Optical Fiber Temperature and Humidity Dual Parameter Sensing Based on Fiber Bragg Gratings and Porous Film.

A porous anodic alumina film is proposed to construct an optical fiber temperature and humidity sensor. In the sensor structure, a fiber Bragg grating is used to detect the environment temperature, and the porous film is used to detect the environment humidity. The proposed porous anodic alumina film was fabricated by anodic oxidation reaction, and it is suitable for the use of humidity detection due to its porous structure. Experimental results show the temperature sensitivity of the proposed sensor was 10.4 pm/°C and the humidity sensitivity of the proposed sensor was 185 pm/%RH.

Polar-groups-modified polyimide based on a fiber Bragg grating for relative humidity sensors.

In this work, the effect of the polar groups modified polyimide fiber Bragg grating relative humidity sensor was studied. Polyimide films containing different polar groups were deposited on fiber Bragg gratings by an impregnating method to form different relative humidity (RH) sensors. The experimental results show that the addition of a carboxyl group and a hydroxyl group in the synthesis could improve the humidity sensitivity (2.28 and 1.59 times, respectively) from 35% RH-95% RH. The sensor based on modified polyimide still has good linear response to humidity and temperature. In addition, the sensors containing a carboxyl group and a hydroxyl group can shorten the response time of the humidity sensor and improve the stability of the sensor at the same time.

Thin-film-based optical fiber Fabry-Perot interferometer used for humidity sensing.

A thin-film-based optical fiber Fabry-Perot interferometer that consists of ZrO2 and SiO2 porous thin films is designed and fabricated by electron beam physical vapor deposition. Since the SiO2 porous thin film has the capability of water adsorption, the proposed Fabry-Perot interferometer is appropriate to detect humidity. Experimental results show that the prepared sensor has a humidity detection range from 0.06% RH to 70% RH. A cycling test shows that the humidity sensor has a responding or recover time of 4 s and good repeatability among different humidity environments. Especially, the proposed humidity sensor is insensitive to temperature variation and suitable for the detection of low relative humidity.

Hierarchical Control Strategy for the Cooperative Braking System of Electric Vehicle.

This paper provides a hierarchical control strategy for cooperative braking system of an electric vehicle with separated driven axles. Two layers are defined: the top layer is used to optimize the braking stability based on two sliding mode control strategies, namely, the interaxle control mode and signal-axle control strategies; the interaxle control strategy generates the ideal braking force distribution in general braking condition, and the single-axle control strategy can ensure braking safety in emergency braking condition; the bottom layer is used to maximize the regenerative braking energy recovery efficiency with a reallocated braking torque strategy; the reallocated braking torque strategy can recovery braking energy as much as possible in the premise of meeting battery charging power. The simulation results show that the proposed hierarchical control strategy is reasonable and can adapt to different typical road surfaces and load cases; the vehicle braking stability and safety can be guaranteed; furthermore, the regenerative braking energy recovery efficiency can be improved.