| Fatigue refers to the material under cyclic stress fracture occurred or performance changes, and fatigue life refers to material fatigue occurs when the number of stress cycles. Testing fatigue life of instruments are known as fatigue testing machine. Fatigue testing machine is divided into: Electromagnetic excitation type, electric, servo-type three types. Electro-hydraulic servo fatigue test system is characterized by a large force, working stroke length, drawback is that control more complex, these systems are inefficient and more energy. The electromagnetic vibrating can be tested for its resonant load components, and therefore have a role in a short time, high efficiency, energy conservation features. Electromagnetic excitation in the international study compared achievement vibration platform, including the United Kingdom INSTRON Corporation, Germany SINCO TEC Corporation.In the fatigue process, when the experimental treatment of test components actuated system, the measured components will be affected by vibration, when the excitation signal's frequency components being tested is identical to the natural frequency, will have resonance, then the experimental system is Comparison of energy conservation. So one of the important steps in the experiment is to find the resonant frequency, we can use quickly swept sine sweep signal to determine the resonance frequency.The traditional electromagnetic Incentive-Type Fatigue Life Testing System are based on industrial computer control center. Work: data collection, conversion, calculation, display, storage and real-time control of dynamic processes, all accomplished by the host computer. Although computer technology now fully capable, but the integration of lumped there are many convenient system architecture issues, prominent problem is the excessive burden the host computer, All the tasks required to complete at the same time cause the task thread crowded, limiting the dynamic process of real-time control. Followed by a fixed structure, it also brings the hardware resources, limiting the flexibility of system expansionNow, , I based on DSP chips to design a small electromagnetic TMS320LF2407A Encouraging fatigue test system. System, there are two experimental approaches: one is fixed frequency to a constant force load test; a sine sweep signal through the loading mechanism to find the resonant frequency, then resonant frequency of the loading experiments, such experiments to compare the energy conservation. Experimental Selection and configuration of the specific control value is input through the keyboard or the DSP and host computer serial communication to achieve. Control values by the DSP chip will be written to the corresponding parameters of D / A converter, D / A converter output and the phase difference between two independent 180-degree sine wave, multi-stage amplification through the amplifier after a control signal to control excitation winding The current size of electromagnetic force of the object parts of the loading process. The force signal, displacement signal through the low-pass filtering, amplification and other signal conditioning measures, to send A / D converter, and finally sent to the DSP chip, with the target signal are compared, after adjustment by the PID control, optimal control signal . Interaction with the liquid crystal display the size, frequency and force load times. Components being tested to fatigue failure, the system will automatically stop imposing force, and shows the number ultimate load force.This study includes the following:1. Electromagnetic actuator design;2. High-power amplifier design;3.DSP chip TMS320LF2407A internal structure, function, and F2407A external circuit structures;4.DSP software build tools;5. A variety of functions in the DSP, software programming, including: digital filtering, A / D converter, D / A conversion, peak detection, sine sweep signal generation, liquid crystal display, keyboard input, the number of experiments records, stop judging, etc. ;6. The study of the PID algorithm. |
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