The displacement of the origin of the accelerometer coordinate system relative to the origin of the base coordinate system is calculated by homogeneous transformation. The second order derivative of this displacement ...The displacement of the origin of the accelerometer coordinate system relative to the origin of the base coordinate system is calculated by homogeneous transformation. The second order derivative of this displacement is the acceleration of the origin to the accelerometer coordinate system. By means of the attitude relationship between the base coordinate system and the accelerometer coordinate system, the acceleration components on the three coordinate axes is obtained. Utilizing the Coriolis rotation coordinate theorem, the three components are also calculated. The homogeneous transtbrmation method and vector differential method lead to identical results.展开更多
This paper presents an automatic compensation algorithm for needle tip displacement in order to keep the needle tip always fixed at the skin entry point in the process of needle orientation in robot-assisted percutane...This paper presents an automatic compensation algorithm for needle tip displacement in order to keep the needle tip always fixed at the skin entry point in the process of needle orientation in robot-assisted percutaneous surgery. The algorithm, based on a two-degree-of-freedom （2-DOF） robot wrist （not the mechanically constrained remote center of motion （RCM） mechanism） and a 3-DOF robot ann, firstly calculates the needle tip displacement caused by rotational motion of robot wrist in the arm coordinate frame using the robotic forward kinematics, and then inversely compensates for the needle tip displace- ment by real-time Cartesian motion of robot arm. The algorithm achieves the function of the RCM and eliminates many mechanical and virtual constraints caused by the RCM mechanism. Experimental result demonstrates that the needle tip displacement is within 1 inm in the process of needle orientation.展开更多
For an electronic chart display and information system (ECDIS), the most important function is the route design. In this paper, a novel approach to developing ECDIS was given and then an effective method was proposed ...For an electronic chart display and information system (ECDIS), the most important function is the route design. In this paper, a novel approach to developing ECDIS was given and then an effective method was proposed for route design and automatic check. The mathematical model and logical relationship for coordinate transformation were also provided. They were adopted in ECDIS developing, which was based on the researeh of the Vxworks real-time operating system. The actual system application implies that the method is practical and can help navigation very well.展开更多
Light pen coordinate measuring system(LPCMS)is a kind of portable coordinate measuring technique based on vision metrology.In classical LPCMS,the measuring range is limited to the camera’s field of view.To overcome t...Light pen coordinate measuring system(LPCMS)is a kind of portable coordinate measuring technique based on vision metrology.In classical LPCMS,the measuring range is limited to the camera’s field of view.To overcome this defect,a new LPCMS is designed in this paper to fulfil whole space coordinate measurement.The camera is installed on a turntable instead of a tripod,so that the camera can rotate to track the movement of the light pen.The new system can be applied to large scale onsite measurement,and therefore it notably extends the application of LPCMS.To guarantee the accuracy of the new system,a method to calibrate the parameters of the tracking turntable is also proposed.Fixing the light pen at a stationary position,and changing the azimuth angles of the turntable’s two shafts,so that the camera can capture the images of the light pen from different view angles.According to the invariant spatial relationship between the camera and the pedestal of the tracking turntable,a system of nonlinear equations can be established to solve the parameters of the turntable.Experimental results show that the whole space coordinate measuring accuracy of the new system can reach 0.25 mm within 10 m.It can be concluded that the newly designed system can significantly expand the measuring range of LPCMS without losing too much accuracy.展开更多
This paper presents a flexible and high speed digital scan converter (DSC) with the ability to handle high frequency ultrasound imaging in real-time. The characteristics in imaging system such as focus length of trans...This paper presents a flexible and high speed digital scan converter (DSC) with the ability to handle high frequency ultrasound imaging in real-time. The characteristics in imaging system such as focus length of transducer, the swing radius and sampling length etc. could be changed easily in compliance with the researcher's application based on this flexible digital scan converter. Linear interpolation is employed to achieve the coordinate transformations algorithm. Custom-built software is programmed to preliminarily handle the algorithm according to different ultrasound imaging applications. High performance FPGA will implement high speed interpolation calculation based on the preliminary data which are stored in the DDR2 SDRAM from the software. 64 bit 66 MHz PCI is employed to accomplish high speed data transmission. Experiment has shown that more than 500 frame rate could be achieved based on this high speed digital scan converter. The designed flexible and high speed digital scan converter could be used in current FPGA based high frequency ultrasound imaging system.展开更多
