I want to map a particular route duty cycle for a vehicle. During that time, how to calculate the engine RPM when the vehicle runs in that particular route. I already know the vehicle specification like its Engine max power, Engine max torque, Tyre rolling radius, individual gear ratios, Rear axle ratio. My question is:- Driver may use any gear at anytime depending upon the route condition. When I am running a vehicle in a particular route, how to calculate Engine RPM??
Dear Arul, If I figured out well enough, you need to calculate i.e measure each time of the route, your power and torque. P = ωT therefore knowing P and T each time you can calculate your rpm (ω), which should be variable. Of course different arrangements have to be done for different kind of vehicles (otto, diesel, hybrid, electric etc) mainly because a gear box has different rpm than the engine (electric cars does not have a gear box).
Ok. But is there any possibility for getting the Engine RPM without measuring Power(P) & Torque(T)??
I am using a mechanical Gear box, mechanical engine.
I have only vehicle speed, Engine max power, Engine max torque, Tyre rolling radius, individual gear ratios, Rear axle ratio as input
If you have vehicle speed, things are much easier! v = ωR where R is the radiant of the wheal. Therefore the ω of the wheal is known. Now you have to find the ω of the gear box. Usually (but not always) there is a 1:1 ratio when puting the highest transmission relation i.e 5th speed. In any case if the individual gear ratios are known, your requested ω (engine rpm) can be calculated from the gear ratio. Each time the transmission ratio is changed (each time the driver changes the lever), the rpm also changes.
Is there any formula to calculate Engine RPM continuously throughout a Route based on my known inputs : vehicle speed, wheel RPM, RAR. I know the individual gear ratios. But I don't know when each gear is used...
I am not sure if I undestand well. Each car and each transmission gear manufacturer gives a relation for gear boxes. For example a nissan micra has the following data for the gear ratios (for manual transmission):
1st 3,333:1
2d 1,782:1
3d 1,207:1
4th 0,902:1
5th 0,756:1
reverse 3,417:1
Other cars have different ratios.
Of course there is no formula for the drivers behaviour, about "when he is changing the lever". On the other hand v = dx/dt, dx = vdt and x = int(vdt) = int (ωRdt). For each different ω (rpm) there is a different distance x, so for the total route a formula should be: total X = Σχ = χ1+χ2+...χn = int(ω1R1dt) +int (ω2R2dt) +...+int (ωnRndt). All the above ω and R have a relation to each other, so it should be obtained a formula Σχ = ωR [a1*int1(dt) +a2*int2(dt) +...] where a1, a2, ...the ratios. Knowing Σχ, ratios, R, and the Δt time using a specific gear ratio, you can find the rpm ω. I hope it was useful...
Yes the suggestion was useful. Let me try it with my raw data's. ..
Thanks
Arul, it sounds like your engine does not have a CAN bus? Because you should be able to measure engine speed using a scan tool.
Otherwise, you have to back out the engine speed from the vehicle speed and the various ratios from tire to engine flywheel. You will need to know the rolling radius of the tires to get the rotational speed of the wheels, and you will need to know the gear. I assume you do not have a torque converter on the transmission input?
If the engine is running at a fixed power its RPM will remain constant. Its road speed is affected by road conditions and the behavior of the driver. When gear ratios are changed the clutch separates the engine from the gear box but the engine remains running at the same speed at the same power. Only the output speed from the gear box is changed. If there is a speed indicator on your engine think of connecting it to a digital read-out and use a data logger to record engine RPM at any time.
I don't think you will be able to measure engine speed with those input data. You will need either to measure the rotation through ECU or by accelerometer measurement (and FFT algorithm).
As majority of combination of vehicle speed and power can be achieved using multiple gears, this cannot be readily done. From vehicle speed and power you can estimate what gear a professional driver would probably use, and get an estimate of rpm that way, but even that is not a definite answer.
To echo what Michal wrote, you need to assume a shift schedule so that you know what gear the vehicle is using.
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