A high dynamics algorithm based on steepest ascent method for GNSS receiver

High dynamic conditions impose critical challenges on Global Navigation Satellite System(GNSS)receivers,leading to large tracking errors or even loss of tracking.Current methods that intend to improve receivers’adaptability for high dynamics require either complicated structures or prior statistical information of noises.This paper proposes a high dynamics algorithm based on steepest ascent method that can circumvent the deficiencies of existing methods.First,the relationship between the error of carrier tracking and the maximum of Fast Fourier Transform(FFT)outputs is established,and a performance function based on the steepest ascent method is designed.It can keep stable in high dynamics.Second,a new carrier-tracking loop is constructed by deploying the performance function.When the variation of GPS receiver acceleration ranges from 10 g to 100 g,compared with the PLL that either loses lock or keeps tracking accuracy less than 33.89 Hz,the experimental results show that the proposed method can not only keep tracking,but also achieve tracking accuracy more than 2.77 Hz.

Modified attitude factor graph fusion method for unmanned helicopter under atmospheric disturbance

The Unmanned Aerial Helicopter(UAH)has attracted increasing attention in the military and civil areas with the unique flight performance.The significant impact on the attitude measurement performance of UAHs by the strong airflow disturbance is an essential factor threatening flight safety.To improve the attitude measurement performance of UAHs under atmospheric disturbance,an attitude fusion method over the factor graph is applied and provides the plug-and-play capability.Based on the relationship between position,velocity and attitude,a new attitude correction algorithm for the Modified Attitude Factor Graph Fusion(MAFGF)navigation method is designed and constructed through the fused position and velocity information.Finally,results of simulation and experiment are given to show the effectiveness of the proposed method.

A multipath mitigation algorithm for GNSS signals based on the steepest descent approach

Multipath interference seriously degrades the performance of Global Navigation Satellite System(GNSS)positioning in an urban canyon.Most current multipath mitigation algorithms suffer from heavy computational load or need external assistance.We propose a multipath mitigation algorithm based on the steepest descent approach,which has the merits of less computational load and no need for external aid.A new ranging code tracking loop is designed based on the steepest descent method,which can save an early branch or a late branch compared with the narrow-spacing correlation method.The power of the Non-Line-of-Sight(NLOS)signal is weaker than that of the Line-of-Sight(LOS)signal when the LOS signal is not obstructed and with a relatively high Carrier Noise Ratio(CNR).The peak position in the X-axis of the ranging code autocorrelation function does not move with the NLOS interference.Meanwhile,the cost function is designed according to this phenomenon.The results demonstrate that the proposed algorithm outperforms the narrow-spacing correlation and the Multipath Estimated Delay Locked Loop(MEDLL)in terms of the code multipath mitigation and computation time.The Standard Deviation(STD)of the tracking error with the proposed algorithm is less than 0.016 chips.Moreover,the computation time of the proposed algorithm in a software defined receiver is shortened by 24.21%compared with the narrow-spacing correlation.

3D/4D printed versatile fibre-based wearables for embroidery, AIE-chemosensing, and unidirectional draining

Fibre-based wearables for embroidery,chemosensing,and biofluid’s unidirectional draining with goodflexibility,tunability,and designability drive technological advance.However,synthetic polymerfibres are non-degradable,threatening the environment and human health.Herein,we have developed versatile microfibre-based wearables by combining many advantages in one platform of biodegradable polylactic acid(PLA)and melt electrowriting strategy.Diverse potential applications of PLA wearables are achieved byflexibly designing their printingfiles,components and structures.Three-dimensional printingfiles are generated from two-dimensional images to fabricate‘embroidery-like’patterns.PLA/aggregation-induced emissionfluorogens(AIE)chemosensors exhibit colorimetric andfluorescent colour changes upon exposure to amine vapours.Janus PLA-cotton textiles with a hydropho-bic/hydrophilic structure could facilitate unidirectional draining of sweats which is favourable for the management of temperature and humidity on the surface of skin.The proposed platform can not only broaden the design possibilities in 3D/4D printing but also offer wide potential applications for functional wearables.