METHOD FOR DETERMINATION OF MEAN ENGINE TORQUE

• US 20090132182A1
• Filed: 11/17/2004
• Published: 05/21/2009
• Est. Priority Date: 11/17/2004
• Status: Active Grant

• Current Assignee: Volvo Lastvagnar AB (AB Volvo)
• Original Assignee: Volvo Lastvagnar AB (AB Volvo)
• Inventors: Ahlinder, Sven, Wattwil, Fredrik, Fredriksson, Krister
• Granted Patent: US 7,742,882 B2
• Time in Patent Office: Days
• US Class Current: 702/41
• CPC Class Codes: F02D 2041/288 for performing a transformation into the frequency domain, e.g. Fourier transformation
• CPC Class Codes: F02D 2200/1004 Estimation of the output torque
• CPC Class Codes: F02D 41/0097 using means for generating speed signals
• CPC Class Codes: F02D 41/1497 With detection of the mechanical response of the engine
• CPC Class Codes: G01L 3/24 Devices for determining the value of power, e.g. by measuring and simultaneously multiplying the values of torque and revolutions per unit of time, by multiplying the values of tractive or propulsive force and velocity

Abstract

The invention relates to a method for producing a value T being representative of the mean engine torque generated on a crank-shaft of an internal combustion engine, comprising the steps of producing a speed vector including values being representative of instantaneous speeds of the engine during a sampling period, determining a mean engine speed n during said sampling period from the speed vector, determining a value P_x, being representative of the frequency contribution of the speed vector at the frequency x*n, where x is a pre-selected order, and producing a value T being representative of the mean engine torque on the crankshaft during said sampling period, wherein T is derived from a mathematical expression including a polynomial having at least a term k*n*P_x, where k is a polynomial constant. The invention also relates to a device for producing a value T.

Claims

1. A method for producing a value T being representative of mean engine torque generated on a crankshaft of an internal combustion engine, comprising the steps of

producing a speed vector including values being representative of instantaneous speeds of the engine during a sampling period,

determining a mean engine speed n during the sampling period from the speed vector

determining a value Px being representative of the frequency contribution of the speed vector at the frequency x*n, where x is a pre-selected order, and

producing a value T being representative of the mean engine torque on the crankshaft during the sampling period wherein T is derived from a mathematical expression including a polynomial having at least a term k*n*Px, wherein k is a polynomial constant.

2. A method according to claim 1, wherein T is derived from a mathematical expression including the polynomial:

k0+k1*Px+k2*n+k3*n*Px, where k0, k1, k2 and k3 are polynomial constants.

3. A method according to claim 1, wherein T=k0+k1*Px+k2*n+k3*n*Px, where k0, k1, k2 and k3 are polynomial constants.

4. A method according to claim 1, wherein the selected order x=(the number of cylinders of the engine)/2.

5. A method according to claim 1, wherein the engine is a two-stroke engine, and the selected order x is equal to the number of cylinders.

6. A method according to claim 1, wherein the sampling period corresponds to at least 10 rotations of the engine.

7. A method according to claim 1, wherein the speed vector comprises values t being representative of instantaneous speeds of the combustion engine being the passages of time between subsequent rotational indexing references arranged in connection with a flywheel or crankshaft of the combustion engine.

8. A method according to claim 7, wherein the method comprises a compensation step when generating the speed vector, wherein effects of irregularities in an arrangement of the rotational indexing references are compensated for.

9. A method according to claim 1, wherein the value Px is determined using phase-amplitude transformation of the speed vector.

10. A method according to claim 1, wherein the value Px is determined using a Fourier series analysis of the speed vector.

11. A method according to claim 9, wherein the value Px is determined solving an equation system:

[A]×

[C]=[V], wherein V is a speed vector containing f samples, and A is a matrix for k orders

