# Dynamic High-Type Interval Type-2 Fuzzy Logic Control for Photoelectric Tracking System
## 5 Conclusions  
A IT2 FLC-DHTC is constructed and verified in an FFSM platform. On the premise of ensuring the stability of the system, the dynamic and steady-state performance is improved, and the goal of dynamic high-type control is achieved.  
Adding an integrator to a traditional closed-loop control system can effectively improve the steady-state accuracy of the system. However, the increase of integrators will aggravate the oscillation of the system. In order to avoid system divergence, a dynamic adjustment mechanism is introduced to change the number of integrators with the state of the system, that is, the type of the system. From the experimental results, the dynamic high-type controller can effectively improve the steady-state accuracy of the system while avoiding the system oscillation.  
Compared with traditional position controllers, fuzzy logic controller shows great advantages in handling uncertainties, which benefits from the inherent characteristics of FLC. In this paper, a FLC is introduced as the on-off switch of the integrator, and also control the gain of the integrator. By reasonably designing the fuzzy rule base and membership function, the FLC can adjust the on-off and gain of the integrator in real time according to the system state, which effectively improves the system's response speed, steady-state accuracy, and ability to handle uncertainties.  
IT2 FLC introduces a three-dimensional membership function, which further improves the fuzzy controller's ability to handle uncertainties. From the experimental results, compared with IT1 FLC, IT2 FLC's ability to handle uncertainties is significantly improved. In addition, in order to speed up the calculation speed of IT2 FLC, the WTNT type-reduction algorithm constructed in this paper has faster calculation speed and better steady-state accuracy than the traditional TR algorithm, and has been successfully applied to real-time control systems, with good engineering application value.  
Future work will continue on the combination of FLC and DHTC. DHTC is a relatively new field. The current mainstream control structure type does not exceed type-3, and the combination of FLC and DHTC does not exceed type-2. If the type can be broken to a higher level, the steady-state accuracy of the system can undoubtedly be further improved, which has important research significance in the engineering field that requires high precision. In addition, the research of the type-2 FLC is also in the preliminary stage, the application field is almost blank, and there are many worthy research areas waiting for us to explore. I believe that in the near future, fuzzy control and high-type control can shine in the field of control, let us wait and see.  
Figure 15: Comparison of three TR algorithms.  
**Author Contributions:** Conceptualization, S.Q., T.Z. and Y.M.; Data curation, S.Q.; Formal analysis, S.Q. and T.Z.; Funding acquisition, Q.B.; Investigation, S.Q. and Q.B.; Methodology, S.Q. and Y.M.; Software, W.T.; Supervision, C.Z.; Validation, C.Z.; Writing - original draft, S.Q.; Writing--review & editing, S.Q., C.Z. and Y.M. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The APC was funded by Institute of Optics and Electrics, Chinese Academy of Sciences, China.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.