Zhi Hua Feng

Proportional-integral-plus control of robotic excavator arm utilising state-dependent parameter model

This paper is concerned with the design of a control system for a robotic excavator known as the Lancaster University Computerised and Intelligent Excavator (LUCIE). A nonlinear proportional-integral-plus (PIP) control algorithm is developed for regulating movement of excavator arm. The nonlinear dynamics of the hydraulic driven arm is represented using the quasi-linear state-dependent parameter (SDP) model, in which the parameters are functionally dependent on other variables in the system. The model is subsequently utilised to develop a new approach to control system design, based on nonlinear PIP pole assignment. Implementation results demonstrate improved tracking performance of excavator arm in comparison with both linear proportional-integral-derivative (PID) and conventional (linearised) fixed-gain PIP control.

Analysis of Deflections and Stresses for Laminated Composite Plates Based on a New Higher-Order Shear Deformation Theory

Based on the new simple third-order shear deformation theory, the deflections and stresses of the simply surported symmetrical laminated composite plates are obtained by using the principle of virtual work .The solutions are compared with the solutions of three-dimensional elasticity theory, the first-order shear deformation theory and the Reddy’s higher order shear deformation theory . Results show that the presented new theory is more reliable, accurate, and cost-effective in computation than the first-order shear deformation theories and other simple higher-order shear deformation theories.

Stochastic Principal Parametric Resonances of Composite Laminated Beams

This paper presents a detailed study on the stochastic stability, jump, and bifurcation of the motion of the composite laminated beams subject to axial load. The largest Lyapunov exponent which determines the almost sure stability of the trivial solution is quantificationally resolved and the results show that the increase of the bandwidth facilitates the almost sure stability of the trivial response. The stochastic jump and bifurcation of the response are numerically calculated through the stationary joint probability and the results reveal that (a) the higher the excitation frequency is, the more probable the jump from the stable stationary nontrivial solution to the stable stationary trivial one is; (b) the most probable motion is around the nontrivial solution when the bandwidth is smaller; (c) the outer flabellate peak decreases, while the central volcano peak increases as the value of the excitation load decreases; and (d) the overall tendency of the response is that the probable motion jumps from the stable stationary nontrivial branch to the stable stationary trivial one as the fiber orientation angle of the first lamina with respect to the -axis of the beam increases from zero to a smaller angle.

Nonlinear Dynamics of a Parametrically Excited Laminated Beam: Deterministic Excitation

The nonlinear dynamic equation of a laminated beam subject to parametrically deterministic excitation is derived based on the general von Karman-type equations and the Reddy third-order shear deformation plate theory. The first mode parametric resonance is taken into consideration using Galerkin approach. The modulation equations are obtained with the method of multiple scales. The frequency-amplitude and force-amplitude characters are investigated. Results show that the nonlinear behaviors belong to hardening effect.

Research on Alarming Device for Warp Stop Motions of Computer Sewing Machines

Owing to spandex silks are very thin and transparent, it is very hard to spot the broken warp without alarm during sewing or weaving. Therefore, the key to solve the problem is to shutdown and alarm timely when warps break. The ways and principles of common warp stop are analyzed in this paper, a new type of warp stop motions is developed for textile purposes to avoid inconveniences and malfunctions of the traditional method. Alarming rate and stability can be improved effectively by the compact and lightweight design of drop stitches, controlling system with converting functions as well as the modified testing, protection, reset.

Dynamic Analysis and Balance Design for a Constant Temperature Oscillator Based on ADAMS

In this paper the rigid-flexible coupling dynamic characteristics for an existing constant temperature oscillator based on ADAMS has been investigated. The unbalance load caused by the rotation of the eccentric mass is carefully calculated. In view of this phenomenon, a new centroid adjustable balancing head is put forward, and the scheme is verified by ADAMS.

Numerical and Experimental Investigation on the Weighing System of an Incubator Shaker

In order to solve the weighing problem of a type of incubator shakers, a new weighing method, combined with numerical analysis and experimental verification, is proposed. The numerical analysis based on the software of ANSYS Workbench indicates that the sum of the two-point strain in the mechanism is found to be constant and there is a fine linearity relationship between the sum of the two-point strain and the weight of load, so as to offer a measurement method for indirect measurement of the loading weight and this measuring method has been verified by experiment.

Transverse Vibration of Axially Accelerating Moving Fabric: Experiment and Analysis

Axially moving fabric can be met in many textile devices. In most cases, the transverse vibrations of fabric can cause a series of negative influents to the product. In this paper, the transverse vibration of axially accelerating moving fabric, which is excited by velocity fluctuations, is investigated by experimental method. The harmonic varying velocity is achieved through a brushless DC motor controlled by PWM technology based on the embedded microcontroller LPC1768. An inductive non-contact displacement sensor is used to measure transversal vibration of fabric. The motor speed is measured by a photoelectric encoder. The experimental data is processed by measurement platform based on Labview and the analysis is given. Laboratory measurements demonstrate the effect of velocity fluctuations on transverse vibration of fabric, particularly near the parametric resonance region.

Vibration Suppression of Yarns via Sliding-Mode Control

In this paper, a dynamic model of yarn in sizing machines is proposed. The fluxion in moving speed is taken into consideration. By sliding-mode control, the transverse vibration control of the yarns is studied and the control law based on varied tensions is designed. Numerical simulation are carried out using the finite difference approach and results show that the convergence rate of spacing errors of the yarn is fast and the transverse vibration can be well reduced.

Effect of Easing Device on an Air-Jet Loom of Double Back Rest System

In order to release the influence of shedding motion on warp tension fluctuation, easing device is often set on short looms with single back rest system. With the decrease of the beam’s diameter, the wrapping angle formed by warp and the active back rest will become bigger, and the effect of the easing device will be more significant. However, the wrapping angle of the double back rest system is a constant while the change of the beam’s diameter. The effect of easing device on air-jet looms of double back rests system is analyzed in this paper, and conclusion has been made that the easing device can be eliminated on the double back rests system.