Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their...Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their control valves can unload in the neutral position and eventually lead to serious hydraulic leakage over long operation periods. In response to the problems noted above, a multifunctional automatic hydraulic steering circuit is presented. The system design is composed of a 5-way-3-position proportional directional valve, two pilot-controlled check valves, a pressure-compensated directional valve, a pressurecompensated flow regulator valve, a load shuttle valve, and a check valve, among other components. It is adaptable to most open-center systems with constant flow supply and closed-center systems with load feedback. The design maintains the lowest pressure under load feedback and stays at the neutral position during unloading, thus meeting the requirements for steering. The steering controller is based on proportional-integral-derivative(PID) running on a 51-microcontroller-unit master control chip. An experimental platform is developed to establish the basic characteristics of the system subject to stepwise inputs and sinusoidal tracking. Test results show that the system design demonstrates excellent control accuracy, fast response, and negligible leak during long operation periods.展开更多
时速160 km 提速单线半自动闭塞区段，由于站间距离限制，两站间距小于两站的双接近区段的长度之和时，两站的接近区段之间发生联系（穿袖）。结合衡茶吉铁路信号工程，介绍了采用有绝缘移频轨道电路、站联电路、特殊轨道电路设备，并...时速160 km 提速单线半自动闭塞区段，由于站间距离限制，两站间距小于两站的双接近区段的长度之和时，两站的接近区段之间发生联系（穿袖）。结合衡茶吉铁路信号工程，介绍了采用有绝缘移频轨道电路、站联电路、特殊轨道电路设备，并结合四线制方向电路的一种方案，解决单线区段地面载频自动改频难题。展开更多
This paper presents a mechanical reliability study of 3-dB waveguide hybrid couplers in submillimeter and terahertz bands.To show the necessity of improving the mechanical properties of the coupler’s branch in submil...This paper presents a mechanical reliability study of 3-dB waveguide hybrid couplers in submillimeter and terahertz bands.To show the necessity of improving the mechanical properties of the coupler’s branch in submillimeter and terahertz bands,a comprehensive study regarding the displacement of hybrid branch variation with varying width-length ratio and height-length ratio has been completed.In addition,a modified 3-dB waveguide hybrid coupler is designed and presented.Compared with the traditional branch structure,the proposed hybrid consists of a modified middle branch with circular cutouts at the top and bottom on both sides instead of the traditional rectangle branch,which increases the branch size and improves its mechanical reliability while achieving the same performance.Simulation results show that the deformation of the modified hybrid branch is 22%less than those of other traditional structure designs under the same stress.In practice,a vibration experiment is set up to verify the mechanical reliability of hybrid couplers.Measurement results show that the experiment deteriorates the coupling performance.Experimental results verify that the performance of the novel structure coupler is better than that of a traditional structure branch hybrid coupler under the same electrical properties.展开更多
针对扬声器阵列指向性声源对驱动电路的需求,设计了一种大功率、高效率以及低失真的8通道数字功放输出级电路。对影响电路实现的关键因素进行了深入分析,通过电路结构以及死区时间的优化设计,降低了总谐波失真、噪声和通道间相位延迟。...针对扬声器阵列指向性声源对驱动电路的需求,设计了一种大功率、高效率以及低失真的8通道数字功放输出级电路。对影响电路实现的关键因素进行了深入分析,通过电路结构以及死区时间的优化设计,降低了总谐波失真、噪声和通道间相位延迟。测试表明,输出功率为1 W时THD+N(Total Harmonic Distortion+Noise,总谐波失真加噪声)达到0.087 5%,20 Hz^22 k Hz频段信噪比达到89.172 d B,通道间相位延迟介于-0.62°^+0.1°之间,单通道效率达到92.1%。展开更多
基金Project supported by the Synergistic Innovation Center of Modern Agricultural Equipment and Technology,China(No.NZXT01201401)
文摘Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their control valves can unload in the neutral position and eventually lead to serious hydraulic leakage over long operation periods. In response to the problems noted above, a multifunctional automatic hydraulic steering circuit is presented. The system design is composed of a 5-way-3-position proportional directional valve, two pilot-controlled check valves, a pressure-compensated directional valve, a pressurecompensated flow regulator valve, a load shuttle valve, and a check valve, among other components. It is adaptable to most open-center systems with constant flow supply and closed-center systems with load feedback. The design maintains the lowest pressure under load feedback and stays at the neutral position during unloading, thus meeting the requirements for steering. The steering controller is based on proportional-integral-derivative(PID) running on a 51-microcontroller-unit master control chip. An experimental platform is developed to establish the basic characteristics of the system subject to stepwise inputs and sinusoidal tracking. Test results show that the system design demonstrates excellent control accuracy, fast response, and negligible leak during long operation periods.
基金Project supported by the National Natural Science Foundation of China(Nos.61771116 and 62022022)the National Key R&D Program of China(No.2018YFB1801502)the China Postdoctoral Science Foundation(No.2021TQ0057)。
文摘This paper presents a mechanical reliability study of 3-dB waveguide hybrid couplers in submillimeter and terahertz bands.To show the necessity of improving the mechanical properties of the coupler’s branch in submillimeter and terahertz bands,a comprehensive study regarding the displacement of hybrid branch variation with varying width-length ratio and height-length ratio has been completed.In addition,a modified 3-dB waveguide hybrid coupler is designed and presented.Compared with the traditional branch structure,the proposed hybrid consists of a modified middle branch with circular cutouts at the top and bottom on both sides instead of the traditional rectangle branch,which increases the branch size and improves its mechanical reliability while achieving the same performance.Simulation results show that the deformation of the modified hybrid branch is 22%less than those of other traditional structure designs under the same stress.In practice,a vibration experiment is set up to verify the mechanical reliability of hybrid couplers.Measurement results show that the experiment deteriorates the coupling performance.Experimental results verify that the performance of the novel structure coupler is better than that of a traditional structure branch hybrid coupler under the same electrical properties.
文摘针对扬声器阵列指向性声源对驱动电路的需求,设计了一种大功率、高效率以及低失真的8通道数字功放输出级电路。对影响电路实现的关键因素进行了深入分析,通过电路结构以及死区时间的优化设计,降低了总谐波失真、噪声和通道间相位延迟。测试表明,输出功率为1 W时THD+N(Total Harmonic Distortion+Noise,总谐波失真加噪声)达到0.087 5%,20 Hz^22 k Hz频段信噪比达到89.172 d B,通道间相位延迟介于-0.62°^+0.1°之间,单通道效率达到92.1%。
