This article proposes a novel soft pneumatic actuator inspired by the segmented structure of earthworms. The actuator adopts a new structure of free bottom to eliminate the constraint of the bottom and enlarge the bending capacity of the actuator. Through simulation, it is found that the new actuator improves the bending angle by 20% and output force by 40% compared with traditional actuator. Moreover, key parameters of the actuator are analyzed to acquire their effect on bending angle and bending linearity. A guideline for the design and optimization of the actuator is proposed. To validate the simulation results, we build up a test platform to test bending angle and output force of the actuators, the results shows that errors between the simulation and the test remained in the limit of about 10%. Finally, a three-jaw soft gripper is fabricated and its grasping strategy is studied. The quantitative analysis shows its excellent adaptability and load capacity.

Laser-induced ultrasound scanning imaging is proposed and utilized for the detection of the printed circuit board (PCB) delamination defect in this present study. Initially, based on the principle of laser-induced ultrasound scanning imaging, a three-dimensional mathematical model of the ultrasonic excitation by pulsed laser acting on the surface of PCB is established and analyzed. Furthermore, based on the established laser ultrasonic nondestructive testing system, single-point testing is investigated on the PCB specimen. A-scan experiments were carried out by transmission and reflection approaches, respectively. Moreover, the influence of the signal receiving position on the discrimination of defective signals and the effect of wavelet transform denoising parameters on the signal-to-noise ratio were investigated. Eventually, based on the laser-induced ultrasound scanning imaging inspection system, the defects of simulated debonding flat bottom holes are detected and studied. The different algorithms or parameters (Fast Fourier Transform, variance, extremum, and principal component analysis, etc.) are employed to extract the characteristic information are analyzed. The experimental results are compared with the traditional infrared thermal wave imaging (lock-in thermography). The experimental results indicate that laser-induced ultrasound scanning imaging has the advantages of high-resolution imaging for the defect with a small diameter. Therefore, it is of great significance to study a set of feasible laser-induced ultrasound scanning imaging for PCB delamination defect detection.

The deployer uses a voice coil actuator (VCA) to control precisely the separation velocity of CubeSats with different masses. This article proposes a novel VCA with a new structure of double magnetic circuits featuring high thrust density. Unlike the conventional design, the new design achieves high thrust density by using a new structure of double magnetic circuits to concentrate the magnetic flux in the airgap and alleviate the magnetic saturation in the yoke. An improved equivalent magnetic circuit is developed to reveal the performance improvement of the novel VCA. The electromagnetic characteristics of the new VCA are investigated and compared with the conventional counterparts by finite element analysis and experimental tests. One VCA deployer prototype has been fabricated and testedexperimentally to validate the thrust density and separation characteristics.

Defects, such as delamination and debonding, are critical to the performance of carbon fiber-reinforced polymer (CFRP) composites. In recent years, non-destructive testing techniques have been improved for the inspection of these defects among CFRPs. In this study, an all-optical and non-destructive laser ultrasonic technique with an optical microphone detection module has been presented to detect the artificial subsurface defects among the CFRP composites. A finite element simulation based on the thermo-mechanical coupling model was used to study the process of nanosecond pulsed laser excitation of the CFRP laminate to produce ultrasound and the propagation behavior of ultrasound among the CFRP laminate. A series of non-contact laser ultrasonic testing experiments were carried out to study the flat bottom holes of different sizes via a laser ultrasonic detection system. The artificial subsurface defects were reliably identified by the presented all-optical laser ultrasonic system imbedded in the optical microphone using four feature images.

The non-contact electromagnetic detumbling technologies for space debris and defunct satellites attract a lot of interest from many researchers, in which service satellites use one or two electromagnetic devices onboard to generate a controllable torque to reduce the rotation of the target so that the robotic arm can capture the target without hazardous collisions. However, there are many challenges in modeling the interactions between electromagnetic devices and the target. In this study, the electromagnetic devices and the target are simplified as magnetic dipoles and a slowly rotating conducting shell with typical shape, respectively. The interactions of one and two magnetic dipoles with a slowly rotating conducting spherical shell are derived. Then, the interaction between a slowly rotating conducting non-spherical geometry (a cube or a cylinder) and two magnetic dipoles is calculated numerically. The numerical results show that non-spherical geometries can be regarded as spherical shells in terms of calculating the electromagnetic interactions when the magnetic dipoles are far away from the geometries.