In this paper, the anti-disturbance formation flight control of quadrotor UAVs system is realized based on terminal sliding mode control. The generalized error state is designed for each quad-rotor UA V, based on whic...
In this paper, the anti-disturbance formation flight control of quadrotor UAVs system is realized based on terminal sliding mode control. The generalized error state is designed for each quad-rotor UA V, based on which the formation control target is proposed. In order to achieve the goal of anti-disturbance formation control, a formation controller based on terminal sliding mode control is designed. Finally, the general error states of all quadrotor UAVs converge to zero to achieve the desired formation. Finally, a simulation example is given to verify the effectiveness of the proposed algorithm.
Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is ***,a three-impulse ...
Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is ***,a three-impulse contingency return trajectory scheme is presented by combining the Lambert transfer and maneuver at the special ***,a calculation model of three-impulse contingency return trajectories is ***,fast calculation methods are proposed by adopting the high-order Taylor expansion of differential algebra in the twobody trajectory dynamics model and perturbed trajectory dynamics ***,the performance of the proposed methods is verified by numerical *** results indicate that the fast calculation method of two-body trajectory has higher calculation efficiency compared to the semi-analytical calculation method under a certain accuracy *** to its high efficiency,the characteristics of the three-impulse contingency return trajectories under different contingency scenarios are further analyzed *** findings can be used for the design of contingency return trajectories in future manned lunar landing missions.
Images data from the micro cone-beam computed tomography (CBCT) are acquired from a rotation of an object located between an X-ray generator and a flat panel detector; therefore, the rotational position of the motor i...
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ISBN:
(纸本)9781665489041
Images data from the micro cone-beam computed tomography (CBCT) are acquired from a rotation of an object located between an X-ray generator and a flat panel detector; therefore, the rotational position of the motor is very important for image quality of 3D cross-section images. This study focuses on designing the position control of the stepping motor using the motion module, which enhances the control 4-axis motor’s efficiency to optimize and increase the accuracy of motor movement. We designed the stepping motor position control system to control the movement of the micro CBCT system to perform ten circular rotations in a single scanning process. A phantom was used to verify the rotational image accuracy by considering the image at the same position each round. Comparison of the motor movement with and without the motion module showed slight differences of projection images causing artifacts in cross-section images. Thus, the design of the rotation position control using the motion module circuit yielded good performance in terms of precision and rotational accuracy on the CBCT.
In the field of image compression, the traditional JPEG encoding uses a lot of multiplication operations in the discrete cosine transform and quantization. In order to reduce the computational complexity and meet the ...
In the field of image compression, the traditional JPEG encoding uses a lot of multiplication operations in the discrete cosine transform and quantization. In order to reduce the computational complexity and meet the real-time requirements of the system, a low-complexity 8*8 orthogonal transformation matrix is proposed for low-bit-rate image compression, which only contains 0 and 1, without multiplication and shift operations. In addition, an approximate quantization table is designed to replace the traditional quantization table, in which addition and multiplication are not required, only shift operations are required. The results show that the image quality obtained by approximate quantization is basically the same as that of standard quantization, and the proposed coding framework can also be implemented on FPGA.
This editorial summarizes the contributions to the Special Issue Biodiversity conservation and ecological restoration of vulnerable ecosystems in the Anthropocene',established under the Journal of Plant Ecology.
This editorial summarizes the contributions to the Special Issue Biodiversity conservation and ecological restoration of vulnerable ecosystems in the Anthropocene',established under the Journal of Plant Ecology.
With the improvement of the informatization of the power system, the risk of cyber attack is also increasing. This paper proposes a risk assessment and prevention strategy for cyber attack against substations. Firstly...
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Radar data, which have incomparably high temporal and spatial resolution, and lightning data, which are great indicators of severe convection, have been used to improve the initial field and increase the accuracies of...
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Radar data, which have incomparably high temporal and spatial resolution, and lightning data, which are great indicators of severe convection, have been used to improve the initial field and increase the accuracies of nowcasting and short-term forecasting. Physical initialization combined with the three-dimensional variational data assimilation method(PI3 DVarrh) is used in this study to assimilate two kinds of observation data simultaneously, in which radar data are dominant and lightning data are introduced as constraint conditions. In this way, the advantages of dual observations are adopted. To verify the effect of assimilating radar and lightning data using the PI3 DVarrh method, a severe convective activity that occurred on 5 June 2009 is utilized, and five assimilation experiments are designed based on the Weather research and Forecasting(WRF) model. The assimilation of radar and lightning data results in moister conditions below cloud top, where severe convection occurs;thus, wet forecasts are generated in this *** results show that the control experiment has poor prediction accuracy. Radar data assimilation using the PI3 DVarrh method improves the location prediction of reflectivity and precipitation, especially in the last 3-h prediction, although the reflectivity and precipitation are notably overestimated. The introduction of lightning data effectively thins the radar data, reduces the overestimates in radar data assimilation, and results in better spatial pattern and intensity predictions. The predicted graupel mixing ratio is closer to the distribution of the observed lightning,which can provide more accurate lightning warning information.
The existing safety automation equipment are designed to perform in an integrated and centralized way, with the strategy of one device corresponding to one function, and with strong coupling inside the equipment, whic...
The existing safety automation equipment are designed to perform in an integrated and centralized way, with the strategy of one device corresponding to one function, and with strong coupling inside the equipment, which brings the problems of repeatability and complexity in management, increases the management workload, and is difficult to standardize the management; Therefore, it is necessary to design the platform architecture for the safety automation equipment from top to bottom, adopt new rapid link technology and establish common standard communication transmission protocol to standardize the consistency of data transmission; to isolate the collection module and the digital part in terms of hardware part to achieve hardware decoupling; and to divide the basic strategy logic and advanced strategy logic of functional strategy in terms of digital part, to adopt independent hardware intelligent plug-in for special strategy software, form the minimum basic function Amass Unit, set up the data center of equipment, adopt virtual agent mechanism, so as to achieve software decoupling, and form the digit-module decoupling platform architecture of "high integration and loose coupling" for safety automation equipment, which will provide the key technical basis for the standardized management of safety automation equipment.
Resource-based cities (RBC) primarily depend on the extraction and processing of natural resources, resulting in a relatively simplistic economic structure. However, the emergence of the digital economy (DIGITAL) brin...
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