The collision and wear caused by inevitable clearance in kinematic pair have an effect on the dynamic characteristics of the mechanism.Therefore,we established the dynamic model of a 3RSR(R is the revolute joint and S...The collision and wear caused by inevitable clearance in kinematic pair have an effect on the dynamic characteristics of the mechanism.Therefore,we established the dynamic model of a 3RSR(R is the revolute joint and S is the spherical joint)parallel mechanism with spherical joint clearance based on the modified Flores contact force model and the modified Coulomb friction model using Newton-Euler method.The standard quaternion was introduced in the constraint equation,and the four-order Runge-Kutta method was adopted to solve the 3RSR dynamic model.The simulation results were compared and analyzed with the numerical results.The geometrical parameters of the worn ball socket were solved based on the Archard wear model,and the geometrical reconstruction of the worn surface was carried out.The geometric reconstruction parameters were substituted into the dynamic model,which was to analyze the dynamic response of the 3RSR parallel mechanism with wear and spherical joint clearance.The simulation results show that the irregular wear occurs in the spherical joint with clearance under the presence of the impact and friction force.The long-term wear will increase the fluctuation of the contact force,thereby decreasing the movement stability of the mechanism.展开更多
In order to grasp the dynamic behaviors of 4-UPS-UPU high-speed spatial parallel mechanism, the stress of driving limbs and natural frequencies of parallel mechanism were investigated. Based on flexible multi-body dyn...In order to grasp the dynamic behaviors of 4-UPS-UPU high-speed spatial parallel mechanism, the stress of driving limbs and natural frequencies of parallel mechanism were investigated. Based on flexible multi-body dynamics theory, the dynamics model of 4-UPS-UPU high-speed spatial parallel mechanism without considering geometric nonlinearity was derived. The stress of driving limbs and natural frequencies of 4-UPS-UPU parallel mechanism with specific parameters were analyzed. The relationship between the basic parameters of parallel mechanism and its dynamic behaviors, such as stress of driving limbs and natural frequencies of parallel mechanism, were discussed. The numerical simulation results show that the stress and natural frequencies are relatively sensitive to the section parameters of driving limbs, the characteristic parameters of material on driving limbs, and the mass of moving platform. The researches can provide important theoretical base of the analysis of dynamic behaviors and optimal design for high-speed spatial parallel mechanism.展开更多
BK channels are widely expressed in both excitable and non-excitable cells and known to be involved in many physiological processes,such as vascular smooth tone regulation,neuronal firing and endocrine cell secretion[...BK channels are widely expressed in both excitable and non-excitable cells and known to be involved in many physiological processes,such as vascular smooth tone regulation,neuronal firing and endocrine cell secretion[1].Recently, the BK channels have展开更多
为解决语音增强任务中语音信息未充分利用的问题,提出一种基于深度学习的方法,即融合精确比值掩蔽的门控扩张循环卷积神经网络(gate-dilated recurrent convolutional neural network with accurate ratio masking, GDRCNN-ARM)。GDRCN...为解决语音增强任务中语音信息未充分利用的问题,提出一种基于深度学习的方法,即融合精确比值掩蔽的门控扩张循环卷积神经网络(gate-dilated recurrent convolutional neural network with accurate ratio masking, GDRCNN-ARM)。GDRCNN由编码器、循环卷积层和解码器3部分组成,编码器中借助扩张卷积和门控机制实现对上下文语音信息的捕获,进行并行处理;循环卷积层采用GRU且引入多头注意力机制,捕捉网络中的长期依赖关系;解码器采用逐层解码且通过跳跃连接进行编码器信息的复用,实现对语音细节的还原。实验数据表明,GDRCNN网络在参数量和模型大小方面明显优于DNN、CRN等网络,PESQ平均提高了0.612、0.158,STOI平均提高了0.072、0.020,在语音增强和泛化方面表现出色。展开更多
