adapter. The first step is to know where to send the pilot information (on which COM port).

Note: If the location of the pilot is not known, you can use the Port Monitor function of TZ to detect what port the heading is coming in on; usually this is the same port as the pilot (most pilots have a bi-directional communication with the PC to listen for pilot sentence from the PC and send Heading information to the PC).

Most Autopilots use the APB sentence to get course to steer, cross track error and Waypoint ID. TimeZero is set to output this sentence by default along with the XTE sentence. Other data to output is dependent on what the pilot will accept or need. For example, some pilots need to receive speed from the computer, in that case the VTG or RMC sentence will need to be turned ON. The user can find this information in the owner’s manual for their autopilot.

Once you know which sentences to send to the pilot, open the Connection Wizard (under the TimeZero button) and select Data Output and Pilot. Click on "Serial Port" and select the COM port where the pilot is connected to and select the appropriate Baudrate (usually 4800). Select the sentences to output to the pilot. If you don't know which sentences to select, you can try APB, XTE and RMC.

Note that the APB sentence has two modes: “Magnetic North” and “True North”. This setting defines the North Reference that will be used inside the APB sentence for the Bearing to Waypoint (or CTS) information. If the Autopilot is connected to a Magnetic Heading sensor, you should use "Magnetic North". If the Autopilot is connected to a True Heading Sensor (such as a Satellite Compass or Gyrocompass), you should use "True North". Note that most installations are using a Magnetic Compass, so the APB default setting (“Magnetic North”) should be used.

Note: Also be sure that TimeZero and the autopilot are set to display the same North reference. You can adjust the North reference in TimeZero by adjusting the "Bearing Display" setting in the Units Options.

Once the settings have been adjusted in the Connection Wizard, click on "Next" and "Finish"

Connection and Configuration (NMEA2000)

TimeZero can also send Pilot information using NMEA2000. Unlike with NMEA0183, there is no sentence selection (called "PGN") as the NMEA2000 is much more standardized for pilot information. In TimeZero, you just need to make sure that "NMEA2000 Pilot Output" is checked from the last page of the Connection Wizard.

Note: This option will only be available when an Actisense NGT1-USB has been configured as a NMEA2000 input.

Checking this option will automatically output the following PGNs when a route is activated:

  • PGN 129283 - Cross Track Error

  • PGN 129284 - Navigation Data

  • PGN 129285 - Navigation Route/WPT Information (used to transmit the name of the destination waypoint)

Test the Connection

On the NavData panel in TimeZero, configure to display CTS (Course to Steer), XTE (Cross Track Error), and DTW (distance to waypoint). Configure the pilot to display a “steering page” or a service page with the same information. Note that "CTS" may be referenced on the pilot as "Bearing", "BPW" (bearing position to waypoint) or "BRG". The "DTW" may be referenced on the pilot as "RNG", "Range" or "DIST".

Once you have configured the NavData panel in TimeZero and can also display that information on the pilot, simply activate a route/waypoint in TimeZero. Look at the pilot screen and make sure that the data matches what the software displays.

If the data does not match (course to steer for example), make sure that the Pilot and TimeZero are using the same North reference (Magnetic or True). If the course to steer is off by 1 or 2 degree, this might be due to the difference in the magnetic variation table built in the Pilot (or Heading Sensor) and the magnetic variation used by TimeZero. To avoid the pilot (or heading sensor) from making any variation calculations (going from True North to Magnetic North or the opposite), make sure that TimeZero is sending Magnetic bearing if the heading sensor used by the pilot is a magnetic sensor and True bearing if the heading sensor used by the pilot is a true heading sensor (Satellite Compass or Gyrocompass).

Note: With NMEA0183 connection, only the APB sentence allows you to select Magnetic or True bearing. If you use the RMB sentence, it will always send True Bearing (as per the NMEA0183 specification). For that reason, if you have a magnetic compass, it is better to use the APB sentence and make sure that it is set up in TimeZero for “Magnetic North”.

If no information appears at all on the Autopilot ("--" for example), check the following if you use a NMEA0183 connection:

  • Wiring: are the wires reversed? Or going into the improper input on the pilot?

  • COM port number: is TZ outputting on the correct port?

