Abstract:One of the key issues in control design for Active Magnetic Bearing (AMB) systems is the tradeoff between the simplicity of the controller structure and the performance of the closed-loop system. To achieve this tradeoff, this paper proposes the design of a fractional order Proportional-Integral-Derivative (FOPID) controller. The FOPID controller consists of only two additional parameters in comparison with a conventional PID controller. The feasibility of FOPID for AMB systems is investigated for rotor suspension in both the radial and axial directions. Tuning methods are developed based on the evolutionary algorithms for searching the optimal values of the controller parameters. The resulting FOPID controllers are then tested and compared with a conventional PID controller, as well as with some advanced controllers such as Linear Quadratic Gausian (LQG) and H ∞ controllers. The comparison is made in terms of various stability and robustness specifications, as well as the dimensions of the controllers as implemented. Lastly, to validate the proposed method, experimental testing is carried out on a single-stage centrifugal compressor test rig equipped with magnetic bearings. The results show that, with a proper selection of gains and fractional orders, the performance of the resulting FOPID is similar to those of the advanced controllers.

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One of the key challenges for long range Unmanned Aerial Systems (UAS) is the limitation of the communication capability. Many existing communication technics are conventionally adopted in UAS to improve the quality of the communication such as satellite communication, cellular networks, and relay aircrafts. However, the mentioned solutions often incur several drawbacks including costs, complexity, communication delay, or inefficient power consumption. LoRaWAN is one of the recently emerging communication technics used in the Low Power Wide Area Networks (LPWAN) technology. It has a promising potential to improve the coverage of UAS communication, since it can transmit/receive signals below the noise floor in a very long range with very low energy consumption by using the waveform modulation technique called Chirp Spread Spectrum (CSS). In this paper, we show the potential of LPWAN as the supplementary communication in UAS. The experiment results show that LoRaWAN can maintain the communication capability beyond 80 km where the popular RF device, RFD900x, has lost its ability to communicate at this distance.

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