针对现有PLC实验教学中存在的一些问题,以模块化生产加工实训系统(Modular Production System即MPS)中4个典型工位为原型,依托虚拟现实技术开发了一个仿真教学平台;平台包括上位机、下位机以及通讯模块,下位机通过三维建模、通讯数据解...针对现有PLC实验教学中存在的一些问题,以模块化生产加工实训系统(Modular Production System即MPS)中4个典型工位为原型,依托虚拟现实技术开发了一个仿真教学平台;平台包括上位机、下位机以及通讯模块,下位机通过三维建模、通讯数据解析以及Unity3D交互设计开发,上位机为PLC编程端,可编程控制下位机,上位机和下位机之间通过通讯模块连接;经测试,上述仿真教学平台可以利用PLC对虚拟环境中的工艺对象实施控制策略,从而替代实训设备进行PLC实训教学,对实际的自动化生产线规划也有一定的参考价值。展开更多
On-orbit spacecraft face many threats,such as collisions with debris or other spacecraft.Therefore,perception of the surrounding space environment is vitally important for on-orbit spacecraft.Spacecraft require a dyna...On-orbit spacecraft face many threats,such as collisions with debris or other spacecraft.Therefore,perception of the surrounding space environment is vitally important for on-orbit spacecraft.Spacecraft require a dynamic attitude tracking ability with high precision for such missions.This paper aims to address the above problem using an improved backstepping controller.The tracking mission is divided into two phases:coarse alignment and fine alignment.In the first phase,a traditional saturation controller is utilized to limit the maximum attitude angular velocity according to the actuator’s ability.For the second phase,the proposed backstepping controller with different virtual control inputs is applied to track the moving target.To fulfill the high precision attitude tracking requirements,a hybrid attitude control actuator consisting of a Control Moment Gyro(CMG)and Reaction Wheel(RW)is constructed,which can simultaneously avoid the CMG singularity and RW saturation through the use of an angular momentum optimal management strategy,such as null motion.Finally,five simulation scenarios were carried out to demonstrate the effectiveness of the proposed control strategy and hybrid actuator.展开更多
Background Laparoscopic surgery is a surgical technique in which special instruments are inserted through small incision holes inside the body.For some time,efforts have been made to improve surgical pre training thro...Background Laparoscopic surgery is a surgical technique in which special instruments are inserted through small incision holes inside the body.For some time,efforts have been made to improve surgical pre training through practical exercises on abstracted and reduced models.Methods The authors strive for a portable,easy to use and cost-effective Virtual Reality-based(VR)laparoscopic pre-training platform and therefore address the question of how such a system has to be designed to achieve the quality of today's gold standard using real tissue specimens.Current VR controllers are limited regarding haptic feedback.Since haptic feedback is necessary or at least beneficial for laparoscopic surgery training,the platform to be developed consists of a newly designed prototype laparoscopic VR controller with haptic feedback,a commercially available head-mounted display,a VR environment for simulating a laparoscopic surgery,and a training concept.Results To take full advantage of benefits such as repeatability and cost-effectiveness of VR-based training,the system shall not require a tissue sample for haptic feedback.It is currently calculated and visually displayed to the user in the VR environment.On the prototype controller,a first axis was provided with perceptible feedback for test purposes.Two of the prototype VR controllers can be combined to simulate a typical both-handed use case,e.g.,laparoscopic suturing.A Unity based VR prototype allows the execution of simple standard pre-trainings.Conclusions The first prototype enables full operation of a virtual laparoscopic instrument in VR.In addition,the simulation can compute simple interaction forces.Major challenges lie in a realistic real-time tissue simulation and calculation of forces for the haptic feedback.Mechanical weaknesses were identified in the first hardware prototype,which will be improved in subsequent versions.All degrees of freedom of the controller are to be provided with haptic feedback.To make forces tangible in the simulation,characteristic values 展开更多
Wind energy systems (WESs) based on doubly-fed induction generators (DFIGs) have enormous potential for meeting the future demands related to clean energy. Due to the low inertia and intermittency of power injection, ...Wind energy systems (WESs) based on doubly-fed induction generators (DFIGs) have enormous potential for meeting the future demands related to clean energy. Due to the low inertia and intermittency of power injection, a WES is equipped with a virtual inertial controller (VIC) to support the system during a frequency deviation event. The frequency deviation measured by a phase locked loop (PLL) installed on a point of common coupling (PCC) bus is the input signal to the VIC. However, a VIC with an improper inertial gain could deteriorate the damping of the power system, which may lead to instability. To address this issue, a mathematical formulation for calculating the synchronizing and damping torque coefficients of a WES-integrated single-machine infinite bus (SMIB) system while considering PLL and VIC dynamics is proposed in this paper. In addition, a power system stabilizer (PSS) is designed for wind energy integrated power systems to enhance electromechanical oscillation damping. A small-signal stability assessment is performed using the infinite bus connected to a synchronous generator of higher-order dynamics integrated with a VIC-equipped WES. Finally, the performance and robustness of the proposed PSS is demonstrated through time-domain simulation in SMIB and nine-bus test systems integrated with WES under several case studies.展开更多
