Based upon the standard deviations for the intercept and the slope of a linear regression line, as well as by differentiating both Beer＇s law and a linear relationship between transmittance and concentration at high ...Based upon the standard deviations for the intercept and the slope of a linear regression line, as well as by differentiating both Beer＇s law and a linear relationship between transmittance and concentration at high transmission, it is proved that the relative spectrophotometric error of a measurement becomes greater as the sample concentration only decreases. Further, it is demonstrated that the present knowledge with regard to the error in absorption spectrophotometry is necessary to be reexamined. The total scale of transmittance can literally be used for measurements, unfolding workable dynamic ranges about two orders of magnitude lower than usually and thus absorption spectrophotometry can efficiently compete with other methods of analysis with respect to detection limits.展开更多
Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to b...Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to be,especially when multi-exciters are used as actuators to precisely actuate large flexible structure.It is necessary to consider these effects to ensure the force generated by each exciter is the same as required.In this paper,a robust control method is proposed for the multi-input and multi-output(MIMO)structural vibration control system to trace the target actuating force of each exciter.A special signal is designed and put into the coupled mul-ti-exciter-structure system,and the input and output signals of the system are used to build a dynamic model involving both the dynamical characters of the exciters and the structure using the subspace identification method.Considering the uncertainty factors of the multi-exciter/structure system,an H-infinity robust controller is designed to decouple the coupling between structure and exciters based on the identified system model.A MIMO vibration control system combined with a flexible plate and three electromagnetic exciters is adopted to demonstrate the proposed method,both numerical simulation and model experiments showing that the output force of each exciter can trace its target force accurately within the requested frequency band.展开更多
文摘Based upon the standard deviations for the intercept and the slope of a linear regression line, as well as by differentiating both Beer＇s law and a linear relationship between transmittance and concentration at high transmission, it is proved that the relative spectrophotometric error of a measurement becomes greater as the sample concentration only decreases. Further, it is demonstrated that the present knowledge with regard to the error in absorption spectrophotometry is necessary to be reexamined. The total scale of transmittance can literally be used for measurements, unfolding workable dynamic ranges about two orders of magnitude lower than usually and thus absorption spectrophotometry can efficiently compete with other methods of analysis with respect to detection limits.
基金supported by the National Natural Science Foundation of China(Grant Nos.11072198,11102162)111 Project of China(Grant No.B07050)
文摘Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to be,especially when multi-exciters are used as actuators to precisely actuate large flexible structure.It is necessary to consider these effects to ensure the force generated by each exciter is the same as required.In this paper,a robust control method is proposed for the multi-input and multi-output(MIMO)structural vibration control system to trace the target actuating force of each exciter.A special signal is designed and put into the coupled mul-ti-exciter-structure system,and the input and output signals of the system are used to build a dynamic model involving both the dynamical characters of the exciters and the structure using the subspace identification method.Considering the uncertainty factors of the multi-exciter/structure system,an H-infinity robust controller is designed to decouple the coupling between structure and exciters based on the identified system model.A MIMO vibration control system combined with a flexible plate and three electromagnetic exciters is adopted to demonstrate the proposed method,both numerical simulation and model experiments showing that the output force of each exciter can trace its target force accurately within the requested frequency band.
