# Advancements and Applications of Rim-Driven Fans in Aerial Vehicles: A Comprehensive Review
## 7 Control  
RDFs are hindered in their ability to scale due to various design, construction, and operational limitations. When it comes to larger aircraft, multiple RDFs must be used for propulsion purposes. Recently, cooperative control among multiple RDFs has been gaining significant interest. In order to improve the efficiency, convenience, and safety of airplane navigation, it is important to understand the cooperative control mechanisms utilized among RDFs.  
The installation of position sensors on RDTs can prove to be a challenging task. Consequently, the utilization of sensorless control technology is deemed to be a superior alternative, as supported in [77; 78; 79]. Currently, the control technology in question exhibits a certain degree of sophistication and is capable of achieving control outcomes that are deemed satisfactory. Nevertheless, the precision of control for motors operating at low velocities remains an area that requires further enhancement. The pursuit of high-performance control for RDT drive motors entails the development of anti-chattering and sensorless control algorithms. The sensorless control algorithms for RDT motors encompass a range of techniques, such as direct calculation, back-EMF integration, model reference adaptive, and various observer methods [79; 80; 81; 82]. In the context of RDT motor sensorless control, the optimization and tuning of adjustable parameters play a pivotal role in determining the efficacy of the rotor speed and position estimation algorithm. It is important to note that changes in motor parameters or external conditions necessitate corresponding adjustments to the controller's adjustable parameters. However, the manual parameter adjustment process can be quite complex and may not yield highly accurate results. Henceforth, it is plausible to amalgamate the parameter-tuning optimization algorithm with the RDTmotor sensorless control algorithm to enhance the precision of rotor speed and position estimation. The utilization of an improved particle swarm optimization (PSO)-based sensorless control algorithm can effectively mitigate the chattering phenomenon that arises during the estimation of the speed and position of the RDT motor. Additionally, this algorithm can significantly minimize the discrepancy between the estimated speed and the predetermined speed [80].  
Traditional PM motors' common control techniques work well with RDTs. For instance, A simple RDT control system was introduced by [PERSON] et al. [83].  
The high-speed permanent-magnet synchronous motor (PMSM) used in RDFs has been identified as having several issues such as a slow response speed, electromagnetic torque oscillation, and poor robustness. To address these problems, a research study was conducted to compare and analyze three different control strategies for the PMSM (Id = 0), maximum torque per ampere (MTPA), and d-axis current flux-weakening based on field-oriented control (FOC) [84]. The study also verified the effectiveness of each strategy under actual operating conditions. The findings indicated that all three control strategies enabled the electromagnetic torque of the low-speed motor to track the input load torque. While the Id = 0 FOC approach exhibited the quickest response time at 4000 rpm, it suffered from electromagnetic torque oscillation during start-up at 8000 rpm. The MTPA control strategy was able to resolve this problem by establishing a precise relationship between the d and q-axis current vector, resulting in an enhanced motor response speed at 8000 rpm. Ultimately, the d-axis current flux-weakening control strategy proved to be the most suitable option for the drive control strategy because it generated an improvement in the motor response speed during start-up with no load or sudden load changes, ultimately raising both the motor response and control robustness. Overall, this research study focused on addressing the response time and electromagnetic torque oscillation of a high-speed PMSM in RDFs by comparing and contrasting several drive control strategies.