共查询到18条相似文献,搜索用时 453 毫秒
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电液伺服系统非线性振动机理及试验研究 总被引:1,自引:0,他引:1
电液伺服系统是非线性动力学系统,在工作过程中容易出现非线性振动、噪声、冲击和爬行等异常现象,而且诱因不易确定,严重影响系统的稳定性。根据非线性动力学原理,建立电液伺服系统的非线性动力学模型。通过理论研究,探索非线性液压弹簧力和非线性摩擦力等非线性因素对系统动力学特性的影响规律。指出非线性液压弹簧力作用可以用Duffing方程描述,非线性摩擦力作用可以用Van Der Pol方程描述。用研究非线性动力学系统的有效方法:时间历程、频闪采样、功率谱等,对实测信号进行深入分析,多方位揭示电液伺服系统非线性振动的机理及诱因。结果表明,非线性液压弹簧力引起的"跳跃现象"和非线性摩擦力引起的极限环型振荡的共同作用是导致系统发生非线性振动的一个主要诱因,值得关注。 相似文献
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《液压与气动》2020,(8)
针对交变载荷作用下的液压缸动力学特性,进行了数值仿真分析研究。首先,阐述了液压弹簧刚度非线性变化引起的软硬弹簧现象,以及时变摩擦力随速度变化呈现出负阻尼特征的产生机理,指出二者耦合作用是造成液压缸出现非线性动态特性的根本原因;之后,采用数值方法离散时间域步长,基于Taylor展开法确定摩擦阻尼,通过迭代求解非线性微分方程,获得活塞的速度、位移等性能参数曲线;最后,通过具体算例,采用MATLAB软件对交变载荷作用下液压缸的动态特性进行数值仿真分析。仿真结果表明,所提方法与实测出现的时域波形复杂、尖峰繁多等现象相符,可以较好地模拟液压缸的非线性运动规律,能够对工程实际提供指导。 相似文献
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为验证液压缸非线性力对半主动升沉补偿系统的影响,设计了一种半主动升沉补偿系统的非线性模型,并提出了提高系统补偿效率的方法。首先建立液压缸受到的非线性摩擦力和非线性弹簧力的仿真模型,然后将非线性力的影响加入到被动和半主动升沉补偿仿真模型中,最后提出了增大液压缸和蓄能器之间的油管直径的方法以提高半主动升沉系统补偿效率。仿真结果表明:在峰值为6 m,周期为10 s的规则正弦波浪作为船舶升沉位移输入时,非线性摩擦力会使被动和半主动升沉补偿系统的补偿效率降低,而非线性弹簧力对系统的影响较小,可以忽略不计。提出的方法能有效提高半主动升沉补偿系统补偿效率。 相似文献
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大型起竖设备四级液压缸因内部结构复杂,且负载很大,摩擦力特性较为复杂,以往对其动力学建模时常常忽略摩擦力。而快速起竖系统要求对速度进行精确规划控制,以减缓换级冲击,且液压缸结构稳定性分析时也需要准确找到危险工况,其中摩擦力是很关键的一个因素。LuGre摩擦模型能较好描述大部分情况下的摩擦稳态、瞬态特性,据此,考虑滑动油膜动态等性方程,基于LuGre模型对四级缸摩擦力建模,而后对风载荷、起竖力等进行分析,进而对起竖过程动力学建模。该研究所建的全新动力学模型可为起竖速度的精确控制和油缸应力应变及模态分析提供参考。 相似文献
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电液伺服振动试验系统低速和换向时的非线性摩擦力测量和补偿是提高运输环境试验和地震模拟试验等控制精度的重要途径。为了定量获取液压振动台的非线性摩擦力,基于Stribeck效应建立了改进的电液伺服振动试验系统非线性摩擦力理论模型,并结合液压振动台的力平衡方程建立了非线性摩擦力待辨识参数的目标函数。提出一种基于位移闭环控制的简便方法对不同速度下的液压振动台油缸压力差进行测量,得到振动台液压缸与活塞杆之间的摩擦力随速度变化的数值规律。采用基于拟随机序列的混合遗传算法对非线性摩擦力理论模型的4个参数进行了辨识。试验结果证明了本研究方法的可行性,为液压振动试验系统加速度波形失真补偿提供了一定参考。 相似文献
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由于受倾覆力及刚体表面粗糙度影响,液压柱塞泵斜盘-滑靴运动副(滑靴副)在相对运动时处于混合润滑状态。斜盘和滑靴表面接触引起弹性和塑性变形,进而产生表面接触力。接触力与油膜厚度密切相关,在油膜特性分析时不应被忽略。提出一种基于流体动压润滑理论的滑靴副油膜特性(油膜厚度、压力分布、油膜间隙流量)的分析与计算方法,考虑了滑靴副粗糙表面的支撑力影响。在雷诺流体动压润滑方程基础上,考虑滑靴副刚体表面粗糙度水平和油膜厚度,计算液压柱塞泵不同工况下的表面接触支撑力,并将接触力融入运动副的受力方程。提出了基于改进的雷诺流体动压润滑方程的数值计算方法,并进行了仿真分析,通过间接对比滑靴副间隙流量的仿真结果,证实了提出方法的有效性和结果的准确性。 相似文献
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《机械工程学报(英文版)》2015,(5)
The previous sensitivity analysis researches are not accurate enough and also have the limited reference value, because those mathematical models are relatively simple and the change of the load and the initial displacement changes of the piston are ignored, even experiment verification is not conducted. Therefore, in view of deficiencies above, a nonlinear mathematical model is established in this paper, including dynamic characteristics of servo valve, nonlinear characteristics of pressure-flow, initial displacement of servo cylinder piston and friction nonlinearity. The transfer function block diagram is built for the hydraulic drive unit closed loop position control, as well as the state equations. Through deriving the time-varying coefficient items matrix and time-varying free items matrix of sensitivity equations respectively, the expression of sensitivity equations based on the nonlinear mathematical model are obtained. According to structure parameters of hydraulic drive unit, working parameters, fluid transmission characteristics