【作者】 张弓；

【导师】 柯坚；

【作者基本信息】 西南交通大学 ， 驱动技术与智能系统， 2009， 博士

【摘要】 电液比例阀是电液比例控制技术的核心元件,它以传统的工业用液压控制阀为基础,采用模拟式电气—机械转换装置,将电气信号转换为位移信号,按输入电气信号指令,连续成比例地控制液压系统的液流压力、流量或方向等参数。电液比例阀与伺服控制系统中的电液伺服阀相比,虽然其性能在某些方面还有一定的差距。但是,其显著的优点是抗污染能力强,减少了由于污染而造成的工作故障,提高了液压系统的工作稳定性和可靠性,因此更适合于工业过程。另一方面,比例阀的成本比伺服阀低,而且不包含敏感和精密的部件,更容易操作和保养,已在许多液压控制场合获得广泛的应用。然而,传统的电液比例阀是以比例电磁铁作为驱动装置的电—液信号转换元件,由于其固有特性的限制,导致电液比例阀无论是响应时间还是响应速度都不是很快。响应速度较快的,流量却比较小。为此,本文提出超高速电液比例阀。超高速电液比例阀能实现液压控制系统液流方向和流量的控制,满足电液比例控制系统高速、高精度、大流量、低成本和抗污染的综合要求。超高速电液比例阀采用动圈式电—机械转换器作为驱动装置的电—机械转换元件,控制性能很好,某些性能指标达到甚至超过了电液伺服阀。首先,针对常规动圈式电—机械转换器在电磁力、响应时间和响应速度等性能上的不足,从其核心部分——永磁体结构入手,对比单个永磁体不同的磁化技术和多个永磁体不同的磁化阵列结构,提出了一种新颖永磁体沿外磁场磁力线方向磁化、8片瓦型有气隙Halbach磁化阵列型动圈式电—机械转换器。通过对设计的动圈式电—机械转换器静态磁场、参数化磁场、瞬态磁场、温度场、涡流磁场、功率损耗和趋肤效应等的分析,表明该动圈式电—机转换器具有良好的动静态性能,无论电磁力,还是响应时间和响应速度都比常规结构有较大的提高。接着,从超高速电液比例阀的液压部分着手,根据其结构和原理,并结合功率键合图法和CFD计算,分析了超高速电液比例直动式先导阀、叠加式单向节流阀和主控阀的静态和动态特性,得到超高速电液比例阀高频和快速响应的机理。然后,针对常规电液比例阀建模的局限性,根据包含各种非线性特征的孔流量方程,为超高速电液比例阀模型建立统一的非线性数学方程。获得关于阀芯几何属性和物理模型参数对通过比例阀端口流量的关系式,得到能分析正遮盖、负遮盖和零遮盖比例阀的流量方程,此时流量被表达为关于阀芯遮盖参数和其他常规参数的连续非线性函数。同时,对超高速电液比例阀统一模型的非量纲分析表明,模型的精确性独立于模型参数之外,统一模型的误差仅依赖于液压阻尼系数。为了确保超高速电液比例阀的性能可靠,必须监测比例阀的临界参数,以确定故障是否出现。但是,在比例阀运行过程中,直接测量某些参数将会是非常困难的。本文提出三种参数估计方法,一般最小二乘法、极大似然估计法和模糊RBF网络法,用来估算超高速电液比例直动式先导阀的弹簧刚度。估计结果与实际结果相差不大,表明这三种方法是可行的。最后,通过对超高速电液比例直动式先导阀的实验研究,可知实验结果与仿真结果基本吻合,表明所设计的电液比例阀具有高频和快速响应特性,能较好地满足高速电液比例控制技术的要求。更多还原

