ADAPTIVE CONTROLLER AND ITS APPLICATION IN FORCE SYSTEM OF ASYMMETRIC CYLINDER CONTROLLED BY SYMMETRIC VALVE

Partial pressure, system vibration and asymmetric system dynamic performance exit in asymmetric cylinder controller by symmetric valve hydraulic system. To solve this problem in the force control system, model reference adaptive controller is designed using equilibrium point stability theory and output error equation polynomial. The reference model is selected in such a way that it meets the system dynamic performance. Hardware configuration of asymmetric cylinder controlled by asymmetric valve hydraulic system is replaced by intelligent control algorithm, thus the cost is lowered and easy to application. Simulation results demonstrate that the proposed adaptive control sheme has good adaptive ability and well solves asymmetric dynamic performance problem. The designed adaptive controller is fairly robust to load disturbance and system parameter variation.     

Physical modelling of fluid flow in electric arc furnace caused by impinging gas jets

Abstract

The interaction of liquid steel and an inclined impinging oxygen jet in an electric arc furnace (EAF) is of interest both commercially and scientifically. The bath activity in the EAF may vary from a surface splash ejected to high elevation to intense subsurface mixing. The system is appropriately modelled using water and nitrogen with scaled flowrates. In previous work, the gas/liquid contact was investigated by use of a geometrically similar 1/3rd scale three-dimensional water model. The cavity formed by the jet contacting the liquid surface was characterised by four modal regimes. These regimes were seen to depend on the lance angle, the height of the lance and the jet flowrate. To investigate the evolutionary mechanisms of the cavity regimes, a two-dimensional water model study was undertaken. The two-dimensional water model was a rectangular viewing tank with an inner movable glass wall that allowed a very thin slice of the system to be obtained. The shape of the cavity formed on the water surface was seen clearly along with the expected cavity oscillations. High speed video footage of the two-dimensional system allowed the cavity oscillation to be directly observed. The gas-liquid interaction produced a wave that travelled along the surface of the cavity until it reached the cavity crest where it was torn from the liquid surface and dispersed in a splash. It is the regular progression of the wave's nodes and antinodes along the cavity surface that makes the cavity appear to oscillate. When the wave reaches the crest of the cavity, it will either fall back into the path of the gas jet or be projected as a splash depending on the verticality of the cavity surface. The two-dimensional work, along with the initial three-dimensional investigation, has shown that the troublesome splash in the EAF is caused by how the lance is positioned directionally or azimuthally. By changing the lance angle or height the deleterious splashing of molten metal may be prevented, ameliorated or controlled. The frequency of the wave production was determined from the high speed video footage. The cavity oscillation was found to be a function of the size of the cavity, the inclined height of the lance and the modal regime being produced. Alterations to the flow through the lance had only a moderate effect on the frequency of oscillation indicating that velocity was not the major influential factor.     

Characterisation of structure of iron ore sinter and its behaviour during reduction at low temperatures

Abstract

Various sinter microstructures were produced in the laboratory using the same iron ore blend, varying only the sinter basicity and the carbon content of the blend via limestone and coke additions, respectively. The sinter cakes were subjected to low temperature, size degradation tests and their structural composition was determined. A relationship has been established between sinter structural composition and its size degradation under low temperature reducing conditions. Also, varying the gas composition led to development of a new reduction test procedure, which is more sensitive to microstructural variations than the conventional standard test (reduction degradation index, RDI).     

PLC在转炉风机煤气回收中的应用与研究

介绍转炉一次除尘风机及煤气回收系统中应用的可编程控制器(简称PLC)系统，对系统调试生产过程中遇到的几个问题进行分析与研究，并提出建议和改进方法。     

Gait Pattern Adaptation for an Active Lower-Limb Orthosis Based on Neural Networks

This work deals with neural network (NN)-based gait pattern adaptation algorithms for an active lower-limb orthosis. Stable trajectories with different walking speeds are generated during an optimization process considering the zero-moment point (ZMP) criterion and the inverse dynamic of the orthosis–patient model. Additionally, a set of NNs is used to decrease the time-consuming analytical computation of the model and ZMP. The first NN approximates the inverse dynamics including the ZMP computation, while the second NN works in the optimization procedure, giving an adapted desired trajectory according to orthosis–patient interaction. This trajectory adaptation is added directly to the trajectory generator, also reproduced by a set of NNs. With this strategy, it is possible to adapt the trajectory during the walking cycle in an on-line procedure, instead of changing the trajectory parameter after each step. The dynamic model of the actual exoskeleton, with interaction forces included, is used to generate simulation results. Also, an experimental test is performed with an active ankle–foot orthosis, where the dynamic variables of this joint are replaced in the simulator by actual values provided by the device. It is shown that the final adapted trajectory follows the patient intention of increasing the walking speed, so changing the gait pattern.     

