Development of underwater electric manipulator based on interventional autonomous underwater vehicle (AUV)

In applications such as marine rescue,marine science,archaeology,and offshore industries,autonomous underwater vehicles(AUVs)are frequently used for survey missions and monitoring tasks,with most operations being performed by manned submersibles or remotely operated vehicles(ROVs)equipped with robotic arms,as they can be operated remotely for days without problems.However,they require expensive marine vessels and specialist pilots to operate them.Scientists exploring oceans are no longer satisfied with the use of manned submersibles and ROVs.There is a growing desire for seabed exploration to be performed using smarter,more flexible,and automated equipment.By improving the field operation and intervention capability of AUVs,large-scale and long-range seafloor exploration and sampling can be performed without the support of a mother ship,making it a more effective,economical,convenient,and rapid means of seafloor exploration and sampling operations,and playing a critical role in marine resource exploration.In this study,we explored the integration technology of underwater electric robotic arms and AUVs and designed a new set of electric manipulators suitable for water depths greater than 500 m.The reliability of the key components was analyzed by finite element analysis and,based on the theory of robot kinematics and dynamics,simulations were performed to verify the reliability of the key components.Experiments were conducted on land and underwater,trajectory tracking experiments were completed,and the experimental data in air and water were compared and analyzed.Finally,the objectives for further research on the autonomous control of the manipulator underwater were proposed.

Development of A Deep Ocean Electric Autonomous Manipulator

This paper describes an underwater 3500 m electric manipulator （named Huahai-4E, stands for four functions deep ocean electric manipulator in China）, which has been developed at underwater manipulation technology lab in Huazhong University of Science and Technology （HUST） for a test bed of studying of deep ocean manipulation technologies. The manipulator features modular integration joints, and layered architecture control system. The oil-filled, pressure-compensated joint is compactly designed and integrated of a permanent magnet （PM） brushless motor, a drive circuit, a harmonic gear and an angular feedback potentiometer. The underwater control system is based on a network and consisted of three embedded PC/104 computers which are used for servo control, task plan and target sensor respectively. They communicate through User Datagram Protocol （UDP） multicast communication in Vxworks OS. A supervisor PC with a virtual 3D GUI is fiber linked to underwater control system. Furthermore, the manipulator is equipped with a sensor system including a unique ultra-sonic probe array and an underwater camera. Autonomous grasp strategy based multi-sensor is studied. The results of watertight test in 40 MPa, joint＇s efficiency test and autonomous grasp experiments in tank are also presented.

Efficiency of electrical manipulation in two-dimensional topological insulators

We investigate the efficiency of electrical manipulation in a two-dimensional topological insulator by inspecting the electronic states of a lateral electrical potential superlattice in the system. The spatial distribution of the electron density in the system can be tuned by changing the strength of the externally applied lateral electrical superlattice potential. This provides us the information about how efficiently one can manipulate the electron motion inside a two-dimensional topo- logical insulator. Such information is important in designing electronic devices, e.g., an electric field effect transistor made of the topological insulator. The electronic states under various conditions are examined carefully. It is found that the dispersion of the mini-band and the electron distribution in the potential well region both display an oscillatory behavior as the potential strength of the lateral superlattice increases. The probability of finding an electron in the potential well region can be larger or smaller than the average as the potential strength varies. These features can be attributed to the coupled multiple-band nature of the topological insulator. In addition, it is also found that these behaviors are not sensitive to the gap parameter of the two-dimensional topological insulator model. Our study suggests that the electron density manipulation via electrical gating in a two-dimensional topological insulator is less effective and more delicate than that in a traditional single-band semiconductor.

