无刷直流电机转速伺服系统反步高阶滑模控制

针对无刷直流电机转速伺服系统高性能非线性鲁棒控制, 提出一种新型的多滑模反步高阶滑模非线性控制方法. 在控制律设计的每一步都引入二阶滑模Super-Twisting 算法, 无需计算变量导数, 消除了滑模抖振, 并在第1 级子系统虚拟控制律设计中提出一种改进的二阶滑模Super-Twisting 算法. 与传统双闭环PI 控制相比, 能够令系统的动静态性能更好, 转矩脉动更小, 鲁棒性更强; 与标准Super-Twisting 算法相比, 进一步提高了系统对阶跃负载扰动的抑制能力. 最后通过仿真分析表明了所提出方法的有效性.

     

大型浮吊滑动摩擦材料回转支撑力学行为

针对浮吊的轻量化设计,采用非金属滑动摩擦材料Nylatron 703XL取代以往的滚动式回转支撑.对Nylatron 703XL材料试样进行压缩试验,获得材料的压缩性能曲线,发现这种材料的压缩性能曲线呈现明显的非线性特征,对结构分析的影响显著.针对2×8 000 t大型浮吊,用Abaqus计算得到不同工况对Nylatron 703XL垫圈的力学响应和规律.计算分析摩擦因数对垫圈力学行为的影响.结果认为:Nylatron 703XL具有取代金属结构的能力,可以作为滑动摩擦材料;其在工程机械承载结构上应用的潜力巨大.     

FEM considering local bending effects for flat sliding isolators

Presented in this paper are an advanced analytical model and finite element formulations including the local bending moment effect for the flat sliding system. This study reveals that the local bending effect is a very important factor. The results presented in this paper show that the design of the isolation without considering this effect may endanger structures during earthquakes. The new formulations taking into consideration the local effect provide an effective tool for the more realistic simulation of the behavior of flat-sliding-isolated structures subjected to earthquake loadings. The proposed finite element formulations can be applied directly for both two- and three-dimensional analyses without any further assumption, and can generally be placed at any location in the structure. The implementation of the proposed techniques in existing finite element computer codes is a simple task. Examples of structures equipped with flat-sliding isolators is also given to demonstrate the paramount findings through the proposed formulations. Results obtained from the numerical analyses suggest that the local bending moment effects are extremely important, and should be taken into account to assure the safety of isolated-structures during earthquakes.     

摩擦式离合器滑摩过程及温度场分析

为更真实地反映摩擦式离合器滑摩过程中的温度场,提出1种利用动力学软件与有限元软件相互辅助分析的方法.在试验测得的负载扭矩的基础上,建立摩擦片和内鼓轮及气胎的模型;利用MSC Adams对摩擦式离合器进行动力学仿真,通过对摩擦片加压计算出滑摩时间和主、从动端的相对转速;将该相对转速用于有限元热机耦合场分析,通过摩擦片和内鼓轮的相对转动形成滑摩、生成热量,得离合器各时刻的温度场.结果表明：离合器在接触后3.064 s时主、从动端接合完毕,且摩擦片瞬态最高温度只有65.83℃.该方法对摩擦式离合器滑摩过程及温度场分析具有一定的实际意义.     

具有次优保性能滑动模态的静态输出反馈滑模控制

针对一类不确定系统,提出了一种具有次优保性能滑模面的静态输出反馈滑模控制方法.首先将滑模面的设计问题等价为一个对称矩阵的求解问题,基于等效控制法,推导了保性能滑模面存在的充分条件.然后基于迭代线性矩阵不等式(iterative linear matrix inequality,ILMI)方法,给出了次优保性能线性滑模面的求解算法,最后基于线性矩阵不等式(linearmatrix inequality,LMI)方法,设计了输出反馈滑模控制器,使得闭环系统渐近稳定且切换函数能在有限时间内到达零.该方法首次实现了输出反馈滑模面的优化,且具有保守性小、无需对被控系统模型进行坐标变换的优点.仿真结果验证了本文方法的优越性.     

永磁球形电机的少保守性滑模控制

永磁球形电机轨迹跟踪控制方法常常利用高增益的控制输出来保证系统的鲁棒性及跟踪控制的快速性.但这种保守控制会带来较大的控制作用,甚至导致执行器饱和.为了减少控制的保守性,本文设计了一种带有非线性干扰观测器的模糊滑模控制器来解决球形电机的轨迹跟踪问题.利用干扰观测器对不确定性、摩擦、外界干扰、负载扰动等进行估计,并在控制输入端进行补偿实现对干扰的抑制.并利用滑模控制器抵消干扰观测器的干扰观测误差及不可观测部分的干扰,为了减少滑模的抖振,本文利用模糊逻辑对该部分进行逼近,并利用模糊的输出增益代替滑模的切换增益.此外通过Lyapunov方程证明了本文控制器的稳定性.仿真结果表明在存在模型不确定性及各种干扰的情况下,本文的轨迹跟踪控制具有良好的动静态性能和少保守性.     

