Research Of Digital Ultra-low Frequency Excitation Power Amplifier Based On ARM

Because of the small size, low power consumption, low testing cost, easy to use,electromagnetic excitation fatigue testing system gets an extremely wide rage ofapplication in the fatigue life test and other fields that need special incentives. Inforeign countries, the electromagnetic excitation fatigue testing system has becomethe standard configuration of equipment of vehicle component fatigue life test. InChina, many vehicle and parts manufacturers import electromagnetic excitationfatigue testing system. There are few of such self-developed equipment in thedomestic market, so the relevant research of electromagnetic excitation fatigue testingsystem is not only meaningful to the domestic related testing technique anddevelopment, but also can save costs, save energy, obtain good economic benefit.As the main parts, excitation power amplifier and its controller directlydetermines the performance of the fatigue testing system. Before this issue ispresented, analog electronics design is widely used and excitation power amplifier isdeveloping. There are many aspects, such as driving ability, efficiency andanti-interference, need to be improved or redesigned with new technologies. So theresearch of digital ultra-low frequency excitation power amplifier based on ARM isproposed.The significant study of this issue has two aspects. On one hand, this paperadopts ARM microprocessor to design the digital excitation power amplifier of theoriginal “electromagnetic resonance dynamic load testing system”. It studies a varietyof SPWM modulation methods, and summarizes the modulation method which issuitable for the ARM microprocessor. It achieves two way SPWM control signals ofphase difference of180°for coordinated control of excitation current. The purpose isto improve the function and efficiency of the excitation power amplifier. At the sametime, it also has laid the foundation for the structure mode change of electromagneticresonance type dynamic loading test system, from lumped integration structure intothe structure of the upper and lower machine. On the other hand the true peak current detection and automatic equalization adjustment module hardware circuit is designed,placed in each branch of the parallel array structure of the excitation power amplifier.The current branch can adjust automatic, real-time, independent equilibrium in thesame reference volume.In the process of research, it optimizes the design of hardware circuit ofexcitation power amplifier, including the choice of parallel array structure and themain circuit design, the temperature control module design and various designs forprotecting circuits. Centering on the control core power amplifier of ARM9(S3C2410)microprocessor, the hardware circuit design and software development functionalmodule are carried out. It includes: the A/D acquisition module which achieves theforce value and two current values; the PWM signal output module which producestwo SPWM control signal; the serial communication module which transfers controlcommands and information feedback between computer and ARM microprocessor;the man-machine interface module which realizes parameter setting, modification anddisplay the working condition; digital PID control module that realizes the real-timecontrol and closed-loop regulation of excitation force.Finally, the various designed functional modules and digital excitation poweramplifier based on ARM are experimentally verified in the range of control ultra-lowfrequency signals. Through a lot of repetitive detection experiments, it verifies thefeasibility and effectiveness of the functional modules of the present study. It verifiesthe stability and reliability of the ultra-low frequency excitation power amplifier basedon ARM, and achieves the intended purpose of the study.