We report a multipass cell (MPC) that consists of two inexpensive silver (or gold)-coated plane mirrors and a biconvex lens instead of expensive concave spherical mirrors. The silver (or gold)-coated two plane mirrors are separated by a biconvex lens with an inner hole for the detection of the gas flow. The two mirrors (diameter of 50.8 mm) and the convex lens (diameter of 50.8 mm) are mounted on an optical board with a dimension of 75 mm * 75 mm * 30 mm and 75 mm * 75 mm * 21 mm, and the inner diameter of the two quartz glass tubes is 48 mm with a hole for the detection of the gas in flow and out flow. For example, the plane MPC, which is ∼236 cm3 with 130 times reflections, is much smaller than a traditional concave spherical mirror based on a Herriott or a White MPC, which is ∼700 cm3 with 80 times reflections, and offers an effective optical path-length of about 31.32 m. This low cost, compact MPC is very suitable for various applications, such as climate change, environmental monitoring, and agriculture.
In order to compensate the measurement errors of the on-machine measurement system caused by the XY worktable error accurately under the influence of multiple factors, the structural characteristics of the XY worktable are analyzed in detail. The dynamic positioning error model of the XY worktable motion components such as the grating measurement systems, the ball screw assemblies, the guide rail system manufacturing errors and the friction forces under the influence of the above factors are established, and the theoretical model of the dynamic positioning error of the XY worktable is derived. It can be seen from the analysis process that the main factors affecting the dynamic positioning error are the movement speed of the worktable, the weight of the workpiece to be measured, the installation position of the workpiece and the friction force. The actual model parameters are substituted into the theoretical model to calculate the dynamic positioning error of the worktable under different influencing factors by using the technical indicators of the experimental platform. From the analysis of calculation results, it can be seen that the dynamic positioning error is the smallest when the moving speed of the worktable is 12 mm/s, and this velocity is defined as the best measuring speed，which lays a good theoretical foundation for improving the dynamic machining accuracy of machine tools and the measurement accuracy of on-line measurement system.
In order to reduce the additional influence of the thermal-force coupling deformation of the Computerized Numerical Control(CNC)machine tools bed based on the grating measurement, the concept of the thermal-force coupling deformation critical point in the direction of the grating installation line of the machine bed is proposed. In order to accurately determine the thermal-force coupling deformation critical point of the machine bed, the BV75 CNC machine tool is taken as an example. The factors that cause the deformation of CNC machine bed are analyzed by using material theory, thermos-elastic and nonlinear thermal deformation theory. According to the actual structure size of the machine tool ,a 3D model is established. The heat sources and load conditions of the machine bed deformation are theoretically analyzed, and the finite element thermal- force coupling analysis of worktable is carried out. The deformation critical point in the direction of grating installation line of machine tool bed is determined by theoretical modeling and finite element analysis. Under loading single heat source, the multi heat sources and the different size and position load, the comparison experiments of the thermal deformation of the machine bed and the zero shift errors of the grating measurement are carried out. The experimental results show that the bed thermal deformation is the main source of the grating additional error, and the workpiece loading position will cause the bed deformation. The position of thermal-force coupling deformation critical point is different from the thermal deformation critical point. The zero position and the indication error of the grating can be reduced by fixing the grating on the thermal-force coupling deformation. An accurate grating error prediction compensation model can be established, which is use for the subsequent error compensation of the on-machine measurement system of the CNC machine tools.
The signal quality of traveling wave and the measurement accuracy of parasitic time grating can be improved by optimiz ing its structure. This optimization process can be guided through building the electrical traveling wave equation with respect to the structure and the traveling wave signal generation principle. Based on Ansoft Maxwell simulation, the important electromagnetic parameters and the main uncertainty sources were analyzed and determined respectively. In the simulation parameters such as the excitation signal frequency, the gap width, the relative area of the probe, the coils number, the excitation signal amplitude and the core length were set to different values. It can be seen from the simulation results that excitation signal frequency, the gap width, the relative area between the probe and the rotor are the major factors to influence the angular measuring accuracy of parasitic time grating sensor. Meanwhile, the coils number, the excitation signal amplitude and the core length are the secondary factors. The analysis result can be utilized to optimize the structure of parasitic time grating and correct measurement error.
