correcting autopilot overshoot

[bstory]

My boat consistently (even with the latest s/w update) has an overshoot of 35+ degrees before correcting to the set course. The manual says to adjust rudder gain, however, this is not an available option for the evolution. What do you recommend?

Autopilot and related equipment list:
EVOLUTION EV1 SENSOR CORE E70096
ACU-200
P70 COLOUR A/P HEAD: SAIL E22166
RAYPILOT TYP 1
MFD e95 E70021

Thanks.

-Bob.

[Chuck - Raymarine - Moderator]

Bstory,

Unlike prior generations of autopilots, the Evolution autopilots are commonly installed without a rudder reference transducer. Should symptoms such as you have reported occur, then installation of a rudder reference transducer would be among the actions taken to address the issue. You may verify whether an a rudder reference transducer has been installed by powering the autopilot ON while dockside and then observe the autopilot control head's rudder bar to determine whether the displayed rudder bar responds to movement of the wheel.

[bstory]

Hi Chuck - yes, the rudder angle is displayed at the top of the P71 display and responds to the wheel movement.

-Bob.

[Chuck - Raymarine - Moderator]

Bob,

Am I correct in assuming that you are referring to the pilot's operation when Track mode is engaged? What is the autopilot's Response Level currently configured to? Also, what is value of the maximum deviation (MENU->SET-UP->DIAGNOSTICS->ABOUT DISPLAY ... scroll the displayed list of information to the bottom to find this value) sensed by the autopilot?

[bstory]

Response is set to Cruising and deviation is 7.

-Bob.

[Chuck - Raymarine - Moderator]

Bob,

It is recommended that you change the Response Level to Performance for better tracking. Please additionally note that an autopilot's primary function when operating in Track mode is to keep the vessel on the course line established by the chartplotter via a GoTo Waypoint/Cursor Position or Follow Route command ... as the corresponding course line identifies a path which has been inspected by the operator to be of safe depth and free of obstructions. Correspondingly, when Track mode is commanded, the autopilot will attempt to join the course line as quickly as possible rather than establish a new course from the vessel's present position to the destination waypoint. Should the latter be desired, then use the Reset XTE feature. As such, when initially entering into Track mode, it is recommended that the vessel's speed be slowed until the vessel joins with course line, at which time safe speed may then be resumed.

[bstory]

Chuck - I was out on the vessel for the w/e and changed the Response Level to Performance as you suggested. I still got the 35 degree overshoot. I have noticed this behaviour when on course and I select go to waypoint at cursor OR when I have a Route planned and I arrive at one waypoint and am asked to accept the next waypoint.

-Bob.

[Chuck - Raymarine - Moderator]

Bob,

What is the length and manufacturer's specified displacement of the vessel?

Did you perform a Factory Reset, re-execute the Dockside Wizard, and then re-perform the deviation/vessel handling cruise following the R4 Evolution autopilot software update?

Within the system diagnostics of your autopilot, what is reported for the maximum deviation?

Did you confirm that the autopilot was fitted with a rudder reference transducer (examine the ACU's rudder terminals to determine whether something is connected to them)?

What model of drive unit has been installed?

What is the hard over to hard over time?

What is the arrival circle radius of your MFD configured to?

What is the cubic capacity of the vessel's steering ram?

[bstory]

Chuck - below are my responses to your questions .....

What is the length and manufacturer's specified displacement of the vessel?
35' 5" 14,800 lbs

Did you perform a Factory Reset, re-execute the Dockside Wizard, and then re-perform the deviation/vessel handling cruise following the R4 Evolution autopilot software update?
yes

Within the system diagnostics of your autopilot, what is reported for the maximum deviation?
6 degrees

Did you confirm that the autopilot was fitted with a rudder reference transducer (examine the ACU's rudder terminals to determine whether something is connected to them)?
yes there is

What model of drive unit has been installed?
Autopilot and related equipment list:
EVOLUTION EV1 SENSOR CORE E70096
ACU-200
P70 COLOUR A/P HEAD: SAIL E22166
RAYPILOT TYP 1
MFD e95 E70021

What is the hard over to hard over time?
no idea how to find this

What is the arrival circle radius of your MFD configured to?
if you mean in the MFD's alarm menu, it was set to off recently but before that was 650'

[Chuck - Raymarine - Moderator]

Bob,

Per our conversation yesterday, unlike Auto mode which is designed to steer the vessel to a heading specified by the user, Track mode is not designed to steer the vessel to any specific heading. The function of Track mode is to keep the vessel within a corridor surrounding the course line (path of safe navigation) which has been established at the moment that a Go To Cursor / Waypoint or Follow Route. When initially commanded, Track mode will seek to quickly have the vessel join the course line ... depending on the distance which the vessel has moved from the course line prior to commanding the autopilot into Track mode and the direction that the vessel is then heading, the heading commanded by the autopilot to join the track line may differ significantly from the bearing from the vessel's current position to the waypoint/cursor position being navigated to ... again, the autopilot will seek to join the course line as quickly as possible, not steer immediately toward the waypoint / cursor position. The width of the corridor and how aggressively the autopilot will initially attempt to join the course line is determined by the autopilot's Response Level configuration setting. The most narrow corridor and minimum time to initially join the course line (this may also incur the greatest deviation from the vessel's current bearing to waypoint) will be achieved with the Response Level configured to the PERFORMANCE setting.

Accordingly, it is recommended that when engaging track mode that the vessel be maneuvered into close proximity of the course line and be heading in the direction of the waypoint / cursor position prior to engaging Track mode.