Study On Monitor Method Of Automobile Braking And Steering Performance Based On Accelerometer

With the increase of automobile tenure amount as well as ceaseless raise of driving speed ,the driving security of automobile is subjected to a concern more and more.And the driving security is most close to braking and steering.Although there are many safety detecting lines can be used to detect automobile braking and steering performance periodically at present,but lack well timed, so it is necessary to develop a kind of car-carried system that can monitor braking and steering performance of automobile and discover potential safety hazard in good time.The subject of the thesis research is to improve the active safety of vehicle.This thesis developped a kind of car-carried system that can monitor braking and steering performance of automobile based on the SCA1000 two-axes accelerometer,system with the AT89S8252 single Chip Microcontroller as detection and control unit,and including two rear axes wheel rotative velocity sensor and save and display to equipment etc.Accelerometer can measure Linear acceleration of automobile ,then calculate automobile speed and displacement by integral.Automobile speed can be calculated by average value of two rear rotative velocity when it don't brake or slip .Monitoring contents of the system includes automobile brake performance and steady steering characteristic.The Evaluating indicator of The automobile brake performance include brake distance,wheel slip rate,Mean Fully Developed Deceleration ,braking direction stability performance ,automobile steady steering characteristic can be Evaluated by lateral acceleration gain curve and fixed the steering wheel angle turn radius variety value .respectively.Main contents of the thesis are as follows:1.Analyzed evaluation method and principle of automobile brake and steer performance from the theories,The Analyzed evaluation method and principle of automobile brake and steer performance from the theories, mainly includes the analysis of brake process.Deducing a calculation formula fit for program,including calculation formula of the brake instance,wheel slip rate ,mean fully developed deceleration and automobile curve brake instance .Deducing linear two freedom automobile model Movement differential equation,put forward the concept of lateral acceleration gain ,and proved it's true by MATLAB simulation.Analyzing requirement of the accelerometer installment position and giving a concrete method to evaluate the automobile steady steering characteristic . 2.According to the thesis's main research mission, designing a whole project of system hardware first all.After that choosing hardware and designing electric circuit of each parts ,drawing the circuit principle diagram, being respectively carry on experiment, drawing PCB plank, carrying on EMC design in the meantime..The hardware design mainly include system power design,base circuit design of single chip Microcontroller,sensor circuit design,display and alarm equipment circuit design and serial communication circuit design.3.As designing the hardware, carry on the software design synchronously, which mainly include accelerometer signal processing program design, wheel rotative velocity sensor the signal processing program design,the LCD display program design,information save program design, serial communication program design and software anti- interference program design.The software language of the apply advanced language of C51.4.Experiment mainly include the accelerometer test experiment:: to carry on the accelerometer standardization check the circuit connection whether right and debug program.The electromagnetism type wheel rotative velocity sensor test to experiment ,and carry on standardization to the speed of car , the check circuit link whether right and debug program;carry on serial communication experiment between single chip Microcontroller and PC ;Write the analytical the virtual instrument program with the LabVIEW language, carry on simulation and analyze experiment the result .Attention question is that the thesis use a great deal of integral calculus Calculation, so exist the error accumulation problem .If time is longer, even the accurate calculation will also cause the error accumulation,causing the calculation lose really, so calculating time can't obtain too long.To test this ,may keep the vehicle Equal velocity running,to test influence of this kind of error accumulation,if in some time wheel rotative velocity same as calculated vehicle speed ,explaining then this system is dependable.