Wavefront reconstruction and correction under strong turbulence has become a crucial issue for adaptive optics systems. An approach using a plenoptic sensor has attracted high attention recently. However, the existing reconstruction and correction algorithms based on the plenoptic sensor are sometimes unsatisfactory. Therefore, we propose a modified approach based on the checkerboard algorithm to reconstruct the wavefront. By means of a weighted summation, the reconstruction accuracy is clearly increased. We propose using the direct-gradient method to correct the disturbed wavefront after reconstruction, and our experimental results demonstrate the effectiveness with only one correction step.

A new kind of fringing electrostatic actuation mode is developed. In this new actuation mode, the expression of fringing electrostatic force is found. The nonlinear dynamic analysis of this new actuation mode is presented by using the Method of Multiple Scales. An experiment is designed to observe the dynamic behaviors of this structure. It is observed that the resonance frequency rises with the increase of the initial displacement and the decrease of the slit gap; a smaller slit gap makes marked change of the resonance frequency in the same range of the initial displacement; the increase of the vibration amplitude is linear with the increase of the initial displacement; the fringing electrostatic force has a larger impact on the frequency response of the nonlinear vibration when the initial displacement, the beam length and the actuated voltage are larger. This new fringing electrostatic actuation mode can be used in a micro tactile sensor. The results of dynamic analysis can provide support for sensor design. Based on the dynamic investigations into the micro cantilevered beam actuated by fringing electrostatic force; three usage patterns of the sensor are introduced as follows. Firstly, measuring resonance frequency of the micro beam can derive the initial displacement. Second, the initial displacement can be derived from vibration amplitude measurement. Third, jump phenomenon can be used to locate the initial displacement demand.

The conventional sliding mode control (SMC) strategy for direct torque control of switched reluctance motors suffers from severe chattering and prolonged dynamic response. Accordingly, an enhanced SMC strategy is proposed to mitigate motor chattering and suppress torque ripple. On the basis of the conventional exponential approximation rate, a compensation factor and a fractional order are incorporated. Meanwhile, the sigmoid function, characterized by superior smoothness, is employed to replace the sign function that induces severe chattering, thereby attenuating the motor torque ripple. At the same time, in response to the challenge of parameter tuning arising from motor nonlinearity and the abundance of parameters, the sparrow search algorithm (SSA) is employed to optimize the controller parameters. The motor control models before and after the improvement are constructed in MATLAB/Simulink, and the sparrow search algorithm (SSA) is employed to optimize the controller parameters for both cases. Comparative results indicate that the improved control strategy and parameter optimization method can effectively suppress motor torque ripple and enhance the dynamic response characteristics of the system under various operating conditions and rotational speeds.

Adaptive optics systems will encounter challenges under strong atmospheric turbulence conditions. Recently, a modified approach based on plenoptic sensor has attracted considerable attention. However, after wavefront correction under strong turbulence, we found that the existing wavefront reconstruction algorithm has difficulty in accurately reconstructing the residual aberrations. Therefore, we proposed a local threshold checkerboard algorithm to improve the accuracy of wavefront reconstruction by thresholding specific areas of central sub-apertures of the plenoptic sensor. In order to demonstrate the effectiveness of our algorithm, we designed and built an experimental platform. The platform included a deformable mirror, which we were able to adjust to simulate several different aberration conditions. Afterwards the direct-gradient method was used for correction of the residual aberrations, which were reduced to less than 0.1λ(RMS), demonstrating the effectiveness of our algorithm.