Control of Wheeled Robots

A nonholonomic model of a wheeled robot with one steering wheel is considered. The model accounts for dynamic effects. The motion-planning problem for this model is solved by reducing it to a linear two-point boundary-value problem__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 4, pp. 117–125, April 2005.     

State-Space Generalized Predictive Control for Redundant Parallel Robots

Abstract

The article deals with the design and properties of generalized predictive control (GPC) for path control of redundant parallel robots. Redundant parallel classification means redundant number of actuators, i.e., more actuators than degrees of freedom of the robot. Control of such structures suffers from several new control problems like potential inconsistency of steady state positions or nonuniqueness of control actions. The article explains classical direct derivation of GPC and its modification based on square root two-step design of control actions for solving the control problems. As an example for verification of algorithms, a prototype of a planar redundant parallel robot is used. Both design approaches are compared and several possibilities of extensions are presented for taking into consideration additional requirements, like smooth course of actuators or fulfillment of the anti-backlash condition.     

Parameter Identification and Control of Ground Temperature

A numerical thermal management system for the ground structure is presented. The system consists of two parts, i.e. the identification analysis of thermal conductivity and the thermal control analysis for the ground. The former is carried out by using the nonlinear least squares method and the latter is based on the optimal control theory. The formulations of these methods are presented and they are applied to an actual putting green in a golf course. Reasonable thermal conductivity of the ground is identified by parameter estimation and the ground temperature is theoretically controlled as illustrated by numerical examples.     

折叠式柔性结构振动主动控制的研究

建立了具有刚性运动基的折叠式柔性结构振动主动控制实验系统，采用带实时预测误差修正的预测控制算法进行了这类结构振动主动控制的实验研究。实验结果表明，在实验建模的基础上设计预测控制器对折叠式柔性结构进行振动主动控制，能够有效地抑制柔性结构的振动和提高刚性基姿态定向精度。     

机敏柔性梁的振动主动控制

提出了用于机敏结构中振动主动控制的仿人控制算法,对压电阻尼技术进行了理论和实验研究,给出了传感器,执行器和受控结构之间的关系,用ＰＺＴ作执行元件实现了柔性梁振动主动控制系统,给出了实验结果。     

随机参数天线结构的概率优化设计

研究了具有随机参数天线结构基于概率的优化设计问题。同时考虑了结构物理参数、几何尺寸和作用荷载等的随机性;应用有限元方法与结构可靠性理论对抛物面天线反射面精度的可靠性和结构单元强度、稳定性和可靠性进行了分析;在此基础上构建了基于概率的天线背架结构优化设计模型。对8m口径天线结构的优化结果表明:文中提出的天线结构分析和优化设计模型与方法是合理可行的。     

Unexpected Results in Structural Optimization*

ABSTRACT

Examples are presented to show that optimal designs may have unexpected properties that require particularly careful formulation of problems of structural optimization.     

模型不确定压电柔性结构的多目标振动控制

以压电柔性结构为对象,考虑其被控模态参数的不确定性和因剔除残余模态所引起的动态不确定性,建立了结构的不确定线性分式模型;根据不确定模型设计了一个对结构进行振动控制的动态输出反馈控制器,使闭环系统满足鲁棒稳定、扰动抑制、极点配置约束及控制输入约束等性能要求;并利用线性矩阵不等式,将具有多个性能要求的振动控制问题转化为具有线性矩阵不等式约束和线性目标函数的凸优化问题。最后以简支压电柔性梁为例,设计了一个融合多性能指标的动态输出反馈非同位控制器,并给出了仿真结果。     

斜拉索附加带刚度阻尼器的参数优化分析

斜拉索的风雨振动及其控制是目前国内外研究的热点问题之一.其中,阻尼器减振技术得到了广泛的应用,但是,对于阻尼器的一些非理想因素如阻尼器刚度的影响,尚缺乏研究.本文对斜拉索附加带刚度的阻尼器的模态阻尼比进行了分析,通过分析复频率的变化,在阻尼器安装点距拉索锚固点长度与拉索长度之比远远小于1的假设下,得到了考虑刚度影响的拉索阻尼器的模态阻尼比的近似解析解.该近似解析解与数值计算得到的精确解对比吻合良好.对于斜拉索减振,与忽略刚度影响的阻尼器类似,带刚度的阻尼器同样存在着通用设计优化曲线.阻尼器所带有的刚度将显著的减小拉索-阻尼器系统所能获得的最大模态阻尼比,而所对应的阻尼器最优阻尼值将增大.     

