Limiting interactions in decentralized control of MIMO systems

Despite the closed-loop performance advantages of centralized multivariable controllers, the great majority of industrial process control applications is still based on decentralized controllers. Because of their single loop structure, decentralized controllers cannot suppress the interactions of the plant, which are only taken into account in the controller tuning phase. Therefore, it would be useful in many cases to delimit in some way the undesirable effects of the coupling between inputs and outputs of the closed loop system. A control algorithm to achieve this goal is developed in the paper. The proposal is applicable even to processes with non-minimum phase transmission zeros (provided their off-diagonal transfer functions have their zeros in the left-half-plane). Based on sliding mode attributes, the proposed scheme can be easily added to a previously designed decentralized control system.     

Highly robust position control of BLDDSM using an improved integral variable structure systems

A highly robust position controller for brushless direct drive servo motors (BLDDSM) is presented using a new improved variable structure system with an integral-augmented sliding surface. With the proposed technique, the reaching phase is completely removed by the integral sliding surface. The dynamics of its ideal sliding mode is analytically obtained from a given initial condition to the origin without any reaching phase. In order to choose a suitable integral sliding surface, the optimal regulator theory is effectively applied. Moreover, the suggested control technique can exhibit the output response identical to that previously designed in the integral sliding surface for all the load variations and parameter uncertainties. The usefulness of the proposed algorithm is illustrated through the comparative experiment studies on the position controls of BLDDSM under load variations.     

Adaptive Fuzzy Sliding Mode Controller for the Kinematic Variables of an Underwater Vehicle

This paper address the kinematic variables control problem for the low-speed manoeuvring of a low cost and underactuated underwater vehicle. Control of underwater vehicles is not simple, mainly due to the non-linear and coupled character of system equations, the lack of a precise model of vehicle dynamics and parameters, as well as the appearance of internal and external perturbations. The proposed methodology is an approach included in the control areas of non-linear feedback linearization, model-based and uncertainties consideration, making use of a pioneering algorithm in underwater vehicles. It is based on the fusion of a sliding mode controller and an adaptive fuzzy system, including the advantages of both systems. The main advantage of this methodology is that it relaxes the required knowledge of vehicle model, reducing the cost of its design. The described controller is part of a modular and simple 2D guidance and control architecture. The controller makes use of a semi-decoupled non-linear plant model of the Snorkel vehicle and it is compounded by three independent controllers, each one for the three controllable DOFs of the vehicle. The experimental results demonstrate the good performance of the proposed controller, within the constraints of the sensorial system and the uncertainty of vehicle theoretical models.     

基于滑模变结构控制的电动助力转向系统

针对汽车电动助力转向系统，提出滑模变结构控制方法，建立其运动方程，确定了滑模变结构控制器。台架实验结果表明这种滑模变结构控制器与PD控制器相比，其控制方法简单，同时具有更好控制效果。     

XM84-165型地下矿用三牙轮钻头

XM 84-165型地下矿用牙轮钻头是适用于穿凿硬至极坚硬矿岩的一种钻头,它采用了先进的全滑动密封轴承。本文着重介绍了该钻头的设计参数、结构特点以及工业性试验和使用效果。     

Segregation of Liquid Phase in the Extruded Semisolid Metal

The influence of stress and strain on the solid/liquid segregation formed in deformed semisolid metal was studied. The compression experiment at a low constant strain rate was conducted on a Gleeble 1500 thermo-mechanical simulator.The stress and strain fields of the samples were calculated by finite element method. The experiment results and the modeling results prove that the hydrostatic pressure gradient is the driving force for solid/liquid segregation. The segregated liquid phase usually agglomerates in the micropores and shear bands are created by sliding of equiaxed dendrite grains. The sliding among the grains is influenced by the solid fraction and grain size of the semisolid slurry,so as the solid fraction and grain size change, the morphology of the segregated liquid changes.     

Wear behavior of BCS glass ceramic coating on stainless still slab

The present study aims to assess the friction and wear characteristics of BSC glass-ceramic on 304L stainless steel, fabricated by air spray method.The dry sliding friction and wear behavior were investigated using a 4?mm diameter AISI52100 steel pin on disk geometry under 3–39?N loads, at different sliding speeds in dry conditions.Average friction coefficients (COF)and wear rates were varied in the range between 0.6–0.8 and 26?×?10^?2–0.001?mm³/N?m respectively. The results show that, the frictional behavior of glass-ceramic-metal couples depended on the metal transferred from the steel pin to the glass-ceramic's surface and the applied loads. It was found that the running–in period of G39 last shorter than the G3 one, also in the case of G39 the steady state friction coefficient was lower than G3.The wear tracks were examined using scanning electron microscope, it was revealed that, the intrinsic porosity of coat has affected on the amounts of debris as an important factor for the COF values.     

一种广义模糊神经网络等效滑模同步伺服系统

针对永磁同步伺服系统参数摄动、非线性及不确定因素等问题,提出了一种新型模糊神经网络等效滑模控制方案。利用一维输入的径向基神经网络与等效滑模复合控制器,实现了PMSM系统的快速跟踪控制。该方案对负载扰动、系统参数变化等具有很强的自适应性和鲁棒性,并且综合了模糊控制、神经网络的优点,是一种较理想的智能控制策略。在MATLAB环境下的仿真结果表明控制器具有良好的动静态品质,并且工程实现方便,为提高PMSM伺服系统性能提供了一个有效途径。     

Stable control of nonlinear systems using neural networks

A neural-network-based direct control architecture is presented that achieves output tracking for a class of continuous-time nonlinear plants, for which the nonlinearities are unknown. The controller employs neural networks to perform approximate input/output plant linearization. The network parameters are adapted according to a stability principle. The architecture is based on a modification of a method previously proposed by the authors, where the modification comprises adding a sliding control term to the controller. This modification serves two purposes: first, as suggested by Sanner and Slotine,¹ sliding control compensates for plant uncertainties outside the state region where the networks are used, thus providing global stability; second, the sliding control compensates for inherent network approximation errors, hence improving tracking performance. A complete stability and tracking error convergence proof is given and the setting of the controller parameters is discussed. It is demonstrated that as a result of using sliding control, better use of the network's approximation ability can be achieved, and the asymptotic tracking error can be made dependent only on inherent network approximation errors and the frequency range of unmodelled dynamical modes. Two simulations are provided to demonstrate the features of the control method.     

直流蒸汽发生器滑模模糊控制

直流蒸汽发生器对控制的要求较高.滑模控制的鲁棒性使系统对不同的负荷变化、不同的外界干扰不敏感,模糊控制简化了控制器的设计,减弱由滑模变结构引起的抖振现象,能实现更好的控制效果.本文主要阐述了一种不用系统模型的滑模模糊控制器对直流蒸汽发生器进行控制的设计方法,仿真结果表明该控制器的控制效果较理想.