Chattering-free sliding mode control with unidirectional auxiliary surfaces for miniature helicopters

Purpose – This article proposes a chattering-free sliding mode control scheme with unidirectional auxiliary surfaces (UAS-SMC) for small miniature autonomous helicopters (Trex 250). Design/methodology/approach – The proposed UAS-SMC scheme consists of a nested sequence of rotor dynamics, angular rate, Euler angle, velocity and position loops. Findings – It is demonstrated that the UAS-SMC strategy can eliminate the chattering phenomenon exhibiting in the convenient SMC method and achieve a better approaching speed. Originality/value – The proposed control strategy is implemented on the helicopter and flight tests clearly demonstrate that a much better performance could be achieved, compared with convenient SMC schemes

The working principles of the max-pooling operator and the convolutional filter.

The working principles of the max-pooling operator and the convolutional filter.</p

The PSNR values of the limited-angle CT images.

The blue points with circle masks present the PSNR values of the CT images reconstructed by FBP. The orange points with rhombus masks present the PSNR values of the results by DLFBP. The gray points with square masks present the PSNR values of the results by DCNN [32].</p

Subgroup analyses for effective rate and mortality.

Subgroup analyses for effective rate and mortality.</p

Effect of rifaximin plus lactulose versus lactulose alone on the risk of mortality.

Effect of rifaximin plus lactulose versus lactulose alone on the risk of mortality.</p

The baseline characteristics of included studies and patients.

The baseline characteristics of included studies and patients.</p

The values of the parameters in the deep learning layers.

The values of the parameters in the deep learning layers.</p

The limited-angle results of one head slice with the projections within the angular range [0 90°] by using DCNN [32], FBP and DLFBP.

The incomplete singoram has a size of 180 × 731 pixels. The corrupted sinograms generated by the forward projection have a size of 720 × 731 pixels. All CT images have a size of 512 × 512 pixels after cutting off the surrounding blank region. Some regions of these images, indicated by the yellow box, are enlarged for better visualization.</p

The sparse-view results of one synthetic phantom with an incomplete sinogram with 90 views by using DCNN [32], FBP and DLFBP.

The incomplete singoram has a size of 90 × 731 pixels. The corrupted sinograms generated by the forward projection have a size of 720 × 731 pixels. All CT images have a size of 512 × 512 pixels after cutting off the surrounding blank region. Some regions of these images, indicated by the yellow box, are enlarged for better visualization.</p

aPSNR values of limited-view results.

aPSNR values of limited-view results.</p