计及阻尼影响的六自由度并联机构模态空间设计及控制

发布时间：2018-06-23 07:52

本文选题：并联机构 + 阻尼耦合　；参考：《哈尔滨工业大学》2015年博士论文

【摘要】：六自由度并联机构以其承载能力强、刚度大、精度高的优点在工业中受到广泛的应用。但由于并联机构固有的强非线性动力学特性,使得系统在物理空间内各自由度之间存在强耦合特性,这种强耦合特性导致传统基于物理空间设计的控制器很难获得理想的高控制品质。目前国内外学者提出了一种新颖的模态空间控制策略,在粘性比例阻尼的假设条件下,基于模态解耦思想将物理空间内强耦合的多输入多输出系统转化为模态空间内相互独立的单输入单输出系统,对各阶模态单自由度系统进行独立控制最终实现提升并联机构控制性能、扩展系统频宽的目的。在工业应用中,并联机构各关节阻尼不可忽略,此时模态空间出现非粘性比例阻尼耦合现象,破坏了模态空间的解耦条件,严重制约了模态空间控制策略的发展。为此,本文对并联机构各关节阻尼引起的耦合非线性进行深入的机理分析,提出从结构设计角度消除模态空间阻尼耦合的新思路,扩展了模态空间控制策略的适用范围,具有十分重要的理论与工程应用价值。本文从惯性参数辨识、结构设计、控制策略三方面进行研究。模态空间控制策略高控制品质的发挥首先受到了系统惯性参数的影响,而现有的惯性参数辨识方法未考虑并联机构各关节阻尼引起的耦合非线性,在辨识原理上存在缺陷。为此,本文提出一种消除阻尼耦合特性影响的惯性参数辨识方法。在建立考虑各关节阻尼特性的完整动力学模型基础上,分析阻尼耦合与惯性参数辨识之间的关系,通过重新构造包含阻尼耦合引起的各自由度相位差信息的辨识方程,从机理上消除阻尼耦合引起的惯性参数辨识误差。同时,针对干摩擦引起的辨识误差,给出基于波形失真度的辨识误差量化评价指标及辨识误差的修正方法。仿真与实验结果验证了该辨识方法的有效性。基于模态解耦的设计方法则从结构角度提供了一种消除系统动力学耦合特性的有效途径,具有机械解耦性质的并联机构为模态空间控制策略发挥其优越控制品质奠定基础。但现有设计方法忽略了并联机构各关节阻尼引起的模态阻尼耦合特性,导致其设计理论无法有效的对工业级低机械成本并联机构进行指导。为此,本文在对包含系统阻尼特性的振动方程进行模态分析的基础上给出模态参数的封闭解析解,进而揭示模态阻尼耦合特性与结构参数的内在联系,提出通过改变结构参数降低系统非粘性比例阻尼耦合成分从而使模态空间控制策略仍然适用的新方法。同时,针对并联机构在大运动范围时由于位姿引起的模态频率耦合特性进行分析,基于模态灵敏度给出全局模态频率耦合评价指标。最后以降低阻尼耦合特性及全局频率耦合特性为综合优化目标,获得消除阻尼耦合影响的全局模态解耦结构优化方法。最后,在通过结构设计消除模态阻尼耦合影响之后,本文发现并联机构的关节阻尼特性引起了新的模态空间高频过阻尼现象,限制了系统频宽的进一步提高。为此,本文结合液压控制理论,提出一种通过动压反馈技术实现降低系统阻尼比从而将系统频宽扩展至模态频率附近的模态空间控制策略,并给出控制器的解析设计方法。同时,为了将模态空间控制策略应用于具有大运动范围的并联机构,本文对位姿引起的模态耦合特性进行研究,基于消除模态跃迁的模态参数实时求解算法,将模态空间控制策略扩展形成全局模态空间控制器。实验结果表明该控制器可大幅提高系统控制性能,并具有结构简单、适用范围大、设计方便的优点,为模态空间控制策略应用于工程实践奠定基础。
[Abstract]:The six degree of freedom parallel mechanism is widely used in industry because of its strong bearing capacity, large stiffness and high precision. However, due to the inherent strong nonlinear dynamic characteristics of the parallel mechanism, the system has strong coupling characteristics between the degrees of freedom in the physical space. This strong coupling characteristic leads to the traditional control based on the physical space design. It is difficult to obtain ideal high control quality. At present, a novel mode space control strategy is proposed by scholars at home and abroad. Under the assumption of viscous proportional damping, the multi input and multi output system with strong coupling in physical space is transformed into a single input single input single output system in a modal space based on the modal decoupling idea. The independent control of each order mode single degree of freedom system can finally achieve the purpose of improving the control performance of the parallel mechanism and expanding the frequency width of the system. In industrial applications, the damping of the joints of the parallel mechanism can not be ignored. At this time, the non viscous damping coupling phenomenon appears in the modal space, which destroys the decoupling condition of the modal space and seriously restricts the modal space. For this reason, this paper analyzes the coupling nonlinearity caused by the joint damping of the parallel mechanism, and puts forward a new idea to eliminate the coupling of modal space damping from the angle of structure design, and extends the scope of application of modal space control strategy, which has very important theoretical and engineering application value. Three aspects of inertia parameter identification, structural design and control strategy are studied. The high control quality of the modal space control strategy is affected first by the inertial parameters of the system, and the existing inertia parameter identification method does not take into account the coupling non-linearity caused by the joint damping of the parallel mechanism, and there is a defect in the identification principle. For this reason, this