STATE ESTIMATION DEVICE FOR INTERNAL COMBUSTION ENGINE, STATE ESTIMATION SYSTEM FOR INTERNAL COMBUSTION ENGINE, DATA ANALYSIS DEVICE, AND CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

A state estimation device for an internal combustion engine includes: a storage device that stores mapping data, the mapping data being data defining a mapping that takes as an input an internal combustion engine state variable and that generates as an output an estimated value for estimating the state of the internal combustion engine; and an execution device that executes an acquisition process of acquiring the internal combustion engine state variable and an estimation process of calculating the estimated value based on the output of the mapping. The mapping data is data learned by machine learning. When the estimated value is out of an acceptable range, the execution device executes a guard process of adjusting the estimated value to a value close to or within the acceptable range. When executing the guard process, the execution device calculates the value after the guard process as the estimated value.