The registration of point cloud is important for large object measurement.A measurement method for coordinate system transformation based on robot is proposed in this paper.Firstly,for obtaining extrinsic parameters,t...The registration of point cloud is important for large object measurement.A measurement method for coordinate system transformation based on robot is proposed in this paper.Firstly,for obtaining extrinsic parameters,the robot moves to three different positions to capture the images of three targets.Then the transformation matrix X between camera and tool center point(TCP) coordinate systems can be calculated by using the known parameters of robot and the extrinsic parameters,and finally the multi-view coordinate system can be transformed into robot coordinate system by the transformation matrix X.With the help of robot,the multi-view point cloud can be easily transformed into a unified coordinate system.By using robot,the measurement doesn't need any mark.Experimental results show that the method is effective.展开更多
The bifurcations of orbit flip homoclinic loop with nonhyperbolic equilibria are investigated. By constructing local coordinate systems near the unperturbed homoclinic orbit, Poincare maps for the new system are estab...The bifurcations of orbit flip homoclinic loop with nonhyperbolic equilibria are investigated. By constructing local coordinate systems near the unperturbed homoclinic orbit, Poincare maps for the new system are established. Then the existence of homoclinic orbit and the periodic orbit is studied for the system accompanied with transcritical bifurcation.展开更多
A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanc...A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanced AC loading. The unbalanced load is characterized in the d-q-0 rotating coordinate based on symmetrical sequence components. Also, the mathematical model of the load converter in both a-b-c and d-q-0 coordinates is derived by using the average large signal model. Then, two control strategies for the load converter are presented. The first one uses the conventional d-q-0 controller to ensure the voltage and current regulation. The second one is a newly proposed control strategy based on the decomposition of the voltage and current into in-stantaneous positive, negative, and zero sequences. These three sequences are controlled independently in their own reference frames as DC signals. The performance of the load converter using these two control strategies is compared. Simulation results show the validity and capability of the newly proposed control strategy.展开更多
文摘The displacement of the origin of the accelerometer coordinate system relative to the origin of the base coordinate system is calculated by homogeneous transformation. The second order derivative of this displacement is the acceleration of the origin to the accelerometer coordinate system. By means of the attitude relationship between the base coordinate system and the accelerometer coordinate system, the acceleration components on the three coordinate axes is obtained. Utilizing the Coriolis rotation coordinate theorem, the three components are also calculated. The homogeneous transtbrmation method and vector differential method lead to identical results.
文摘This paper presents an automatic compensation algorithm for needle tip displacement in order to keep the needle tip always fixed at the skin entry point in the process of needle orientation in robot-assisted percutaneous surgery. The algorithm, based on a two-degree-of-freedom （2-DOF） robot wrist （not the mechanically constrained remote center of motion （RCM） mechanism） and a 3-DOF robot ann, firstly calculates the needle tip displacement caused by rotational motion of robot wrist in the arm coordinate frame using the robotic forward kinematics, and then inversely compensates for the needle tip displace- ment by real-time Cartesian motion of robot arm. The algorithm achieves the function of the RCM and eliminates many mechanical and virtual constraints caused by the RCM mechanism. Experimental result demonstrates that the needle tip displacement is within 1 inm in the process of needle orientation.
文摘For an electronic chart display and information system (ECDIS), the most important function is the route design. In this paper, a novel approach to developing ECDIS was given and then an effective method was proposed for route design and automatic check. The mathematical model and logical relationship for coordinate transformation were also provided. They were adopted in ECDIS developing, which was based on the researeh of the Vxworks real-time operating system. The actual system application implies that the method is practical and can help navigation very well.
