Theoretical Research Of FIR Algorithm-Based In Vehicle Dynamic Weighing Systems

The development of communication and transportation industry hasundoubtedly played an active role in the construction of national economy.However, the overloading of trucking vehicles, which is known as stealthy killersof the highway, remains incessant in despite of repeated prohibition. Harmscreated by overloading are of manifolds, accelerating road damage, increasingroad maintenance cost, leading to substantial run off of taxation and toll fee,bringing about frequent occurrence of traffic accidents, seriously polluting theenvironment, speeding up vehicle wear-off etc. So that it becomes more and moreimportant to reinforce control over road transportation. Dynamic weighing, i.e.weighing the vehicle on its moving state, with the characteristic of higherefficiency and time-saving, avoids the disturbance to the traffic in the weighingprocess, as compared with static weighing. Vehicle dynamic weighing is thetechnical precondition to the modernized and scientific management ofreinforcing overloading control and forcing overloading control regulations. Andthe study of dynamic weighing system is of economic significance and socialvalue in assurance of appropriate use of the roads.For the Vehicle dynamic weighing systems, the weighing accuracy and thespeed of the vehicle moving are the most important standard specification. Itindicates the technical level of the vehicle dynamic weighing systems.Comparatively the popular one at present is the axle --Axle serious appearance,measures the load of a vehicle's every axle, then through the test system calculateout whole vehicle weight. When the static behavior weighs, the tire of the vehicleacts on steadily on the platform of the axle except that the true axle is heavy, Anyother external forces are not interfered. So that accurate weighing can be easilyrealized.This text puts forword a kind of FIR digital filtering method after referringseveral kinds of methods, The method has good filtering effectiveness and makesit easy to modify parameters and to realize it etc. Because the operation amount ofFIR algorithm is heavy, it is difficult to accomplish real-time processing if simpleto come and realize with one-chip computer. So we come and realize FIRalgorithm with FPGA, one-chip computer is used to do some supplementarywork. In a word, the design is described in 3 parts in this dissertation. The first partanalyses the motion state and the motive characteristics of the automobile that setsout from the weighing noumenon. The second introduces the theory andrealization of the hardware design. The third introduces the nature of VHDL andthe realization of FIR algorithm and then the flow chart of the program on singlechip microprocessor chiefly. And introduces the theory of FIR algorithm, thestructure chart of realization and then analyses the results of experiments. Thefollowing describe the above in detail. The first part explained in Chapter 2. Trends when weighing, vehicle weighthe platform with certain speed through axle, the time of action is very short toplatform (within several hundred), And except that the true axle is heavy, there isinterference strength that a lot of factors produce on the platform of function, Forinstance: speed, vehicle one's own resonance, the road surface encouraging,driving force of the tire, etc. We can say true serious to flood among various kindsof interference strength, it cause enormous difficulty to realize high-accuracymeasurement to trends weigh. So how accurately measures the true weight on axleunder the function of uncertain degree interfere force at random in external world,Become the technological difficult point and key of the dynamic axle testingsystem. Putting in order on the interference existed, analyzing and synthesizing it,we can probe into the measure and test way that can reduce or dispel theseinterfere from whole angle to test system, Undoubtedly it is helpful to the progressof the high-accuracy trends to weigh and systematic development of test. The second part explained in Chapter 3 tells the theory and realization ofhardware design. The core of the design is single chip microprocessor and FPGA.The author explains each component of the hardware. The design of digital filterand basic digital circuit is completed by FPGA. The hardware realizing thefiltering algorithm runs fast and can realize real-time processing. Moreover, FPGAis programmed conveniently and easy to update. The author uses single chipmicroprocessor which is cheap and universally applied to display andcommunicate to the host. It effectively shares the burden of FPGA (actually FPGAcan realize the function too) in this way, and the programming is easy. So theauthor explains the structure characteristics and adjacent hardware circuit designof single chip microprocessor and FPGA in big space. There must be amplifyingand filtering circuit because the signal from senor is weak and contains noise. Thetheory and realization of amplifying and filtering circuit are told in detail in thedissertation. And there must be A/D converting circuit to convert the analog signalto digital signal recognized by FPGA and single chip microprocessor. The authoruses high-speed and 12-bit A/D converter AD1674 to ensure the converting speedand precision. The digital displayer is used to display the data. Display by74LS164 through serial interface of single chip microprocessor is programmedconveniently and takes up little CPU resource. MAX232 communicating circuitrealizes the communication to the host in favor of data storing and inquiring. The third part explained in Chapter 4 discusses the software design. Theauthor tells why VHDL is used and then give the procedure of VHDL design. Theauthor analyses the reason why programming devices are selected. In VHDLdesign, the problem of burr is difficult to solve, the author introduces how burr isproduced and some ways to restrain it. At last, the author gives the program ofFIR algorithm and explains it in detail. In single chip microprocessor programming, C51 language is explained first,then the author gives the mathematics model of dynamic weighing systems. Atlast the author tells the way in which program is designed. In addition, this part introduces the basic theory of FIR algorithm and theexperiment result . In section 4.2, the author explains the basic theory of FIRalgorithm, infers all the important formula, compares the window function andillustrates the affect of window function on results. The author also gives the...