Joint Stiffness Control of a Two-Link Flexible Arm

In this study, results are presented for the control of impactinduced transient oscillations on a two-link flexible arm by varying thestiffness of an elbow actuator. Case studies were conducted to determinethe effectiveness of the control method as various arm parameters suchas payload, length, elbow angle, and elbow stiffness changed. Theresults of selected cases were then verified experimentally anddemonstrated that the suggested controller was effective, robust, andquite insensitive to parameter variations.     

互联结构振动控制元件参数研究

针对双塔结构所具有的模型不精确及承受随机外力作用这一特点，在控制方法选择方面，为保证系统控制的顺利实现，本文引入了能够对模型不精确具有较好控制效果的广义预测控制策略；在优化目标选择方面，为降低控制系统的能量，以控制增益矩阵的Frobenius范数做为优化目标；在优化算法方面，为降低计算工作量，引入并改进了传统的遗传算法。通过优化计算得到系统参数几组次优解，这些解可以供设计者进行选择。最后给出了计算实例。算例表明这一方法是有效的。     

Minimum Time Control of Flexible Spacecraft by Hamilton's Principle

Modern space vehicles structure requisites are getting more and more stringent and complex as mission tasks become more sophisticated. This leads to the necessity of developing analysis methods that take into account structure flexibility and the need of reducing manoeuvre time as much as possible. In this work, a method based on the Hamilton Principle in its weak mixed form is developed, in which co-ordinates derivatives do not appear, but only their virtual variations. The proposed formulation is able to take into account system flexibility and saturation constraints on control torques and forces. A non-linear variational condition is obtained, which can be solved by means of a time-finite-element technique to give the minimum-time solutions of the control problem. The solutions for slewing manoeuvres are given, along with a new solution of the distributed optimal control problem.     

柔性结构振动的有限目标控制

根据实际问题的背景 ,分别提出了局部状态保持和有限目标控制两个问题。首先讨论了局部状态保持问题 ,给出了一个局部状态能局部状态保持的充分必要条件 ,并说明了如何选择控制力 ,即找到一个反馈增益矩阵 ,使该局部状态满足局部关态保持的条件 ,然后提出了有限目标控制的思想 ,进行了初步探讨 ,针对一特殊情况给出一个设计方法     

挠性自适应结构振动控制的分析与实验研究

采用自适应结构的原理和方法,对压电元件用于挠性结构振动控制的一些问题进行了探讨。对压电驱动器与结构的匹配关系进行了理论分析,对模态传感/驱动器在挠性悬臂板结构中的布置方案进行了优化设计,并进行了结构的振动控制实验,从而验证了方法的有效性     

A Variational Formulation for Multicriteria Structural Optimization*

Multicriterion structural optimization problems stated as minimization of the maximum of a set of weighted criteria are considered. Interpretation of the min-max problem as a simple minimization problem for an upper bound on the criteria leads to a formulation that is convenient for analysis of problems with global as well as local objectives. The method is demonstrated on multipurpose design of a vibrating cantilever, on design of a     

The Effect of a Geometrical Parameter on the Deformation of a Hinged Flexible Noncircular Cylindrical Shell

The exact analytical solution of a nonlinear boundary-value problem is used to study the effect of a generalized geometric parameter, which characterizes thickness and curvature, on the subcritical and postcritical deformation of a hinged infinite noncircular cylindrical shell. The load on the shell is nonuniformly distributed over its cross section. The deflection of the shell is plotted for various values of the geometric parameter     

Parameter identification of fractional-order chaotic systems using different Meta-heuristic Optimization Algorithms

Nonlinear Dynamics - Fractional-order chaotic systems (FOCS) parameter identification is an essential issue in chaos control and synchronization process. In this paper, different recent...     

带有末端集中质量的双连杆柔性机械臂主动控制

对带有末端集中质量的双连杆柔性机械臂的主动控制进行了研究,给出系统的动力学方程,采用非线性解耦反馈控制方法分别得出系统大范围运动方程和柔性臂的动力学方程,采用机械臂逆动力学方法和LQR方法分别设计大范围运动控制律和压电作动器控制律.仿真结果显示,本文控制方法能够有效地进行机械臂的轨迹跟踪,柔性臂的弹性振动可以得到有效抑制.