I found that the ABS-sensor based TPMS works
10-07-2013, 12:05 PM
#1
AudiWorld Expert
Thread Starter
I found that the ABS-sensor based TPMS works
unfortunately, this is how I found out. The car told me the Front-Right tire was low in pressure, and I immediately got out and found that one was at 27psi while the others were at 36psi. So indeed the faster spinning smaller (flat) wheel caused this to be detected. This is better in a sense than the pressure-sensor based systems that don't know which corner of they car they are on so just tell you that one is low. What I'm not certain of is whether this system just detects *relative differences* in rotational speed due to inflation differences, or if it sets it based on *absolute values*. That is, if 4 tires all deflate evenly, will it report all 4, or not report any? If it's looking for relative differences (vs other tires), it won't report any, but if it's looking for differences from what it was set at once upon a time, then it would. Also, if you wanted to have front tires filled more/less than rear tires, could you? In thinking this through, I'm thinking that it does actually set it based on the rotations of the tire when you tell it to be set, and only reports a problem when that tire gets below some threshold relative to what that tire was set at - and completely ignores any relevance to the other tires. Anyone know for sure?
As an aside, our last 4 cars have had 4 different systems:
Q5 - ABS rotation based
A3 - pressure sensors with setable button to store values
Tiguan - pressure sensors with non-changeable default setting for all 4 tires
996tt - I put a gauge on the tire
As an aside, our last 4 cars have had 4 different systems:
Q5 - ABS rotation based
A3 - pressure sensors with setable button to store values
Tiguan - pressure sensors with non-changeable default setting for all 4 tires
996tt - I put a gauge on the tire
10-07-2013, 12:24 PM
#2
AudiWorld Super User
Mark, some additional info on the system here:
Audi is taking a new approach, one that uses sensor data fusion to determine tire pressure loss. And one of the sensors being used is the tire itself.
FMVSS 138 is a regulation created by the National Highway Traffic Safety Administration (NHTSA). The objective of this regulation is to alert drivers if the pressure in a tire is down by 25%. All vehicles built since September 2007 are required to have a tire pressure monitoring system (TPMS). As Dr. Thomas Roscher, development engineer, Tire Pressure Monitoring Systems, Product Quality Assurance, Audi of America, points out, in Europe, where there isn't an FMVSS 138 on the books, drivers tend to check their tire pressure every two or three months. In the U.S ... well, let's just say that the frequency is not that high.
Early on, when the regulation was being developed, it was thought that there would be two ways to accomplish the necessary TPMS functionality: direct and indirect. The standard is really technology neutral. The issue is accomplishing the task, not stipulating how it is to be accomplished.
According to Urban Forssell, president and CEO of NIRA Dynamics AB (Linkoeping, Sweden; www.niradynamics.se), the first generation of indirect systems, of which there were a handful in production, "had in common a comparison of wheel speed pairwise. You make an assumption that only one tire at a time loses air, and you make the comparison." He points out, "If all four tires lost air at the same time, you'd never know it."
Consequently, indirect TPMS generation one didn't cut it since FMVSS 138 also requires pressure loss detection on all four tires. So all vehicle manufacturers have opted for what is a more straightforward approach, which is the direct TPMS. What this means is that there are pressure sensors mounted inside each tire; there is transmission of that information to a processor that then activates the alert if necessary. While this approach certainly meets the requirements, Roscher acknowledges that drivers pretty much don't care whether their TPMS system is indirect or direct--until there are some changes. For example, the driver may decide that he wants to swap summer tires for winter tires. Or the driver wants to buy some new tricked-out wheels. Or the batteries in the sensors run out. All of this results in additional charges to the customer. Not only would there be the cost for new sensors for the new tires or wheels, but also the additional cost related to the service at the tire dealer, as the regulation stipulates that the tire dealer and the customer are certain that the TPMS system works as required after any changes (e.g., this may necessitate a calibration phase during which time the vehicle would need to be driven, and undoubtedly hourly rates would apply).