【Abstract】 The electro-hydraulic proportional valves, based on the conventional industry hydraulic control valves, are key components of electro-hydraulic proportional control techniques. Using analog electro-mechanical conversion devices, they can convert electric signals into displacement signals, and control the parameters such as pressure, flow and direction of hydraulic systems continuously and proportionally according to the electronic input reference signals. The electro-hydraulic proportional valves offer prominent advantages of strong anti-contamination abilities compared to electro-hydraulic servovalves of servo control systems, in spite of certain poor characteristics in some perspectives. They are more suitable for industrial environments because they are less prone to malfunction due to fluid contamination and can improve the stability and reliability of hydraulic systems. In addition, proportional valves are much less expensive, since proportional valves do not contain sensitive, precision components, they are easier to handle and maintain, and are becoming increaingly popular in fluid power control applications. However, the conventional electro-hydraulic proportional valves are the electro-hydraulic signals conversion components by way of the proportional solenoid which offers as the driving device. Due to the limitation of proportional valves’ natural characteristics, the response time and response speed of electro-hydraulic proportional valves are not very swift, the response speed is slightly faster while the flow is smaller.Towards this end, in this paper, an ultra-high-speed electro-hydraulic proportional valve is proposed, which can control the flow and direction of hydraulic control systems, and can satisfy the synthetical requirements of high response, high accuracy, high flow, low cost and anti-contamination characteristics of electro-hydraulic proportional control systems. The moving coil electromechanical converter is used as the electro-mechanical conversion component of the driving device for an ultra-high-speed electro-hydraulic proportional valve. Ultra-high-speed electro-hydraulic proportional valve enjoys advantages of control performance, and some performance indexes are achieved and even exceeded those of electro-hydraulic servovalve.Above all, in order to improve the characteristics of conventional moving coil electro-mechanical converter, such as weak points on electro-magnetic force, response time, response speed, studied from permanent magnet structure that is key component of moving coil electro-mechanical converter, different magnetization techniques of single permanent magnet and different magnetization array structures of multiple permanent magnets are compared in this paper. A novel moving coil electro-mechanical converter using eight-pieces tegular Halbach magnet array with air gap magnetized along the external field force lines is proposed as well. The analyses on magnetostatic field, parametric field, transient field, thermal field, eddy current field, power loss and shin effect of moving coil electro-mechanical converter demonstrate that the redesigned moving coil electro-mechanical converter possesses the good dynamic and static performance, electro-magnetic force, the response time and response speed are improved enormously than those of conventional structures.Subsequently, this paper studies from the hydraulic parts of electro-hydraulic proportional valve, and analyzes the dynamic and static characteristics of electro-hydraulic proportional direct operated pilot valve, stacked unidirectional throttle valve and main control valve in terms of the structure and principle, with the combination of power bond graph and computational fluid dynamics. The mechanism of high frequency and rapid response is put forward as well.Afterwards, aiming at overcoming the limitation of the generic electro-hydraulic proportional valves modeling, the paper first develops an orifice flow equation that involves various nonlinear effects and then proposes the unified nonlinear equations for an ultra-high-speed electro-hydraulic proportional valve model. These equations relate the spool geometric properties and physical model parameters to the flow rate through the proportional valve ports. The development focuses on obtaining the flow rate equations applicable to overlapped, underlapped and critical center proportional valves. Here, the flow rates are expressed as a continuous but nonlinear function of lapping parameters, as well as other conventional parameters. Meanwhile, a non-dimensional analysis of the unified model for an ultra-high-speed electro-hydraulic proportional valve confirms that the accuracy of the model is independent of the choice of model parameters, unified model errors depend on the value of the hydraulic damping coefficient alone.To ensure reliable performance of ultra-high-speed electro-hydraulic proportional valves, it is important to be able to monitor certain critical parameters of proportional valves in order to determine whether a fault is occurring. However, direct measurement of these parameters during proportional valves operation may be exceedingly difficult. In this paper, three well-known parameter estimation techniques, the ordinary least squares, the maximum likelihood and fuzzy RBF neural network, are used to estimate the spring constant of an ultra-high-speed electro-hydraulic proportional direct operated pilot valve. The results agree well with the real values, providing a promising indication of their potential.Eventually, the experimental investigations of an ultra-high-speed electro-hydraulic proportional direct operated pilot valve present that the experimental results are fairly good agreement with the simulation results. The results show that the developed electro-hydraulic proportional valve offers extremely high frequency and rapid response characteristics, and can satisfy the requirements of high speed electro-hydraulic proportional control techniques.更多还原