Static electrical contact resistance (ECR) has been well researched. To investigate the dynamic performance of electrical connector under vibration, a test apparatus is built to measure the ECR with high precision. The ECRs are tiny and suffer from noise. Therefore, a wavelet packet transform-based denoising method is proposed. This method can filter noise with frequency components ranging from low to high. The dynamic characteristics of ECR are presented after an analysis of the measured results. Moreover, the connector intermittent fault (IF) performance under vibration is characterized and analyzed. Finally, an ECR model for rough surfaces under vibration is proposed, based on which the discovered laws are theoretically analyzed. The detected dynamic characteristic of ECR and IF can support an online diagnosis of connectors in further research.

The lateral line is a critical mechanosensory organ that enables fish to perceive the surroundings accurately and rapidly. Massive efforts have been made to build an artificial lateral line system rivaling that of fish for underwater vehicles. Dipole source localization has become a standard problem for evaluating the sensing capabilities of the developed systems. In this paper we propose, for the first time, the MUSIC (multiple signal classification) method in order to achieve high-resolution dipole source localization based on spatial spectrum estimation. We also present the MVDR (minimum variance distortionless response) method by making an improvement to the previous Capon's method. Experiments are conducted on a linear prototype of lateral line canal and the localization performance of these two methods are compared. The results show that the MUSIC method provides an overall localization resolution improvement of 10.4% and maintains similar levels of localization accuracy compared with the MVDR method. Further studies show that the MUSIC method has the potential of localizing two closer incoherent dipole sources with a minimum lateral separation of 20 mm, versus 70 mm for the MVDR method, at a dipole-array distance of half the array length. Both localization methods have strong robustness to the vibrational state of the dipole source. Our work provides a promising and robust way to meet the high-resolution and multi-source sensing requirements of underwater vehicles.

The dependency matrix is widely used in fault diagnosis as a valid diagnostic model. However, the conventional dependency matrix-based diagnosis method pays more attention to the extension and improvement of the dependency matrix, and the timeliness is rarely discussed. To solve the problem and improve the diagnosis efficiency, fast diagnosis method using two search algorithms is proposed. The hash function is introduced, and the dependency matrix is transformed into the key-value pairs. The binary search algorithm is brought in to locate the desired failure mode by splitting the dependency matrix. Thus, the fault diagnosis is converted into a search process, which can improve the diagnosis efficiency by making full use of the advantages of the search algorithms. Finally, a numerical simulation is utilized to verify the proposed method. The proposed methods are applied to matrices of different sizes. The results show that the hash-based diagnosis method has significantly better efficiency, making it more suitable for onboard diagnosis. On the other hand, the binary search-based method is advantageous from a memory perspective only when the matrix size is small.

Multidirectional monitoring is highly expectable for stretchable strain sensors by which the randomly orientated cracks or the maximum strain of all directions need to be accommodated. Many current types of research exploit laminated sensors and rosette designs to obtain the desired behavior in several discrete directions. However, this can lead to complex fabricating and resolving processes, as well as significant measurement errors. Our work proposes an isotropic stretchable strain (ISS) sensor that utilizes the in-plane curved sensing film from graphene/silver nanowires (AgNWs), which exhibits uniform sensitivity in all directions within 30 ^∘ and the potential extending to 360 ^∘ . The ISS sensor, whose curved shape is optimized based on splines and the quantitative sensing model, is fabricated by a flash stamp machine and followed by vacuum filtration. Experimental results show that the ISS sensor possesses equivalent sensing properties in 30 ^∘ with excellent linearity and durability. Thus our customized sensor is applied to multidirectionally monitor the stretchable surface without consideration for the sensor orientation and the resolving process. Most importantly, the ISS sensor and its design method provide an efficient route for future sensor design with expected properties, not limited to isotropy.

The flight control system plays an important role in adjusting the attitude of manned or auto-pilot aircrafts. To reduce the fault diagnosis time and accelerate the maintenance actions, many flight control systems have adopted the design for testability. Testability demonstration for the flight control system is needed to check the indexes of testability such as fault detection rate and fault isolation rate. Currently, the standards and statistical methods for the testability demonstration planning have the problems such as large sample, long test period and it is not optimal for the flight control systems which are of complex structure and high cost. A testability demonstration planning method based on the sequential probability ratio test method is proposed as it can decrease the sample size with almost the same operation characteristic as the classical method. Firstly, the decision factor and rules of the sequential probability ratio test method and truncated decision rules are introduced. Secondly, the establishment of failure mode set based on the failure rate for the sequential probability ratio test method is illustrated. Finally, the demonstration of fault detection rate for a flight control system is implemented with the given method and steps. Software named testability demonstration and evaluation system which can calculate the decision criteria, plot decision chart, select failure mode and make decisions is used to assist the implementation of the test. The result shows that the fault detection rate passes the test with a credible performance and the actual sample size is remarkably decreased while comparing with the classical method.