Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197146
T. Kosugi, S. Katsura
In the field of teleoperations, visual or haptic information is utilized in order to obtain the situation at a remote side. Conventionally, various teleoperations have been constructed and are mainly based on visual information. However, tactile sensation which is important information when devices are in contact with environment is not able to be obtained with this approach. To tackle this problem, research on haptic transmission in the real-world by using a bilateral control has been attracting attention. For transmitting haptic information, a master-slave system should be constructed. As for the configuration, it does not always the same structure. From this point of view, teleoperation systems are classified into two types of systems. One is a fixed type system and the other is a mobile type system. Particularly, this paper focuses on the latter type system which has the characteristic that the synchronization must be attained between the different types of signals with regard to the dimension (e.g. between position and velocity) while the force transmission is also realized. In response to this requirement, a bilateral control with dimensional scaling on the basis of modal decomposition was proposed. However, the structures of controllers in the modal space have not been fully analyzed. Therefore, this paper clarifies the design procedure of the bilateral control with dimensional scaling taking into account the interference between the common and differential modes. Experimental results show the validity of the controller design.
{"title":"An approach to controller design of bilateral control with dimensional scaling","authors":"T. Kosugi, S. Katsura","doi":"10.1109/AMC.2012.6197146","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197146","url":null,"abstract":"In the field of teleoperations, visual or haptic information is utilized in order to obtain the situation at a remote side. Conventionally, various teleoperations have been constructed and are mainly based on visual information. However, tactile sensation which is important information when devices are in contact with environment is not able to be obtained with this approach. To tackle this problem, research on haptic transmission in the real-world by using a bilateral control has been attracting attention. For transmitting haptic information, a master-slave system should be constructed. As for the configuration, it does not always the same structure. From this point of view, teleoperation systems are classified into two types of systems. One is a fixed type system and the other is a mobile type system. Particularly, this paper focuses on the latter type system which has the characteristic that the synchronization must be attained between the different types of signals with regard to the dimension (e.g. between position and velocity) while the force transmission is also realized. In response to this requirement, a bilateral control with dimensional scaling on the basis of modal decomposition was proposed. However, the structures of controllers in the modal space have not been fully analyzed. Therefore, this paper clarifies the design procedure of the bilateral control with dimensional scaling taking into account the interference between the common and differential modes. Experimental results show the validity of the controller design.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"214 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74949853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197148
T. Shiraishi, H. Fujimoto
The purpose of this paper is development of high-precision trajectory tracking control for nonminimum-phase continuous-time systems with unstable zeros. This paper proposes a two degree of freedom control system design method that is based on a novel factorization method for nonminimum-phase continuous-time systems. First, nonminimum-phase continuous-time systems is factorized to minimum-phase system and zero-phase system in continuous-time domain. The feedforward controller is constructed from inverse system of each factorized system. The inverse system of the minimum-phase system is designed by multi-rate perfect model following control theory, and the inverse system of zero-phase system is designed by zero-phase FIR filter. Finally, This paper shows the effectiveness of proposed method by simulation and experimental results.
{"title":"Trajectory tracking control method based on zero-phase minimum-phase factorization for nonminimum-phase continuous-time system","authors":"T. Shiraishi, H. Fujimoto","doi":"10.1109/AMC.2012.6197148","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197148","url":null,"abstract":"The purpose of this paper is development of high-precision trajectory tracking control for nonminimum-phase continuous-time systems with unstable zeros. This paper proposes a two degree of freedom control system design method that is based on a novel factorization method for nonminimum-phase continuous-time systems. First, nonminimum-phase continuous-time systems is factorized to minimum-phase system and zero-phase system in continuous-time domain. The feedforward controller is constructed from inverse system of each factorized system. The inverse system of the minimum-phase system is designed by multi-rate perfect model following control theory, and the inverse system of zero-phase system is designed by zero-phase FIR filter. Finally, This paper shows the effectiveness of proposed method by simulation and experimental results.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"322 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73650573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197023
C. Mitsantisuk, M. Nandayapa, K. Ohishi, S. Katsura
In the robot systems and intelligent machines, the gear-box or mechanisms are connected with the motor to transmit the actuator torque to a distant joint. Generally, its elasticity causes resonance frequency in the system. By using the conventional PID controller, this method cannot perform well in this situation. Much research has proceeded with the aim of reducing vibration. A new effective control method, the resonance ratio control, has been introduced as a new way to guarantee the robustness and suppress the oscillation during task executions for a position and force control. In this paper, two techniques are proposed for improving the performance of resonance ratio control: 1) A new multi encoder based disturbance observer (MEDOB) is shown to estimate the disturbance force on the load side. The proposed observer is not necessary to identify the nominal spring coefficient. 2) A coefficient diagram method (CDM) has been applied to calculate a new gain controller. A new resonance ratio gain has been presented as 2. The effectiveness of the method is verified by simulation and experimental results.