In order to develop micro-nano probe having error self-correcting function and good rigidity structure, a new micro-nano probe system was developed based on six-dimensional micro-force measuring principle. The structure and working principle of the probe was introduced in detail. The static nonlinear decoupling method was established with BP neural network to do the static decoupling for the dimension coupling existing in each direction force measurements. The optimal parameters of BP neural network were selected and the decoupling simulation experiments were done. The maximum probe coupling rate after decoupling is 0.039% in X direction, 0.025% in Y direction and 0.027% in Z direction. The static measurement sensitivity of the probe can reach 10.76με / mN in Z direction and 14.55με / mN in X and Y direction. The modal analysis and harmonic response analysis under three dimensional harmonic load of the probe were done by using finite element method. The natural frequencies under different vibration modes were obtained and the working frequency of the probe was determined，which is higher than 10000 Hz . The transient response analysis of the probe was done, which indicates that the response time of the probe can reach 0.4 ms. From the above results, it is shown that the developed micro-nano probe meets triggering requirements of micro-nano probe. Three dimension measuring force can be measured precisely by the developed probe, which can be used to predict and correct the force deformation error and the touch error of the measuring ball and the measuring rod.
The impact of high pressure water-jet on the different materials target will produce different reflective mixed sound. In
order to reconstruct the reflective sound signals distribution on the linear detecting line accurately and to separate the
environment noise effectively, the mixed sound signals acquired by linear mike array were processed by ICA. The basic
principle of ICA and algorithm of FASTICA were described in detail. The emulation experiment was designed. The
environment noise signal was simulated by using band-limited white noise and the reflective sound signal was simulated
by using pulse signal. The reflective sound signal attenuation produced by the different distance transmission was
simulated by weighting the sound signal with different contingencies. The mixed sound signals acquired by linear mike
array were synthesized by using the above simulated signals and were whitened and separated by ICA. The final results
verified that the environment noise separation and the reconstruction of the detecting-line sound distribution can be
The reasons why the coordinate measuring machine (CMM) dynamic error exists are complicate. And there are many elements which influence the error. So it is hard to build an accurate model. For the sake of attaining a model which not only avoided analyzing complex error sources and the interactions among them, but also solved the multiple colinearity among the variables. This paper adopted the Partial Least-Squares Regression (PLSR) to build model. The model takes 3D coordinates (X, Y, Z) and the moving velocity as the independent variable and takes the CMM dynamic error value as the dependent variable. The experimental results show that the model can be easily explained. At the same time the results show the magnitude and direction of the independent variable influencing the dependent variable.
The dynamic error sources of CMM were analyzed and the character of the dynamic error data was investigated in this
paper. Based on the character, the dynamic error model of CMM was built by using Bayesian statistical principle
combined with the standard quantity interposition method. The specific error model building procedures was deduced.
The CMM dynamic error separating and contrasting experimental devices were designed by using the laser
interferometer and the measuring block group. The theoretical analysis and the experiment result indicate that all
influences of the CMM dynamic error sources is considered in the model building method by using Bayesian statistical
principle combined with the standard values interposition method which meets the CMM working condition. The error
model accuracy reaches 2.4 μm and meets the CMM demand. The needed error data size is greatly reduced by using the
dynamic error model building method. The error separating principle by lapping-in the measuring block group is simple,
which is implemented easily and meets the timing dynamic error correcting needs of the ordinary CMM user.
The designing principle's analysis and the structure design using modern accuracy design concept of nanometer two dimension working table are introduced. The source of the uncertainty is overall analyzed. The error separating and correcting method is designed. The influence on the measurement result of the autocollimator and the interferometer produced by the angle error of the orthogonal prism is analyzed on principle. The preview experiments are done. The results indicate that the light path deflection using orthogonal prism has no influence on the error separating result, but without absolute zero position has obvious influence on the error separating result. The error correcting result shows that the precision demand of nanometer two-dimensional working table can be met.