Automatic profiling control using a boom-type roadheader requires an understanding of horizontal and vertical swing angles of the cutting boom. In this study the vertical angle of the cutting boom is discussed. First,...Automatic profiling control using a boom-type roadheader requires an understanding of horizontal and vertical swing angles of the cutting boom. In this study the vertical angle of the cutting boom is discussed. First, a vertical swing detection model for the cutting boom is established. Then, a kinematic analysis of the vertical swing mechanism is made and formulae describing the geometrical relationship between the vertical swing of the cutting boom and the telescopic length of vertical hydraulic lift cylinders and vertical swing angle of the boom are presented. Various factors such as complexity of the calculation model, the difficulty of installing the sensor and the cost are compared for two methods. Finally, directly measuring the vertical swing angle of the cutting boom with a tilt sensor is decided to be the more simple and effective method. The detection sensitivity and the vertical cutting error of a tilt sensor are studied. Vibration tests on an EBZ160 roadheader were performed in a coal mine. The characteristic vibration frequencies are analyzed. A design of a vibration isolation mount for the tilt sensor is presented. It makes the detection device work more reliably under conditions where vibration is present and lays a foundation for the implementation of an automatic roadhead cutter. A tilt sensor is installed on an EBZ160 and an EBZ200, and experiments have been done in a coal mine. The re- suits show that the experimental result is favorable and achieves the goal of automatic control of the vertical swing of the cutting boom.展开更多
In order to control the growth of space debris,a novel tethered space robot(TSR) was put forward.After capture,the platform,tether,and target constituted a tethered combination system.General nonlinear dynamics of the...In order to control the growth of space debris,a novel tethered space robot(TSR) was put forward.After capture,the platform,tether,and target constituted a tethered combination system.General nonlinear dynamics of the tethered combination system in the post-capture phase was established with the consideration of the attitudes of two spacecrafts and the quadratic nonlinear elasticity of the tether.The motion law of the tethered combination in the deorbiting process with different disturbances was simulated and discussed on the premise that the platform was only controlled by a constant thrust force.It is known that the four motion freedoms of the tethered combination are coupled with each other in the deorbiting process from the simulation results.A noticeable phenomenon is that the tether longitudinal vibration does not decay to vanish even under the large tether damping with initial attitude disturbances due to the coupling effect.The approximate analytical solutions of the dynamics for a simplified model are obtained through the perturbation method.The condition of the inter resonance phenomenon is the frequency ratio λ_1=2.The case study shows good accordance between the analytical solutions and numerical results,indicating the effectiveness and correctness of approximate analytical solutions.展开更多
Cross-flows around two,three and four circular cylinders in tandem,side-by-side,isosceles triangle and square arrangements are simulated using the incompressible lattice Boltzmann method with a second-order accurate c...Cross-flows around two,three and four circular cylinders in tandem,side-by-side,isosceles triangle and square arrangements are simulated using the incompressible lattice Boltzmann method with a second-order accurate curved boundary condition at Reynolds number 200 and the cylinder center-to-center transverse or/and longitudinal spacing 1.5D,where D is the identical circular cylinder diameter.The wake patterns,pressure and force distributions on the cylinders and mechanism of flow dynamics are investigated and compared among the four cases.The results also show that flows around the three or four cylinders significantly differ from those of the two cylinders in the tandem and side-by-side arrangements although there are some common features among the four cases due to their similarity of structures,which are interesting,complex and useful for practical applications.This study provides a useful database to validate the simplicity,accuracy and robustness of the Lattice Boltzmann method.展开更多
基金support from China University of Mining and Technology (Beijing)Financial supports for this work provided by the National Hi-tech Research and Development Program of China (No.2008AA062201)
文摘Automatic profiling control using a boom-type roadheader requires an understanding of horizontal and vertical swing angles of the cutting boom. In this study the vertical angle of the cutting boom is discussed. First, a vertical swing detection model for the cutting boom is established. Then, a kinematic analysis of the vertical swing mechanism is made and formulae describing the geometrical relationship between the vertical swing of the cutting boom and the telescopic length of vertical hydraulic lift cylinders and vertical swing angle of the boom are presented. Various factors such as complexity of the calculation model, the difficulty of installing the sensor and the cost are compared for two methods. Finally, directly measuring the vertical swing angle of the cutting boom with a tilt sensor is decided to be the more simple and effective method. The detection sensitivity and the vertical cutting error of a tilt sensor are studied. Vibration tests on an EBZ160 roadheader were performed in a coal mine. The characteristic vibration frequencies are analyzed. A design of a vibration isolation mount for the tilt sensor is presented. It makes the detection device work more reliably under conditions where vibration is present and lays a foundation for the implementation of an automatic roadhead cutter. A tilt sensor is installed on an EBZ160 and an EBZ200, and experiments have been done in a coal mine. The re- suits show that the experimental result is favorable and achieves the goal of automatic control of the vertical swing of the cutting boom.
基金Project (51475411) supported by the National Natural Science Foundation of ChinaProject (LY15E070002) supported by Zhejiang Provincial Natural Science Foundation of China
文摘In order to control the growth of space debris,a novel tethered space robot(TSR) was put forward.After capture,the platform,tether,and target constituted a tethered combination system.General nonlinear dynamics of the tethered combination system in the post-capture phase was established with the consideration of the attitudes of two spacecrafts and the quadratic nonlinear elasticity of the tether.The motion law of the tethered combination in the deorbiting process with different disturbances was simulated and discussed on the premise that the platform was only controlled by a constant thrust force.It is known that the four motion freedoms of the tethered combination are coupled with each other in the deorbiting process from the simulation results.A noticeable phenomenon is that the tether longitudinal vibration does not decay to vanish even under the large tether damping with initial attitude disturbances due to the coupling effect.The approximate analytical solutions of the dynamics for a simplified model are obtained through the perturbation method.The condition of the inter resonance phenomenon is the frequency ratio λ_1=2.The case study shows good accordance between the analytical solutions and numerical results,indicating the effectiveness and correctness of approximate analytical solutions.
基金supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education
文摘Cross-flows around two,three and four circular cylinders in tandem,side-by-side,isosceles triangle and square arrangements are simulated using the incompressible lattice Boltzmann method with a second-order accurate curved boundary condition at Reynolds number 200 and the cylinder center-to-center transverse or/and longitudinal spacing 1.5D,where D is the identical circular cylinder diameter.The wake patterns,pressure and force distributions on the cylinders and mechanism of flow dynamics are investigated and compared among the four cases.The results also show that flows around the three or four cylinders significantly differ from those of the two cylinders in the tandem and side-by-side arrangements although there are some common features among the four cases due to their similarity of structures,which are interesting,complex and useful for practical applications.This study provides a useful database to validate the simplicity,accuracy and robustness of the Lattice Boltzmann method.