{"title":"Resonance ratio control based on coefficient diagram method for force control of flexible robot system","authors":"C. Mitsantisuk, M. Nandayapa, K. Ohishi, S. Katsura","doi":"10.1109/AMC.2012.6197023","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197023","url":null,"abstract":"In the robot systems and intelligent machines, the gear-box or mechanisms are connected with the motor to transmit the actuator torque to a distant joint. Generally, its elasticity causes resonance frequency in the system. By using the conventional PID controller, this method cannot perform well in this situation. Much research has proceeded with the aim of reducing vibration. A new effective control method, the resonance ratio control, has been introduced as a new way to guarantee the robustness and suppress the oscillation during task executions for a position and force control. In this paper, two techniques are proposed for improving the performance of resonance ratio control: 1) A new multi encoder based disturbance observer (MEDOB) is shown to estimate the disturbance force on the load side. The proposed observer is not necessary to identify the nominal spring coefficient. 2) A coefficient diagram method (CDM) has been applied to calculate a new gain controller. A new resonance ratio gain has been presented as 2. The effectiveness of the method is verified by simulation and experimental results.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"9 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88717557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197053
K. Maeda, H. Fujimoto, Y. Hori
In this paper, a four-wheel driving force distribution method based on driving force control is proposed. Driving force control is a traction control method, previously proposed by the authors' research group, which generate appropriate driving force based on the acceleration pedal. However, this control method can not completely prevent reduction of driving force when a vehicle runs on an extremely slippery road. If the length of a slippery surface is shorter than the vehicle's wheel base, the total driving force is retained by distributing the shortage of driving force to the wheels that still have traction. On the other hand, when either the left or right side runs on a slippery surface, yaw-moment is suppressed by setting total driving forces of left and right wheels to be the same. Therefore, four-wheel driving force distribution method is proposed for retaining driving force on instantaneous slippery roads, and suppressing yaw-moment on split ones. The effectiveness of the proposed distribution method is verified by simulations and experiments.
{"title":"Four-wheel driving-force distribution method for instantaneous or split slippery roads for electric vehicle with in-wheel motors","authors":"K. Maeda, H. Fujimoto, Y. Hori","doi":"10.1109/AMC.2012.6197053","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197053","url":null,"abstract":"In this paper, a four-wheel driving force distribution method based on driving force control is proposed. Driving force control is a traction control method, previously proposed by the authors' research group, which generate appropriate driving force based on the acceleration pedal. However, this control method can not completely prevent reduction of driving force when a vehicle runs on an extremely slippery road. If the length of a slippery surface is shorter than the vehicle's wheel base, the total driving force is retained by distributing the shortage of driving force to the wheels that still have traction. On the other hand, when either the left or right side runs on a slippery surface, yaw-moment is suppressed by setting total driving forces of left and right wheels to be the same. Therefore, four-wheel driving force distribution method is proposed for retaining driving force on instantaneous slippery roads, and suppressing yaw-moment on split ones. The effectiveness of the proposed distribution method is verified by simulations and experiments.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"12 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86604343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197111
Kazuaki Ito, Yuichi Katsuki, Wataru Maebashi, M. Iwasaki
This paper presents a feedback controller design approach of a ball screw-driven table system in the microscopic displacement region. Since friction behaves as a nonlinear spring in the microscopic displacement region, while it behaves as Coulomb and a viscous friction in the coarse displacement region, frequency characteristics of the system vary depending on the above regions. In this paper, the stability condition in the microscopic displacement region is clarified, and the appropriate parameters of the feedback controller are obtained. The effectiveness of the proposed control approach has been verified using a prototype of a ball screw-driven table system.
