The Design Of Precision Signal Generator Based On DSP And Application In Mechanical Tests

Mechanical equipment is everywhere and crucial in country’s industry, residents’ daily life andsocial security, thus, the safety and reliability of mechanical equipment is an important topic introubleshooting and equipment monitoring studies. With increasing levels of technology, it is becominglarger of the mechanical equipment systems and getting closer between the various parts, therefore, thefault of any part may cause the stagnation of the whole system, bringing the enterprise or country hugelosses. Thus, it is a top priority in diagnostic and testing equipment for the safe production andlivelihood.In mechanical engineering for some important parts (spindle, machine base, etc.) reliability testing,often need to generate vibration exciter, the mechanical operation of the vibration test whether theamount of impact on the service life of machinery and running. In addition, in some vibration testmodeling is essential.In order to get better detection and fault diagnosis in mechanical equipment, thisstudy is about data acquisition and testing system based on OMAPL138, constituted of CPU module,A/D acquisition module, D/A output module, memory module, wireless communication module, GPSmodule and so on. OMPL138chip is a kind of DaVinci architecture processor just launched by TI inrecent years, including the family of ARM9and C674x DSP, which are adopted by asymmetricdual-core low-power processors, it has the advantages of both DSP’s high-speed digital signalprocessing performance and reduced instruction computer (RISC) technique.This system can be divided into two smaller systems, a data acquisition system, and the other is asignal generator systems. It is not only capable of data collection, but also can send signal to excite theobjects, which brings great convenience to the test. In the design of signal generating system, DSPdownloads the program codes from FLASH, and then generates and stores the waveform data inexternal memory. After that, EDMA transfers the waveform data to buffer, then MCASP read the datafrom the buffer, and finally transmit the data to D/A chip for processing and output in IIS way. Thesystem can generate five kinds of standard waveforms including sine wave, triangle wave, square wave,narrowband random wave as well as white noise, it can also take frequency and amplitude sweep forsine wave, triangle wave and square wave. Plus, the sine wave’s distortion can reach0.0064%(thestandard is between0.02%and0.08%), it can be available to meet the most of the mechanical vibrationtest experiments.This paper mainly describes the signal generator design in the system, it has studied the theory ofthe sine wave, triangle wave, square wave and white noise signal. The hardware design withOMAPL138as the core includes as follows: CPU reset circuit design, D/A digital-analog conversion circuit design, power supply circuit design. Software Design includes as follows: McASP and EDMAcommunication design and the signal codes programming. Finally, after the debugging and testing, thesystem can meet the majority of the testing requirements.The main innovations of the design:1Adopt DSP as the core for data processing, and fully take advantage of the high-speed datacomputing of DSP, it can fast calculates the complex algorithm in the waveform codes effectively.2Take the function calculation to replace the traditional methods of analog circuits and DDS (directdigital synthesis) chip to generate waveforms, therefore, it is not only in high precision, but also reducesthe cost of hardware design in the system.2Adopt EDMA’s data transmission method (Enhanced Direct Memory Access); EDMA isindependent with CPU, and it can be responsible with the bulk data transmission, so that DSP can focuson data processing.3Direct and data acquisition instrument together, in the test to reduce the instrument use,simplifies the testing process4In order to verify the accuracy and distortion frequency signal generator, the experimental testshave been100Hz sine wave parameters. Test results, the waveform distortion is0.0077%, the frequencyaccuracy of3E-6, amplitude accuracy is1.8E-3. Application in engineering in mechanical tests. Modaltesting conducted vibration isolator, to the test requirements.