线控转向系统的自适应高阶滑模控制

车辆线控转向(steer-by-wire,SbW)系统存在摩擦力矩及回正力矩等不确定动态特性,难以实现精确建模与有效控制.为此,提出一种基于自适应模糊逻辑系统的自适应高阶滑模(adaptive higher-order sliding mode, AHOSM)方法,实现SbW系统的有效控制.首先,通过自适应模糊逻辑系统逼近SbW系统的未知动态,使控制器的设计不再需要摩擦力矩及回正力矩的动力学模型;其次,采用高阶滑模和自适应增益技术削弱传统滑模控制器存在的抖振现象;再次,通过构造Lyapunov函数设计增益自适应律补偿逼近误差和系统不确定项对控制精度的影响,该方案不需要系统不确定项的界已知,且能够避免增益过估计现象;最后,通过稳定性分析证明该控制器可以在有限时间内建立实际滑动模态,数字仿真和硬件在环实验进一步验证了该控制方法的有效性和优越性.     

自适应非奇异终端滑模控制及其在BPMSM中的应用

为提高终端滑模控制中状态变量的全局快速收敛性, 提出一种自适应变速指数趋近律. 该趋近律引入状态变量的一阶范数, 根据状态变量距离平衡点的远近自适应调整指数趋近速度和等速趋近速度, 从而实现缩短趋近时间的同时削弱系统抖振. 应用该趋近律设计无轴承永磁同步电机(BPMSM) 转子速度及径向位移非奇异终端滑模控制器, 仿真结果表明, 该方法能快速地跟踪转速及径向位移给定值, 系统超调及稳态静差小, 具有较强的鲁棒性.

     

Finite‐time sliding mode observer for uncertain nonlinear systems based on a tunable algebraic solver

In this paper, a finite‐time sliding mode observer for nonlinear systems with unknown inputs is proposed. The observer is based on a method for the solution of time‐varying algebraic equations. This algebraic solver is shown to converge in finite time by means of Lyapunov analysis; furthermore, a way to tune it so that it converges after a user‐defined amount of time is presented. Through the use of this technique and sliding mode differentiators, the state variables and unknown inputs of a class of nonlinear systems, which do not need to be affine in the inputs, can be estimated without the explicit use of state transformations. Both the algebraic solver and the proposed observer are illustrated through simulation examples. Copyright © 2017 John Wiley & Sons, Ltd.     

考虑输入饱和的离散最优积分滑模控制

针对含有匹配有界干扰的线性离散系统, 提出一类最优积分滑模控制算法. 在系统开环极点位于单位圆内(上) 的前提下, 考虑输入饱和, 可以实现系统状态的半全局稳定. 该算法是低增益反馈和积分滑模的有益结合, 通过低增益反馈使输入饱和得到满足, 通过滑模控制增强了系统对干扰的鲁棒性; 另外, 该算法可以使特定的性能指标达到最优, 使系统稳态误差达到??(??²) 的量级. 仿真结果验证了所提出算法的有效性.

     

A study of the stabilizing process of unstable structures by dynamic relaxation method

In this paper, the stabilizing process of unstable structures is studied by dynamic relaxation method. The process of applying the internal force to unstable structures is called as stabilizing process of unstable structure. The initial behavior of unstable structures such as cables, pneumatic structures or cable domes, are unstable state because of no initial internal stiffness. The dynamic relaxation method is the energy minimization technique that searches the static equilibrium state by simple vector iteration method. Because the dynamic relaxation method does not need to assemble the tangential stiffness matrix of structure during each iteration of the stabilizing process, the computational effort and CPU run-time can be reduced. The finite difference integration technique is used to integrate the dynamic equilibrium equation for static equilibrium state. Some numerical examples are presented to confirm the efficiency and applicability of dynamic relaxation method.     

无抖振离散滑模趋近律

针对离散滑模趋近律形式多样且容易产生高频抖振的问题,提出了离散滑模趋近律的一般形式,并给出了无抖振的到达条件及其理论证明,从一般意义上为离散滑模趋近律的设计提供了理论依据。针对满足匹配条件的不确定系统,给出了切换函数收敛域的推导方法,推导了无抖振的最小收敛域。以典型的高氏指数趋近律为例,利用无抖振的到达条件,对其一般形式进行了无抖振改进,验证了所提出方法的有效性。     

New synthesis algorithm of static output feedback sliding mode control for a class of uncertain systems

Based on a kind of regular form,a Lyapunov matrix with special structure is presented to design the sliding surface matrix conveniently and then an effective algorithm is developed on it. A simple static output feedback sliding mode control law without extra dynamic equation is given, such that the predefined shding surface is reached in finite time for the general matching uncertainties. In the reported result, this extra dynamic equation is used for evaluating the norm bound of the unmeasured state vector. Finally, some examples are studied to illustrate the proposed approach.     