paper An inertial parameter identification method is proposed to eliminate the influence of damping coupling characteristics. On the basis of a complete dynamic model considering the damping characteristics of each joint, the relationship between the damping coupling and the identification of the inertia parameters is analyzed. By reconstructing the identification equation of the phase difference information of each degree of freedom, which is caused by the damping coupling, the mechanism is eliminated from the mechanism. In addition to the inertia parameter identification error caused by damping coupling, the identification error evaluation index based on the waveform distortion and the correction method of identification error are given. The simulation and experimental results verify the validity of the identification method. The design method based on the mode decoupling provides the structure angle. It is an effective way to eliminate the coupling characteristics of the system dynamics. The parallel mechanism with mechanical decoupling properties lays the foundation for the mode space control strategy to play its superior control quality. However, the existing design method ignores the modal damping coupling characteristics caused by the joint damping of the parallel mechanism, which leads to the failure of the design theory to be effective. In this paper, a closed analytical solution of modal parameters is given on the basis of the modal analysis of the vibration equation containing the damping characteristic of the system, and the internal relationship between the modal damping coupling characteristics and the structural parameters is revealed, and the non viscous proportion resistance of the system is reduced by changing the structural parameters. The new method of modal space control is still applicable by the synthesis of the coupling system. At the same time, in view of the modal frequency coupling characteristics caused by the position and attitude of the parallel mechanism in large motion range, the global modal frequency coupling evaluation index is given based on the modal sensitivity. Finally, the damping coupling characteristic and the global frequency coupling characteristic are reduced. As a comprehensive optimization goal, the global modal decoupling optimization method is obtained to eliminate the damping coupling effect. Finally, the joint damping characteristics of the parallel mechanism are found to cause a new modal space high frequency over damping after the damping coupling effect is eliminated by structural design, which limits the further enhancement of the system bandwidth. In this paper, based on the hydraulic control theory, this paper proposes a modal space control strategy which can reduce the system damping ratio by dynamic pressure feedback and expand the system frequency to the modal frequency, and gives the analytical design method of the controller. At the same time, in order to apply the modal space control strategy to a parallel mechanism with large motion range. In this paper, the modal coupling characteristics caused by position pose are studied. Based on the real time solving algorithm of modal transition, the modal space control strategy is extended to form a global modal space controller. The experimental results show that the controller can greatly improve the control performance of the system, and has a simple structure, large scope of application and convenient design. Advantages lay the foundation for the application of modal space control strategy in engineering practice.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH112

【相似文献】