Abstract: A learning control system includes a movement trajectory generation unit, a learning control unit, a feedback control unit, and an uncertainty compensation unit. The movement trajectory generation unit includes a movement trajectory generator; the movement trajectory generator is configured to generate a reference movement trajectory; a position measured signal is subtracted from the reference movement trajectory to obtain a position error signal which is input to the learning control unit; the learning control unit is configured to generate a feed-forward signal which is added with the position error signal to obtain a corrected error signal; and the corrected error signal is input to the feedback control unit; the feedback control unit includes a feedback controller configured to generate a feedback control quantity which is input to the uncertainty compensation unit; and the uncertainty compensation unit is configured to generate the position measured signal.

Abstract: An air-coupled ultrasonic plane stress detection method for a composite material based on dual-modal sound-time ratios of a Lamb wave includes: S1: assembling a detection device; S2: based on the detection device and the dual-modal sound-time ratios of the Lamb wave in S1, using unidirectionally loaded stress to obtain different stress coefficient relations; S3: based on the stress coefficient relations in S2, solving stress coefficients; S4: based on the stress coefficients in S3, acquiring three sound-time ratios; S5: based on the sound-time ratios in S4, describing a stress state of a detection point; and S6: repeating S4 and S5 till completing detection and scanning. The method improves the accuracy of stress coefficient calibration and air-coupled ultrasonic stress representation of a composite material panel greatly.

Abstract: A learning control system includes a movement trajectory generation unit, a learning control unit, a feedback control unit, and an uncertainty compensation unit. The movement trajectory generation unit includes a movement trajectory generator; the movement trajectory generator is configured to generate a reference movement trajectory; a position measured signal is subtracted from the reference movement trajectory to obtain a position error signal which is input to the learning control unit; the learning control unit is configured to generate a feed-forward signal which is added with the position error signal to obtain a corrected error signal; and the corrected error signal is input to the feedback control unit; the feedback control unit includes a feedback controller configured to generate a feedback control quantity which is input to the uncertainty compensation unit; and the uncertainty compensation unit is configured to generate the position measured signal.

Abstract: The disclosure provides a method, system, device and medium for online monitoring of a plane stress field without baseline data based on a piezoelectric transducer array. Since Lamb waves have complex multi-mode characteristics, a suitable excitation frequency needs to be selected according to geometric dimensions of the structure to be measured, and then, only low-order mode Lamb waves are excited inside the measured structure to avoid serious waveform aliasing. For isotropic measured objects, anisotropic characteristics will be generated under the action of pre-stresses, that is, the propagation velocities of ultrasonic waves in all directions are different, but there is a linear relationship between velocity changes in different propagation directions and stresses. Therefore, there is still a linear relationship between the difference of velocity changes in different propagation directions and the stress.

Abstract: A method, system, device, and medium for online stress monitoring without baseline data based on single-mode multi-frequency signal fusion are provided.

Abstract: Provided is a large high-speed rotary equipment gap stacking assembly apparatus and assembly method based on digital twin, and relates to the technical field of engine assembly measurement. The disclosure solves the problem of unbalanced rotation of the rotary parts caused by large assembly error during multi-stage rotary parts are stacked in a gap way. The disclosure includes the assembly apparatus entity and the assembly method; the assembly apparatus entity is configured to establish data communication with the upper computer through data acquisition apparatus, and upper computer is configured to establish a virtual assembly model; the virtual assembly model and optimal coaxiality of the multi-stage rotary parts in gap stacking can be obtained according to the assembly method, and the assembly process can be controlled by using the virtual assembly model and the optimal coaxiality. The disclosure is suitable for controlling the assembly process of the rotary parts.

