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The supporting stiffness analysis of the eight-cable 6-DOF cable-driven parallel robot is conducted, and the force/position hybrid control is carried out on this basis. Firstly, the cable-driven parallel robot is described systematically. Secondly, a kinematic analysis is conducted according to the principle of vector closure. The force of the mobile platform is analysed, and the static equilibrium equation is derived by Newtonian mechanics. After that, the relationship between the load change and the position change is described by the stiffness matrix in the operational space, the analytical expression of the supporting stiffness is deduced, and the influencing factors of supporting stiffness are analysed. Moreover, the factors of system stiffness, mobile platform posture accuracy and force control stability are considered, integrating the force/position hybrid controller. The simulation results show that the position error of the mobile platform is effectively reduced by the force/position hybrid control strategy, which is designed based on the stiffness analysis. Finally, the accuracy and effectiveness of the stiffness model and the force/position hybrid control strategy are verified by experiments.

An algorithm for solving the forward position solution problem of the parallel robot based on Levenberg-Marquardt method is proposed. A kinematics model of a redundantly constrained cable-driven parallel robot is established，and the mechanism is parameterized to solve the inverse position solution problem. The nonlinear equations of forward kinematics are established，and the original pose of the end effector is taken as the iterative initial value to solve the forward position solution problem by applying the proposed algorithm. The Matlab/Simulink/xPC tool is used for simulation experiments. The complex periodic circular curve is selected as the motion trajectory of the parallel robot for the real-time simulation. It is verified that the algorithm can achieve accurate forward position solution and smooth motion trajectory，and has good real-time performance. Five pose combinations are selected to verify the high efficiency of the algorithm. The calculation results show that the algorithm has fewer iterations，shorter computation time and higher accuracy，which provides a theoretical guidance for real-time monitoring and complex control strategies of parallel robots.

Nanosized titanium oxide (TiO2) material is a promising photocatalyst for the degradation of organic pollutants, whereas the difficulty of its recycling hinders its practical application. Herein, we reported the preparation of a novel titanium oxide/polysulfone (TiNPs/PSF) composite hollow microspheres by the combination of Pickering emulsification and the solvent evaporation technique and their application for the photodegradation of methyl blue (MB). P25 TiO2 nanoparticles dispersed on the surface of PSF microspheres. The porosity, density and photoactivity of the TiNPs/PSF composite microsphere are influenced by the TiO2 loading amount. The composite microsphere showed good methyl blue (MB) removal ability. Compared with TiO2 P25, and PSF, a much higher MB adsorption speed was observed for TiNPs/PSF microspheres benefited from their porous structure and the electrostatic attractions between the MB+ and the negatively charged PSF materials, and showed good degradation efficiency. For TiNPs/PSF composite microsphere with density close to 1, a 100% MB removal (10 mg L−1) within 120 min at a catalyst loading of 2.5 g L−1 can be obtained under both stirring and static condition, due to well dispersing of TiO2 particles on the microsphere surface and its stable suspending in water. For the non-suspended TiNPs/PSF composite microsphere with density bigger than 1, the 100% MB removal can be only obtained under stirring condition. The removal efficiency of MB for the composite microspheres retained 96.5%, even after 20 cycles. Moreover, this composite microsphere also showed high MB removal ability at acidic condition. The high catalysis efficiency, excellent reusability and good stability make this kind of TiNPs/PSF composite microsphere a promising photocatalyst for the water organic pollution treatment. [ABSTRACT FROM AUTHOR]

Nanosized titanium oxide (TiO 2 )-based photocatalysts have exhibited great potential for the degradation of organic contaminants, while their weak absorption of visible light limits the photocatalytic efficiency. Herein, a novel reduced graphene oxide/TiO 2 -polyphenylenesulfone (rGO/TiO 2 -PPSU) hybrid ultrafiltration membrane has been successfully prepared via a non-solvent induced phase-separation method, in which the synergistic coupling between the rGO and TiO 2 could endowed the fabricated membranes with visible-light-driven efficient photocatalytically degradation of organic pollutants and outstanding photocatalytic and antifouling properties. Compared with the PPSU membranes prepared with Graphene oxide and TiO 2 , respectively, the rGO/TiO 2 -PPSU membrane demonstrated significant photodegradation towards phenazopyridine hydrochloride (PhP) solution under ultraviolet light (improved about 71 and 43%) and visible light (improved about 153 and 103%). The permeability and flux recovery rates of the membrane indicated that the high flux of the rGO/TiO 2 -PPSU membrane can be greatly restored after fouling, due to the improved self-cleaning properties under visible light static irradiation. With the properties of high performance of photocatalytic degradation and good self-cleaning ability, the rGO/TiO 2 -PPSU membrane would have great potential in water treatment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Dai, Zhang, Wang, Chen, Chen, Qian and Yu.)