Audi is opting for the indirect route. That's right: indirect TPMS. Although the generation 1 approach didn't work, NIRA Dynamics, which didn't participate in that technology, has developed a software-based system that, explains Forssell, has sufficiently robust algorithms such that it can handle the NHTSA requirement of detecting 25% of tire pressure loss within 20 minutes while driving at a speed of 31 to 62 mph; the detection time is generally much faster than NHTSA's 20-minute requirement. There are no wheel-mounted battery-powered sensors. No radio frequency transmitters or receivers. Rather, the NIRA Dynamics system, designated TPI (for "Tire Pressure Indicator"), makes use of the wheel speed sensors that are part of the antilock braking system (ABS) and electronic stability control system (ESC). A processor is needed as well.
"Wheel speed sensors have been around since the introduction of ABS, and have proven to be mature, stable and reliable," Forssell says. They are used as input to the NIRA Dynamics software. At first, the processor that will make the calculations is a stand-alone system. For example for the '09 Audi A6, there will be what Roscher describes as a "little gray box." That's the processor. "Eventually," he says, "it will be integrated into the ESC processor." It is simply a matter, going forward, of making accommodations for the indirect TPMS system in the controller.
Essentially, the NIRA Dynamics TPI system "learns" the radii and frequency characteristics of properly inflated tires. Then, it is able to detect whether there are deviations from normal, which would be a result of the loss of tire pressure (e.g., when a tire loses pressure, there is a change in the radius as the tire rotates, which has a consequent effect on the measured parameters). The system can detect a change in any or all of the tires (remember that the previous indirect systems measured pairs of tires unlike this one, which has inputs from each of the tires).
Because there aren't additional sensors, there is less cost and complexity with this system, Roscher explains. He goes on to point out that there is a customer benefit because as this is a software-based system, when wheels or tires are changed, all the driver and/or tire dealer needs to do is recalibrate the system (this essentially consists of selecting a reset function, then driving the car with properly inflated tires-period). Forssell adds, "You can change and even supersize your tires and the system will learn about them."
According to Forssell, Audi is the first vehicle manufacturer that is standardizing on this indirect TPMS system. It is anticipated that the full lineup of Audi vehicles will be equipped with the system by the 2011 model year.
Mfr link: http://www.niradynamics.se/scripts/resource.php?id=11
Audi rolls with indirect TPMS: meeting the NHTSA regulation for tire pressure monitoring typically means putting pressure sensors inside tires.
Audi is taking a new approach, one that uses sensor data fusion to determine tire pressure loss. And one of the sensors being used is the tire itself.
FMVSS 138 is a regulation created by the National Highway Traffic Safety Administration (NHTSA). The objective of this regulation is to alert drivers if the pressure in a tire is down by 25%. All vehicles built since September 2007 are required to have a tire pressure monitoring system (TPMS). As Dr. Thomas Roscher, development engineer, Tire Pressure Monitoring Systems, Product Quality Assurance, Audi of America, points out, in Europe, where there isn't an FMVSS 138 on the books, drivers tend to check their tire pressure every two or three months. In the U.S ... well, let's just say that the frequency is not that high.
Early on, when the regulation was being developed, it was thought that there would be two ways to accomplish the necessary TPMS functionality: direct and indirect. The standard is really technology neutral. The issue is accomplishing the task, not stipulating how it is to be accomplished.
According to Urban Forssell, president and CEO of NIRA Dynamics AB (Linkoeping, Sweden; www.niradynamics.se), the first generation of indirect systems, of which there were a handful in production, "had in common a comparison of wheel speed pairwise. You make an assumption that only one tire at a time loses air, and you make the comparison." He points out, "If all four tires lost air at the same time, you'd never know it."
Consequently, indirect TPMS generation one didn't cut it since FMVSS 138 also requires pressure loss detection on all four tires. So all vehicle manufacturers have opted for what is a more straightforward approach, which is the direct TPMS. What this means is that there are pressure sensors mounted inside each tire; there is transmission of that information to a processor that then activates the alert if necessary. While this approach certainly meets the requirements, Roscher acknowledges that drivers pretty much don't care whether their TPMS system is indirect or direct--until there are some changes. For example, the driver may decide that he wants to swap summer tires for winter tires. Or the driver wants to buy some new tricked-out wheels. Or the batteries in the sensors run out. All of this results in additional charges to the customer. Not only would there be the cost for new sensors for the new tires or wheels, but also the additional cost related to the service at the tire dealer, as the regulation stipulates that the tire dealer and the customer are certain that the TPMS system works as required after any changes (e.g., this may necessitate a calibration phase during which time the vehicle would need to be driven, and undoubtedly hourly rates would apply).
