Realization Of Unload Vehicle Control Signals Long-distance Transmission In Power Station

In some large power station,coal is transmitted to the top of silo by strap transport firstly,then coal is ladeden and unladeden by the vehicle on the top of silo.It will impact the production efficiency ,output and quality of production that whether the dolly can arrive the right position accurately in time,connect with the input of silo,carry and unlade the coal.Now most dollies are controlled long-distance by cable and PLC,it's speed and precision is very high.But it need to set special cable net.and Investment is larger, the capability price rate is lower.Cable is prone to abrasion,aging and brings hidden trouble to the control system.It is not fit the works for operating in spot longtime,because the environment of spot is very tough.All kinds of signal are sent from control house in hundreds or thousands miles away.In this case,signals are not fit for transmittion by cable.In this paper,I have studied on the method of dolly control used in power station,metallurgy,coloured metal,coal,dock and port widely in the background of Gujarat Power station,and given a new method that transmitting the control signals of dolly by wireless communication. I have compared wireless communication module,CDPD and GSM-SMS with each other,analyzed their using area and speciality and chosen wireless communication module as the communication method.Then in this paper I have introduced the basic theory of wireless communication and compared the Symbol Error Rate and frequency belt possessive rate of 2ASK,2FSK and 2PSK by accounting.PSK system is best,but it need more technique,only fitting for the high speed communication in digital and computer communication.The SER of FSK is better than ASK,but need more bandwidth,so FSK is fit for lower speed transmission.The SER of PSK is worst,so it is hardly used in industry.The transmission of dolly control signals need not high speed,so FSK is chosen as the object.Because the changing of binary baseband signal may bring the phase mutation of carrier wave,so the MSK is appear.In order to reduce bandwidth more,the GMSK is appear.I have compared SER and spectrum of 2FSK,MSK and GMSK by Matlab software. In the precondition of the same SER,GMSK bandwidth is smallest.Transmitting 1Kbit/s date in the precondition of different SNR and modulation,the SER of 2FSK is highest,it's effect is worst.The SER of MSK and GMSK is similar,GMSK is a little better than MSK,so GMSK modulation is chosen finally.Comparing the SER and spectrum of GMSK in different BT by Matlab,it can be seen that the distributing of GMSK spectrum is compact and concentrative and SER is increasing along with the decreasing of BT,the value of BT is 0.25 in normal.The hardware consists of wireless communication module HAC-LM,Atmel single-chip AT89S52,TI serial ADC chip TLC2543,NS DAC0832 and so on.The wireless communication module and AT89S52 are connected by RS-232 interface.The input of digital signal is substituted by key-press switches,output is substituted by the on & off of LED. The input of analog signal is made by potentiometer,the output is showed by the brightness of LED and measured by multimeter.Pause-wait protocol and FEC are adopted as the error control protocol,the wireless sending and receiving of digital and analog signal are completed in assemble language.The sending and receiving of digital and analog signal is good in test,the correctness is very high,but there are some error and fluctuation in analog signal receiving,the precision is not very high.There are still a few shortages in this paper and need to be perfect more.such as no expanding for the I/O of single-chip,because the input of digital signal is not much,so it's not fit the industry field; the input of digital signal is not sent by the relay switch in industry spot but substituted by keypress switches without light coupling,so the electromagnetism disturber is not included;the output of digital signal is only showed by the LED,completing the transmitting of digital signal,and need to be tested in driving circuit outside.These shortages need to be perfected in practice working and finished product according with industry require.