一种特殊3-UPU并联平台机构瞬时运动特性

利用反螺旋和主螺旋的方法分别研究了一种特殊3-UPU并联平台机构上下平台平行时的瞬时运动特性.得出该机构在上下平台平行时,机构具有沿坐标轴轴线方向的移动和以x、y坐标轴轴线或其平行的直线为轴线的转动,是三自由度机构.绘制了上下平台平行时所有运动螺旋的空间分布图.研究结果丰富了欠秩三自由度并联机构的理论,对机器人的控制以及轨迹规划等诸多问题都有很重要的意义.     

平面5R并联机器人约束误差影响分析

少自由度并联机器人中的过约束构型,具有结构简单、刚度大的优点,但其依赖运动副轴线间的特殊几何约束关系,如平行、垂直、汇交于一点等,来实现预期的动平台自由度。此类机构有对几何约束条件敏感的缺点,约束误差的存在将对机构产生一系列不良影响。基于此,以平面5R并联机器人为对象,在分析其过约束特性基础上,研究运动副轴线几何约束误差导致的回路封闭变形协调条件。应用矩阵力法计算强制装配引起的机构附加内力以及连杆的变形,从而分析动平台的寄生运动以及机构的应变能波动。对一种具体的5R并联机器人进行仿真分析,计算结果揭示了过约束机构对运动副轴线几何约束误差的敏感性以及约束误差与过约束共同作用下对并联机器人性能的影响机理。     

虚设机构法正确性的论证

并联机器人多回路非对称机构应用非常广泛 ,对其作运动分析一直采用应用很好的虚设机构法去建立其影响系数矩阵。但虚设机构法的科学性并没有进行严格的论证。为了提供更广泛的应用基础 ,在这里对其合理性 ,正确性进行了讨论 ,给出了理论上的证明。     

液压油缸检测机器人设计与分析

提出一种便携式大变径全驱式的油缸检测机器人,该机器人采用模块化设计思想,分为运动机构和转台机构两部分。运动机构采用周向三轮定位全驱机构和双丝杆剪刀式主动变径机构相结合,通过对称式设计,在实现油缸内行走及变径的同时,保证运动机构中心轴线始终与油缸内壁中心轴线平行。转台机构可实现转动和支撑两种运动,通过对称式刚性支撑腿设计,使转台稳定支撑在管道内。机器人直径190 mm～450 mm,重量12 kg,可携带。测试表明检测机器人具有良好的检测性能和大变径适应性,适用于大口径油缸内壁的检修检测。     

虚设机构法正确性的论证

并联机器人多回路非对称机构应用非常广泛，对其作运动分析一直采用应用很好的虚设机构法去建立其影响系数矩阵。但虚设机构法的科学性并没有进行严格的论证。为了提供更广泛的应用基础，在这里对其合理性，正确性进行了讨论，给出了理论上的证明。     

少自由度并联机构真实运动分析

利用螺旋理论分析组成少自由度并联机构的转动副轴线和移动副轴线之间的几何关系,根据运动副轴线之间的关系,分析由于加工、安装等原因造成的机构运动副轴线可能存在的误差形式。给出当机器人存在不相交误差和不平行误差时,少自由度机器人的各分支对于机器人的动平台的约束形式,以及存在这些约束下,少自由度并联机器人可能实现的运动形式。对具有相同分支的少自由度并联机器人建立误差模型。给出机器人动平台的真实运动模型,试验验证了前面分析的正确性。     

四自由度混联式码垛机器人动态静力学分析

针对四自由度混联式码垛机器人采用平行四杆机构的串并联新型结构,利用动态静力学方法将瞬时惯性力系转化为静力系,通过机器人整体及其子系统的力系平衡方程建立了机器人的动态静力学模型。利用Matlab软件编写了水平轴和受力状态的程序,并进行了仿真运算和分析。该模型已成功应用于工业码垛机器人的设计和校核,样机的良好运行表明了该模型的正确性。     

3-RTT并联机器人奇异位形空间分析

采用基于机构瞬时运动分析的方法，建立了3—RTT并联机器人的奇异位形判别阵。分析了3—RTT机器人处于奇异位形时机构所满足的几何条件。编制了基于三维搜索算法的奇异位形空间分析程序，时实例进行搜索计算和分析，给出了3-RTT机器人的奇异位形空间的图形，并对其分布规律进行了分析。     

