一种球面2-DOF冗余驱动并联机器人的优化设计

提出了一种基于兼顾全域性能指标和局域性能指标相对性能综合最优的机器人机构尺寸优化设计方法,运用VB、Matlab软件编写优化程序,并通过范例给出了该优化程序的使用方法,实现了球面2-DOF冗余驱动并联机器人机构在不同应用场合下兼顾不同性能的尺寸优化设计。

基于H_∞控制理论的2-DOF内模控制器设计及其在电力系统中的应用

给出一种基于H∞ 控制理论的二自由度内模控制器设计方法 .考虑了标称模型与实际模型之间存在乘性摄动时的失配性 ,利用适当的状态变换 ,将跟踪问题的控制器设计转化成一个调节问题的标准H∞ 控制器设计问题 ,再利用H∞ 输出动态反馈完成了控制器设计 .以电力系统模型为例设计了一个二自由度H∞ 励磁控制器 。

基于拓扑优化的平面2-DOF柔顺并联机构构型设计

目的运用拓扑优化技术设计一种平面2-DOF(Degrees-of-Freedom)柔顺并联机构,使其具有微米级别的微运动特性。方法依据平面2-DOF并联原型机构的受力情况进行运动特性分析,基于同构封闭矢量映射原理构建平面2-DOF柔顺并联机构的微分运动Jacobian矩阵,表达多自由度的柔顺并联机构从输入到输出间各关节的运动关系。定义柔度为优化目标函数,微分运动Jacobian矩阵为运动条件,材料体积分数为约束条件,构建平面2-DOF柔顺并联机构材料属性的有理近似模型,并运用移动渐进线法优化求解。结果优化后的平面2-DOF柔顺并联机构构型在x方向的位移为-0.0089mm,在y方向的位移为0.0053 mm,同时,其沿x方向和y方向的微位移理论值为-0.0031 mm和0.0067 mm。结论与并联原型机构的运动特性相比,平面2-DOF柔顺并联机构优化后的微运动特性具有一致性,均为微米级。

平面并联2-DOF机构运动的计算机模拟逼近法

提出了用计算机模拟逼近法分析平面2-DOF机构的运动,运用该方法进行了运动分析。先采用CAD的几何约束、尺寸约束、尺寸方程和尺寸驱动技术,构造2-DOF机构的模拟机构。再用两个相同且彼此靠近的模拟机构,构造速度模拟机构,求解机构上确定点的速度和角速度。最后用两个相同且彼此靠近的速度模拟机构,构造加速度模拟机构,求解机构上确定点的加速度和角加速度。计算机模拟结果与解析法的结果比较表明,该方法具有简单、快捷、直观、求解精度高的优点,而且可以完成复杂机构的运动分析,为平面连杆机构运动分析提供了更有效的工具。

球面2-DOF冗余驱动并联机器人静力学全解

以球面2-DOF冗余驱动并联机器人为研究对象,在考虑构件弹性的情况下,采用传统的拆杆法建立机构的静力学平衡方程,利用积分法求出各杆件变形,再运用小变形叠加原理建立机构的变形补充协调方程,共得到42个方程,但该机构为冗余机构,共有43个未知数,为此采用输入力优化方法,得到该机构静力学全解。通过数值算例,绘制输出轴在外载荷作用下沿给定轨迹的受力图。研究为该机构在工程中的结构设计与应用提供了静力学理论基础。

球面2-DOF冗余驱动并联机器人机构误差分析

将环路增量法应用于多环路并联机构的误差分析中,并提出环路选取原则。基于D-H参数,结合冗余驱动机构特点,采用环路增量法,建立兼顾位置和姿态两类误差的球面2-DOF冗余驱动并联机器人机构误差模型。该误差模型除包含机构的结构参数误差外,同时还将由于加工和装配等原因出现的各转动副轴线和球心之间的偏差考虑进来,更全面地反映了机构的工程实际情况。基于该误差模型进一步分析球面机构出现卡死现象的原因,预估了机构误差,为该机构样机的运动学标定研究奠定了理论基础。

利用约束螺旋理论综合的空间对称2-DOF并联机构

首先按运动功能对两自由度空间并联机构进行分类,得到了空间2Ryz型(绕y轴和z轴转动)和1Rz1Tz型(绕z轴转动和沿z轴移动)的两自由度机构;给出了两类并联机构的分支约束螺旋系和机构约束螺旋系,以及保证所有分支约束螺旋的合成是期望的机构约束螺旋系的几何条件。对这两种空间并联机构运用约束螺旋综合理论进行系统的型综合,得到了可实现连续运动的具有绕定平台平面内两轴转动的并联机构以及沿着定平台法线方向移动和绕其转动的两自由度并联机构;得到了两自由度并联机构各种类型的分支链结构,以及两类机构的结构约束特性。将少自由度对称并联机构类型由原来的9类扩充到11类,丰富了机构类型。

Limit cycle oscillation suppression of 2-DOF airfoil using nonlinear energy sink

This paper presents a novel mechanical attachment, i.e., nonlinear energy sink （NES）, for suppressing the limit cycle oscillation （LCO） of an airfoil. The dynamic responses of a two-degree-of-freedom （2-DOF） airfoil coupled with an NES are studied with the harmonic balance method. Different structure parameters of the NES, i.e., mass ratio between the NES and airfoil, NES offset, NES damping, and nonlinear stiffness in the NES, are chosen for studying the effect of the LCO suppression on an aeroelastic system with a supercritical Hopf bifurcation or subcritical Hopf bifurcation, respectively. The results show that the structural parameters of the NES have different influence on the supercritical Hopf bifurcation system and the subcritical Hopf bifurcation system.