基金State Administration of Science,Technology and Industry for the National Defense(No.JSJL2014206B001)。
文摘Light pen coordinate measuring system(LPCMS)is a kind of portable coordinate measuring technique based on vision metrology.In classical LPCMS,the measuring range is limited to the camera’s field of view.To overcome this defect,a new LPCMS is designed in this paper to fulfil whole space coordinate measurement.The camera is installed on a turntable instead of a tripod,so that the camera can rotate to track the movement of the light pen.The new system can be applied to large scale onsite measurement,and therefore it notably extends the application of LPCMS.To guarantee the accuracy of the new system,a method to calibrate the parameters of the tracking turntable is also proposed.Fixing the light pen at a stationary position,and changing the azimuth angles of the turntable’s two shafts,so that the camera can capture the images of the light pen from different view angles.According to the invariant spatial relationship between the camera and the pedestal of the tracking turntable,a system of nonlinear equations can be established to solve the parameters of the turntable.Experimental results show that the whole space coordinate measuring accuracy of the new system can reach 0.25 mm within 10 m.It can be concluded that the newly designed system can significantly expand the measuring range of LPCMS without losing too much accuracy.
文摘This paper presents a flexible and high speed digital scan converter (DSC) with the ability to handle high frequency ultrasound imaging in real-time. The characteristics in imaging system such as focus length of transducer, the swing radius and sampling length etc. could be changed easily in compliance with the researcher's application based on this flexible digital scan converter. Linear interpolation is employed to achieve the coordinate transformations algorithm. Custom-built software is programmed to preliminarily handle the algorithm according to different ultrasound imaging applications. High performance FPGA will implement high speed interpolation calculation based on the preliminary data which are stored in the DDR2 SDRAM from the software. 64 bit 66 MHz PCI is employed to accomplish high speed data transmission. Experiment has shown that more than 500 frame rate could be achieved based on this high speed digital scan converter. The designed flexible and high speed digital scan converter could be used in current FPGA based high frequency ultrasound imaging system.
基金supported by the National Natural Science Foundation of China(Nos.60808020 and 61078041)the National Science and Technology Support Program(No.2014BAH03F01)+2 种基金the Tianjin Research Program of Application Foundation and Advanced Technology(No.10JCYBJC07200)the Tianjin Small and Medium Enterprise Innovation Fund(No.12ZXCXGX11800)the Technology Program of Tianjin Municipal Education Commission(No.20130324)
文摘The registration of point cloud is important for large object measurement.A measurement method for coordinate system transformation based on robot is proposed in this paper.Firstly,for obtaining extrinsic parameters,the robot moves to three different positions to capture the images of three targets.Then the transformation matrix X between camera and tool center point(TCP) coordinate systems can be calculated by using the known parameters of robot and the extrinsic parameters,and finally the multi-view coordinate system can be transformed into robot coordinate system by the transformation matrix X.With the help of robot,the multi-view point cloud can be easily transformed into a unified coordinate system.By using robot,the measurement doesn't need any mark.Experimental results show that the method is effective.
基金supported by the National Natural Science Foundation of China (No. 10801051)the Shanghai Leading Academic Discipline Project (No. B407)
文摘The bifurcations of orbit flip homoclinic loop with nonhyperbolic equilibria are investigated. By constructing local coordinate systems near the unperturbed homoclinic orbit, Poincare maps for the new system are established. Then the existence of homoclinic orbit and the periodic orbit is studied for the system accompanied with transcritical bifurcation.
文摘A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanced AC loading. The unbalanced load is characterized in the d-q-0 rotating coordinate based on symmetrical sequence components. Also, the mathematical model of the load converter in both a-b-c and d-q-0 coordinates is derived by using the average large signal model. Then, two control strategies for the load converter are presented. The first one uses the conventional d-q-0 controller to ensure the voltage and current regulation. The second one is a newly proposed control strategy based on the decomposition of the voltage and current into in-stantaneous positive, negative, and zero sequences. These three sequences are controlled independently in their own reference frames as DC signals. The performance of the load converter using these two control strategies is compared. Simulation results show the validity and capability of the newly proposed control strategy.