6_PUS并联机器人运动学性能参数优化设计

采用雅可比矩阵条件数方法在并联机器人全域工作空间内,对影响6_PUS风洞并联支撑机器人性能指标的主要结构参数进行了优化分析。通过仿真发现该机器人动平台、球铰位置、拉杆长度、平行梁宽度等参数对其运动性能有较大的影响,总体上看6_PUS并联机器人的加速度性能要好于速度性能,而要使机器人获得最佳的综合性能,则需要对这些参数进行综合优化。通过对这些参数和性能关系之间的全面考虑,最后选定了并联机器人的主要设计参数,使机构性能达到了设计的要求。     

一种新型助力机器人奇异位形分析

设计了一种助力机器人结构并把该机构简化为一个3)URS机构,该机构可以实现动、定两平台的相对平行运动。根据修正的Grbler)Kutzbach公式计算出并联机构的自由度为6。在进行机构奇异性分析时,将该机构模型简化为一个含有两个动平台的机构,推导出了机构的运动学雅克比矩阵;分析了该机构的奇异位形,指出了机构处于奇异位形时的条件。     

Over-constraints and a unified mobility method for general spatial mechanisms Part 2: Application of the principle

The pre-research on mobility analysis presented a unified-mobility formula and a methodology based on reciprocal screw theory by HUANG, which focused on classical and modern parallel mechanisms. However its range of application needs to further extend to general multi-loop spatial mechanism. This kind of mechanism is not only more complex in structure but also with strong motion coupling among loops, making the mobility analysis even more complicated, and the relevant research has long been ignored. It is focused on how to apply the new principle for general spatial mechanism to those various multi-loop spatial mechanisms, and some new meaningful knowledge is further found. Several typical examples of the general multi-loop spatial mechanisms with motion couple even strong motion couple are considered. These spatial mechanisms include different closing way: over-constraint appearing in rigid closure, in movable closure, and in dynamic closure as well; these examples also include two different new methods to solve this kind of issue: the way to recognize over-constraints by analyzing relative movement between two connected links and by constructing a virtual loop to recognize over-constraints. In addition, over-constraint determination tabulation is brought to analyze the motion couple. The researches above are all based upon the screw theory. All these multi-loop spatial mechanisms with different kinds of structures can completely be solved by following the directions and examples, and the new mobility theory based on the screw theory is also proved to be valid. This study not only enriches and develops the theory and makes the theory more universal, but also has a special meaning for innovation in mechanical engineering.     

Over-constraint and a Unified Mobility Method for General Spatial Mechanisms Part 1: Essential Principle

Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms(GMSMs) is more difficult to obtain correct results. The reason is that its multi-loop is formed through several times of closings and there also exists motion coupling even strong coupling, where the over-constraints are concealed. However, the mobility analysis for this kind of mechanisms has been paid few attentions. A new systemic methodology for analyzing mobility is proposed for GMSMs also based on the screw theory. The key issue for mobility analysis is to recognize the over-constraint. Firstly, three theorems are given and point out: the reason and site of over-constraint occurrence, calculating the number of over-constraints by the screw theory, and how to analyze the over-constraints for a single-loop mechanism as well. Then, three closing forms for GMSMs are proposed including rigid closure, movable closure and dynamic closure, and for the three different forms the different analysis methods are also given. Especially, for the most difficult issue of GMSMs with the multi-loop closure in many times and the inevitable motion coupling, two important methods are proposed: "recognizing over-constraints by analyzing relative movement" and "recognizing over-constraints by virtual loop". The two methods are well used to solve the issue. Above-mentioned principles are not only systematic and effective but also unified. They provide a theoretical basis for the general multi-loop spatial mechanisms.     

Multi-loop control of UPS inverter with a plug-in odd-harmonic repetitive controller

This paper proposes an improved multi-loop control scheme for the single-phase uninterruptible power supply (UPS) inverter by using a plug-in odd-harmonic repetitive controller to regulate the output voltage. In the suggested control method, the output voltage and the filter capacitor current are used as the outer and inner loop feedback signals, respectively and the instantaneous value of the reference voltage feedforwarded to the output of the controller. Instead of conventional linear (proportional-integral/-resonant) and conventional repetitive controllers, a plug-in odd-harmonic repetitive controller is employed in the outer loop to regulate the output voltage, which occupies less memory space and offers faster tracking performance compared to the conventional one. Also, a simple proportional controller is used in the inner loop for active damping of possible resonances and improving the transient performance. The feedforward of the converter reference voltage enhances the robust performance of the system and simplifies the system modelling and the controller design. A step-by-step design procedure is presented for the proposed controller, which guarantees stability of the system under worst-case scenarios. Simulation and experimental results validate the excellent steady-state and transient performance of the proposed control scheme and provide the exact comparison of the proposed method with the conventional multi-loop control method.     

