The Design Of Interpolating The Optical Encorder Based On TMS320F2812

The optical encorder is a sensor used in displacement measure which intergrates light,mechanics and electircs all together,it's widely used in the industry production.And in many cases,we need a optical encorder with enough high accuracy.Now adopting shaftless drive system in the industry printer business has become the representation of creativity and modernlization in the printer business,and a basic way to realize with both a better production and economic effiency. Shaftless drive system is a kind of closed loop control system whose angular velocity and angle are all synchronized,there needs both a speed and postion sensor in this system,and to reduce the system's complexity and also the cost,in the servo system,there usually place only the positon encorder,and the angular velocity is come from the time differential part of angle. Shaftless drive system all uses optical encorder whose precision is beyond 100 million lines/round.The standard resolution of the SERCOS system is 360 million lines/round.If we want to measure an angle with very high accuracy,possibly there are two ways:the one is to use a optical encorder originally has enough high accuracy,the other is to interpolate the optical encorder that we currently have.Normarlly,combine both of them is the best way to the problem.However,the output signal of the encorder card usually has many kinds of errors,it is not fit to use it directly as the source of the interpolation.So,This text is mainly about a way which can automatically corrects the error in the optical encorder,it automatically correct the error according to the input from the optical encorder.That largely improved the order of the signal,and it can be used both in the incremental optical encorder and also the absolute optical encorder,so that it can increase the optical encorder's anti-jamming factor and can make the optical encorder work in many even very bad conditions.This project mainly use the TMS320F2812 to increase the accuracy of the interpolator,and the actual design uses the method of numeric computation,it makes the way looks like easy and flexible.The hardware design mainly includes:the hardware designed AD calibration;And in the hardware,there adopts a kind of power supply for the operational amplifier with ultra low noise and ripple,and the operational amplifier too is with ultra low noise design;In the future, the product mainly uses a DARAM to communicate and get the control information;But in the test and estimate of the PCB board,we choose NI's virtual instrument card NI 6552 as the show window for the output. At the other hand,in the software design,sample 2 set of data which both includes 50 samples,and uses multiple value to fit a simple equation set with 5 elements,then use Gauss method to resolve the equation set,and then the error parameters of the signal is obtained and the interpolating construction can be carried out;The result is consisted with 2 parts,they are:the interpolation part and the large number part,the large number part is from the count of the 2812's QEP,the other is from the ADC then the output of the computation;Before we calculate the error parameters of the signal,there adopts an improving MT method to calculate the speed of the motor first;When caculating the interpolation part,unlike the way we did in the past,here chooses a new way that first transform the input sine,cosine signal into a zigzag waveform,and adds the compensation to constructs a more perfect zigzag waveform,then we can calculate the interpolation part in an easier way which is lineral.