参考模型前馈2-DOF指令跟踪H_∞控制器设计研究

结合二自由度控制和参考模型控制系统设计原理,提出了一种参考模型前馈控制的二自由度控制系统设计结构。通过推导给出了标准H∞控制广义被控对象的状态空间方程实现形式,并运用该理论研究了导弹俯仰通道指令跟踪系统鲁棒H∞控制器设计问题。文中采用LMI凸优化进行二自由度鲁棒H∞控制器设计,简化了传统方法设计控制器的求解过程。仿真结果表明,应用该方法设计的闭环系统具有良好的快速跟踪特性,说明了该方法的正确性和有效性。

Vibration response analysis of 2-DOF locally nonlinear systems based on the theory of modal superposition

Many important vibration phenomena which simultaneously contain quadratic nonlinear stiffness and damping exist in the complicated vibrating systems under practical circumstances. In this paper, we established a 2-degree-of-freedom (DOF) nonlinear vibration model for such a system, deduced the differential equations of motion which govern its dynamics, and worked out the solutions for the governing equations by the principle of superposition of nonlinear normal modes (NLNM) based on Shaw’s theory of invariant manifolds. We conducted numerical simulations with the established model, using superposition of nonlinear normal modes and direct numerical methods, respectively. The obtained results demonstrate the feasibility of the proposed method in that its calculated data varies in a similar tendency to that of the direct numerical solutions.

FLEXIBLE 2-DOF STEERING MODEL OF MULTI-AXLE HEAVY-DUTY VEHICLE

A flexible two degrees of freedom (2-DOF) steering model of multi-axlevehicle (MAV) is presented with considering the effect of frame flexibility based on the classic2-DOF model. A method to calculate the frame flexibility is derived by using three moments equation.The steering stability of MAV is analyzed. The steering performance of MAV is also researched infrequency domain. Simulation results show that the dynamic effects of flexible model are more severethan rigid model and the flexible effect of frame will weaken the steering stability of MAV.Different disposals of steering axles lead to different steering characteristics of MAV. Thein-phase steering mode improves the steering characteristics and stability at high speed. Theanti-phase steering mode increases the steering mobility at low vehicle speed.

Two Improvements on Numerical Simulation of 2-DOF Vortex-Induced Vibration with Low Mass Ratio

Till now, there have been lots of researches on numerical simulation of vortex-induced vibration. Acceptable results have been obtained for fixed cylinders with low Reynolds number. However, for responses of 2-DOF vortex-induced vibration with low mass ratio, the accuracy is not satisfactory, especially for the maximum amplitudes. In Jauvtis and Williamson＇s work, the maximum amplitude of the cylinder with low mass ratio m＊=2.6 can reach as large as 1.5D to be called as the ＂super-upper branch＂, but from current literatures, few simulation results can achieve such value, even fail to capture the upper branch. Besides, it is found that the amplitude decays too fast in the lower branch with the RANS-based turbulence model. The reason is likely to be the defects of the turbulence model itself in the prediction of unsteady separated flows as well as the unreasonable setting of the numerical simulation parameters. Aiming at above issues, a modified turbulence model is proposed in this paper, and the effect of the acceleration of flow field on the response of vortex-induced vibration is studied based on OpenFOAM. By analyzing the responses of amplitude, phase and trajectory, frequency and vortex mode, it is proved that the vortex-induced vibration can be predicted accurately with the modified turbulence model under appropriate flow field acceleration.

基于VCGA2-DOF PID控制器优化设计

遗传算法提供了一种复杂系统优化问题求解的通用框架,它通过对生物遗传和进化过程的模仿,来实现对问题的最优解的自适应搜索。针对基本遗传算法应用中早熟和慢收敛问题,应用改进的遗传算法,将适应度引入对操作因子的自适应调整,并给出了基于Matlab编程的实例。在此基础上,针对二自由PID的控制器优化设计问题,运用改进的遗传算法,在Matlab上进行了控制器参数的设计和仿真。结果表明,改进的遗传算法具有更快的收敛速度、更高的效率及全局收敛性,是一种适于工程应用的参数寻优方法。

Controllability and Observability of 2-DOF Permanent Magnet Maglev System with Linear Control

A new type of 2-DOF(degree of freedom) magnetic levitation system for multi-DOF levitation is proposed. In this system, the force of permanent magnets are used for levitation and controlled by adjusting the reluctance of the magnetic circuit. Using permanent magnets, the feature of this system is effective for saving energy and avoiding heat generation. First, the principle of the levitation system and typical reluctance control methods are described. Second, an experimental device based on the principle is introduced. Finally, the feasibility of this system is considered from linear control theory.

