Direct Torque Measurement versus Speed derived torque
Direct Torque Measurement versus Speed derived torque
(OP)
I have a question which I hope people can give some answers to.
Today the torque of an engine or transmission is construed from speed sensors fitted to either the crankshaft, input and/or output shafts.
I've learned that many companies now want to measure torque directly using either the strain or the shear stress in a rotating shaft.
Why is a direct torque measurement better than a speed sensor derived torque measurement when speed is a component of torque?
Is it today with transmission losses that make speed sensing less accurate than direct torque measurement.
You can see an example of what I mean in the link below.
Today the torque of an engine or transmission is construed from speed sensors fitted to either the crankshaft, input and/or output shafts.
I've learned that many companies now want to measure torque directly using either the strain or the shear stress in a rotating shaft.
Why is a direct torque measurement better than a speed sensor derived torque measurement when speed is a component of torque?
Is it today with transmission losses that make speed sensing less accurate than direct torque measurement.
You can see an example of what I mean in the link below.
RE: Direct Torque Measurement versus Speed derived torque
Regards
Pat
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RE: Direct Torque Measurement versus Speed derived torque
I don't work for an automotive company, but I have dealt with sensors like this throughout my career and I have never heard of deriving torque/power from speed measurements alone.
ISZ
RE: Direct Torque Measurement versus Speed derived torque
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Direct Torque Measurement versus Speed derived torque
If it is not the case that the speed sensors are used to derive engine or transmission torque then can you identify how this is accomplished today.
Then having identified the above can you indicate why companies are now seeking to measure torque directly on a rotating shaft.
What I'm trying to identify here is the reason to move from the current system to direct torque measurement - is it measurement error, lack of accuracy due to the interference of other torque effects. etc..
I understand how the MDI technology works (see also ABB Torductor, Magcanica,NCTE Gmbh, Transence Technology, etc..) but I am trying to figure out (which they don't identify) why this would necessairly be better?
RE: Direct Torque Measurement versus Speed derived torque
A common way to measure torque is to measure the force required to react the torque at the mounting structure for the engine or dynomometer.
A reason to want to measure shaft torque directly is that you cannot always capture all the force reactions in a real-world (outside of the lab) setting, and sometimes you'd like to know what torque really is. Take a gas compression skid as an example - there are many ways for the torque of the engine to be reacted at the engine and compressor mounts, and if there is a rigid structure connecting the engine to the compressor (as you have with a transmission) then there is very little (or no) external reaction required. Without a direct shaft torque measurement, you can't precisely know engine output power, which is something you might like to know for controlling your equipment.
RE: Direct Torque Measurement versus Speed derived torque
The degrees change of alignment or the time delay from one to the other as a fraction of the time for one complete revolution should provide enough data provided you know the torsional rigidity of the shaft.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Direct Torque Measurement versus Speed derived torque
RE: Direct Torque Measurement versus Speed derived torque
What makes you think OEMs are measuring torque directly on prodction cars? My guess would be to improve the responsiveness of systems like torque vectoring.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Direct Torque Measurement versus Speed derived torque
ISZ