The Matrix-Based Framework: Its Role as a Job-Agent Supervisory Controller

The paper deals with systems consisting of multiple agents executing jobs by influencing the environment through effectors, gathering information from the environment through sensors and communicating with the other agents through communication channels. A paradigm shift is proposed: from building systems executing jobs, to agents acquiring resources (effectors and receptors) so that they can execute the jobs assigned to them. A supervisory controller coordinates the adequate sequencing of jobs and resolves contentions. With our proposed decomposition into layers, a generic framework leading to the reuse of previously produced software and the extraction of useful portions can be achieved. The presented transition function-based formalism can be applied to specifying programming frameworks for robot controllers executing very diverse tasks. Formalization introduces rigor into the discussion of the structure of embodied agent controllers.     

An Adaptive Controller Dominant-Type Hybrid Adaptive and Learning Controller for Trajectory Tracking of Robot Manipulators

This paper proposes a new hybrid adaptive and learning control method based on combining model-based adaptive control, repetitive learning control (RLC) and proportional–derivative control to consider the periodic trajectory tracking problem of robot manipulators. The aim of this study is to obtain a high-accuracy trajectory tracking controller by developing a simpler adaptive dominant-type hybrid controller by using only one vector for estimation of the unknown dynamical parameters in the control law. The RLC input is adopted using the original learning control law, adding a forgetting factor to achieve the convergence of the learning control input to zero. We will improve and prove that the adaptive dominant-type controller could be applied for tracking a periodic desired trajectory in which adaptive control input increases and becomes dominant of the control input, whereas the other control inputs decrease close to zero. The domination of the adaptive control input gives the advantage that the proposed controller could adjust the feed-forward control input immediately and it does not spend much time relearning the learning control input when the periodic desired trajectory is switched over from the first trajectory to another trajectory. We utilize the Lyapunovlike method to prove the stability of the proposed controller and computer simulation results to validate the effectiveness of the proposed controller in achieving the accurate tracking to the periodic desired trajectory.     

High-speed positioning of an industrial robot based on Preview-Learning control

In this study, a numerical procedure for designing kinematic parameters of SCARA-type manipulators is proposed to yield such a design that the resulting manipulator has the fastest cycle time for a given task. To achieve this goal, an optimization problem is formulated to minimize the cycle time by determining geometric parameters such as the link lengths and the locations of manipulators as well as the trajectory. The representative task to get the cycle time is defined as CP (continuous path) motion along the path crisscrossing the standard working area. A gradient projection algorithm is used to obtain the optimal design with the assumption that each actuator should exert a torque and angular velocity within the capacity of specific commercially available direct-drive motors. SCARA-type manipulators of both absolute coordinate and relative coordinate types are designed to reduce the cycle times. The results show that the absolute coordinate manipulator produces a shorter cycle time than the relative coordinate manipulator in optimal designs.     

Biomimetic Pinching Movements of a Musculo-Skeletal Dual-Finger Model

The present paper investigates pinching movements using an index finger and a thumb actuated by redundant nonlinear digitorum muscles mimicking the configuration of human fingers. A dual-finger model with 2-d.o.f. joints for each finger and redundant nonlinear digitorum muscles is formulated to mimic the structure of human fingers. First, the kinematics and dynamics of the overall finger–object system, as well as the nonlinear muscular dynamics, are derived in accordance with the results of physiological studies. Next, a sensory-motor control law is proposed to enable stable pinching simultaneously with orientation regulation of an object. This control law includes an internal force term generated by co-construction of the redundant muscles. It is shown that the internal force term can modulate the damping factor in the joint space by its nonlinearity. Based on this effect, it is then shown by numerical simulation that our sensory-motor control law with co-contraction of each digitorum muscle makes it possible to realize pinching movements. Therefore, the pinching movements may be realized by means of a musculo-skeletal dual-finger system with the sensory-motor control law and co-contraction of redundant digitorum muscles.     

A Robust Solution to the Stereo-Vision-Based Simultaneous Localization and Mapping Problem with Steady and Moving Landmarks

The problem of visual simultaneous localization and mapping (SLAM) is examined in this paper using recently developed ideas and algorithms from modern robust control and estimation theory. A nonlinear model for a stereo-vision-based sensor is derived that leads to nonlinear measurements of the landmark coordinates along with optical flow-based measurements of the relative robot–landmark velocity. Using a novel analytical measurement transformation, the nonlinear SLAM problem is converted into the linear domain and solved using a robust linear filter. Actually, the linear filter is guaranteed stable and the SLAM state estimation error is bounded within an ellipsoidal set. A mathematically rigorous stability proof is given that holds true even when the landmarks move in accordance with an unknown control input. No similar results are available for the commonly employed extended Kalman filter, which is known to exhibit divergence and inconsistency characteristics in practice. A number of illustrative examples are given using both simulated and real vision data that further validate the proposed method.