Current Issue : April - June Volume : 2015 Issue Number : 2 Articles : 4 Articles
A novel approach for modeling and control of servo systems with backlash and friction is proposed based on the characteristic\nmodel. Firstly, to deal with friction-induced nonlinearities, a smooth Stribeck frictionmodel is introduced.Thebacklash is modeled\nby a continuous and derivable mathematical function. Secondly, a characteristic model in the form of a second-order slowly timevarying\ndifference equation is established and verified by simulations. Thirdly, a composite controller including the golden-section\nadaptive control law and the integral control law is designed and the stability of the closed-loop system is analyzed. The simulation\nand experimental results show that the proposed control scheme is effective and can improve the steady-state precision and the\ndynamic performance of the servo system with backlash and friction...
In this study, various carburizing compounds charcoal, cow bone, CaCO3 were added as energizer for the\ncarburizing compounds in percentage of 10%. To produce another compound to pack carburized mild steel 1020 AISI\nfor investigates the influence of these compounds on wear resistance.\nMany Cylindrical specimens for the adhesion wear tests were prepared from the used metal with dimensions (10x20mm)\naccording to ASTM (G99-04) specifications\nThree Heat Treatment process namely pack Carburizing Quenching, and Tempering were done. Firstly the mild steels\nspecimens are carburized at 925�° C for 2hr as soaking time and slow cooling in furnace then carburizing specimens\nwere re heating to 870 �°C for half hr. and water Quenching .Tempering was done at 160�°C for 1 hour and air cooled. the\nCarburized and Tempered mild steels are subjected for different kind of test such as Adhesive Wear Test with pin on\ndesk method, Hardness Test were taken using Vickers micro-hardness tester and optical microscope is used for\nmicrostructure examination X-ray diffraction for phases observation.\nThe result showed that all carburizing compound were contributed in increasing wear resistance and the compound of\ncow bone with 10% CaCO3 as energizer had a carburizing case depth of 2.32 mm which gives the highest wear\nresistance while charcoal compound gives a case depth of 1.1 mm .The work shows that cow bone can be used as\ncompounds and energizer in pack carburization of mild steel. The hardness profile plot of the 90 wt.% 10% caco3 cow\nbone carburized mild steel was also higher than the other compositions and this value contributed on improvements of\nwear resistance....
Road friction information is very important for vehicle active braking control systems such as ABS, ASR, or ESP. It is not easy\nto estimate the tire/road friction forces and coefficient accurately because of the nonlinear system, parameters uncertainties, and\nsignal noises. In this paper, a robust and effective tire/road friction estimation algorithm for ABS is proposed, and its performance\nis further discussed by simulation and experiment. The tire forces were observed by the discrete Kalman filter, and the road friction\ncoefficient was estimated by the recursive least square method consequently. Then, the proposed algorithmwas analysed and verified\nby simulation and road test. A sliding mode based ABS with smooth wheel slip ratio control and a threshold based ABS by pulse\npressure control with significant fluctuations were used for the simulation. Finally, road tests were carried out in both winter and\nsummer by the car equipped with the same threshold based ABS, and the algorithm was evaluated on different road surfaces. The\nresults show that the proposed algorithm can identify the variation of road conditions with considerable accuracy and response\nspeed....
On average, additives make up to 7% of a typical lubricant base. Commonly, they\nare blended with lube oils to enhance specific features thereby improving their qualities.\nUltimately, additives participate in the performance of car engine oils. Using an analytical\ntool, attenuated total reflectance fast transform infrared spectroscopy, various grades of car\nengine oils, at different mileages, were analyzed. Sulfate oxidation and wear were found to\ntrigger chemical processes which, in the long run, cause lubricant degradation while carbonyl\noxidation was observed to occur only at a slow rate. Based upon data obtained from infrared\nspectra and using a curve fitting technique, mathematical equations predicting the theoretical\nrates of chemical change due to the aforementioned processes were examined. Additive\ndepletions were found to obey exponential regression rather than polynomial. Moreover,\nbreakpoint (breakpoint is used here to denote the initiation of deterioration of additives) and\ncritical mileage (critical mileage defines the distance at which the lubricant is chemically\nunusable) of both samples were determined....
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