Audi is opting for the indirect route. That's right: indirect TPMS. Although the generation 1 approach didn't work, NIRA Dynamics, which didn't participate in that technology, has developed a software-based system that, explains Forssell, has sufficiently robust algorithms such that it can handle the NHTSA requirement of detecting 25% of tire pressure loss within 20 minutes while driving at a speed of 31 to 62 mph; the detection time is generally much faster than NHTSA's 20-minute requirement. There are no wheel-mounted battery-powered sensors. No radio frequency transmitters or receivers. Rather, the NIRA Dynamics system, designated TPI (for "Tire Pressure Indicator"), makes use of the wheel speed sensors that are part of the antilock braking system (ABS) and electronic stability control system (ESC). A processor is needed as well.
"Wheel speed sensors have been around since the introduction of ABS, and have proven to be mature, stable and reliable," Forssell says. They are used as input to the NIRA Dynamics software. At first, the processor that will make the calculations is a stand-alone system. For example for the '09 Audi A6, there will be what Roscher describes as a "little gray box." That's the processor. "Eventually," he says, "it will be integrated into the ESC processor." It is simply a matter, going forward, of making accommodations for the indirect TPMS system in the controller.
Essentially, the NIRA Dynamics TPI system "learns" the radii and frequency characteristics of properly inflated tires. Then, it is able to detect whether there are deviations from normal, which would be a result of the loss of tire pressure (e.g., when a tire loses pressure, there is a change in the radius as the tire rotates, which has a consequent effect on the measured parameters). The system can detect a change in any or all of the tires (remember that the previous indirect systems measured pairs of tires unlike this one, which has inputs from each of the tires).
Because there aren't additional sensors, there is less cost and complexity with this system, Roscher explains. He goes on to point out that there is a customer benefit because as this is a software-based system, when wheels or tires are changed, all the driver and/or tire dealer needs to do is recalibrate the system (this essentially consists of selecting a reset function, then driving the car with properly inflated tires-period). Forssell adds, "You can change and even supersize your tires and the system will learn about them."
According to Forssell, Audi is the first vehicle manufacturer that is standardizing on this indirect TPMS system. It is anticipated that the full lineup of Audi vehicles will be equipped with the system by the 2011 model year.
Mfr link: http://www.niradynamics.se/scripts/resource.php?id=11
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uberwgn (12-12-2020)
10-07-2013, 12:37 PM
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Well simple is almost always better. My only complaint with Audi's indirect method is that you need to drive for a period of time before a low tire is recognized. I also got a screw in the tire and I had already gone from home onto the freeway before it noticed. Better than nothing though.
I don't know that it 'does', but it 'could' detect all four tires going low because you enable the TPMS for your current pressures which would suggest it's not using predfined values.
I don't know that it 'does', but it 'could' detect all four tires going low because you enable the TPMS for your current pressures which would suggest it's not using predfined values.
10-07-2013, 12:53 PM
#5
AudiWorld Super User
Depending on the market, Audi uses both systems
http://www.audi.com/com/brand/en/too...m.browser.html
Detailed process is explained here:
http://www.audienthusiasts.com/VagComABS.html
Tyre pressure monitoring system
Tyre pressure monitoring systems provide early detection of pressure loss on one or more wheels and warn the driver accordingly.
Tyre pressure monitoring display
The tyre pressure monitoring display measures the tyre pressures indirectly. It uses the signals from the ABS/ESP wheel speed sensors to detect differences in rotational speed between the individual wheels, which provide an indication of pressure loss. The same signals are used to analyse characteristic vibrations of the separate wheels, which may also point to a potential loss of pressure. A warning display alerts the driver so that the tyre pressures can be checked as soon as a pressure loss occurs.
