Announcing a complete solution to mapping engine efficiency

[RobertSmalls]

How many channels is your datalogger, and are there any vacant channels? I'd like to be able to record the current in and out of my hybrid battery, and maybe some other things like engine RPM (from which to infer what gear I'm in) and air intake temperature.

Does your model distinguish between braking, deceleration fuel cutoff, rough roads, and ordinary rolling resistance?

[kubark42]

Originally Posted by RobertSmalls

How many channels is your datalogger, and are there any vacant channels? I'd like to be able to record the current in and out of my hybrid battery, and maybe some other things like engine RPM (from which to infer what gear I'm in) and air intake temperature.

Does your model distinguish between braking, deceleration fuel cutoff, rough roads, and ordinary rolling resistance?

1) I have to check to be absolutely sure, but I believe I left at least 4 analog inputs free. I made as many through-hole pads as possible on the remaining unused pins, and the ADC is not at all used, so you can definitely add what you'd like.

2) There's (almost) no need to for a second rpm sensor. You can measure rpm from the fuel injection signal, although the "almost" case is that when you're in engine braking mode you no longer have a direct measurement of engine speed.

However, by knowing the gear ratios, you can always observe the engine speed based on car speed, except in cases where you've shifted while engine braking. Even then, just as soon as you reapply the throttle, the observer will catch up and switch to the appropriate gear.

3) My model just estimates thrust force, without any attempt to know where the force is coming from. My assumption is that any positive thrust force on a moving car is from the engine pushing. (Note that this is not the case for a car at rest on a slope. You can have a positive thrust force due to the brakes.) I only calculate efficiency at these times.

Unfortunately, we cannot directly measure the difference between rough roads and smooth ones. This is within the capability of the observer, but in order to have that level of precision you would have to have much more accurate sensors. Specifically, you'd need a danged good elevation profile for your road. Also, a throttle position sensor would help.

The problem comes from the fact that the observer tries to filter noise based on the model it expects. If you need a strong filter, which is the case when your measurements are noisy, then you have trouble reacting to these kind of perturbations. If, however, your model is quite good and your sensors are quite precise, you can extend the model along those lines. So it would be mathematically trivial to extend the model to 18 dimensions and include an estimation of C_rr (rolling resistance coefficient) that can adapt very rapidly, but as a consequence it would be harder to tune it so that you had reliable readings.

I'm not sure if I'm explaining this well, but it's sort of a give and take. A few years ago, my 17-dimension model couldn't have worked due to inaccuracy in sensors (specifically the accelerometer and timers). Now that we have better sensors, we can go further into detail in the model.

It would be interesting to see (and is indeed something I hope to do with a new model we're developing for an ASME conference) how well these parameters can be estimated. In theory, you have no need for a roll-down test, as this is already included in the model, but in reality the observer might not be stable enough to both rapidly converge to the real drag values (which is what you're asking for when you want to be able to detect changes in road quality), and yet still converge to useful force estimations.

[jfitzpat]

Originally Posted by RobertSmalls

Mr. Fitzpatrick,

I take it from your posts here and in the "reliable PCB" thread that your specific field of expertise is Antagonism Engineering. Consider also the fact that you are a self-described grumpy old man. Your posts have been longer than necessary, drifting off-topic, and full of sublte personal insults and irrelevant questioning of the qualifications of our guest experts.

Please change. You appear to have considerable technical knowledge and experience. Can you apply it primarily to improving EcoModder projects, instead of simply pointing out their shortcomings?

It is a valid point, but largely driven by experience and working environment. In my world, technology is separate from personal. If the post cat emissions read lean, and the instrumentation is working, then that is reality, and we work back from there.

Clearly, the culture here is somewhat reversed. When personal testimonial is that lead free solder is problematic, and that lead free solder has not presented a major health risk for 100 years, then pointing out that a) lead free solder has been the non-problematic norm for the 40M people in California for years and b) lead poisoning used to be named for professions that worked extensively with leaded solder is being "antogonistic".

