Backward motion commonly exists in the stick-slip linear piezoelectric actuator, resulting in deterioration of the output performance and limiting their applications. To solve the problem, a stick-slip linear piezoelectric actuator with suppressed backward motion, achieved using an active-locking mechanism (ALM) with two mechanisms, is proposed in this paper. One mechanism involves stick-slip driving, while the other actively suppresses backward motion by clamping the slider during the backward driving process through efficient control. A prototype actuator was designed and manufactured to verify the feasibility of this method, and an experimental system was established to obtain the detailed parameters. Also, to verify the feasibility and effectiveness of the suppression effect on backward motion of the proposed actuator, the output performance of the traditional stick-slip actuator and the actuator with the ALM were compared. Based on the results, we demonstrate that the maximum output speed and maximum output force of the prototype are 2.26 mm s ⁻¹ and 1.6 N under a voltage of 100 V, respectively.

A CNC machine tool is an industry mother machine in manufacturing industry. As its key rotating part, bearings in the spindle system of machine tools usually suffer great noise during operation. This paper puts forward a method based on DRSN-Transformer algorithm which can diagnose rolling bearing faults accurately under conditions with high noise. Firstly, we add Gaussian white noise of different signal-to-noise ratios (SNRs) into the original vibration signal, and continuous wavelet transform (CWT) is performed to the vibration signal with noise to construct wavelet time-frequency map. Then, the soft threshold module in the deep residual shrinkage networks (DRSN) can achieve the better effect of noise reduction. And the multi-head attention in the Transformer can pay attention to the important features on different subspaces, so as to enhance the overall feature extraction ability of the model. Finally, the output of the classification module is utilized to obtain the fault diagnosis results. The experimental results show that the proposed method can reach the accuracy of at least 98% under different SNRs condition, which fully verifies the method proposed in this paper can still obtain higher accuracy in strong noise environments. The method in this paper provides a certain reference for fault diagnosis for the spindle system for machine tools.

We demonstrate a global calibration method for the laser plane using a 3D calibration board to generate the two horizontal coordinates and a height gauge to generate the height coordinate of the point in the laser plane. A sigmoid-Gaussian function for the candidate centers is employed to normalize the eigenvalues of the Hessian matrix to prevent centers missing or muti-centers. Then camera calibration and laser plane calibration are accomplished at the same time. Finally the reconstructed 3D points are transformed to the horizontal plane by the forward process that involves one translation and two rotations. The parametric equation of the 3D curve is reconstructed by the inverse process that performs on the 2D fitting curve.

A calibration method adopting Plücker matrices is proposed to explore the laser plane in a structured light measurement. The calibration model establishes the geometrical relationship among the camera, 2D target, and laser plane. The laser plane is constructed by multiple Plücker matrices of the dual 3D crossing lines between the laser plane and target planes in the camera coordinate system. Moreover, the validity of this calibration method is experimentally analyzed through the impact factors of noise magnitude and number of images. The mean errors of three directional angles of the normal vector to the laser plane are $-0.174°$, 0.170°, and $-0.022°$, respectively. The variances of the errors of three directional angles are 0.069°, 0.046°, and 0.160°, respectively. The maximal absolute errors of three directional angles are 1.362°, 1.351°, and 1.347°, respectively. The experiments prove that the calibration method is available to provide an accurate calibration for the laser plane.

A reconstruction method is provided to improve the measurement of the binocular vision. The image projections of the 3-D point on the 3-D reference are analyzed by the multiple view geometry. The Plücker coordinates of the two screw projection lines are constructed by the image points. The line segment perpendicular to two projection lines is generated from the direction vector and the end points of the line segment. As the bilinear products of the Plücker coordinates between the perpendicular line and the projection lines are zero, the end points of the perpendicular line segment are parameterized by the Cramer's Rule. The reconstruction error of the distance between two parameterized 3-D points is employed as the minimized objective of the cost function. The impact factors and the enhancements of the reconstruction accuracy are investigated by the experiments comparing with the original method. The method contributes the error descents of 27.19%, 38.29%, 19.01%,and 16.31% for the test lengths of 50, 100, 150, and 200 mm. Therefore, the results demonstrate that reconstruction method of the binocular vision provides the higher accuracy and application potentials.

Equation construction of a laser plane demonstrates a remarkable importance for vision measurement systems based on the structured light. Here we create a simple 1D target with a cone at the bottom and a checkered pattern on the top to calibrate the equation of the laser plane in the view field of a camera. A group of 2D coordinates of the intersection points are extracted from the images with the 1D target at different positions. The objective function is constructed to optimize the coefficients of the laser plane by minimizing the difference between the distance from the feature point to the the origin point and the length of the 1D target. The projective lines of the optimized laser plane on the 3D calibration board overlap the real intersection lines in the experimental images. Finally, the comparison work about the influences of the non-Gaussian noise and point number is investigated experimentally. The experiments show that the method of the distance optimal object from the feature point to the origin point provides an accurate and robust calibration for the laser plane in structured light measurement.