and measured friction-velocity curves, the simulation analysis of hydraulic drive unit is completed on the MATLAB/Simulink simulation platform with the displacement step 2 mm, 5 mm and 10 mm, respectively. The simulation results indicate that the developed nonlinear mathematical model is sufficient by comparing the characteristic curves of experimental step response and simulation step response under different constant load. Then, the sensitivity function time-history curves of seventeen parameters are obtained, basing on each state vector time-history curve of step response characteristic. The maximum value of displacement variation percentage and the sum of displacement variation absolute values in the sampling time are both taken as sensitivity indexes. The sensitivity indexes values above are calculated and shown visually in histograms under different working conditions, and change rules are analyzed. Then the sensitivity indexes values of four measurable parameters, such as supply pressure, proportional gain, initial position of servo cylinder piston and load force, are verified experimentally on test platform of hydraulic drive unit, and the experimental research shows that the sensitivity analysis results obtained through simulation are approximate to the test results. This research indicates each parameter sensitivity characteristics of hydraulic drive unit, the performance-affected main parameters and secondary parameters are got under different working conditions, which will provide the theoretical foundation for the control compensation and structure optimization of hydraulic drive unit. 相似文献
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Yong-hui Park Hun-kee Lee Kyu-tae Park Hyun-chul Park 《Journal of Mechanical Science and Technology》2016,30(3):975-982
We studied a mold oscillating mechanism for continuous casting. An equivalent hydraulic servo system model was established including a non-linear property and line volume near the hydraulic cylinder. The analysis focused on a practical behavior of the system. To observe an oscillated object and dynamic responses, an equivalent stiffness, damping ratio and simple mass-damper-spring 1-DOF model were established by Karl-Erik Rydberg’s research, and showed hydraulic cylinder pressure and line volume near the hydraulic cylinder. Especially, hydraulic pressure including statue of a mechanical and hydraulic cylinder was analyzed in the time and frequency domain. The results were validated by comparing responses between the 1-DOF model and the nonlinear hydraulic servo system model. The line volume that connects the hydraulic cylinder and the hydraulic servo valve has great effect on damping ratio and natural frequency of the hydraulic servo system. When the line pipe has high volume compared to normal statue, the hydraulic cylinder pressure has sharp peak frequencies that are located on natural frequency and its duple-harmonic terms with sideband peaks; (±2×exciting frequency) space. Based on this fact, we investigated the model using sensitivity analysis, and explained an oscillating mechanism about the mold oscillator by applying additional spring. A design of robust control for the mold oscillator was suggested by Negative strip time criterion, and maximum additional spring stiffness was shown. 相似文献