As the latest research direction of train-to-train communication,virtual coupling train formation technology has attracted the attention of many scholars.This paper studies the influence of time delay on the formation...As the latest research direction of train-to-train communication,virtual coupling train formation technology has attracted the attention of many scholars.This paper studies the influence of time delay on the formation of virtual coupled trains.We proposed a distributed PID controller,which means that trains can still form a stable fleet operation under the influence of communication delay and control delay.After modelling and analysis,the research uses Matlab to conduct simulation,involving two sets of experiments.Factors including speed,acceleration,position,position error,expected distance between adjacent trains and actual distance between adjacent trains are simulated.The results demonstrate that the distributed PID controller can effectively control the impact of time delay on the virtual coupling fleet.展开更多
Doubly-fed induction generator(DFIG)-based wind farms(WFs)are interfaced with power electronic converters.Such interfaces are attributed to the low inertia generated in the WFs under high penetration and that becomes ...Doubly-fed induction generator(DFIG)-based wind farms(WFs)are interfaced with power electronic converters.Such interfaces are attributed to the low inertia generated in the WFs under high penetration and that becomes prevalent in a fault scenario.Therefore,transient stability enhancement along with frequency stability in DFIG-based WFs is a major concern in the present scenario.In this paper,a cooperative approach consisting of virtual inertia control(VIC)and a modified grid-side converter(GSC)approach for low voltage ride-through(LVRT)is proposed to achieve fault ride-through(FRT)capabilities as per the grid code requirements(GCRs)while providing frequency support to the grid through a synthetic inertia.The proposed approach provides LVRT and reactive power compensation in the system.The participation of the VIC in a rotor-side converter(RSC)provides frequency support to the DFIG-based WFs.The combined approach supports active power compensation and provides sufficient kinetic energy support to the system in a contingency scenario.Simulation studies are carried out in MATLAB/Simulink environment for symmetrical and unsymmetrical faults.The superiority of the proposed scheme is demonstrated through analysis of the performance of the scheme and that of a series resonance bridge-type fault current limiter(SR-BFCL).展开更多
文摘针对现有PLC实验教学中存在的一些问题,以模块化生产加工实训系统(Modular Production System即MPS)中4个典型工位为原型,依托虚拟现实技术开发了一个仿真教学平台;平台包括上位机、下位机以及通讯模块,下位机通过三维建模、通讯数据解析以及Unity3D交互设计开发,上位机为PLC编程端,可编程控制下位机,上位机和下位机之间通过通讯模块连接;经测试,上述仿真教学平台可以利用PLC对虚拟环境中的工艺对象实施控制策略,从而替代实训设备进行PLC实训教学,对实际的自动化生产线规划也有一定的参考价值。
基金the support provided by the National Natural Science Foundation of China(No.61973153)the National Key Research and Development Plan of China(No.2016YFB0500901)the Open Fund of the National Defense Key Discipline Laboratory of Micro-Spacecraft Technology of China(No.HIT.KLOF.MST.201705)
文摘On-orbit spacecraft face many threats,such as collisions with debris or other spacecraft.Therefore,perception of the surrounding space environment is vitally important for on-orbit spacecraft.Spacecraft require a dynamic attitude tracking ability with high precision for such missions.This paper aims to address the above problem using an improved backstepping controller.The tracking mission is divided into two phases:coarse alignment and fine alignment.In the first phase,a traditional saturation controller is utilized to limit the maximum attitude angular velocity according to the actuator’s ability.For the second phase,the proposed backstepping controller with different virtual control inputs is applied to track the moving target.To fulfill the high precision attitude tracking requirements,a hybrid attitude control actuator consisting of a Control Moment Gyro(CMG)and Reaction Wheel(RW)is constructed,which can simultaneously avoid the CMG singularity and RW saturation through the use of an angular momentum optimal management strategy,such as null motion.Finally,five simulation scenarios were carried out to demonstrate the effectiveness of the proposed control strategy and hybrid actuator.
