**6. Conclusions**

As a crucial and critical factor in monitoring the internal state of an engine, pressure identification is significantly essential. In this paper, aimed at solving problems associated with reliability and cost of invasive pressure sensors, virtual cylinder pressure identification sensor based on EKF and FAMFS is proposed. This new method employs three key steps:


To further verify the validity of the proposed method, data collected from a genuine engine (EA211) provided by the China FAW Group Corporate R&D Center was used. Test results demonstrate that the proposed method exhibits grea<sup>t</sup> performance for tracking crank speed and the engine's real-time cylinder pressure. By comparing the identified pressure outputs with measurement results, the cumulative error percentage for cylinder pressure was below1.8%, the error percentage of IMEP each cycle was no more than 5.4%, and the error associated with speed was less than 9.6%, when A/F Ratio coefficient was set to 0.85. However, the cumulative error percentage for cylinder pressure was below 1.4%, the error percentage of IMEP each cycle was no more than 4.9%, and the error associated with speed was less than 1.7%, when A/F Ratio coefficient was setup at 0.95. The effectiveness and instantaneity are thereby proven and shown to be capable of achieving the desired accuracy despite the uncertainty of the engine's power stroke. The closer the A/F ratio set to optimal A/F ratio, the more exact the identified pressure will be. Furthermore, it is important to note that the proposed method is valid, in general, and may be applied to more complex situations.

**Author Contributions:** Study design and investigation, Q.W. and T.S.; Methodology, Q.W.; Resources, Q.W.; Supervision, D.G.; Writing—original draft, Q.W.; Writing—review & editing, Q.W., T.S., Z.L., D.G.

**Funding:** The author(s) disclose receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the National Natural Science Foundation of China (grant numbers 51806143) and sponsored by Shanghai Sailing Program (No. 19YF1434600).

**Conflicts of Interest:** The author(s) declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