{"title":"Feedback controller design considering plant dynamics of table drive system in microscopic displacement region","authors":"Kazuaki Ito, Yuichi Katsuki, Wataru Maebashi, M. Iwasaki","doi":"10.1109/AMC.2012.6197111","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197111","url":null,"abstract":"This paper presents a feedback controller design approach of a ball screw-driven table system in the microscopic displacement region. Since friction behaves as a nonlinear spring in the microscopic displacement region, while it behaves as Coulomb and a viscous friction in the coarse displacement region, frequency characteristics of the system vary depending on the above regions. In this paper, the stability condition in the microscopic displacement region is clarified, and the appropriate parameters of the feedback controller are obtained. The effectiveness of the proposed control approach has been verified using a prototype of a ball screw-driven table system.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"5 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90539837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197059
Shunsuke Yajima, W. Yamanouchi, S. Katsura
This paper proposes a novel dimensional scaling bilateral control for mobile-hapto. The dimensional scaling bilateral control realizes force feedback between the master and the slave with different motion areas. By this system, an operator can manipulate velocity of the slave, and feel reaction force at the slave. For realizing this system, force and position responses of the master and the slave are transformed to a modal space. And force and position controllers are constructed in the modal space. In the conventional method, however, a precise bilateral controller is not achieved because the dynamics in the modal space is not considered. Therefore, in this paper, the dynamic behaviors in the modal space is described, and a decoupling control system with the disturbance observer in the modal space is realized by the proposed method. Finally, the validity of the proposal is verified by simulation and experimental results.
{"title":"A novel dimensional scaling bilateral control for realization of mobile-hapto","authors":"Shunsuke Yajima, W. Yamanouchi, S. Katsura","doi":"10.1109/AMC.2012.6197059","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197059","url":null,"abstract":"This paper proposes a novel dimensional scaling bilateral control for mobile-hapto. The dimensional scaling bilateral control realizes force feedback between the master and the slave with different motion areas. By this system, an operator can manipulate velocity of the slave, and feel reaction force at the slave. For realizing this system, force and position responses of the master and the slave are transformed to a modal space. And force and position controllers are constructed in the modal space. In the conventional method, however, a precise bilateral controller is not achieved because the dynamics in the modal space is not considered. Therefore, in this paper, the dynamic behaviors in the modal space is described, and a decoupling control system with the disturbance observer in the modal space is realized by the proposed method. Finally, the validity of the proposal is verified by simulation and experimental results.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"61 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90219730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197035
Eray A. Baran, A. Sabanoviç
This paper presents an analytical approach for the prediction of future motion to be used in input delay compensation of time-delayed motion control systems. The method makes use of the current and previous input values given to a nominally behaving system in order to realize the prediction of the future motion of that system. The generation of the future input is made through an integration which is realized in discrete time setting. Once the future input signal is created, it is used as the reference input of the remote system to enforce an input time delayed system, conduct a delay-free motion. Following the theoretical formulation, the proposed method is tested in experiments and the validity of the approach is verified.
{"title":"Predictive input delay compensation for motion control systems","authors":"Eray A. Baran, A. Sabanoviç","doi":"10.1109/AMC.2012.6197035","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197035","url":null,"abstract":"This paper presents an analytical approach for the prediction of future motion to be used in input delay compensation of time-delayed motion control systems. The method makes use of the current and previous input values given to a nominally behaving system in order to realize the prediction of the future motion of that system. The generation of the future input is made through an integration which is realized in discrete time setting. Once the future input signal is created, it is used as the reference input of the remote system to enforce an input time delayed system, conduct a delay-free motion. Following the theoretical formulation, the proposed method is tested in experiments and the validity of the approach is verified.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"29 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84232675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197141
Merve Acer, A. Sabanoviç
The position control of designed 3 PRR flexure based mechanism is examined in this paper. The aims of the work are to eliminate the parasitic motions of the stage, misalignments of the actuators, errors of manufacturing and hysteresis of the system by having a redundant mechanism with the implementation of a sliding mode control and a disturbance observe. x-y motion of the end-effector is measured by using a laser position sensor and the necessary references for the piezoelectric actuators are calculated using the pseudo inverse of the transformation matrix coming from the experimentally determined kinematics of the mechanism. The effect of the observer and closed loop control is presented by comparing the results with open loop control. The system is designed to be redundant to enhance the position control. In order to see the effects of the redundant system firstly the closed loop control for active 2 piezoelectric actuators experiments then for active 3 piezoelectric actuators experiments are presented. As a result, our redundant mechanism tracks the desired trajectory accurately and its workspace is bigger.
