| According to investigation for major displacement sensor in market and relevant information checking,the paper listed four sensors' working principles,which aims at solving problems in manufacturing technique,material cost,accuracy and environmental sensitive.The paper put forward a new measuring method based on the barcode.The main idea of new method is using hierarchical coding barcode ruler in the length measurement on closed long range measuring scenarios and making use of artificial methods of measuring the length to complete the measurement.If the range is too long it would need stratification coding.First of all it would be divided into segment for marking scale roughly,then marking fine scale for accurate position.Using barcode scale,the basic method of automatic length measuring process is getting image of bar code ruler.In the begining this image will specify the length(number of bits),standard and spacing of this bar code.Then maximum measuring range with CCD(Charge-coupled Device)image feeling device TCD1501 for key components of reading barcode scale.By studying the working principle and performance parameters of this process,the paper analyzes the required drive pluse for normal work of TCD1501.Then it uses STC MCU through the assemble language to provide drive pulse for TCD1501 and samples the image induced signals.Meanwhile another STC MCU is adopted to collect output signal of TCD1501 and sent to PC through 485 interface.On the PC,the sampling data is recevied and the code value is reduced,then the final measurement value is obtained by quantitative calculation.The problem of STC MCU memory is too small to storage all the sampled data tmeporary,which is encountered in the debugging process.Although compression algorithms is adopted,owing to over time consuming,it fails to catch up the speed of TCD1501 the sampling output,and leads to data loss.So after discussion and analysis,an optimization scheme is launched,which adopts higher series of STC MCU with 2KB memory to accelerate the speed of data reception and temporary store rather than original compression algorithm.Owing to the change of MCU requirement of new experiment circuit board,it results in the feasibility that cannot be verified immediately.Hence,to approve the new hypothesis methodology is feasible and effective,the barcode number is reduced,on the other hand the distance and maximum range is shorten,so that a complete bar code can be read in 2000 bits scratchpad as well.The experimental prototype was made according to the content of the paper.It has advantages of low material cost,high accuracy,and it can not easily be affected by environment.Now the prototype is studied further for testing and design optimization.Finally the optimize scheme for the entire measurement device was put forward.By using extra MCU to perform the decoding process and the decoding results,then display the measured results to the LCD digital tube,the measuring unit can be used for remote reading and control,at the same time it can be used independently.Additionally it is proposed that the technology of reading the bar code of CCD can be used for the angle measuring devic,and perhaps it will open the new field for the application of the technology. |
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