How does a Raymarine sensor work?

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Bridgeman

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We are having a Raymarine Evolution auto pilot system fitted. Raymarine say" At the centre of every Evolution system is the intelligent EV sensor core, a 9-axis sensor that monitors vessel motion in all three dimensions. The innovative EV sensor core combines advanced solid-state sensors" All magic to me, any ideas what they mean or how it works? I understand the Fluxgate workings is this the same idea?
Thanks. Neil
 
I think they are just using accelerometers to measure how the boat´s movement, forwards, backwards, pitching and rolling etc. By mathematically integrating the acceleration signal the computer can determine actual speed and ultimately distance of movement in a given axis.
The 9 axis thing is probably they are using accelerometers in different positions within the boat or at different angles to better measure pitching and rolling.
modern Cars use accelerometers to control traction control, stability programs and the ABS, and some mobile phones have them inside for various movement or measurement apps and games.
 
kashurst said:
I think they are just using accelerometers to measure how the boat´s movement, forwards, backwards, pitching and rolling etc. By mathematically integrating the acceleration signal the computer can determine actual speed and ultimately distance of movement in a given axis.
The 9 axis thing is probably they are using accelerometers in different positions within the boat or at different angles to better measure pitching and rolling.



modern Cars use accelerometers to control traction control, stability programs and the ABS, and some mobile phones have them inside for various movement or measurement apps and games.
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Hi kashurst. Just one sensor fitted and it gives compass direction to the autopilot but I cant get how it does it.
 
Confusion reigns - do you have the EV sensor? That seemed to be what you were asking about.

If so, yes, it is a multi axis accelerometer system. Integral of acceleration is speed, the integral of which is distance.

Exactly as Kashurst says - if you know where you are to start with, everything else can be derived from acceleration.

One accelerometer for longitudinal acceleration and one for lateral. They could also include vertical acceleration, pitch, roll and yaw, and cross refer it all with GPS Lat and long and SOG / COG.
 
rosssavage said:
Confusion reigns - do you have the EV sensor? That seemed to be what you were asking about.

If so, yes, it is a multi axis accelerometer system. Integral of acceleration is speed, the integral of which is distance.

Exactly as Kashurst says - if you know where you are to start with, everything else can be derived from acceleration.

One accelerometer for longitudinal acceleration and one for lateral. They could also include vertical acceleration, pitch, roll and yaw, and cross refer it all with GPS Lat and long and SOG / COG.
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Thanks Rosssavage. Yes its an EV1. I guess it must calculate between 2 gps positions to give the compass heading using the accelerometer for forward motion? I will do a bit more googling. Cheers. Neil
 
In fact, all you need is GPS COG and mag variation to give compass heading. I would imagine the accelerometers are mainly used for quick reaction to any change from steady state. They work much quicker by sensing the motion of the boat than the old system of waiting for a heading change to be registered. Some of the older Raymarine /Autohelm units had an optional rate gyro to improve performance - these days, solid state MEMS accelerometers are dirt cheap - there's probably three in your phone!
 
It's a fluxgate compass to give heading information with accelerometers to measure change of attitude (including yaw) I think. The sensor has to be mounted away from magnetic interference which is a bit of a giveaway. Even the best inertial nav systems are subject to some drift and heading is actually the worst for this which is pretty much all inertial systems use a gyro platform to detect rapid change of heading but take heading from some other source.
 
grumpy_o_g said:
It's a fluxgate compass to give heading information with accelerometers to measure change of attitude (including yaw) I think. The sensor has to be mounted away from magnetic interference which is a bit of a giveaway. Even the best inertial nav systems are subject to some drift and heading is actually the worst for this which is pretty much all inertial systems use a gyro platform to detect rapid change of heading but take heading from some other source.
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According to Raymarine brochure all the heading data comes from the EV1, no Fluxgate compass. I think it must work like the compass on mobile phone app as Rosssavage mentioned. All clever stuff.
 
What's the difference between the Raymarine EV1 and this?

http://www.raymarinestore.eu/clearance/heading-sensor/airmar-heading-sensor.html

As far as I can tell, that's an Airmar H2183 heading sensor that is sold as (for example) the Garmin Marine Heading sensor for over £600:

http://www.cactusnav.com/garmin-marine-heading-sensor-cable-p-11111.html

From the blurb on the Raymarine website: "Key features Heading 1° Static Accuracy 2° Dynamic Accuracy No Moving Parts 3-Axis Compass 3-Axis Accelerometer 3-Axis Rate Gyro"
 
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These semiconductor accelerometers and gyros are everywhere the days eg Arduino, Raspberry Pi, Nintendo Wii and every quadcopter. Very cheap to manufacture and very useful.
 
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