{"title":"Sliding-mode control of a flexure based mechanism using piezoelectric actuators","authors":"Merve Acer, A. Sabanoviç","doi":"10.1109/AMC.2012.6197141","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197141","url":null,"abstract":"The position control of designed 3 PRR flexure based mechanism is examined in this paper. The aims of the work are to eliminate the parasitic motions of the stage, misalignments of the actuators, errors of manufacturing and hysteresis of the system by having a redundant mechanism with the implementation of a sliding mode control and a disturbance observe. x-y motion of the end-effector is measured by using a laser position sensor and the necessary references for the piezoelectric actuators are calculated using the pseudo inverse of the transformation matrix coming from the experimentally determined kinematics of the mechanism. The effect of the observer and closed loop control is presented by comparing the results with open loop control. The system is designed to be redundant to enhance the position control. In order to see the effects of the redundant system firstly the closed loop control for active 2 piezoelectric actuators experiments then for active 3 piezoelectric actuators experiments are presented. As a result, our redundant mechanism tracks the desired trajectory accurately and its workspace is bigger.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"16 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83473400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197097
N. Oda, N. Fujinaga
The paper presents an approach to the posture control of redundant manipulator by using visual feedback. The redundant degrees-of-freedom enables several dexterous motion according to environmental information such as obstacle avoidance. In the paper, the hybrid motion controller including both the posture controller by visual feedback and the end-effector motion controller by using encoder signal is proposed. In the posture controller, the manipulator pose is estimated by particle filter from visual information. That means the posture control is completely realized only by vision sensor signal in our approach. The control model for obstacle avoidance in null space is also proposed by using the optical flow field which is detected by vision. The validity is evaluated by several experimental results.
{"title":"Visual posture estimation and control for redundant manipulator","authors":"N. Oda, N. Fujinaga","doi":"10.1109/AMC.2012.6197097","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197097","url":null,"abstract":"The paper presents an approach to the posture control of redundant manipulator by using visual feedback. The redundant degrees-of-freedom enables several dexterous motion according to environmental information such as obstacle avoidance. In the paper, the hybrid motion controller including both the posture controller by visual feedback and the end-effector motion controller by using encoder signal is proposed. In the posture controller, the manipulator pose is estimated by particle filter from visual information. That means the posture control is completely realized only by vision sensor signal in our approach. The control model for obstacle avoidance in null space is also proposed by using the optical flow field which is detected by vision. The validity is evaluated by several experimental results.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"25 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75470644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-03-25DOI: 10.1109/AMC.2012.6197127
T. Nozaki, T. Mizoguchi, K. Ohnishi
A four channel bilateral control is one of the teleoperation techniques. In this control, position control system and force control system should be decoupled precisely. However, there is some interference between position control and force control, if the inertia of the master robot is different from slave side. In this paper, a diagonalization method using modal space observer is proposed for the sake of decoupling position control from force control. This method diagonalizes an equivalent mass matrix in a modal space, which is called task mass matrix. Operationality and reproducibility, which are performance indices, are indicated. Furthermore, root locus plots are shown to analyze the stability. The validity of the proposed method is verified by experiments. In other words, the decoupling effect of the diagonalization method is higher than conventional method, and more stable.
{"title":"Position/force decoupling for micro-macro bilateral control based on modal space disturbance observer","authors":"T. Nozaki, T. Mizoguchi, K. Ohnishi","doi":"10.1109/AMC.2012.6197127","DOIUrl":"https://doi.org/10.1109/AMC.2012.6197127","url":null,"abstract":"A four channel bilateral control is one of the teleoperation techniques. In this control, position control system and force control system should be decoupled precisely. However, there is some interference between position control and force control, if the inertia of the master robot is different from slave side. In this paper, a diagonalization method using modal space observer is proposed for the sake of decoupling position control from force control. This method diagonalizes an equivalent mass matrix in a modal space, which is called task mass matrix. Operationality and reproducibility, which are performance indices, are indicated. Furthermore, root locus plots are shown to analyze the stability. The validity of the proposed method is verified by experiments. In other words, the decoupling effect of the diagonalization method is higher than conventional method, and more stable.","PeriodicalId":6439,"journal":{"name":"2012 12th IEEE International Workshop on Advanced Motion Control (AMC)","volume":"4 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2012-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72548184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：