Similarly, I cannot help that gasoline is too suceptible to temperature to represent .1% accuracy from injector pulse width. I do not control the physics involved, nor did I author the dozens of SAE papers on the subject.

I do have a very low threshold for tolerance of arm waving and BS. So my responses will tend to get less patient when someone cites, incorrectly, mil spec issues regarding solder or starts talking about non existant weather phenomena ("radiated..."). Again, to me it all starts with objective reality. If the military and JPL do tests on reliability, then those results have to be factored into a hypothesis. Similarly, if the FAA doesn't recognize a phenomena, nor can we find it in the NTSB database, then there is no reason to presume it exists.

Obviously, crushing spirits is not productive. But it is hard for me to envision how ignoring conflict with objective reality is helpful either. So better to revert to lurking mode and let the culture here proceed as it is.

Regards,
-jjf

[jfitzpat]

Originally Posted by kubark42

1) I have to check to be absolutely sure, but I believe I left at least 4 analog inputs free.

If you are using the 10 bit ADC in the Atmel, then you need to keep in mind that the inputs are part of a mux. That is, the inputs are being sequentially sampled by the same internal ADC. So, more channels can mean lower sample rates for other sensors.

Originally Posted by kubark42

Unfortunately, we cannot directly measure the difference between rough roads and smooth ones. This is within the capability of the observer, but in order to have that level of precision you would have to have much more accurate sensors. Specifically, you'd need a danged good elevation profile for your road. Also, a throttle position sensor would help.

If you trace back from your references, you should find a paper on this specific problem - basically seperating operational vibration out of a 3 axis accel measurment.

However, it is a difficult path. You might do better to look at the more recent work out of UC Riverside. One of the research projects there on emissions uses a very clever way of directly measuring torque in real time. With torque, their hurdle to efficiency precision was energy content of the fuel, which varies quite a bit depending on blend (how much alcohol, etc.) That's were we came in.

Even if you don't go that far, it should represent a significant improvment in precision.

-jjf

[kubark42]

Originally Posted by RobertSmalls

The correct approach is to engage the clutch until you have just enough kinetic energy to crest the first hill, then disengage the clutch and coast the rest of the way. Also, disengage the clutch if engine speed exceeds the peak of the efficiency curve, and re-engage if that is necessary to climb the first hill. The result will be that once the vehicle gets up to the speed corresponding to peak efficiency, it will hold that speed by running the engine at whatever duty cycle is required (this is familiar to ecomodders as pulse and glide).

Vehicle speed at the crest of each hill will approach zero, and the driver will die of old age before he finishes the course.

Originally Posted by tasdrouille

All you have to do is to generate the energy needed to get to the top of the first hill in the most efficient way possible.

Engage the clutch, start the engine, set engine speed (and load obviously) at max efficiency while climbing till you have just enough kinetic energy to make it over the top of the hill at which point you disengage the clutch while you're still climbing, shutting the engine off automatically, you'll just barely make it over the top and you then coast this way going up and down hill for a while with the engine off and just brake (or barely engage the clutch, the resistance of the engine should stop the car) when you want to stop at the very top of the third hill.

Well, it's Wednesday morning and no one has found the answer yet. I'll get the ball (car?) rolling a little further by letting you know that there is some truth to what you two are proposing, but you're missing the most important part of the solution.

[kubark42]

Originally Posted by jfitzpat

It is a valid point, but largely driven by experience and working environment. In my world, technology is separate from personal. If the post cat emissions read lean, and the instrumentation is working, then that is reality, and we work back from there.

Clearly, the culture here is somewhat reversed. When personal testimonial is that lead free solder is problematic, and that lead free solder has not presented a major health risk for 100 years, then pointing out that a) lead free solder has been the non-problematic norm for the 40M people in California for years and b) lead poisoning used to be named for professions that worked extensively with leaded solder is being "antogonistic".