Electric field manipulation of multiple nonequivalent Dirac cones in the electronic structures of hexagonal CrB_4 sheet

Two-dimensional materials with Dirac cones have significant applications in photoelectric technology. The origin and manipulation of multiple Dirac cones need to be better understood. By first-principle calculations, we study the influence of external fields on the electronic structure of the hexagonal CrB4 sheet with double nonequivalent Dirac cones. Our results show that the two cones are not sensitive to tensile strain and out-of-plane electric field, but present obviously different behaviors under the in-plane external electric field（along the B-B direction）, i.e., one cone holds while the other vanishes with a gap opening. More interestingly, a new nonequivalent cone emerges under a proper in-plane electric field. We also discuss the origin of the cones in CrB4 sheet. Our study provides a new method on how to obtain Dirac cones by the external field manipulation, which may motivate potential applications in nanoelectronics.

Construction and electrical control of ultrahigh-density organic memory arrays at cr yog enic temperature

Investigation into the structural and magnetic properties of organic molecules at cryogenic temperature is beneficial for reducing molec-ular vibration and stabilizing magnetization,and is of great im-portance for constructing novel spintronics devices of better perfor-mance and scaling the device size down to nanoscale.In order to explore the possibility of fabricating molecule-based memory chips of ultrahigh density,two-dimensional close-packed molecular arrays with carboxylic acid molecules were constructed in the current work and the magnetic properties in a low-temperature scanning tunnel-ing microscope were also investigated.The results demonstrated that each nonmagnetic molecule can be controllably and independently switched into a stable spin-carrying state at 4 K by applying a voltage pulse with atomic resolution.Benefiting from the small size of a single molecule as the basic storage bit,the two-dimensional molecular ar-rays allowing controllable electrical manipulations on each molecule can behave as a platform of memory chip with an ultrahigh storage density of∼320 terabytes(Tb)(or∼2500 terabits)per square inch.This work highlights the potential and advantage of employing or-ganic molecules in developing future cryogenic information storage techniques and devices at nanoscale.

Magnetic properties and anomalous Hall effect of Mn3Sn thin films controlled by defects and ferroelectric 0.7Pb(Mg_(1/3)Nb_(2/3))O_(3)–0.3PbTiO_(3) substrate

Noncollinear antiferromagnetic Mn_(3)Sn films have received much attention due to their potential applications in antiferromagnetic spintronic devices. In this work, single-phase polycrystalline antiferromagnetic Mn_(3)Sn thin films were successfully prepared by magnetron sputtering. The defects in the thin films were regulated by adjusting the sputtering power. The relationship among the films structure, the anomalous Hall effect(AHE) and the defects was investigated. High defect concentration in the Mn_(3)Sn films led to large room temperature ferromagnetic moments. The maximum saturation magnetization reached up to ~16 k A·m^(-1)(36 mlB/Mn), which was much larger than the values reported in literatures. The coercive field of38 mT was obtained in a high-quality Mn_(3)Sn film, which effectively reduced the flipping magnetic field. Moreover,the anomalous Hall resistance and coercive field of the Mn_(3)Sn films prepared on the ferroelectric substrates were manipulated through an applied electric field, indicating that the piezoelectric stress has a great influence on the nonzero Berry curvature of the triangular spin structure in the antiferromagnetic materials. These results will promote the potential application of Mn_(3)Sn in high-density and lowpower antiferromagnetic spintronic devices.

Robust Control of Robotic Manipulators in the Task-Space Using an Adaptive Observer Based on Chebyshev Polynomials

In this paper,an adaptive observer for robust control of robotic manipulators is proposed.The lumped uncertainty is estimated using Chebyshev polynomials.Usually,the uncertainty upper bound is required in designing observer-controller structures.However,obtaining this bound is a challenging task.To solve this problem,many uncertainty estimation techniques have been proposed in the literature based on neuro-fuzzy systems.As an alternative,in this paper,Chebyshev polynomials have been applied to uncertainty estimation due to their simpler structure and less computational load.Based on strictly-positive-rea Lyapunov theory,the stability of the closed-loop system can be verified.The Chebyshev coefficients are tuned based on the adaptation rules obtained in the stability analysis.Also,to compensate the truncation error of the Chebyshev polynomials,a continuous robust control term is designed while in previous related works,usually a discontinuous term is used.An SCARA manipulator actuated by permanent magnet DC motors is used for computer simulations.Simulation results reveal the superiority of the designed method.