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Currently, PID control method is mainly used for the pitch control of coal mine roadheader, and the control precision is not high in the case of time-varying and nonlinear hydraulic system during the pitch control of roadheader. The pitch control of roadbeader is realized by controlling the stroke of the hydraulic cylinder. Combining the traditional PID algorithm with fuzzy control and neural network, the accuracy of the stroke control of the hydraulic cylinder can be effectively improved. In order to solve the above problems, a pitch control method for coal mine roadheader based on fuzzy neural network PID is proposed. By analyzing the kinematic relationship of the support part of the roadheader, the mathematical relationship between the pitch angle and the hydraulic cylinder of the support part is obtained. The working principle of the pitch control hydraulic system of the roadheader is introduced, and the hydraulic system and its transfer function model are established. The method combines fuzzy control with neural networks to form a fuzzy neural network. The method optimizes PID control parameters by using the fuzzy neural network. The method combines the mathematical model of the support mechanism and the transfer function model of the hydraulic system to establish a fuzzy neural network PID control model for the pitch angle of the roadheader. It achieves automatic and precise control of the pitch mechanism of the coal mine roadheader. This method can make the pitch mechanism of the roadheader reach the preset position more quickly and accurately, solving the time-varying and nonlinear problems in the pitch control of roadheader. The simulation results show that the fuzzy neural network PID control algorithm reduces tracking errors by 69.34% and 74.49% respectively compared to fuzzy PID and PID control algorithms. The method simulates the pitch control of coal mine roadheaders under sudden and following working conditions through hydraulic cylinder displacement control. The results show that compared with fuzzy PID and PID control algorithms, the fuzzy neural network PID control algorithm has the smallest pitch control tracking error, shortens the average response time to position signals by 27.22% and 50.33% respectively, and has better dynamic control performance.

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The pitch angle of the contra rotation propeller (CRP) has important effect on the aerodynamic interference between the front and aft blades,which can change the aerodynamic performance of the propeller. In order to study the aerodynamic influence of pitch angle on the contra rotation propeller and improve the aerodynamic performance of propellers,at the inlet Mach number of 0.453,the numerical calculation is carried out by adjusting the blade pitch angle after about 6×6 configuration contra rotation propeller,in which the method is used by combining unsteady Reynolds-averaged Navier-Stokes (URANS) equation with SST turbulence model. The T-Rex high quality grid generation technique is used to study the change rule of the pitch angle of contra rotating propeller on aerodynamic interference. The results show that the aft propellers are under the action of pre-swirling air from the front propellers,the aft propellers can absorb a part of the tangential slip flow energy of the front propellers,and the aerodynamic efficiency is higher than that of the front propellers. The aerodynamic parameters of the front and aft propellers fluctuate 12 times in a rotating cycle. When the rotating speed of frond and aft propellers maintains the same,the pitch angle of the front propellers maintains constant,and the pitch angle of the aft propellers is reduced,the aerodynamic efficiency of the front and aft propellers is increased,and the efficiency of aft propellers is improved significantly.

During the landing process of wing-in-ground aircraft,the impact caused by the landing of broken steps is likely to lead to the buckling or damage of the structural surface.The Arbitrary Lagrangian-Eulerian(ALE)finite element method is utilized to simulate the water landing of a wing-in-ground aircraft,and the penalty function method is used in the two-phase interface fluid-solid interaction problem.The effect of different parameters such as horizontal flight velocity,falling velocity,pitch angle on the immersion depth,and overload are analyzed.The results show that the pressure maxima of the aircraft with water landing all occur at the broken step.With the increase of the pitch angle,the peak of vertical overload rises and then falls,while the peak of horizontal overload keeps reducing.When the pitch angle is 7°,the vertical overload peak reaches the highest,which is 1.4 times that of the lowest overload in the pitch angle of 15°.On the other hand,the peak of the horizontal overload rises as the horizontal component of flight velocity increases,and it is visible that there is no discernible effect on the peak of vertical overload.Meanwhile,an approximately linear relationship appears between the peak of vertical overload and the square of falling velocity.The larger the falling velocity,the bigger the peak of vertical overload.