Finite element approach to mathematical modeling of high-speed elastic linkages

A general approach is described for deriving the equations of motion of planar linkages in high-speed machinery. Based on the work of several current authors, well-known displacement finite element method is used to develop the mass and stiffness properties of an elastic linkage. To demonstrate the various steps in the analysis, a 4-bar linkage is utilized; however the method is readily extendible to other planar multi-loop linkages. Starting with a typical elastic planar beam element, the nodal displacement and acceleration expressions are derived including the terms coupling the elastic and rigid-body motions. The linkage is modeled as beam elements and its equations of motion are stated in matrix form. Methods are described for systematic assembly of all elements, resulting in the undamped equations of motion of the total system. Conventional forms of structural damping are reviewed and appended to this paper for inclusion in the equations of motion. This paper also includes assumptions made in order to simplify the analyses here as well as facilitate numerical solutions.     

单螺杆泵定子内螺旋曲面包络镗削技术研究

结合单螺杆泵定子衬套的特殊结构,提出了定子内螺旋曲面加工的新方法即无瞬心包络镗削方法,该方法以螺杆-衬套副的运动原理为依据,以螺杆无瞬心包络铣削加工方法为理论实践基础,利用数控机床实现定子内螺旋曲面廓形的镗削加工。还分析了螺杆在衬套中的运动规律,阐述了无瞬心包络镗削加工技术的基本原理,并论证了该技术实现的可行性。     

四足步行机器人稳定性分析

基于四足步行机器人模型对机器人的瞬时质心坐标进行了计算,得出了瞬时质心的运动规律,分析了各质量模块对机器人质心坐标的影响,对比了瞬时质心位移与几何中心位移的相对关系。给出了四足步行机器人静步态稳定性判定的公式,计算了基于瞬时质心的稳定裕度,并对稳定裕度进行了对比分析。     

Multi-loop decentralized PID control based on covariance control criteria: an LMI approach

PID control is well known and widely applied in industry and many design algorithms are readily available in the literature. However, systematic design of multi-loop or decentralized PID control for multivariable processes to meet certain objectives simultaneously is still a challenging task. Designing multi-loop PID controllers such that the process variables satisfy the generalized covariance constraints is studied in this paper. A convergent computational algorithm is proposed to calculate the multi-loop PID controller for a process with stable disturbances. This algorithm is then extended to a process with random-walk disturbances. The feasibility of the proposed algorithm is verified by applying it to several simulation examples.     

Multi-loop PI controller design based on the direct synthesis for interacting multi-time delay processes

In this article, a new analytical method based on the direct synthesis approach is proposed for the design of a multi-loop proportional-integral (PI) controller. The proposed design method is aimed at achieving the desired closed-loop response for multiple-input, multiple-output (MIMO) processes with multiple time delays. The ideal multi-loop controller is firstly designed in terms of the relative gain and desired closed-loop transfer function. Then, the standard multi-loop PI controller is obtained by approximating the ideal multi-loop controller using the Maclaurin series expansion. The simulation study demonstrates the effectiveness of the proposed method for the design of multi-loop PI controllers. The multi-loop PI controller designed by the proposed method shows a fast, well-balanced, and robust response with the minimum integral absolute error (IAE).     

Evaluation method to determine radial accuracy of high-precision rotating spindle units

In this paper, the authors present a new technique, called the vector indication method, which computes and illustrates the radial error motion of a rotating spindle as the instantaneous vectors on a plane normal to a spindle axis. The radial error motion is measured by two sensors located perpendicularly to each other. A new algorithm is developed to obtain the instantaneous vectors of spindle axis displacement by digital processing. It is revealed that the behavior of displacement of spindle axis can be more precisely known by the vector indication method than by “the Lissajous' figure,” which is one of the conventional methods.