Application of linear active disturbance rejection control for photoelectric tracking system

Dynamic characteristics and tracking precision are studied in the photoelectric tracking system and a linear active disturbance rejection control( LADRC) scheme is proposed for position loop. A current and speed controller is designed by a transfer function model,which is obtained by adaptive differential evolution. Model error,friction and nonlinear factor existing in position loop are treated as ‘disturbance',which is estimated and compensated by generalized proportional integral( GPI)observer. Comparative results are provided to demonstrate the remarkable performance of the proposed method. It turns out that the proposed scheme is successful and has superior features,such as quick dynamic response,low overshoot and high tracking precision. Furthermore,with the proposed method,friction is suppressed effectively.

A plastic strain energy method exploration between machined surface integrity evolution and torsion fatigue behaviour of low alloy steel

To explore the evolution mechanism of multistage machining processes and torsional fatigue behaviour based on strain energy for the first time and provide process optimization of axis parts of low alloy steel for service performance,four multistage machining processes were applied to the 45Cr Ni Mo VA steel,including the Rough Turning process(RT),RT+the Finish Turning process(FRT),FRT+the Grinding process(GFRT)and RT+the Finish Turning process on dry cutting condition(FRT0).The result showed that the FRT process’s average low-cycle torsional fatigue life increased by 50%when it evolved from the RT process.The lower surface roughness of R1.3μm caused the total strain energy to increase by 163.8 Pa mm/mm instead of the unchanged strain energy density,and the crack feature evolved from some specific bulges to flat shear plane characteristics.When the GFRT process evolved from the FRT process,its average fatigue life increased by 1.45 times,compared with the RT process.Plastic strain amplitude decreased by 21%,and the strain energy density decreased by 4%due to more considerable compressive residual stress(-249 MPa).Plastic deformation layer depth had a consistent tendency with surface roughness.In this paper,surface integrity evolutions on cyclic characteristics and fatigue behaviour have also been explained.A fatigue life prediction model based on the energy method for machined surface integrity is proposed.

Stimulated Brillouin scattering evolution and suppression in an integrated stimulated thermal Rayleigh scattering-based fiber laser

The spectral purity of fiber lasers has become a critical issue in both optical sensing and communication fields.As a result of ultra-narrow intrinsic linewidth, stimulated thermal Rayleigh scattering(STRS) has presented special potential to compress the linewidth of fiber lasers. To suppress stimulated Brillouin scattering(SBS), the most dominant disturbance for STRS in optical fibers, a semi-quantitative estimation has been established to illuminate the mechanism of suppressing SBS in a periodic tapered fiber, and it agrees with experimental results. Finally, a linewidth compression device based on STRS is integrated into a single-longitudinal-mode ring-cavity fiber laser with secondary cavities, and its linewidth is verified to be 200 Hz through a self-heterodyne detecting and Voigt fitting method.