This paper addresses trajectory planning and control for a dual-arm free-floating space robot (FFSR) based on predefinedtime stability. Firstly, a class of general nonsingular terminal sliding mode control strategy is proposed to achieve global predefined-time stability by switching a control parameter in a form of function. Then, a high-precision trajectory planning method is proposed for a FFSR using the proposed predefined-time stability theorem, which can make the end-effector and the base reach the desired pose within a prespecified time, and reduce the adverse effect on planning accuracy resulted from the singularity avoidance algorithm and the obstacle avoidance one. Subsequently, a trajectory tracking control strategy is proposed for a FFSR employing the proposed general nonsingular predefined-time terminal sliding mode, and the tracking errors can converge within a predefined time to an arbitrarily small neighborhood of zero in the presence of persistent disturbances. The proposed trajectory planning method has the advantage of pose feedback, so can be combined with the trajectory tracking controller in the control process to further enhance the control performance for the FFSR. Simulation results validate the effectiveness of the proposed methodologies.

This paper addresses fixed-time trajectory tracking for a dual-arm free-floating space robot (FFSR) with the large initial errors and bounded uncertainty. A wrist-based trajectory planning method is improved by fixed-time stability to fast eliminate the error caused by singularity. Then, a novel low-chattering and global-nonsingular fixed-time terminal sliding mode control strategy is studied by state approaching angle and switching sliding mode; the practical fixed-reachable Lyapunov stability analysis is presented for a mechanical control system. In the end, the proposed trajectory planning method and controller are combined to improve the tracking accuracy of end-effector to the nanoscale. Simulation results validate the effectiveness of the proposed methodologies.

High-resolution image transmission is required in safety helmet detection problems in the construction industry, which makes it difficult for existing image detection methods to achieve high-speed detection. To overcome this problem, a novel super-resolution (SR) reconstruction module is designed to improve the resolution of images before the detection module. In the super-resolution reconstruction module, the multichannel attention mechanism module is used to improve the breadth of feature capture. Furthermore, a novel CSP (Cross Stage Partial) module of YOLO (You Only Look Once) v5 is presented to reduce information loss and gradient confusion. Experiments are performed to validate the proposed algorithm. The PSNR (peak signal-to-noise ratio) of the proposed module is 29.420, and the SSIM (structural similarity) reaches 0.855. These results show that the proposed model works well for safety helmet detection in construction industries.

To avoid the problem of complex remodeling when using different types of multiple three-phase permanent-magnet synchronous motor (MTP-PMSM), this article proposes a general decoupling (GD) modeling method. Compared with the traditional vector space decomposition (VSD) modeling method and the multi- dq modeling method, the proposed GD modeling method can realize comprehensive decoupling and no complex reconstruction is needed when the structure of MTP-PMSM changes. Based on the proposed GD modeling method, a unified control framework is established for MTP-PMSM. Besides, a general fault-tolerant control method is developed for MTP-PMSM drives with open-phase fault or open-switch fault through current compensation. The simulation and experiment have been conducted to prove the feasibility and superiority of the proposed GD modeling and control methods of MTP-PMSM drive.

To suppress the current harmonics of open-end winding (OW) permanent-magnet synchronous motor (PMSM) drive with low switching frequency, a 3D model predictive control (3D-MPC) strategy is proposed in this paper. First, the reference voltages of OW-PMSM are calculated through deadbeat control. Then, the subspaces near the reference vector are selected to reduce the number of candidate vectors from 27 to 7. After that, the number of candidate vectors is further reduced to 4 by using the voltage cost function. Finally, the optimal vector is obtained by traversing the 4 candidate vectors with the current cost function. In this way, both low switching frequency and high current precision can be guaranteed. On the basis of the proposed 3D-MPC strategy, a novel fault-tolerant control scheme considering the third-order harmonic in the flux linkage is proposed to fully eliminate the torque ripple of open-end winding PMSM drive with open-phase fault. The experiments are carried out to validate the proposed strategy.