  • Some (older) pilots don’t recognize the “II” NMEA Talker. Try to change the NMEA talker to "GP" (on the output setup page of the connection wizard)

  • Check the Navigation source on your Autopilot. Some pilot have two or more inputs that can be switched. The “Navigation Source” port must match the input port of the pilot connected to the computer

  • Check the input baud rate of the pilot. Most of the time it is set to the regular 4800bps, but it may be changed sometimes (38.4Kbps)

  • Check if the pilot is using RS232 or RS422 and if the COM port used by TimeZero uses the same protocol

When you have confirmed that the data matches in TimeZero and on the pilot (at minimum XTE and CTS), you can perform a sea trial

Pilot not steering properly during a sea trial

If the data is correctly sent by TimeZero to the pilot (with matching values), but if the pilot is not steering properly (not following a straight line or not steering in the correct direction), check the following points:

Note: At this point, we are not troubleshooting TimeZero itself but the pilot. TimeZero’s “responsibility” is only to send a good value to the pilot. If the pilot is not steering properly at this point, then something needs to be adjusted on the pilot itself (or the compass needs to be calibrated)

Check Pilot behavior in “Auto Mode”

Every pilot has an “Auto” mode which does not rely on any external Navigation information (unlike the “Nav” or “Navigation” mode which relies on XTE and/orcCTS sent by a “Navigator” such as TimeZero). Testing the pilot in “Auto” mode allows to validate its correct behavior in standalone mode. When engaging the “Auto” mode, the pilot simply takes a snapshot of the heading at the time the user presses the “Auto” button and it simply holds that course. If the pilot is unable to navigate a straight course in Auto mode, it will not be able to navigate a straight course in “Nav” mode either. In that case, adjust the pilot parameters until having a satisfactory “Auto” mode behavior.

Note: Some pilots allow to change course while in auto mode by turning the rotary knob. It is a good idea to change the course in Auto mode to see how the pilot react to change of course order.

Check the Heading Sensor

If the Pilot behaves correctly in “Auto” mode, but has problems following a route in “Nav” mode, then the problem is likely coming from the heading sensor. Understand that when TimeZero is sending an order to the pilot, via the Course to Steer sentence (ex: "go to 273 degree"), the pilot can only rely on its heading sensor to know where 273 degree is. If the heading sensor sends a wrong value, then TimeZero and the Pilot will not agree on where 273 degree is, resulting in an erratic behavior (pilot seems to follow an alternate course).

First, make sure that TimeZero and the Pilot are receiving the heading value from the same heading sensor. This will help when troubleshooting the heading sensor value. Then make sure that the heading value displayed on the pilot matches the value displayed in TimeZero (configure heading in the NavData panel to compare the value). If the values don’t match, make sure that the pilot and TimeZero are using the same North Reference (Magnetic or True).

Once you checked that the heading is the same on the pilot and TimeZero, add a Course Over Ground (“COG”) data box in TimeZero. On a calm day (low wind, no current, low wave), steer your boat on a straight line at 6-10Kn. In these conditions, the direction you are going (COG) should match the heading of the boat. In other words, the Heading and COG values displayed in TimeZero should be the same (+/- 1 degree). Repeat this process in various directions (heading North, heading South, heading East and heading West). If the heading and COG values don’t match (offset more than 2-3 degrees), then the heading sensor needs to be calibrated if you want the “Nav” mode to steer in the correct direction.

Pilot not handling correctly the change of Waypoint

If the Pilot “overshoots” a Waypoint, make sure that you have setup a Waypoint Switching Radius large enough in TimeZero to allow the pilot to start the turn before it actually reaches the Waypoint. The Waypoint Switching Radius can be adjusted from the Routes Options.

Also, make sure that the counter rudder gain (parameter of the pilot) is set up properly for your boat. This parameter varies with the “inertia” of your boat. Some pilots (like the Furuno Pilots) learn this parameter dynamically and gets better after a couple of turns.  This information will be found in the pilot manufacturer’s documentation.

Summary

Here what to keep in mind when configuring a pilot with TimeZero:

  • Make sure that the pilot is correctly connected to TimeZero (NMEA0183 or NMEA2000, Port COM, Baudrate, Wiring)

  • Select the correct NMEA0183 output sentence (in most of the cases, APB, XTE and RMC will work) or check "NMEA2000 Pilot Output" from the last page of the Connection Wizard (when using NMEA2000)

  • Make sure to match the bearing readout in TimeZero and on the Pilot (Magnetic or True) and make sure to send a bearing that has the same reference as the heading sensor (magnetic in most cases)

  • Activate a route and make sure that XTE and CTS match on TimeZero and on the Pilot (display these two information on the pilot)

  • Make sure that the heading sensor used by TimeZero is the same heading sensor used by the Pilot and make sure it is properly calibrated. Remember that a heading sensor that is offset by 3 or more degrees will cause the pilot to steer the boat by the same error!