| Cryomicroscope is an important tool in the research of low temperature biology and medicine. With the help of cryomicroscope, the dynamic, micron-scale, visual investigation of freezing and thawing processes in living tissues and individual cells can be carried out.In this essay, the historical development and current status of cryomicroscope and the tempareture control algorithms are briefly introduced. A microscope system with computer-controlled temperature based on semiconduct cooler and a piecewise fuzzy intergal control algorithms are anaylzed. For this cryomicroscope, the arrange of temperature reaches -10℃ ～ +40℃, the minimum cooling rate can reach 5℃/min and the maximum warming rate can reach 10℃/min, the static precision can reach ± 0.5 ℃The following is about the main work of this task:1. According to the requirment of user, give a design of the platform of the whole system. PC is elected as a contol unit. The temperature signal is gathered by A/D data collection card. The common microscope is also being refited.2. The part of hardware is designed and realised. Such as Pt100 temperature sensor, hot resistance signal conditioning and H bridge reversible driver.3. The part of software is designed and realised. It's written by Visual Basic 6.0 with a friendly Man-machine interface, and consisted of hardware interface programming, data sampling, digital filter, data processing, PWM output, etc.4. Due to the characteristics of the controlled object are big delay lag and big inertia, a kind of control arithmetic named piecewise fuzzy intergral control is designed. Because of good adaptability and dynamic performance, fuzzy control without accurate mathematic model is applied on the first level. The second level is applied with self-adjust fuzzy PID control. It has good static precision, robust and reliability.From the results of experiments, they are substatiated that the piecewise fuzzy intergral control presented in this paper is effective for... |
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