Study on Water hydraulic System

本文研究了两种纯水液压系统的驱动和控制方法。第一种是使用水压伺服阀的方法，其目标是高速和高性能控制。第二种方法是使用ON/OFF电磁阀，其目的是避免由微生物等污染物引起的水压系统故障。由于水的体积模量大，使用伺服阀的位置控制系统表现出良好的性能。但由于水的特性，力控制比位置控制更困难。负载压力的微分反馈是有效的补偿力控制。采用扰动力矩观测器进行运动控制是有效的，并有望作为补偿水润滑不足引起的大摩擦力的控制方法。采用开关电磁阀的PWM和微分PWM控制方法，通过适当调整PID控制器的参数，显示出良好的阶跃响应性能。 ...更多信息 在阶跃响应中，压力变化和噪声不会引起严重的问题，因为阀的切换在稳定时间内最多发生几次。连续位置控制采用PWM和微分PWM控制方法，具有良好的跟随特性。但在这种情况下，阀门的切换总是发生，并导致噪音行为。与PWM控制相比，差分PWM控制的压力变化略低，位置响应更平滑。PWM载波周期的显著缩短，使位置控制更加平滑，力控制更加稳定。以3自由度纯水液压机械手为例，对纯水液压系统进行了高性能控制。到目前为止，已经进行了初步的控制实验。上述驱动和控制方法以及一些其他方法将被应用于实现具有高性能、对水污染的鲁棒性和低水平噪声的水压机械手。少

Two kinds of driving and control methods for a water hydraulic system are investigated in this study. The first is a method using a water hydraulic servovalve, which aims high speed and high performance control. The second is a method using ON/OFF solenoid valves, which aims to avoid failures of water hydraulic-system caused by contaminants such as microorganisms.A position control system using a servovalve shows good performance due to large bulk modulus of water. But force control is more difficult than position control because of the property of water. Derivative feedback of load pressure is effective to compensate the force control. Usage of a disturbance torque observer is effective to motion control and is expected as a control approach to compensate large friction force caused by low lubrication of water.The PWM and differential PWM control method using ON/OFF solenoid valves show good performances in stepwise responses by using PID controllers with suitably adjusted parameters. … More In the step responses pressure variations and noises do not cause serious problems, because the switching of valves occurs, at most, several times in settling time. On the other hand, continuous position control shows good following characteristic by the PWM and differential PWM control method. But in this case, switching of valves always occurs and it causes noisy behaviors. The differential PWM control gives slightly lower pressure variations and smoother positional responses than the PWM control. Remarkable shortening of PWM carrying wave period provides smoother position control and enables stable force control.We made a 3 D-O-F water hydraulic manipulator as one concrete example of water hydraulic system required high performance control. Preliminary control experiments have been made so far. The driving and control methods described above and some other methods will be applied to realize a water hydraulic manipulator with high performance, robustness against contamination of water, and lower level noises. Less