Angular velocity/angular acceleration calculator, torque estimator, and combustion state estimator

1. An angular velocity/angular acceleration calculator for a crankshaft in an internal combustion engine, the calculator comprising:

a crank angle detection device that detects a crank angle in said internal combustion engine and a time at said crank angle;

a crank angle correction device that corrects, in accordance with a predetermined crank angle pitch, said crank angle and said time both detected by said crank angle detection device; and

an angular velocity/angular acceleration calculation device that calculates an angular velocity and an angular acceleration of said crankshaft by converting a function of said time with respect to said crank angle corrected by said crank angle correction device so as to be regarded as a periodic function, and utilizing a derivative of said converted function with respect to said crank angle obtained from a discrete Fourier transform of said converted function.

2. The angular velocity/angular acceleration calculator according to claim 1 , wherein

said angular velocity/angular acceleration calculation device converts said function so as to be regarded as a periodic function with application of a window function.

3. The angular velocity/angular acceleration calculator according to claim 1 , wherein

said angular velocity/angular acceleration calculation device removes frequency components of said discrete Fourier transform that have a frequency higher than a predetermined frequency.

4. A torque estimator in an internal combustion engine, the estimator comprising:

an angular velocity/angular acceleration calculator for a crankshaft in the internal combustion engine, the calculator including,

a crank angle detection device that detects a crank angle in said internal combustion engine and a time at said crank angle,

a crank angle correction device that corrects, in accordance with a predetermined crank angle pitch, said crank angle and said time both detected by said crank angle detection device, and

an angular velocity/angular acceleration calculation device that calculates an angular velocity and an angular acceleration of said crankshaft by converting a function of said time with respect to said crank angle corrected by said crank angle correction device so as to be regarded as a periodic function, and utilizing a derivative of said converted function with respect to said crank angle obtained from a discrete Fourier transform of said converted function; and

an axial torque calculation device that calculates an axial torque of said crankshaft by applying said crank angle corrected by said crank angle correction device and said angular velocity and said angular acceleration of said crankshaft calculated by said angular velocity/angular acceleration calculator to an equation of motion for a system including a piston, a connecting rod, and said crank in said internal combustion engine.

5. The torque estimator according to claim 4 , wherein

said axial torque calculation device uses said equation of motion in which said connecting rod has a mass thereof on said piston end and on said crank end based on a two-mass model.

6. The torque estimator according to claim 4 , further comprising:

an external torque estimation device that estimates an external torque according to the torque obtained in accordance with said equation of motion at a peculiar crank angle allowing said equation of motion to be regarded as a relational equation among a moment of inertia, an angular acceleration, and the external torque around the crankshaft.

7. The torque estimator according to claim 6 , further comprising:

a gas pressure torque calculation device that calculates a gas pressure torque by subtracting said external torque estimated by said external torque estimation device from said axial torque calculated by said axial torque calculation device.

8. The torque estimator according to claim 7 , further comprising:

a gas pressure work calculation device that calculates a gas pressure work by integrating said gas pressure torque calculated by said gas pressure torque calculation device in a predetermined range of said crank angle.

9. A combustion state estimator that estimates a combustion state of an internal combustion engine, the internal combustion engine including a crankshaft, said estimator comprising:

an estimator unit that estimates the combustion state of the internal combustion engine in accordance with at least one of an angular acceleration calculated by an angular velocity/angular acceleration calculator, a gas pressure torque calculated by a gas pressure torque calculation device, and a gas pressure work calculated by a gas pressure work calculation device,

wherein said angular velocity/angular acceleration calculator includes,

a crank angle detection device that detects a crank angle in said internal combustion engine and a time at said crank angle,

a crank angle correction device that corrects, in accordance with a predetermined crank angle pitch, said crank angle and said time both detected by said crank angle detection device, and

an angular velocity/angular acceleration calculation device that calculates an angular velocity and the angular acceleration of said crankshaft by converting a function of said time with respect to said crank angle corrected by said crank angle correction device so as to be regarded as a periodic function, and utilizing a derivative of said converted function with respect to said crank angle obtained from a discrete Fourier transform of said converted function,

said gas pressure torque calculation device includes,

said angular velocity/angular acceleration calculator,

an axial torque calculation device that calculates an axial torque of said crankshaft by applying said crank angle corrected by said crank angle correction device and said angular velocity and said angular acceleration of said crankshaft calculated by said angular velocity/angular acceleration calculator to an equation of motion for a system including a piston, a connecting rod, and said crank in said internal combustion engine,

an external torque estimation device that estimates an external torque according to the torque obtained in accordance with said equation of motion at a peculiar crank angle allowing said equation of motion to be regarded as a relational equation among a moment of inertia, an angular acceleration, and the external torque around the crankshaft, and

a gas pressure torque calculation device that calculates the gas pressure torque by subtracting said external torque estimated by said external torque estimation device from said axial torque calculated by said axial torque calculation device, and

said gas pressure work calculation device includes,

said gas pressure torque calculation device, and

a gas pressure work calculation device that calculates the gas pressure work by integrating said gas pressure torque calculated by said gas pressure torque calculation device in a predetermined range of said crank angle.