State detection system for internal combustion engine, data analysis device, and hybrid vehicle

A state detection system for an internal combustion engine, the state detection system being applied to the internal combustion engine including a crankshaft that is mechanically coupled with a motor-generator, the state detection system being configured to detect a predetermined operating state of the internal combustion engine, the predetermined operating state involving a variation in a combustion state between cylinders, the state detection system comprising:

• a memory configured to store mapping data, the mapping data being data that defines a detection mapping, the detection mapping being a mapping between an input and an output, the input being a first waveform variable and a second waveform variable and the output being a value of a combustion state variable, and the detection mapping including a joint operation of the first waveform variable and the second waveform variable based on a parameter learned by machine learning, the first waveform variable being a variable including information on a difference in rotation speed of the crankshaft between the cylinders during a period when combustion torque is generated in each of the cylinders, the second waveform variable being a variable indicating time series data of a state quantity indicating a drive state of the motor-generator, the combustion state variable being a variable relating to a degree of variation in the combustion state between the cylinders;
• and
• a processor configured to execute an acquisition process and a determination process, the acquisition process being a process of acquiring values of the first waveform variable and the second waveform variable, the value of the first waveform variable being acquired based on an output of a sensor that detects a rotation behavior of the crankshaft, the determination process being configured to determine whether or not the internal combustion engine is in the predetermined operating state, based on an output value of the detection mapping that takes the values of the first waveform variable and the second waveform variable acquired in the acquisition process as an input.