Abstract: The present disclosure proposes a non-baseline on-line stress monitoring system and monitoring method based on multi-mode Lamb wave data fusion. A Lamb wave dispersion curve is established according to geometric dimensions and material parameters of a measured object, a cut-off frequency of a first-order Lamb wave mode is obtained, an excitation frequency of a Lamb wave signal is determined, and then pure Lamb waves in S0 and A0 modes obtained inside the measured object are obtained; an acoustoelastic equation is established, an elastodynamic equation of the measured object under a prestress condition is solved, and linear relationships between a group velocity and a stress of the Lamb waves in the S0 and A0 modes under the excitation frequency are obtained; data is processed through the on-line monitoring system; a stress gradient in a depth direction is calculated, and finally, a stress state of the measured object is represented.

Abstract: A learning control system for a nano-precision motion stage comprises a closed-loop feedback section including a motion trajectory generator, a feedback controller, a motion stage, and a first Fourier transformer; and a feedforward section including a second Fourier transformer, a learning controller, an iteration backward shift operator, and a Fourier inverse transformer. An iteration experiment count j is initialized as j=1, and a j-th frequency domain feedforward signal is initialized to 0; the system is run to collect a frequency domain error signal and a frequency domain position measurement signal; a (j+1)-th frequency domain feedforward signal is updated; and an iteration experiment count j is incremented by 1. The present disclosure can effectively suppress the influence of external noise and disturbances, and improve convergence performance.

Abstract: The disclosure belongs to the technical field of precision test and measurement, and provides a two-dimensional photoelectric autocollimation method and device based on wavefront measurement and correction. According to the disclosure, a link of wavefront measurement and correction of a reference light path is added to a traditional autocollimator measuring method. By using wavefront distortion information of the reference light path in the instrument and driving a deformable mirror to compensate for phase distortion of a beam, the link realizes measurement and control on aberration of the optical system of the autocollimator and improves the imaging quality and spot positioning accuracy of the optical system, thereby improving the angle measurement accuracy of the autocollimator.

Abstract: The present disclosure provides a multi-frequency hybrid heterodyne laser tracker system based on a single light source. According to the laser tracking system proposed in the present disclosure, multi-frequency laser is obtained by conducting multi-acousto-optic frequency shift on a dual-longitudinal-mode laser unit, and an absolute ranging precision gauge is constructed by using a dual-longitudinal-mode interval of a light source. With the frequency shift difference of a multi-acousto-optic frequency shifter, an absolute ranging roughness gauge is constructed, and the relative displacement measurement of dual-frequency light interference is achieved.

Abstract: The disclosure discloses a stress gradient high-efficiency non-destructive detection system based on frequency domain calculation of broadband swept frequency signals, and a detection method thereof. The detection method includes: step 1: calibrating an LCR wave velocity of an object to be measured; step 2: calculating a starting frequency and a cut-off frequency of broadband swept frequency signals based on the LCR wave velocity of the object to be measured in the step 1 and a stress gradient measuring range in a depth direction of the object to be measured; step 3: converting phase delay to time delay information based on the phase delay of the starting frequency and the cut-off frequency in the step 2; and step 4: determining stresses of depths corresponding to different frequency components based on the time delay information in the step 3 to finally realize layer-by-layer scanning of stresses at different depths of the measured object.

Abstract: A method for dynamic output force distribution of a multi-degree-of-freedom over-actuated motion stage includes: establishing a mathematical model G(s) of a motion stage based on a modal representation; setting a time delay interval parameter ?? and an instruction shaper order nCS, and calculating each pulse time delay parameter ?i; calculating matrices Tb and Vb; initializing q=1; defining Hq; calculating intermediate variable {tilde over (T)}jq, {tilde over (V)}, ?Hq, YHq, T?Hq, V?Hq, and ?q; calculating an estimated value ?q of Hq; obtaining an amplitude Aikq of an instruction shaper; q=q+1, until calculation is completed for all logical axis channels; calculating ?(s) by using Aikq; and obtaining a dynamic output force distribution matrix Tf(s). Zero-residue vibration suppression in all controllable flexible modalities can be realized with finite actuator redundancies.

