Method of determining engine torque
A method of controlling a vehicle engine comprising estimating a value for the actual engine torque, comparing this with a further calculated (expected) torque value, and controlling the engine consequent to said comparing, the value for the actual engine torque being determined from the following steps: ⋅a) from a crankshaft signal, providing a plot or signal indicative of instantaneous crankshaft speed; ⋅b) differentiating said plot or signal indicative of instantaneous crankshaft speed with respect to time to determine acceleration values; ⋅c) within a crankshaft/time interval, determining a maximum and a minimum acceleration value from step b); ⋅d) determining the difference between said maximum and minimum acceleration values; ⋅e) determining a torque value dependent on said difference from step d).
1. A method of controlling a vehicle engine comprising estimating a value for the actual engine torque, comparing this with a further calculated (expected) torque value, and controlling the engine consequent to said comparing, the value for the actual engine torque being determined from the following steps:
a) from a crankshaft signal, providing a plot or signal indicative of instantaneous crankshaft speed;
b) differentiating said plot or signal indicative of instantaneous crankshaft speed with respect to time to determine acceleration values;
c) within a crankshaft/time interval, determining a maximum and a minimum acceleration value from step b);
d) determining the difference between said maximum and minimum acceleration values;
e) determining a torque value dependent on said difference from step d).
2. A method as claimed in claim 1 wherein step b) comprises: i) in said crankshaft/time interval, determining a set of values of acceleration from the minima and maxima values of a crankshaft speed signal/plot.
3. A method as claimed in claim 2 wherein said set of values is determined from the maxima and subsequent minima of said plot and from the minima and subsequent maxima.
4. A method as claimed in claim 3 wherein the values of accelerations are determined from the following formulae
ace=(speed Max( n )−speed Min( n )) t int
where speed Max(n) is the speed maxima following the combustion event n; speed Min(n) is the speed minima prior to the combustion event n; and t int is the time between the maxima and the preceding minima;
and/or
ace=(speed Min( n+ 1))−speed Max( n ))/ t int
where speed Max(n) is the speed maxima following a combustion event n; here speed Min(n+l) is the speed minima immediately after the combustion event n; and t int is the time between the minima or maxima and the preceding maxima or minima respectively.
5. A method as claimed in claim 1 comprises determining the torque from said difference from a stored look up table of MAP correlating said differences to torques.
6. A method as claimed in claim 1 wherein step e) is dependent on engine gear.
7. A method as claimed in claim 1 wherein if said computed actual engine torque value differs from said second torque values by more than a 20 threshold, the output torque of the engine is reduced or the engine is disabled.
8. A method as claimed in claim 1 wherein said minimum acceleration values is the negative acceleration values with the highest magnitude.
9. A processor configured to execute stored instructions to perform operations including:
estimating a value for an actual engine torque;
comparing the estimated value with a further calculated (expected) torque value;
controlling an engine consequent to said comparing, the value for the actual engine torque being determined from the following steps:
a) from a crankshaft signal, providing a plot or signal indicative of instantaneous crankshaft speed;
b) differentiating said plot or signal indicative of instantaneous crankshaft speed with respect to time to determine acceleration values;
c) within a crankshaft/time interval, determining a maximum and a minimum acceleration value from step b); and
d) determining the difference between said maximum and minimum acceleration values;
e) determining a torque value dependent on said difference from step d).
10. A non-transitory computer readable medium storing instructions that, when executed by at least one processor, perform operations including:
estimating a value for an actual engine torque;
comparing the estimated value with a further calculated (expected) torque value;
controlling an engine consequent to said comparing, the value for the actual engine torque being determined from the following steps:
a) from a crankshaft signal, providing a plot or signal indicative of instantaneous crankshaft speed;
b) differentiating said plot or signal indicative of instantaneous crankshaft speed with respect to time to determine acceleration values;
c) within a crankshaft/time interval, determining a maximum and a minimum acceleration value from step b); and
d) determining the difference between said maximum and minimum acceleration values.