Similarly, I cannot help that gasoline is too suceptible to temperature to represent .1% accuracy from injector pulse width. I do not control the physics involved, nor did I author the dozens of SAE papers on the subject.

I do have a very low threshold for tolerance of arm waving and BS. So my responses will tend to get less patient when someone cites, incorrectly, mil spec issues regarding solder or starts talking about non existant weather phenomena ("radiated..."). Again, to me it all starts with objective reality. If the military and JPL do tests on reliability, then those results have to be factored into a hypothesis. Similarly, if the FAA doesn't recognize a phenomena, nor can we find it in the NTSB database, then there is no reason to presume it exists.

Obviously, crushing spirits is not productive. But it is hard for me to envision how ignoring conflict with objective reality is helpful either. So better to revert to lurking mode and let the culture here proceed as it is.

Regards,
-jjf

I'm not going to deconstruct your position here, there are better things to be done with time. As you say, crushing spirits is counterproductive, so I see no reason to continue. Being a scientifically pedantic person myself, who is inclined to have little tolerance for inaccuracies in others' statements, I can relate to where you're coming from. I'll hopefully close this parenthesis by encouraging you to read, instead of scan, the posts. You might find that you've been jousting with windmills.

Originally Posted by jfitzpat

If you trace back from your references, you should find a paper on this specific problem - basically separating operational vibration out of a 3 axis accel measurment.

Interesting idea. I can definitely see how that could work, but I'd appreciate a direct citation. I have nothing in my references that would link to this sort of approach.

However, it is a difficult path. You might do better to look at the more recent work out of UC Riverside. One of the research projects there on emissions uses a very clever way of directly measuring torque in real time.
-jjf

I can't not finding it. I did find MERL, but there are several key differences between MERL and my project:

1) They're looking at semi-trucks
2) They did all their testing on flat, straight roads at sea-level.
3) They have giant trailer full of measuring equipment. Clearly not the kind of equipment we already have built into vehicles, or can add for $50 worth of parts.

[dcb]

Originally Posted by kubark42

... but you're missing the most important part of the solution.

Lol, you want to account for topology I'm sure.

To me that is the drivers job though, and juggling all the other variables. so accurate feedback is the most important. What did I win?

[kubark42]

Originally Posted by dcb

Lol, you want to account for topology I'm sure.

To me that is the drivers job though, and juggling all the other variables. so accurate feedback is the most important. What did I win?

Heh. Nice try! Topology is already given: a road that conveniently looks just like a sine wave.

Anyway, I'm certain the hypothetical driver has other things on his mind, like how come suddenly there are no friction losses, what happened to his other 4 speeds, and just what crazy engineer built a road like a sine wave?

[RobertSmalls]

Hmm, produce power until you have enough energy to coast across the finish line, leave the engine off whenever it's not required, cycle the engine off and on to keep the vehicle speed such that the engine speed is at the peak of the efficiency curve. What am I missing?


Aha, here's a clever option. First allow the car to roll backwards in neutral, up the previous hill as far as it will go, then allow it to roll forwards until vehicle speed rises, begins to fall, then reaches the optimum speed for engine efficiency (unless it would never reach that speed, in which case just use the highest forward speed achieved during coasting). Then begin to cycle the engine as above until you have just enough kinetic energy to crest the hill.

[kubark42]

Originally Posted by RobertSmalls

Hmm, produce power until you have enough energy to coast across the finish line, leave the engine off whenever it's not required, cycle the engine off and on to keep the vehicle speed such that the engine speed is at the peak of the efficiency curve. What am I missing?


Aha, here's a clever option. First allow the car to roll backwards in neutral, up the previous hill as far as it will go, then allow it to roll forwards until vehicle speed rises, begins to fall, then reaches the optimum speed for engine efficiency (unless it would never reach that speed, in which case just use the highest forward speed achieved during coasting). Then begin to cycle the engine as above until you have just enough kinetic energy to crest the hill.

So. close. it. hurts. But not quite there yet.