Research Of Anti-slip Strategy In Braking System Of Modern Tramway

With the great support and guidance from our government,tram and light rail have been widely developed around the whole country.Since Shenyang Hunnan Morden Tramway,the first modern tram project in China,was officially put into operation on August 15th,2013,the development of urban rail transit in China has entered a brand-new era.From then on,plenty of cities in China have begun to study and formulate plans for building urban tram and put them into practice.The trams were open in Suzhou,Nanjing,Huai’an,Wuhan and Yunnan Honghezhou in succession,which is the symbol of that the development of modern tram in our country has entered the fast lane.It is widely considered that as one type of the ground transportation,tram always need to share traffic with social vehicles,so good braking performance is the top priority to ensure the safety of vehicles and others.Meanwhile,there exist many bad factors including harsh weather such as rain and snow,fallen leaves or withered grass in the ground transportation,which interference the adhesion performance between wheel and rail.Therefore,excellent anti-slip performance is necessary for vehicle braking system.In this thesis,"adhesion",the most important relationship between wheel and rail,together with corresponding concepts have been analyzed in detail.According to the processing of wheel gliding,the basic force relationship between wheel and rail has been discussed in three stages.Then the anti-slip braking strategy for Shenyang Hunnan Modern Tramway has been studied based on the above analysis and discussion.According to the features of this certain type of tram,the study of anti-slip strategy has been concentrated to four independent wheels of the trailer car bogies.The basis of judging anti-slip is the acquisition and determination of the velocity,so we first study how to determine the reference velocity of the tram.Then we calculate the velocity disparity,slip ratio and deceleration by comparing the linear velocities of four wheels with the reference velocity of tram.By applying the above parameters as criteria and comparing them to the sliding control rules,we detect whether each single wheel is over-decelerated,whether there exists velocity disparity between every two wheels,and whether the slip ratio is too large or too small.To be closer to practical situation,the method of semi-physical simulation is applied in our experiment to verify the proposed anti-slip strategy.The experimental results indicate that the change of braking pressure can follow the change of pre-set velocity curve in time and steadily,proving that this anti-slip braking strategy is effective in controlling the braking pressure when the wheels are sliding.For Shenyang Hunnan Modern Tramway,the research in this thesis can greatly improve the braking performance of the current tram.However,it should be considered that the study of braking and anti-slip control for trams is far from enough nationwide.Although tram and metro both belong to urban rail transit,it is quite different from metro in modes of grouping and controlling,and especially the operating environment.With the wide construction of trams in various cities,it is of great significance to develop an anti-slip braking system that can truly adapt to the characteristics of modern trams.