$A=\left[\begin{array}{cccccc}1& \sin <br><br>\left(\mathrm{\pi <br><br>}\right)& \cos <br><br>\left(\mathrm{\pi <br><br>}\right)& \sin <br><br>\left(2<br><br>\mathrm{\pi <br><br>}\right)& \mathrm{\dots <br><br>}& \cos <br><br>\left(k<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}\right)\\ 1& \sin <br><br>\left(\mathrm{\pi <br><br>}/2\right)& \cos <br><br>\left(\mathrm{\pi <br><br>}<br><br>\text{/}<br><br>2\right)& \sin <br><br>\left(2<br><br><br><br>\mathrm{\pi <br><br>}<br><br>\text{/}<br><br>2\right)& \mathrm{\dots <br><br>}& \mathrm{\dots <br><br>}\\ \mathrm{\dots <br><br>}& \mathrm{\dots <br><br>}& \mathrm{\dots <br><br>}& \mathrm{\dots <br><br>}& \mathrm{\dots <br><br>}& \mathrm{\dots <br><br>}\\ 1& \sin <br><br>\left(\mathrm{\pi <br><br>}/f\right)& \cos <br><br>\left(\mathrm{\pi <br><br>}<br><br>\text{/}<br><br>f\right)& \sin <br><br>\left(2<br><br><br><br>\mathrm{\pi <br><br>}<br><br>\text{/}<br><br>f\right)& \mathrm{\dots <br><br>}& \cos <br><br>\left(k<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}<br><br>\text{/}<br><br>f\right)\end{array}\right]$ $C=\left[\begin{array}{c}{a}_0/2\\ a_1\\ b_1\\ a_2\\ b_2\\ \mathrm{\dots <br><br>}\\ \mathrm{\dots <br><br>}\\ a_k\\ b_k\end{array}\right]$ $V=\left[\begin{array}{c}{t}_1\\ t_2\\ \\ \\ \\ \mathrm{\dots <br><br>}\\ \mathrm{\dots <br><br>}\\ \\ t_f\end{array}\right]$

for coefficients ax and bx of the pre-selected order x, and obtaining the amplitude

P_x=√

{square root over (a_x²+b_x²)}.

12. A method according to claim 11, wherein the value Px is determined by using a Fast Fourier Transform for a phase-amplitude transformation of the speed vector.

13. A method according to claim 12, wherein Px is determined by plotting the Fast Fourier Transform of the speed vector and determining an RMS value of an area under a peak at a frequency x*n.

14. A method according to claim 11, wherein the values t are sampled with a sample interval with a duration of less than or equal to 10 microseconds.

15. A method according to claim 1, wherein the value T is representative of the mean engine torque at the loading conditions during the sampling period, the conditions being selected so as to correspond to at least 50% load.

16. A method according to claim 1, the value T being representative of mean engine torque at engine speeds used during the sampling period, the engine speeds being selected to be at least 1000 rpm.

17. Method for evaluating the function of an engine, comprising the steps of producing a value T according to claim 1, and comparing the value T to a reference value Tref being representative of the engine torque of a standard engine.

18. Device for the production of a value T which is representative of the mean engine torque generated on a crankshaft of an internal combustion engine, comprising

a measuring device for measuring instantaneous speeds of the engine during a sampling period,

calculation means for producing a speed vector of values being representative of the instantaneous speeds of the engine measured during the sampling period,

calculation means to derive a mean engine speed n during the sampling time using the speed vector,

calculation means to derive a value Px being representative of the frequency contribution of the speed vector at the frequency x*n, where x is a pre-selected order, and

calculation means to derive the desired value T being representative of the mean engine torque on the crankshaft during the sampling period wherein T is derived from a mathematical expression including a polynomial having at least a term k*n*Px, wherein k is a polynomial constant, stored in a memory.

19. A device according to claim 18, wherein the measuring device comprises a sensor being arranged for sensing passage of subsequent rotational indexing references associated with a flywheel or a crankshaft of the engine, the passages of time being values t of a speed vector being representatives of instantaneous speeds of the engine.

20. A device according to claim 19, wherein the measuring device comprises a calculation means for determining the speed between the subsequent rotational indexing references.

21. A device according to claim 19, comprising a calculation means for calculating a compensation step when generating the speed vector, wherein effects of any irregularities in the arrangement of the rotational indexing references are compensated for.

22. A device according to claim 18, wherein the values t are sampled with a sample interval with a duration of less than or equal to 10 microseconds.

23. A device according to claim 18, wherein T is derived from a mathematical expression including the polynomial:

k0+k1*Px+k2*n+k3*n*Px , where kθ

, k1, k2 and k3 are polynomial constants, stored in a memory.

24. A device according to claim 18, wherein T=k0+k1*Px+k2*n+k3*n*Px, where k0, k1, k2 and k3 are polynomial constants, stored in a memory.

25. A device according to claim 18, wherein the selected order of the amplitude x=(the number of cylinders of the engine)/2.

26. A device according to claim 18, wherein sampling period corresponds to at least 10 rotations of the engine.