Tyre pressure monitoring system
Tyre pressure monitoring systems, which measure directly, use sensors installed in the wheels. These measure the pressure and temperature inside the tyre and transmit this information to a receiver in the vehicle. The measured tyre pressures are continuously compared with specification values, which are entered by the driver, for example after changing the tyres. The driver can not only check the tyre pressures and temperatures at any time, but also receives a warning if differences arise between the set pressure and the measured pressure. Sensors on all four wheels are necessary for the system to function correctly. If the vehicle is supplied with winter wheels, these will already have the required sensors; otherwise they must be ordered separately from your Audi dealer.
Tyre pressure monitoring systems provide early detection of pressure loss on one or more wheels and warn the driver accordingly.
Tyre pressure monitoring display
The tyre pressure monitoring display measures the tyre pressures indirectly. It uses the signals from the ABS/ESP wheel speed sensors to detect differences in rotational speed between the individual wheels, which provide an indication of pressure loss. The same signals are used to analyse characteristic vibrations of the separate wheels, which may also point to a potential loss of pressure. A warning display alerts the driver so that the tyre pressures can be checked as soon as a pressure loss occurs.
Tyre pressure monitoring system
Tyre pressure monitoring systems, which measure directly, use sensors installed in the wheels. These measure the pressure and temperature inside the tyre and transmit this information to a receiver in the vehicle. The measured tyre pressures are continuously compared with specification values, which are entered by the driver, for example after changing the tyres. The driver can not only check the tyre pressures and temperatures at any time, but also receives a warning if differences arise between the set pressure and the measured pressure. Sensors on all four wheels are necessary for the system to function correctly. If the vehicle is supplied with winter wheels, these will already have the required sensors; otherwise they must be ordered separately from your Audi dealer.
Detailed process is explained here:
http://www.audienthusiasts.com/VagComABS.html
Last edited by spijun; 10-07-2013 at 01:01 PM.
10-07-2013, 02:06 PM
#7
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It does take a bunch of cost out for both Audi, and in due course the owner
I have the direct sensor based system in the D3 A8. Very nicely enabled (the "high" system) with MMI display for all five wheels with real time pressures and temperatures--most implementations don't have that. Also changes color of the readings at any wheel that is outside the spec range, and you can tweak the spec range even via VAG COM. It was also pulled out on the A8's on the current model generation, at least here in US.
The sensor batteries wear out in six years, and a second set is needed for any snow tires. Mine got replaced just inside of CPO, so I get another 6 years on Audi.
Beru, the OE supplier, recently sold this sensor business off to someone as I recall--I think they could see the writing on the wall.
The sensor batteries wear out in six years, and a second set is needed for any snow tires. Mine got replaced just inside of CPO, so I get another 6 years on Audi.
Beru, the OE supplier, recently sold this sensor business off to someone as I recall--I think they could see the writing on the wall.
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10-07-2013, 03:02 PM
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Glad it worked out for you Mark, but the wheel sensors can tell you which is low, it's just the specific implementation on any prior vehicle might not relay that information. My Odyssey will tell me which is low, as well as (if I go to the screen) what the pressures are at each corner. Still, it'll be nice to not have to worry about the sensors going bad or anything since I can check exact pressures myself and all I really need is the notice that something's wrong. 
Last edited by idale; 10-07-2013 at 03:05 PM.
10-07-2013, 04:58 PM
#9
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Glad it worked out for you Mark, but the wheel sensors can tell you which is low, it's just the specific implementation on any prior vehicle might not relay that information. My Odyssey will tell me which is low, as well as (if I go to the screen) what the pressures are at each corner. Still, it'll be nice to not have to worry about the sensors going bad or anything since I can check exact pressures myself and all I really need is the notice that something's wrong.
http://ctny.audiworld.com/mark/s4/smartire/
10-08-2013, 10:59 AM
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I suppose if the system has multiple receivers located near each tire, it can figure it out from the strongest signal. But if the system just has a single located receiver, I'm not sure how it knows when you rotate tires unless you tell it where you moved them to (which is how the SmartTire aftermarket system I had in my S4 worked)
http://ctny.audiworld.com/mark/s4/smartire/
http://ctny.audiworld.com/mark/s4/smartire/