Study on Water hydraulic System

本文研究了水液压系统的两种驱动和控制方法。第一种是采用水液压伺服阀的方法，其目的是实现高速、高性能的控制。第二种是使用ON/OFF电磁阀的方法，其目的是避免微生物等污染物引起的水液压系统故障。采用伺服阀的位置控制系统由于水的体积模量大而表现出良好的性能。但由于水的性质，力的控制比位置的控制更困难。负载压力的导数反馈可以有效地补偿力控制。利用扰动力矩观测器对运动控制是有效的，有望作为一种补偿由于水的低润滑而引起的大摩擦力的控制方法。采用ON/OFF电磁阀的PWM和差分PWM控制方法，通过适当调整参数的PID控制器，在逐步响应中表现出良好的性能。在阶跃响应中，压力变化和噪声不会造成严重的问题，因为阀门的开关在稳定时间内最多发生几次。另一方面，通过PWM和差分PWM控制方法，连续位置控制具有良好的跟踪特性。但在这种情况下，阀门的开关总是发生，它会引起噪音。与PWM控制相比，差分PWM控制提供稍低的压力变化和更平滑的位置响应。显著缩短PWM载波周期提供更平滑的位置控制和稳定的力控制。以3d - o - f水液压机械手为具体实例，研究了水液压系统对高性能控制的要求。目前已经进行了初步的控制试验。将上述驱动和控制方法以及其他一些方法应用于实现高性能、抗水污染鲁棒性和低噪声的水液压机械手。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