Non-linear 2-DOF model and centre manifold theory to study limit cycle oscillations caused by drum-brake judder

This paper presents the research on the laws of systematic-parameter dependent variation in the vibration amplitude of drum-brake limit cycle oscillations (LCO). We established a two-degree non-linear dynamic model to describe the low-frequency vibration of the drum brake, applied the centre manifold theory to simplify the system, and obtained the LCO amplitude by calculating the normal form of the simplified system at the Hopf bifurcation point. It is indicated that when the friction coefficient is smaller than the friction coefficient at the bifurcation point, the amplitude decreases; whereas with a friction coefficient larger than the friction coefficient of bifurcation point, LCO occurs. The results suggest that it is applicable to suppress the LCO amplitude by changing systematic parameters, and thus improve the safety and ride comfort when applying brake. These findings can be applied to guiding the design of drum brakes.

Singularity Analysis of 2-DOF Planar Seven-bar MechanismsUsed in Hybrid Actuators

Based on the Jacobian matrices relating the input speeds with the output speeds of linkages, a general method, which is used for solving the singularities of planar multi-loop multi-DOF linkages, is presented. The four kinds of singularities of 2-DOF planar seven-bar linkages used in hybrid actuators are analyzed in detail by this method. Its five kinds of singular positions whose characteristics are discussed respectively are discovered. Three approaches are proposed on how to avoid the singular positions of planar multi-loop multi-DOF linkages. Based on the assemblability of planar single-loop N-bar chains or linkages, the geometry conditions are investigated and discovered to avoid the singular positions of the linkages. In order to versify aforementioned conclusions, a case is given in which the singular curves are plotted and simulated.

Simulation and Implementation of Real-Time Vision-Based Control System for 2-DoF Robotic Arm Using PID with Hardware-in-the-Loop

Microsoft Kinect sensor has shown the research community that it's more than just an interactive gaming device, due to its multi-functional abilities and high reliability. In this work, online HIL (Hardware-in-the-Loop) experimental data are used to apply human motion imitation to a 2-degree of freedom Lego Mind storm NXT robotic arm. A model simulation of the dc motor used in this experiment is also present in this paper. The acquired input data from the Kinect sensor are processed in a closed loop PID controller with feedback from motors encoders. The applied algorithms solve the overlapping input problem, conducting a simultaneous control of both shoulder and elbow joints, and solving the overlapping input problem as well. The work in this paper is presented as a prototype to assure the applicability of the algorithms, for further development.

Adaptive Control Based on Neural Networks for an Uncertain 2-DOF Helicopter System With Input Deadzone and Output Constraints

In this paper, a study of control for an uncertain2-degree of freedom(DOF) helicopter system is given. The2-DOF helicopter is subject to input deadzone and output constraints. In order to cope with system uncertainties and input deadzone, the neural network technique is introduced because of its capability in approximation. In order to update the weights of the neural network, an adaptive control method is utilized to improve the system adaptability. Furthermore, the integral barrier Lyapunov function(IBLF) is adopt in control design to guarantee the condition of output constraints and boundedness of the corresponding tracking errors. The Lyapunov direct method is applied in the control design to analyze system stability and convergence. Finally, numerical simulations are conducted to prove the feasibility and effectiveness of the proposed control based on the model of Quanser's 2-DOF helicopter.

2-DOF铰接轮式越野挖掘机功率匹配及牵引性能设计

确定了一种2-DOF铰接轮式越野挖掘机行走系统中发动机-泵功率匹配区域和实现原理,并分析了变量泵-变量马达系统工作参数。研究了影响车辆爬坡能力的因素,合理设计了最大牵引力和分动箱传动比。在此基础上设计出该挖掘机在不同工作模式下的牵引特性,为该车行走系统的设计和分析提供了依据。

Design and Analysis of a 2-DOF Actuator with Variable Stiffness Based on Leaf Springs

Variable Stiffness Actuator(VSA)is the core mechanism to achieve physical human–robot interaction,which is an inevitable development trend in robotic.The existing variable stiffness actuators are basically single degree-of-freedom(DOF)rotating joints,which are achieving multi-DOF motion by cascades and resulting in complex robot body structures.In this paper,an integrated 2-DOF actuator with variable stiffness is proposed,which could be used for bionic wrist joints or shoulder joints.The 2-DOF motion is coupling in one universal joint,which is different from the way of single DOF actuators cascade.Based on the 2-DOF orthogonal motion generated by the spherical wrist parallel mechanism,the stiffness could be adjusted by varying the effective length of the springs,which is uniformly distributed in the variable stiffness unit.The variable stiffness principle,the model design,and theoretical analysis of the VSA are discussed in this work.The independence of adjusting the equilibrium position and stiffness of the actuator is validated by experiments.The results show that the measured actuator characteristics are sufficiently matched the theoretical values.In the future,VSA could be used in biped robot or robotic arm,ensuring the safety of human–robot interaction.