Satnav Yaw rate settings

[AlexFacey]

Just out of interest how many owners have played with the yaw rate settings for there Civic?

[TTDegs]

I nearly have a few times....

then thought better of it

[Maldax]

Is this the Yaw settings on the EX? As I think that is onlt for the satnav so it can still track you without a sat signal

[czechplastik]

Originally Posted by AlexFacey

Just out of interest how many owners have played with the yaw rate settings for there Civic?

If I knew what they did I may have a go at it!

[sco77harris]

whats a yaw?

[Charles_Harding]

Originally Posted by sco77harris

whats a yaw?

Isn't it the bit that helps you chew?

"That's OK I can walk to the kerb from here!"

Charles H.

[thiswilldo]

Yaw is the movement of the car going left and right. It applies to aeroplanes and missiles as well.

If the nosecone of a plane moves left or right, this is the Yaw.
If a nosecone goes up and down, this is the pitch. If it tips from side to side, this is the roll....

There you go, now you can drive one of those orange Easyjet things the same as Pottsy.

[Crackers]

Originally Posted by thiswilldo

If the nosecone of a plane moves left or right, this is the Yaw.
If a nosecone goes up and down, this is the pitch. If it tips from side to side, this is the roll....

Monarch Airlines apply all of these movements while taxiiing.

[Pottsy]

The yaw rate is used by the satnav to work out where you are (along with wheel speed) when the GPS is unavailable. The tuning options are for "factory use only", and I suspect it's probably not going to be productive to change the values.

[Skippy]

Yup, it's probably a 'fatctory' setting. I'm surprised it's there though. Previous dead-reckoning systems I've seen use the feeds from the rear axle ABS. this can be self calibrating. I can only assume they're using accelerometers or a gyro, and this needs a calibration value to minimise cumulative error.

[Pottsy]

Yaw Rate Sensor

The yaw rate sensor (located in the navigation unit) detects the direction change (angular speed) of the vehicle. The sensor is an oscillation gyro built into the navigation unit.

Sensor Element Structure

The sensor element is shaped like a tuning fork, and it consists of the piezoelectric parts, the metal block, and the support pin. There are four piezoelectric parts: one to drive the oscillators, one to monitor and maintain the oscillation at a regular frequency, and two to detect angular velocity. The two oscillators, which have a 90-degree twist in the centre, are connected at the bottom by the metal block and supported by the support pin. A detection piezoelectric part is attached to the top of each oscillator. The driving piezoelectric part is attached to the bottom of one oscillator, and the monitoring piezoelectric part is attached to the bottom of the other oscillator.

Oscillation Gyro Principles

The piezoelectric parts have ‘‘electric/mechanical transfer characteristics.'' They bend vertically when voltage is applied to both sides of the parts, and voltage is generated between both sides of the piezoelectric parts when they are bent by an external force. The oscillation gyro functions by utilizing this characteristic of the piezoelectric parts and ‘‘Coriolis force.'' (Coriolis force deflects moving objects as a result of the earth's rotation.) In the oscillation gyro, this force moves the sensor element when angular velocity is applied.

Operation

1. The driving piezoelectric part oscillates the oscillator by repeatedly bending and returning when an AC voltage of 6 kHz is applied to the part. The monitoring-side oscillator resonates because it is connected to the driving-side oscillator by the metal block.
2. The monitoring piezoelectric part bends in proportion to the oscillation and outputs voltage (the monitor signal). The navigation unit control circuit controls the drive signal to stabilize the monitor signal.
3. When the vehicle is stopped, the detecting piezoelectric parts oscillate right and left with the oscillators, but no signal is output because the parts are not bent (no angular force).
4. When the vehicle turns to the right, the sensor element moves in a circular motion with the right oscillator bending forward and the left oscillator bending rearward. The amount of forward/rearward bend varies according to the angular velocity of the vehicle.
5. The detecting piezoelectric parts output voltage (the yaw rate signal) according to the amount of bend. The amount of vehicle direction change is determined by measuring this voltage.

yawgif.gif

[czechplastik]

^^^^^^^
In summary, best left alone....

[Crackers]

Originally Posted by Pottsy

Yaw Rate Sensor
The yaw rate sensor (located in the navigation unit) detects the direction change (angular speed) of the vehicle. The sensor is an oscillation gyro built into the navigation unit.