In response to the problem of reduced system inertia and insufficient frequency regulation capacity due to large-scale wind power connection to the grid, an integrated control strategy scheme for wind turbine inertia support and primary frequency regulation is proposed. In this scheme, the load reduction control of wind turbine is adjusted based on the characteristics of wind turbine slurry distance angle, and the reserve capacity required for wind turbine frequency modulation is reserved, which further solves the combination problem between the frequency change of the power grid and the virtual moment of inertia in the load reduction mode. In addition, the wind turbine speed protection is considered to set the static adjustment coefficient, and combined with the inertia support control, to achieve the wind turbine integrated frequency control strategy. The co-simulation model including wind farm is built in MATLAB/Simulink platform. The results show that the wind turbine can quickly provide virtual rotational inertia support to the grid, reduce the rate of change of the initial grid frequency perturbation, and regulate the output power according to the adjusted static regulation differential coefficients to improve the frequency stability of the wind power connected to the grid, which verifies the rationality of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Aiming at the design difficulties of the key motion mechanism of the model supporting mechanism in the large-scale wind tunnel test， this manuscript proposes a new linear actuation transmission mode based on circular arc motion from the perspective of engineering practicality. This mode realizes the linear actuation function with a limited range of rotation， and overcomes the problems of high manufacturing cost and difficulty in installation and commissioning of large-size and high-precision worm gear pair in the past. To verify the effectiveness of this mode， a comprehensive analysis of the mechanism from aspects of dynamics of mechanism， kinematics of mechanism， control characteristics， stiffness and strength is conducted. At present， the design of the pitching movement transmission mechanism has been applied to the model mechanism of a large wind tunnel. The wind tunnel model has a pitch angle displacement range of 45°， and the radius of the circular motion reaches 2 800 mm. The integrated model features low cost and is easy to maintain.

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to research submarine motion control features in different conditions and com-plex environments in order to solve the problem of actual submarine control and apply it to building an actu-al hydraulic control platform. The paper focuses on the vertical motion of submarines, designs a fast termi-nal sliding mode control algorithm and analyzes the data using the combined simulation and experiment method to study the robustness and reliability of a submarine's vertical motion control system for hydraulic and control. At the same time, the simulation and experiment results analyze the hysteresis and oscillation of the hydraulic steering gear, and effectively reduce the chattering that may be caused by sliding mode variable structure control. This system can be used in simulations to solve the problems of new submarine control characteristics.

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For an unmanned aerial vehicle (UAV) with high-mounted wings, a simplified analytical model is established to analyze the cushioning characteristics of a soft landing airbag system and determine the initial design parameters of the soft landing airbags. A finite element model is established and a series of simulations are conducted to analyze the influence of design parameters and landing attitude angle on cushioning characteristics. Numerical results show that the results obtained by FEM and the analytical model are the same, but the errors of impact response values calculated by two models are still 5% ~ 12. 5% because of the introduction of some assumptions in the analytical model; and the existence of initial landing attitude angles makes the pitch and roll motions of UAV much worse in the later stage of landing process, so that the rigid impact occurs easily. However, a vented airbag system is incapable of avoiding the local damage caused by the rigid impact. The study also shows that the proposed hybrid airbag scheme can provide a reliable soft support in the later stage of soft landing process and reduce the risk of suffering the rigid impact. [ABSTRACT FROM AUTHOR]

Stall regulation is one of the methods to control the output of fixed pitch wind turbines and to avoid overload. It is common that the actual wind turbine power curve differs largely from the theoretical power curve during the power generation processes of wind farms, especially for areas with high winter-summer temperature spread, as high air density in winter times causes frequent over-speed, threatening the security of wind turbines. The power curve of a fixed pitch wind turbine is related to its pitch angle. Wind farms can optimize power curves by adjusting pitch angle in accordance with air density. [ABSTRACT FROM AUTHOR]