This paper introduces a search-and-rescue robot system used for remote sensing of the underground coal mine environment, which is composed of an operating control unit and two mobile robots with ...explosion-proof and waterproof function. This robot system is designed to observe and collect information of the coal mine environment through remote control. Thus, this system can be regarded as a multifunction sensor, which realizes remote sensing. When the robot system detects danger, it will send out signals to warn rescuers to keep away. The robot consists of two gas sensors, two cameras, a two-way audio, a 1 km-long fiber-optic cable for communication and a mechanical explosion-proof manipulator. Especially, the manipulator is a novel explosion-proof manipulator for cleaning obstacles, which has 3-degree-of-freedom, but is driven by two motors. Furthermore, the two robots can communicate in series for 2 km with the operating control unit. The development of the robot system may provide a reference for developing future search-and-rescue systems.
Abstract
The rigid-flexible coupling cable system under large deformation is studied, and the beam element from absolute node coordinate formulation is used to establish flexible cable body of the ...system. Different numerical integral algorithms are discussed for solving the rigid-flexible cable system and an integration strategy which combines Implicit Euler with Minimum Residual Method (MINRES) is proposed. The influence of the position and number of rigid components and different the lengths of the flexible elements on the system dynamics are analyzed. With constant total mass of the system, higher number of rigid components and their uniform distribution contribute to stabilization of the swing of the flexible cable body. When the total length of the cable is constant, increasing the number of beam elements enhances the nonlinear characteristics of the swing motion and damages the stability. The influence of different factors on the movement of large deformation flexible cable body is obtained through modeling and simulation of the rigid-flexible coupling cable system.
This paper presents a novel sensing mode for using mobile robots to collect disaster ground information when the ground traffic from the rescue center to disaster site is disrupted. Traditional ...sensing modes which use aerial robots or ground robots independently either have limited ability to access disaster site or are only able to provide a bird's eye view of the disaster site. To illustrate the proposed sensing mode, the authors have developed a Multi-robot System with Air Dispersal Mode (MSADM) by combining the unimpeded path of aerial robots with the detailed view of ground robots. In the MSADM, an airplane carries some minimal reconnaissance ground robots to overcome the paralyzed traffic problem and deploys them on the ground to collect detailed scene information using parachutes and separation device modules. In addition, the airplane cruises in the sky and relays the control and reported information between the ground robots and the human operator. This means that the proposed sensing mode is able to provide more reliable communication performance when there are obstacles between the human operators and the ground robots. Additionally, the proposed sensing mode can easily make use of different kinds of ground robots, as long as they have a compatible interface with the separation device. Finally, an experimental demonstration of the MSADM is presented to show the effectiveness of the proposed sensing mode.
The melon fruit surface groove (fsg) not only affects peel structure and causes stress-induced fruit cracking but also fits consumers' requirements in different regions. In this study, genetic ...inheritance analysis of three F
populations derived from six parental lines revealed that the fsg trait is controlled by a simple recessive inherited gene. Through bulked segregant analysis sequencing (BSA-seq), the
locus was detected in an 8.96 Mb interval on chromosome 11 and then initially mapped to a region of approximately 1.15 Mb. Further fine mapping with a large F
population including 1,200 plants narrowed this region to 207 kb containing 11 genes. A genome-wide association study (GWAS) with 187 melon accessions also produced the same chromosome region for the
locus. Due to the rare molecular markers and lack of mutations in the coding and promoter regions of the 11 candidate genes in the fine-mapped interval, we conducted
BSA to explore the natural melon panel to predict candidate genes for the
locus. A 1.07 kb segment upstream of
(annotated as the AGAMOUS MADS-box transcription factor) exhibited a correlation with the grooved and non-grooved accessions among the F
individuals, and a natural panel consisted of 17 melon accessions. The expression level of
in the pericarp was higher in grooved lines than in non-grooved lines and was specifically expressed in fruit compared with other tissues (female flower, male flower, root, and leaf). This work provides fundamental information for further research on melon fsg trait formation and molecular markers for melon breeding.
Matrine (MT) is a potential resistance reversal agent. However, it remains unclear whether MT can reverse the resistance of
(
) to β-lactams, and, if so, by what mechanism MT works.
We screened one ...cefaclor (CEC)-resistant strain (clinical strain C7) from eight clinical (
) strains and determined the underlying resistance mechanism. Then, we investigated the reversal effect of MTon the resistance of this strain to CEC.
The production of β-lactamase, overexpression of AcrAB-TolC system, and formation of biofilm might not be responsible for the resistance of clinical strain C7 to CEC. Fourteen mutation sites were found in four PBP genes (
, and
) of clinical strain C7, among which the mutation sites located in
(Y
D and L
R) and
(A
V) genes triggered the resistance to CEC. The minimum inhibitory concentration (MIC) of CEC against clinical strain C7 was reduced by two to eight folds after MT treatment, accompanied by the significant down-regulated expression of mutated
and
genes. Based on such results, we believed that MT could reverse the resistance of
to CEC by inhibiting the mutations in
and
genes. Our research would provide useful information for restoring the antimicrobial activity of β-lactams and improving the therapeutic efficacy of Glässer's disease.
