ABSTRACT
In this paper, the least squares method is used to determine the vertical height of the road space domain. Based on the road estimation method, the active suspension control mode switching model is constructed, and the dynamic characteristics of the vehicle in comfort, safety, and integrated modes are analyzed. The vibration signal is collected by the sensor, and the parameters such as vehicle driving conditions are solved for in reverse. A control strategy for multiple mode switching under different road surfaces and speeds is constructed. At the same time, the particle swarm optimization algorithm (PSO) is used to optimize the weight coefficients of LQR control under different modes, and the dynamic performance of vehicle driving is comprehensively analyzed. The test and simulation results show that the road estimation results under different speeds in the same road section are very close to the results obtained by the detection ruler method, and the overall error is less than 2%. Compared with the active suspension controlled by passive and traditional LQR, the multi-mode switching strategy can achieve a better balance between driving comfort and handling safety and stability, and also improve the driving experience more intelligently and comprehensively.
ABSTRACT
Titanium alloys are widely used in various fields, but their machinability is poor because the chip would easily adhere to the tool surface during cutting, causing poor surface quality and tool wear. To improve the cutting performance of titanium alloy Ti-6Al-4V, experiments were conducted to investigate the effect of micro textured tool on the cutting performances. The cemented carbide tools whose rake faces were machined with line, rhombic, and sinusoidal groove textures with 10% area occupancy rates were adopted as the cutting tools. The effects of cutting depth and cutting speed on feed force and main cutting force were discussed based on experimental results. The results show that the cutting force produced by textured tools is less than that produced by non-textured tools. Under different cutting parameters, the best cutting performance can be obtained by using sinusoidal textured tools among the four types of tools. The wear of micro textured tools is significantly lower than that of non-textured tools, due to a continuous lubrication film between the chip and the rake face of the tool that can be produced because the micro texture can store and replenish lubricant. The surface roughness obtained using the textured tool is better than that using the non-textured tool. The surface roughness Ra can be reduced by 35.89% when using sinusoidal textured tools. This study is helpful for further improving the cutting performance of cemented carbide tools on titanium alloy and prolonging tool life.
ABSTRACT
To further study the discharge characteristics and machining mechanism of micro-electrical discharge machining (micro-EDM), the variation trends of the discharge energy and discharge crater size with actual discharge duration are discussed based on single-pulse experiments. The polarity effect of micro-EDM was analyzed according to the motion characteristics of electrons and ions in the discharge plasma channel. The results show that the discharge current and voltage of micro-EDM were independent of the discharge width and open-circuit voltage. The energy utilization rate of the short-pulse discharge was relatively high, and the energy utilization rate decreased gradually as the discharge duration increased. Even if the mass of the positive ion was much larger than that of the electron, the kinetic energy of the positive ion was still less than that of the electron when bombarding the surface of the electrode. The acceleration and speed of electrons were very high, and the number of times that electrons bombarded the surface of positive electrode was more than 600 times that of positive ions bombarding the surface of the negative electrode during the same time.
ABSTRACT
Diamond-like carbon (DLC) films were deposited on a silicon chip substrate by a metal pulsed magnetic filtered cathodic vacuum arc deposition technique, a direct current magnetron sputtering technique and a pulsed glow discharge plasma enhanced chemical vapor deposition technique. And the characteristics of DLC films were investigated using laser Raman spectroscopy and X-ray photoelectron spectroscopy. The spectra of diamond like carbon were collected using Raman spectrometers with 325 nm flters. It was found that DLC films prepared by various deposition technique have different G-peak, D-peak, T-peak, the full width at half maximum(FWHM)of G-peak, D-peak and T-peak, the intensity ratio I(D)/I(G) and I(T)/I(G) and the sp3 content. Among them, the films grown by metal pulsed magnetic filtered cathodic vacuum arc deposition technique have the largest G-peak wave number and the intensity ratio I(T)/I(G), the minimum of the intensity ratio I(D)/I(G), G-FWHM and the maximum sp3 content; those grown by the direct current magnetron sputtering technique have the 2nd largest G-peak wave number, the intensity ratio I(D)/I(G) and I(T)/I(G) and sp3 content, however, they have the largest G-FWHM, while those grown by the pulsed glow discharge plasma enhanced chemical vapor deposition technique have the minimum G-peak wave number and the intensity ratio I(T)/I(G) and sp3 content, and the maximum intensity ratio I(D)/I(G).
