With the advantages of high efficiency, simple equipment, good controllability, and the fact that they do no surface damage, atmospheric-pressure cold plasma jets are used to make solid surfaces hydrophilic. To transport the plasma jet effectively to the region to be modified and to reduce the amount of thermal damage to the surface during the modification, it is essential to control the transmission and temperature of the plasma jet from the distance. Flexible transmission and pre-cooling methods are proposed in this paper to solve this problem. An experimental device is constructed that mainly comprises the working gas, a power source, and a plasma generator. The test results show that (i) using a flexible catheter can extend the plasma transmission distance significantly and (ii) adjusting the driving voltage and gas flow allows the cold flexible plasma jet (FPJ) to reach several meters. Specially shaped jets such as plasma jet brushes can be generated conveniently based on the FPJ principle, thereby expanding the application range of the plasma. Pre-cooling the working gas with a vortex tube can lead to an FPJ with a simple structure without additional energy input and with a controllable temperature as low as −7 °C. The developed FPJ with a controllable length and temperature can be used to quickly modify various common solid surfaces, convert superhydrophobic surfaces into superhydrophilic surfaces, and preserve the microstructure of workpiece surfaces during modification.
High-precision trajectory tracking control is an important factor in the performance of industrial robots. In this study, a high-precision trajectory tracking strategy was proposed for controlling a degree of freedom serial robot on the basis of improved active disturbance rejection control. An independent control strategy of a single joint was adopted, and the corresponding decoupling control law was designed. An attitude trajectory-planning algorithm based on the circular-blending quaternion curve was improved. The position and attitude trajectories were transformed into the joint trajectory by using a kinematics equation and inverse velocity Jacobian matrix. The above-mentioned transformation link was used as a preprocessing link of the active disturbance rejection control, which is used for replacing the tracking differentiator of a typical active disturbance rejection control to eliminate the effect of the tracking delay. An experimental simulation was conducted by combining MATLAB and ADAMS. Simulation results show that the proposed control strategy can perform the tracking control of a task-space trajectory. The tracking precision of position and attitude trajectories were 0.01 mm and 0.01 s, respectively.
ELID (electrolytic in-process dressing) grinding was proposed by one of the authors for automatic dressing the grinding wheel while performing grinding for a long time. It offers a high effective way and has been widely used for grinding hard and brittle optical materials. However, those surfaces produced by fixed abrasive grinding are characterized by considerable sub-surface damage, micro-crack. Magneto-rheological finishing (MRF) is a novel precision finishing process for deterministic form correction and polishing of optical materials by utilizing magneto-rheological fluid. In this paper, an ultra-precision synergistic finishing process integrated MRF and ELID grinding is proposed for shorten total finishing time and improve finishing quality. A lot of nano-precision experiments have been carried out to grind and finish some optical materials such as silicon, silicon carbide, etc. ELID grinding is employed to obtain high efficiency and high surface quality, and then, MRF is employed to improve further surface roughness and form accuracy. In general, form accuracy of ~ λ/20 nm peak-to-valley (P-V) and surface roughness less than 10 Angstrom are produced in high efficiency.
Large-eddy simulation (LES) and Detached-eddy simulation (DES) were applied to a simple cavity model to calculate the wind buffeting noise respectively. The results were verified by wind tunnel experiments. The results show that LES is more suitable for wind buffeting noise calculation. LES method was employed to calculate automobile side-window buffeting noise. The correctness of results was validated by a road test. In this paper, the acoustically calculated sound pressure level (SPL) spectral curve is used as the initial signal of the acoustic post-processing. Four psychoacoustic objective parameters namely: loudness, sharpness, roughness and fluctuation were obtained by using Matlab R2016a to compile the calculation process. Sound quality evaluation (SQE) of the vehicle is performed via most frequently used SPL and four calculated vehicle comfort index. It can be concluded that with the increase of driving velocity, SPL and loudness show an increasing trend, while roughness, sharpness and fluctuation present a decreasing trend. It can be also summarised that with the increase of window opening degree, SPL and loudness show an increasing trend, sharpness presents a decreasing trend, and roughness and fluctuation display the trend of ups and downs. The main original contribution of this paper is the accurate calculation of wind buffeting noise and the summary of the changing rule of SPL, loudness, roughness, sharpness and fluctuation with the variation of velocity and window opening degree.
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