Local POE model for robot kinematic calibration

A robot kinematic calibration method based on the local frame representation of the product-of-exponentials (Local POE) formula is introduced. In this method, the twist coordinates of the joint axes are expressed in their respective local (body) frames. The advantages of this new approach are threefolds: (1) revolute and prismatic joints can be uniformly expressed in the twist coordinates based on the line geometry; (2) the twist coordinates of the joint axes can be set up with simple values because the local frames can be arbitrarily defined on the links; (3) the kinematic parameters described by the twist coordinates vary smoothly that makes the method robust and singularity-free. By assuming that the kinematic errors exist only in the relative initial poses of the consecutive link frames, the kinematic calibration models can be formulated in a simple and elegant way. The calibration process then becomes to re-define a set of new local link frames that are able to reflect the actual kinematics of the robot. This method can be applied to robot manipulators with generic open chain structures (serial or tree-typed). The simulation and experiment results on a 4-DOF SCARA type robot and a 5-DOF tree-typed modular robot have shown that the average positioning accuracy of the end-effector increases significantly after calibration.     

机器人运动支链构型设计新方法

机器人构型设计中的关键问题就是设计具有确定末端运动特征的支链。提出机器人运动单元、基本运动单元和复合运动单元的概念,给出了各种运动单元的合成原理与部分算法。最后以一类具有平面副运动特征的支链为例,表明该方法简便易行。     

A general framework for geometry design of indexing cam mechanism

Indexing cam mechanism is one of most important mechanisms in automated machineries. This paper presents a general frame for kinematic analysis and geometry design of indexing cam mechanism, such as parallel cam mechanism and roller gear cam mechanism. This method applied screw theory to describe structure of cam mechanism and developed the kinematic equations by using Product of Exponentials Formula (PEF). As long as such structure parameters are given as position and orientation of central line in turret, cam and rollers, geometry modeling of indexing cam can be implemented in a general frame of kinematic equations by applying this method. The paper gives examples to obtain the geometry models of roller gear cam, barrel indexing cam and parallel indexing cam. Our work suggests that this method can avoid the burdensome work on building coordinate systems, transformation matrix and understanding on the mechanism. Moreover, this method can be used to innovate and design new types of indexing mechanism.     

静态锥束CT成像系统的几何标定方法研究

采用X射线源阵列的静态CT成像系统为消除机械运动伪影,提高重建图像质量以及扫描成像效率提供了有效途径。高效、准确的几何标定方法是对X射线源阵列标定的关键。提出通过对一个已知三维标定模板的一次投影成像,采用最小二乘的直接线性变换法实现X射线成像系统的内、外参数准确估计的方法,以此方法用于静态CT扫描成像系统的几何标定。实验和仿真结果表明,该标定方法无需辅助装置,避免了满足要求条件的多次投影成像的过程;不受标定模板空间姿态的限制,一个X射线源与探测器的几何标定只需一次投影成像过程,方法简单、准确、易于操作,适于平面探测器的静态锥束X射线源阵列的成像系统几何参数的准确标定。     

A multi-tube pressure probe calibration method for measurements of mean flow parameters in swirling flows

A simple and sensitive measurement method of multi-tube pressure probes applicable in swirling flow fields is presented in this paper. Determination of flow direction associated with local pitch, , and yaw, ψ, angles, magnitudes of local static and dynamic pressures can be achieved through a calibration method used with 3- and 5-tube versions of a multi-tube pressure probe. The 5-tube probe was tested in a conventional air cyclone where a strong rotational flow prevailed while the 3-tube probe was used in a low swirl flow field in a pipe internally fitted with a helical coiled wire insert. The method is based on the rotational sensitivity of the pressure probe handled through non-dimensional calibration parameters.     

光电经纬仪脱靶量和坐标动态修正

提出了目前采用的脱靶量修正模型的适用条件,采用坐标变换推导经纬仪脱靶量修正公式,获得与球面三角学相一致的推导结果,并在此基础上推导出成像系统无照准轴平行约束条件的通用脱靶量合成公式。采用光学系统的物方焦点作为摄像机系统的投影中心,推导出投影中心与经纬仪回转中心不重合条件下摄像机投影中心在测量坐标系中的坐标值。经测量设备的实际验证,该修正方法突破了现有修正模型的局限性,适用于多传感器经纬仪成像系统     

A relative calibration method for a valve leakage rate measurement system

This paper presents a relative calibration method for an internal valve leakage rate measurement system using both microcontroller and acoustic emission (AE) methods. An air jet was selected to calibrate because it provides a frequency spectrum similar to the AE spectrum obtained from the valve leak, especially in the frequency range of 100-300 kHz. Three AE sensors mounted on a valve were used to validate the system calibration. Ratios between the average energy (AErms) were obtained from each pair of sensors, and these ratios were used to transfer the leakage AErms value. Subsequence, its performance to predict the leakage rate in the laboratory and in the field was tested. The error is less than 5% in almost cases. Its benefit is to reduce the recalibration time when a part of measurement system is changed. Accordingly, inexpensive equipment including an AE sensor was built, and its system performance was revealed.     

基于免疫算法的多变量控制系统PID参数优化方法研究

提出一种基于免疫算法的多变量控制系统PID参数优化方法。首先对免疫算法的步骤和实现过程进行了介绍;接着采用了一种新的、适合多变量系统特点的控制系统性能指标,即用阶跃响应曲线超出期望变化区域的面积的大小来衡量控制系统的优劣。该指标被用于构造免疫算法的适应度函数。论文最后将上述方法用于火电机组负荷控制系统优化,取得了良好的效果。     

A comprehensive method for calibration of volumetric positioning accuracy of CNC-machines

A comprehensive method for measuring the systematic errors of CNC-machine tools has been studied. The method used for measurement and calibration of machine tool errors should be general and efficient. The objectives of this study include:

Identification of material parameters in constitutive model for sheet metals from cyclic bending tests

This paper deals with the identification of material parameters in a constitutive model for sheet metals using the bending moment versus curvature diagrams obtained by cyclic bending tests. The model can describe the cyclic strain hardening by the isotropic hardening and the Bauschinger effect by the kinematic hardening. An optimization technique based on the iterative multipoint approximation concept was used for the identification of the material parameters. This paper describes the experimentation, the fundamentals and the technique of the identification problem, and the verification of this approach.     

基于工艺动作过程的机械执行系统概念设计过程模型

机械产品概念设计的目的是获得产品设计方案,以便为后续的详细设计奠定基础。为了获得较好的产品设计原理方案,需要对机械产品在概念设计阶段的过程模型进一步研究。在前人的研究基础之上,主要针对机械执行系统概念设计过程模型进行研究,提出基于功能-作用原理-工艺动作过程-执行动作-行为-功能载体过程模型和相互之间的映射策略,把产品概念设计的过程模型进一步细化,以更好的符合人们在产品设计过程中的逻辑思维,从而便于提高设计人员的创新能力。