Icing has always been a problem for the aviation industry and the UAV sector. Small and accurate icing sensors can ensure the safety of critical parts of the aircraft and small UAVs in flight. This paper presents an Interdigital-complementary split-ring resonator sensor (ICSRR) that can distinguish water and ice with high accuracy and measure the thickness of ice. Compared with the traditional CSRR structure, the added Interdigital structure can measure ice thickness more sensitively. The sensor detects water and ice based on the change in resonant frequency measured in the scattering parameter S21 coefficient. A prototype sensor was built, and measurements were taken to verify the functionality of the sensor. First, the resonant frequencies under no-load were measured. Second, the process of water icing was characterized using the sensor. Finally, the accuracy of the sensor’s measurement of icing thickness was verified, and the data were fitted. The experimental results show that it is feasible to use the ICSRR sensor to monitor the icing condition and ice thickness.

In this paper, the performance of two Kalman filter (KF) schemes based on the direct estimated model and differencing estimated model for input rate signal was thoroughly analyzed and compared for combining measurements of a sensor array to improve the accuracy of microelectromechanical system (MEMS) gyroscopes. The principles for noise reduction were presented and KF algorithms were designed to obtain the optimal rate signal estimates. The input rate signal in the direct estimated KF model was modeled with a random walk process and treated as the estimated system state. In the differencing estimated KF model, a differencing operation was established between outputs of the gyroscope array, and then the optimal estimation of input rate signal was achieved by compensating for the estimations of bias drifts for the component gyroscopes. Finally, dynamic simulations and experiments with a six-gyroscope array were implemented to compare the dynamic performance of the two KF models. The 1σ error of the gyroscopes was reduced from 1.4558°/s to 0.1203°/s by the direct estimated KF model in a constant rate test and to 0.5974°/s by the differencing estimated KF model. The estimated rate signal filtered by both models could reflect the amplitude variation of the input signal in the swing rate test and displayed a reduction factor of about three for the 1σ noise. Results illustrate that the performance of the direct estimated KF model is much higher than that of the differencing estimated KF model, with a constant input signal or lower dynamic variation. A similarity in the two KFs’ performance is observed if the input signal has a high dynamic variation.

In recent decades, the UAV industry has rapidly developed, with UAVs finding applications in various fields. With the large number of UAVs being put into use, icing problems ensue. In this paper, a microwave icing sensor with a flexible array is introduced for measuring icing on the windward surface of UAVs, and a complementary coupled split-ring resonator (CCSRR) structure sensitive to ice thickness is proposed based on the evolved CSRR structure. The sensor film consists of a metal defect microstrip, a polyimide film, a flexible medium and a metallic ground. The resonance frequencies corresponding to different ice thicknesses are obtained by icing the surface of the sensor defective microstrip structure and then observing the transmission coefficient (S21) fed back from the experimental setup, and a functional relationship between the ice thickness and resonance frequency is established. Compared with traditional icing sensors, flexible structures can better adhere to the surface of a UAV, and the array-based design expands the detection capability of the sensor. This sensor not only measures the thickness of a single point, but also provides feedback on the ice morphology in the icing-sensitive area, which is convenient for the operator to formulate a deicing program.

In this paper, a flexible and stretchable energy harvester based on liquid-metal and fluorinated ethylene propylene (FEP) electret films is proposed and implemented for the application of wearable devices. A gallium liquid-metal alloy with a melting point of 25.0 °C is used to form the stretchable electrode; therefore, the inducted energy harvester will have excellent flexibility and stretchability. The solid-state electrode is wrapped in a dragon-skin silicone rubber shell and then bonded with FEP electret film and conductive film to form a flexible and stretchable energy harvester. Then, the open-circuit voltage of the designed energy harvester is tested and analyzed. Finally, the fabricated energy harvester is mounted on the elbow of a human body to harvest the energy produced by the bending of the elbow. The experimental results show that the flexible and stretchable energy harvester can adapt well to elbow bending and convert elbow motion into electric energy to light the LED in a wearable watch.

Analysing and minimizing energy loss is crucial for high performance disk resonator gyroscopes (DRGs). Generally, the primary energy loss mechanism for high vacuum packaged microelectromechanical system (MEMS) resonators includes thermoelastic damping, anchor loss, and electronic damping. In this paper, the thermoelastic damping, anchor loss, and electronic damping for our DRG design are calculated by combining finite element analysis and theoretical derivation. Thermoelastic damping is the dominant energy loss mechanism and contributes over 90% of the total dissipated energy. Benefiting from a symmetrical structure, the anchor loss is low and can be neglected. However, the electronic damping determined by the testing circuit contributes 2.6%–9.6% when the bias voltage increases from 10 V to 20 V, which has a considerable impact on the total quality factor (Q). For comparison, the gyroscope is fabricated and seal-packaged with a measured maximum Q range of 141k to 132k when the bias voltage varies. In conclusion, thermoelastic damping and electronic damping essentially determine the Q of the DRG. Thus, optimizing the resonance structure and testing the circuit to reduce energy loss is prioritized for a high-performance DRG design.

Many researchers have studied the miniaturization of the hemisphere resonator gyroscope for decades. The hemisphere resonator (HSR), as the core component, has a size that has been reduced to the submillimeter level. We developed a method of batch production of micro-hemisphere shell resonators based on a glass-blowing process to obtain larger hemisphere shells with a higher ratio of height to diameter (H/D), we introduced the chemical foaming process (CFP) and acquired an optimized hemisphere shell; the contrasted and improved H/D of the hemisphere shell are 0.61 and 0.80, respectively. Finally, we increased the volume of glass shell resonator by 51.48 times while decreasing the four-node wineglass resonant frequencies from 7.24 MHz to 0.98 MHz. The larger HSR with greater surface area is helpful for setting larger surrounding drive and sense capacitive electrodes, thereby enhancing the sensitivity of HSR to the rotation. This CFP method not only provides more convenience to control the shape of a hemisphere shell but also reduces non-negligible cost in the fabrication process. In addition, this method may inspire some other research fields, e.g., microfluidics, chemical analysis, and wafer level package (WLP).