基金Project(2018YFB1307900)supported by the National Key R&D Program of ChinaProject(51775473)supported by the National Natural Science Foundation of China+3 种基金Projects(E2018203140,E2019203109)supported by the Natural Science Foundation of Hebei Province,ChinaProject(ZD2019020)supported by the Key Research Project in Higher Education Institutions of Hebei Province,ChinaProject(2017KSYS009)supported by the Key Laboratory of Robotics and Intelligent Equipment of Guangdong Regular Institutions of Higher Education,ChinaProject(KCYCXPT2017006)supported by the Innovation Center of Robotics and Intelligent Equipment of Dongguan University of Technology,China。
文摘The collision and wear caused by inevitable clearance in kinematic pair have an effect on the dynamic characteristics of the mechanism.Therefore,we established the dynamic model of a 3RSR(R is the revolute joint and S is the spherical joint)parallel mechanism with spherical joint clearance based on the modified Flores contact force model and the modified Coulomb friction model using Newton-Euler method.The standard quaternion was introduced in the constraint equation,and the four-order Runge-Kutta method was adopted to solve the 3RSR dynamic model.The simulation results were compared and analyzed with the numerical results.The geometrical parameters of the worn ball socket were solved based on the Archard wear model,and the geometrical reconstruction of the worn surface was carried out.The geometric reconstruction parameters were substituted into the dynamic model,which was to analyze the dynamic response of the 3RSR parallel mechanism with wear and spherical joint clearance.The simulation results show that the irregular wear occurs in the spherical joint with clearance under the presence of the impact and friction force.The long-term wear will increase the fluctuation of the contact force,thereby decreasing the movement stability of the mechanism.
基金Supported by National High Technology Research and Development Program of China （863 Program） （2007AA04Z239） and National Natural Science Foundation of China （60621001, 60975060）
基金Project(51005138) supported by the National Natural Science Foundation of ChinaProject(BS2012ZZ008) supported by Shandong Young Scientists Award Fund,China+2 种基金Project(J09LD54) supported by the Natural Science Foundation of Shandong Education Department of ChinaProject(2011KYJQ102) supported by the Science Foundation of Shandong University of Science and Technology,ChinaProject(HGDML-1104) supported by Jiangsu Key Laboratory of Digital Manufacturing Technology,China
文摘In order to grasp the dynamic behaviors of 4-UPS-UPU high-speed spatial parallel mechanism, the stress of driving limbs and natural frequencies of parallel mechanism were investigated. Based on flexible multi-body dynamics theory, the dynamics model of 4-UPS-UPU high-speed spatial parallel mechanism without considering geometric nonlinearity was derived. The stress of driving limbs and natural frequencies of 4-UPS-UPU parallel mechanism with specific parameters were analyzed. The relationship between the basic parameters of parallel mechanism and its dynamic behaviors, such as stress of driving limbs and natural frequencies of parallel mechanism, were discussed. The numerical simulation results show that the stress and natural frequencies are relatively sensitive to the section parameters of driving limbs, the characteristic parameters of material on driving limbs, and the mass of moving platform. The researches can provide important theoretical base of the analysis of dynamic behaviors and optimal design for high-speed spatial parallel mechanism.
基金supported by Natural Science Foundation of China grants10732070,10602031
文摘BK channels are widely expressed in both excitable and non-excitable cells and known to be involved in many physiological processes,such as vascular smooth tone regulation,neuronal firing and endocrine cell secretion[1].Recently, the BK channels have
文摘为解决语音增强任务中语音信息未充分利用的问题,提出一种基于深度学习的方法,即融合精确比值掩蔽的门控扩张循环卷积神经网络(gate-dilated recurrent convolutional neural network with accurate ratio masking, GDRCNN-ARM)。GDRCNN由编码器、循环卷积层和解码器3部分组成,编码器中借助扩张卷积和门控机制实现对上下文语音信息的捕获,进行并行处理;循环卷积层采用GRU且引入多头注意力机制,捕捉网络中的长期依赖关系;解码器采用逐层解码且通过跳跃连接进行编码器信息的复用,实现对语音细节的还原。实验数据表明,GDRCNN网络在参数量和模型大小方面明显优于DNN、CRN等网络,PESQ平均提高了0.612、0.158,STOI平均提高了0.072、0.020,在语音增强和泛化方面表现出色。