During the test of microelectromechanical system (MEMS) devices, calibration of test cables, loads and test instruments is an indispensable step. Calibration kits with high accuracy, great ...operability and small loss can reduce the systematic errors in the test process to the greatest extent and improve the measurement accuracy. Aiming at the issues of the conventional discrete calibration piece unit, which presents cumbersome calibration steps and large system loss, an integrated electronic calibration chip based on frequency microelectromechanical system (RF MEMS) switches is designed and fabricated. The short-open-load-through (SOLT) calibration states can be completed on a single chip, step by step, by adjusting the on-off state of the RF MEMS switches. The simulation results show that the operating frequency of the electronic calibration piece covers the range of DC~26.5 GHz, the insertion loss in through (thru) state is less than 0.2 dB, the return loss is less than 1.0 dB in short-circuit and open-circuit states, the return loss under load-circuit state is less than 20 dB and its size is only 2.748 mm × 2.2 mm × 0.5 mm. This novel calibration chip design has certain esteem for advancing calibration exactness and effectiveness.
In order to study the influence of compliance parts on spatial multibody systems, a rigid-flexible coupling dynamic equation of a spatial crank-slider mechanism is established based on the finite ...element method. Specifically, absolute node coordinate formulation (ANCF) is used to formulate a three-dimensional, two-node flexible cable element. The rigid-flexible coupling dynamic equation of the mechanism is derived by the Lagrange multiplier method and solved by the generalized α method and Newton–Raphson iteration method combined. Comparison of the kinematics and dynamics response between rigid-flexible coupling system and pure rigid system implies that the flexible part causes a certain degree of nonlinearity and reduces the reaction forces of joints. The elastic modulus of the flexible part is also important to the dynamics of the rigid-flexible multibody system. With smaller elastic modulus, the motion accuracy and reaction forces become lower.
As a high-precision motion mechanism, the kinematics and dynamics of cascade thrust reverser are sensitive to the changes of nonlinear factors which are rarely considered in traditional dynamic ...modeling and optimization. In order to study the effect of nonlinear factors on the dynamics behavior of cascade thrust reverser mechanism, the dynamic model considering joint clearance and flexible component is established. Lankarani–Nikravesh and modified-Coulomb model are used to establish the contact force at the clearance, and the flexible component in the mechanism is modeled by the absolute node coordinate method. The effects of joint clearance value, clearance position, flexible component, and driving speed on the dynamic response of the mechanism are studied. Specifically, the nonlinear characteristics of the mechanism increase with the clearance value, and the joint clearance near the mobile fairing has greater influence on the kinematics and dynamics of blocker door. For the mechanical system with clearances, the flexible component can partially reduce the vibration of the system. The analysis of the motion synchronization of the thrust reverser actuators indicates that the asynchronous movement of actuators may increase the driving forces of actuators especially for the middle actuator.
Formation control is an important problem in cooperative robotics due to its broad applications. To address this problem, the concept of a virtual linkage is introduced. Using this idea, a group of ...robots is designed and controlled to behave as particles embedded in a mechanical linkage instead of as a single rigid body as with the virtual structure approach. As compared to the virtual structure approach, the method proposed here can reconfigure the group of robots into different formation patterns by coordinating the joint angles in the corresponding mechanical linkage. Meanwhile, there is no need to transmit all the robots’ state information to a single location and implement all of the computation on it, due to virtual linkage’s hierarchical architecture. Finally, the effectiveness of the proposed method is demonstrated using two simulations with nine robots: moving around a circle in line formation, and moving through a gallery with varying formation patterns.
Internal combustion engines take up the major position in the power facility market and still encounter some challenges; one key issue is liner cavitation erosion. The impact vibration between piston ...and cylinder generates pressure fluctuation on the wet liner surface and leads to the occurrence of cavitation in the case that coolant pressure falls below its vapor pressure. Piston slap methodology has been improved by considering the dynamic characteristics of the piston. Water coolant passage acoustic features were investigated and the Helmholtz effect between cylinders was confirmed. In order to address the cavitation erosion potential of the engine cylinder, acoustic pressure in the cooling water passage was investigated by boundary element method analysis with the acceleration of the cylinder liner which was obtained from the piston slap program. This study revealed that a certain acoustic mode of the cooling water passage had a dominant effect on the amplitude of water coolant dynamic pressure induced by liner vibration. Measures of eliminating the acoustic mode are believed to be able to suspend pressure fluctuation and furthermore the potential of cavitation.
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