I had not heard of this before. Assuming that the nav unit is GPS based, I guess the motion sensor's purpose is to calculate the vehicle's position when the unit is unable to 'see' its satellites. When my Street Pilot III loses signal, such as when entering a tunnel, it announces loss of signal, freezes the display and updates itself when we pop out again at the other end. This yaw thingy is a neat device!

[Skippy]

Should have known; space-age technology! Where did you dig that out from Pottsy? I played with some AD chips a few years ago - it looks like they've got a lot better since I stoped doing electronics!
Is the cal value to compensate for operation at different latitudes? If so, is it self adjusting (when you turn it on), and the screen allows an override?

In reply to Crackers: the yaw and distance data allow you to dead-reckon from your last known position and heading. The early Philips and Blaupunkt systems had it via rear wheel rotation sensing. Recent GPS receivers are pretty good and don't have so many problems in urban or wooded areas, but will drop fix occasionally, like your tunnel example.

A good reason for having it these days is detecting turn and so being able to check that you have taken the exit from that roundabout it thought you had. The GPS-only units always suffer from a bit of lag, especially when you change direction. GPS can only guess where you are, based on where you were when the last fixes were made.

[Pottsy]

Skippy, I'm not sure whether it's clever enough (or indeed accurate enough) to do proper DR using latitude. The cal value is simply the 2.5 volt neutral position, so when the car is not turning then the thing reads zero.

I strongly suspect that the nav simply uses the yaw rate and wheel speed (which it gets from the wheel impulse generator factored by a tyre factor that it computes when the GPS is working) to DR for the small times there is no GPS signal (including just after system start). It's pretty accurate - it copes perfectly with the Mersey Tunnel, and it tells you to take the "next exit" off a roundabout immediately after the penultimate exit.

These two features alone make the system significantly nicer than a tomtom or similar. But it's not like having three sets of laser gyros...

[Crackers]

Originally Posted by Pottsy

- it copes perfectly with the Mersey Tunnel, and it tells you to take the "next exit" off a roundabout immediately after the penultimate exit.

These two features alone make the system significantly nicer than a tomtom or similar. But it's not like having three sets of laser gyros...

My Street Pilot is often, though not always, savvy enough to tell me exactly when to take the next off on a roundabout. I had sort of figured that it does this more on larger roundabouts and at slow speed on smaller ones. The map and numerical displays are very accurate in displaying time and distance to the next event. I don't know if it has yaw sensing, but if I have understood this right, I am intrigued at the possibility that it might! On the other hand I can also relate to Skippy's observation concerning lag, I have certainly noticed that and especially the delay inherent in recognising that you've gone "off route".

[Pottsy]

Crackers - portable navs don't have these DR (deduced reckoning) systems where they can tell where they are when the GPS system is unavailable. Portable systems are pretty good (I have two here), but a good built in system does have its advantages.

To do DR you need to measure speed (done from the sensor that drives the car speedo) and yaw (there are a few ways of doing this).

[Kremmen]

When I leave work I initially get a good GPS signal but further on down a tree lined road the GPS indicator goes out for about 4 miles.

I have often wondered how the arrow continues to move accurately without a signal.

My TomTom never used to lose the signal down this bit of road!

What I find strange is that it fails with overhanging trees but works in my brick garage with the door shut!

[apemonkeyman]

All this amazing technology yet it still insists I go to France for a burger.

[Bungle]

Originally Posted by Pottsy

Crackers - portable navs don't have these DR (deduced reckoning) systems where they can tell where they are when the GPS system is unavailable. Portable systems are pretty good (I have two here), but a good built in system does have its advantages.

To do DR you need to measure speed (done from the sensor that drives the car speedo) and yaw (there are a few ways of doing this).

Oh how wrong you are Pottsy!

The new Sony one has acceleromoters built in to help out when you go through tunnels or a valley when it can't see the satellites in the sky. It senses change in direction and speed and guesses where your are based on those sensor readings.

My garmin one assumes you are travelling in a straight line and a constant velocity if it temporarily loses signal, though afetr about 30 secs it announces "Lost satellite reception" and gives up, until it gets a new lock.