Abstract: An air-coupled ultrasonic plane stress detection method for a composite material based on dual-modal sound-time ratios of a Lamb wave includes: S1: assembling a detection device; S2: based on the detection device and the dual-modal sound-time ratios of the Lamb wave in S1, using unidirectionally loaded stress to obtain different stress coefficient relations; S3: based on the stress coefficient relations in S2, solving stress coefficients; S4: based on the stress coefficients in S3, acquiring three sound-time ratios; S5: based on the sound-time ratios in S4, describing a stress state of a detection point; and S6: repeating S4 and S5 till completing detection and scanning. The method improves the accuracy of stress coefficient calibration and air-coupled ultrasonic stress representation of a composite material panel greatly.

Abstract: Provided is a large high-speed rotary equipment gap stacking assembly apparatus and assembly method based on digital twin, and relates to the technical field of engine assembly measurement. The disclosure solves the problem of unbalanced rotation of the rotary parts caused by large assembly error during multi-stage rotary parts are stacked in a gap way. The disclosure includes the assembly apparatus entity and the assembly method; the assembly apparatus entity is configured to establish data communication with the upper computer through data acquisition apparatus, and upper computer is configured to establish a virtual assembly model; the virtual assembly model and optimal coaxiality of the multi-stage rotary parts in gap stacking can be obtained according to the assembly method, and the assembly process can be controlled by using the virtual assembly model and the optimal coaxiality. The disclosure is suitable for controlling the assembly process of the rotary parts.

Abstract: An ultrasonic measurement method for plane stress on the basis of a multi-wafer air-coupled transducer relates to the technical field of ultrasonic testing. The method solves problems that a traditional measurement method for plane stress generally computes the plane stress by changing at least 3 different measurement directions and obtaining information such as an acoustic time difference in the 3 measurement directions by using a pair of contact ultrasonic transducers, which is too complicated in operation, and a coupling agent can influence measurement accuracy of the plane stress.

Abstract: A GA-PSO-BP neural network is provided for performing a measurement of a coaxiality error of parts of a rotary equipment and predicting a coaxiality of parts of the rotary equipment in order to solve a problem that a coaxiality error of saddle surface parts is difficult to calculate by building a traditional mathematical model based on a three-dimensional coordinate system transformation due to serious deformation of fitting surfaces of spigots. The GA-PSO-BP neural network method includes the steps of analyzing an influence source of the coaxiality error of multi-stage parts after assembly; then taking an error source as an input and the coaxiality error of the multi-stage parts after assembly as an output; and introducing a genetic algorithm to optimize an initial weight and threshold of a BP neural network, and introducing a particle swarm optimization to find optimal solutions of hyperparameters.

Abstract: Present disclosure relates to a heterodyne grating interferometric method and system for two-degree-of-freedom with high tolerance. The system comprises a separately modulated heterodyne laser (1), an optical prism (23) and a photoelectric detection and signal processing unit (4). The separately modulated heterodyne laser (1) simultaneously outputs two laser beams at different frequencies, which are incident in parallel to a first beamsplitting surface so as to be split, and then a part thereof is incident to a retro-reflector (233) to produce reference beams (53a, 53b), which are incident to a third beamsplitting surface, and the other part traverses a double-diffraction structure formed by a measured grating (3) and retro-reflectors (234a, 234b) to obtain two measured beams (59a, 59b), which are incident to a second beamsplitting surface and then are divided into two parts.

Abstract: The present disclosure provides an approximation-free and iteration-free method for spectral analysis of an intracavity electro-optic modulation type optical frequency comb, a device and a medium.

Abstract: Disclosed are a linkage device, a transceiver module and a plane stress field measuring device and method capable of achieving synchronous adjustment of distance and angle, and relates to the field of ultrasonic non-destructive testing. The existing technical means for measuring plane stress in the field of ultrasonic testing has the shortcomings that the same testing is only applicable for single materials and the deflection angles of transmitting and receiving transducers are inconsistent.

Abstract: A method, system, device, and medium for online stress monitoring without baseline data based on single-mode multi-frequency signal fusion are provided.