一种连续非奇异快速终端滑模控制方法

为解决现有终端滑模控制算法在收敛速度和抖振方面的问题, 提出一种连续非奇异快速终端滑模控制方法. 采用变系数双幂次趋近率和非奇异快速终端滑模面相结合的设计方式, 提高系统状态在趋近和滑动阶段的收敛速度. 通过Lyapunov 稳定性方法证明所提出的控制率可使得状态轨迹在扰动存在的情况下, 在有限时间内快速收敛到一个区域. 与传统方法相比, 所提出的控制率是连续的, 因此抑制了抖振, 拥有更高的控制精度. 将所提出的方法应用于光电稳定平台, 仿真结果验证了算法的有效性.

     

Topology optimization of cellular materials with periodic microstructure under stress constraints

Material design is a critical development area for industries dealing with lightweight construction. Trying to respond to these industrial needs topology optimization has been extended from structural optimization to the design of material microstructures to improve overall structural performance. Traditional formulations based on compliance and volume control result in stiffness-oriented optimal designs. However, strength-oriented designs are crucial in engineering practice. Topology optimization with stress control has been applied mainly to (macro) structures, but here it is applied to material microstructure design. Here, in the context of density-based topology optimization, well-established techniques and analyses are used to address known difficulties of stress control in optimization problems. A convergence analysis is performed and a density filtering technique is used to minimize the risk of results inaccuracy due to coarser finite element meshes associated with highly non-linear stress behavior. A stress-constraint relaxation technique (qp-approach) is applied to overcome the singularity phenomenon. Parallel computing is used to minimize the impact of the local nature of the stress constraints and the finite difference design sensitivities on the overall computational cost of the problem. Finally, several examples test the developed model showing its inherent difficulties.

     

机械臂自适应精确时间滑模控制

考虑机械臂中存在的未建模部分、摩擦力、外加干扰,提出一种自适应精确时间滑模控制方法,实现机械臂各关节角的轨迹跟踪.首先对机械臂进行建模,将未建模部分、摩擦力、外加扰动看作集中扰动;其次,设计一种精确时间收敛滑模面,克服传统终端滑模面收敛时间高估的问题,基于此设计全局精确时间收敛滑模控制方法,使得机械臂系统能够在设定时间实现稳定,并在误差收敛后仍具有较强的鲁棒性;接着,设计低通滤波器削减抖振,通过自适应方法估计扰动上界,避免增益的高估;最后,通过仿真实验验证所提出的控制方法能够严格控制机械臂系统的稳定时间,并降低稳态误差,实现机械臂系统的高精度轨迹跟踪控制.     

An Energy-Based Approach for Contact Force Computation

A new approach for computing resting contact forces between solids is presented, which handles both static and sliding friction, while avoiding the problems arising from previous approaches. Each iteration provides values for all unknowns and needs a constant computation time. The first iteration is a global dynamic solution involving inertia and external forces. The subsequent iterations consist of global redistributions of energy through the solids in order to restrict the values within correct bounds, leading to a progressive refinement of the solution. This allows the termination of the computation when a user-defined level of precision is reached. Convergence is proven in the frictionless case. The method is concise and is easily usable in a motion control system. It was implemented and tested on some examples involving simultaneously static and sliding friction along with motion control.     

Shape optimization of structures under earthquake loadings

The optimum design of structures under static loads is well-known in the design world; however, structural optimization under dynamic loading faces many challenges in real applications. Issues such as the time-dependent behavior of constraints, changing the design space in the time domain, and the cost of sensitivities could be mentioned. Therefore, optimum design under dynamic loadings is a challenging task. In order to perform efficient structural shape optimization under earthquake loadings, the finite element-based approximation method for the transformation of earthquake loading into the equivalent static loads (ESLs) is proposed. The loads calculated using this method are more accurate and reliable than those obtained using the building regulations. The shape optimization of the structures is then carried out using the obtained ESLs. The proposed methodologies are transformed into user-friendly computer code, and their capabilities are demonstrated using numerical examples.     

基于一种新型趋近律的自适应滑模控制

首先, 利用特殊幂次函数和反双曲正弦函数构造一种新型滑模变结构控制趋近律; 然后, 采用该趋近律设计一种自适应滑模控制律, 并证明滑模控制系统误差渐近收敛. 仿真实验表明: 在存在时变转动惯量和摩擦力矩扰动的情况下, 该自适应滑模控制系统具有较高的位置和速度跟踪精度, 并有效减弱了控制输入信号的高频震颤现象; 同时, 采用反双曲正弦函数的自适应律能较好地平滑系统转动惯量估计值, 减小控制输入信号的幅值.

     

机器人系统终端滑模重复学习轨迹跟踪控制

针对非线性机器人系统的轨迹跟踪问题, 提出一种终端滑模重复学习混合控制方案. 该方案综合了重复学习控制和终端滑模技术的特性, 能够有效跟踪周期性参考信号, 抑制周期性和非周期性动态的干扰, 具有较强的鲁棒性和良好的轨迹跟踪性能, 且算法的实现不需要完全已知系统模型信息. 应用Lyapunov 稳定性理论证明了闭环系统的全局渐近稳定性. 三自由度机器人系统数值仿真结果验证了所提出的终端滑模重复学习控制的有效性.