文摘Background Laparoscopic surgery is a surgical technique in which special instruments are inserted through small incision holes inside the body.For some time,efforts have been made to improve surgical pre training through practical exercises on abstracted and reduced models.Methods The authors strive for a portable,easy to use and cost-effective Virtual Reality-based(VR)laparoscopic pre-training platform and therefore address the question of how such a system has to be designed to achieve the quality of today's gold standard using real tissue specimens.Current VR controllers are limited regarding haptic feedback.Since haptic feedback is necessary or at least beneficial for laparoscopic surgery training,the platform to be developed consists of a newly designed prototype laparoscopic VR controller with haptic feedback,a commercially available head-mounted display,a VR environment for simulating a laparoscopic surgery,and a training concept.Results To take full advantage of benefits such as repeatability and cost-effectiveness of VR-based training,the system shall not require a tissue sample for haptic feedback.It is currently calculated and visually displayed to the user in the VR environment.On the prototype controller,a first axis was provided with perceptible feedback for test purposes.Two of the prototype VR controllers can be combined to simulate a typical both-handed use case,e.g.,laparoscopic suturing.A Unity based VR prototype allows the execution of simple standard pre-trainings.Conclusions The first prototype enables full operation of a virtual laparoscopic instrument in VR.In addition,the simulation can compute simple interaction forces.Major challenges lie in a realistic real-time tissue simulation and calculation of forces for the haptic feedback.Mechanical weaknesses were identified in the first hardware prototype,which will be improved in subsequent versions.All degrees of freedom of the controller are to be provided with haptic feedback.To make forces tangible in the simulation,characteristic values
文摘Wind energy systems (WESs) based on doubly-fed induction generators (DFIGs) have enormous potential for meeting the future demands related to clean energy. Due to the low inertia and intermittency of power injection, a WES is equipped with a virtual inertial controller (VIC) to support the system during a frequency deviation event. The frequency deviation measured by a phase locked loop (PLL) installed on a point of common coupling (PCC) bus is the input signal to the VIC. However, a VIC with an improper inertial gain could deteriorate the damping of the power system, which may lead to instability. To address this issue, a mathematical formulation for calculating the synchronizing and damping torque coefficients of a WES-integrated single-machine infinite bus (SMIB) system while considering PLL and VIC dynamics is proposed in this paper. In addition, a power system stabilizer (PSS) is designed for wind energy integrated power systems to enhance electromechanical oscillation damping. A small-signal stability assessment is performed using the infinite bus connected to a synchronous generator of higher-order dynamics integrated with a VIC-equipped WES. Finally, the performance and robustness of the proposed PSS is demonstrated through time-domain simulation in SMIB and nine-bus test systems integrated with WES under several case studies.
文摘As the latest research direction of train-to-train communication,virtual coupling train formation technology has attracted the attention of many scholars.This paper studies the influence of time delay on the formation of virtual coupled trains.We proposed a distributed PID controller,which means that trains can still form a stable fleet operation under the influence of communication delay and control delay.After modelling and analysis,the research uses Matlab to conduct simulation,involving two sets of experiments.Factors including speed,acceleration,position,position error,expected distance between adjacent trains and actual distance between adjacent trains are simulated.The results demonstrate that the distributed PID controller can effectively control the impact of time delay on the virtual coupling fleet.
文摘Doubly-fed induction generator(DFIG)-based wind farms(WFs)are interfaced with power electronic converters.Such interfaces are attributed to the low inertia generated in the WFs under high penetration and that becomes prevalent in a fault scenario.Therefore,transient stability enhancement along with frequency stability in DFIG-based WFs is a major concern in the present scenario.In this paper,a cooperative approach consisting of virtual inertia control(VIC)and a modified grid-side converter(GSC)approach for low voltage ride-through(LVRT)is proposed to achieve fault ride-through(FRT)capabilities as per the grid code requirements(GCRs)while providing frequency support to the grid through a synthetic inertia.The proposed approach provides LVRT and reactive power compensation in the system.The participation of the VIC in a rotor-side converter(RSC)provides frequency support to the DFIG-based WFs.The combined approach supports active power compensation and provides sufficient kinetic energy support to the system in a contingency scenario.Simulation studies are carried out in MATLAB/Simulink environment for symmetrical and unsymmetrical faults.The superiority of the proposed scheme is demonstrated through analysis of the performance of the scheme and that of a series resonance bridge-type fault current limiter(SR-BFCL).
