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首页> 外文会议>International Conference on Fluid Power Transmission and Control(ICFP' 2005); 20050405-08; Hangzhou(CN) >Application of Electrohydraulic Direct Digital Servo in Metal Extension Test Machine
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Application of Electrohydraulic Direct Digital Servo in Metal Extension Test Machine

机译：电液直接数字伺服在金属延伸试验机中的应用

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摘要

Fine controls of stress rate, strain rate and elongation speed are demanded in the extension test of metallic material to correspond to three distinct elongation stages: elastic, yielding and reinforcing. For the hydraulic extension test machine, the loading to the specimens is carried out by an electrohydraulic servo control system, in which the extension of the material is controlled and automatically switched to the different control modes by a control valve. Since the valve plays a key role of both power amplification and electro-to-mechanical transformation in an electrohydraulic servo system, it dominates to a large extent the performance of the whole control system. On the other hand, being a test device or equipment, the extension test machine is demanded to possess high-accuracy for its electrohydraulic servo control system. According to the Chinese National Standard, the error rate for constant force control should be less than 0.2% and that of the force rate less 0.2%. The demand of the electrohydraulic valve is even higher. For this reason a special electrohydraulic digital valve has been developed and applied in the electrohydraulic servo loading system of the material testing machine to meet the requirement of the National Standard. The strategy for the digital control of the valve is discussed and a comparison between the conventional servo/proportional valve and the digital valve is presented. It is pointed out that the superior of the digital valve to the servo/proportional valve is owed to its characteristics of stage control. The nonlinear error of the digital valve can be lowered to 0.1% by appropriate selection to the stage number of the digital valve to meet the National Standard requirement on control accuracy of the extension test machine.
机译：在金属材料的拉伸测试中，需要对应力率，应变率和伸长速度进行精细控制，以对应于三个不同的伸长阶段：弹性，屈服和增强。对于液压拉伸试验机，通过电动液压伺服控制系统对样品进行加载，在该系统中控制材料的拉伸并通过控制阀自动切换到不同的控制模式。由于该阀在电液伺服系统中起着功率放大和机电转换的关键作用，因此在很大程度上控制了整个控制系统的性能。另一方面，作为测试设备，扩展测试机要求其电液伺服控制系统具有高精度。根据中国国家标准，恒力控制的误差率应小于0.2％，而恒力控制的误差率应小于0.2％。电动液压阀的需求更高。因此，开发了一种特殊的电动液压数字阀，并将其应用在材料试验机的电动液压伺服加载系统中，以满足国家标准的要求。讨论了阀数字控制的策略，并比较了传统伺服/比例阀和数字阀。要指出的是，数字阀优于伺服/比例阀的原因在于其阶段控制的特性。通过适当选择数字阀的级数，数字阀的非线性误差可以降低到0.1％，以满足国家标准对扩展试验机控制精度的要求。

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