Wrist Camera-Based Vibration Suppression Control for a Flexible Manipulator

This paper addresses a vision-based method for estimating vibration excited in the tip of a flexible-link manipulator. In this method, estimation of vibration is achieved by observing the variation of image features projected on a wrist camera. It mimics the situation of utilizing a wrist camera in tip vibration control of a space manipulator. In space, a vision sensor can be expected to be a feasible means for measuring the elastic vibration of the space manipulators, since they are more reliable compared with sensors like strain gauges. The method proposed in this paper takes advantage of the frequential characteristics of visual information that are reflected as a blurred background scene. With the high-frequency component of the projected image features, a Kalman filter-based observer is implemented as the estimator for the vibration. This implementation is characterized by the considerations of incorporating the slow sensor of the camera in the fast servo loop and compensation of the time delay due to image processing. With the vibration estimator, vibration suppression control relying solely on a wrist camera becomes possible. This scheme is successfully verified by experiments.     

A compact planar distributed tactile display and effects of frequency on texture judgment

This paper describes the development of a planar distributed tactile display and the evaluation of the results of its effectiveness for displaying textures. The tactile display is composed of a 6 × 5 pin array actuated by 30 piezoelectric bimorphs. The distance between each pin's centers is 1.8 mm. Vertical excursion of each pin is controlled over a 0–0.7 mm range. Perceptual experiments were conducted to evaluate the performance of the system under three conditions: active touch, passive touch with vibration and passive touch without vibration. The experimental results showed that vibrational stimuli helped subjects discriminate tactile patterns. Measurements of the error rate during discrimination tasks were used to find an optimal vibration frequency for stimuli presented at a constant sensation level (32 SLdB above threshold). The experiment was repeated, this time holding the energy transferred mechanically to the fingertip tissue constant. At low frequencies, we found that the passive stimulation allowed subjects to discriminate just as well as active touch of static stimuli did. The results suggested new possibilities for displaying texture using passive touch, constant energy and spatially varied vibration frequency.     

The vibration welding of poly(methyl methacrylate) to itself and to polycarbonate,poly(butylene terephthalate), and modified poly(phenylene oxide)

The weldability of poly(methyl methacrylate) (PMMA) to itself and to polycarbonate (PC), poly(butylene terephthalate) (PBT), and modified poly(phenylene oxide) (M-PPO) is assessed through 120 and 250 Hz vibration welds. Weld strengths equal to those of the base resin have been demonstrated in welds of PMMA and M-PPO to themselves. In welds of PMMA to PC and to M-PPO, weld strengths equal to those of PC and M-PPO, respectively, have been demonstrated. PMMA does not weld well to PBT; the highest weld strength obtained was 21% of the strength of PBT resin.     

MEASUREMENT OF ANGULAR VIBRATION AMPLITUDE BY ACTIVELY BLURRED IMAGES

A novel motion-blur-based method for measuring the angular amplitude of a high-frequency rotational vibration is schemed. The proposed approach combines the active vision concept and the mechanism of motion-from-blur, generates motion blur on the image plane actively by extending exposure time, and utilizes the motion blur information in polar images to estimate the angular amplitude of a high-frequency rotational vibration. This method obtains the analytical results of the angular vibration amplitude from the geometric moments of a motion blurred polar image and an unblurred image for reference. Experimental results are provided to validate the presented scheme.     

Vibration of an adhered microbeam under a periodically shaking electrical force

The vibration analysis of an adhered S-shaped microbeam under alternating sinusoidal voltage is presented. The shaking force is the electrical force due to the sinusoidal voltage. During vibration, both the microbeam deflection and the adhesion length keep changing. The microbeam deflection and adhesion length are numerically determined by the iteration method. As the adhesion length keeps changing, the domain of the equation of motion for the microbeam (unadhered part) changes correspondingly, which results in changes of the structure natural frequencies. For this reason, the system can never reach a steady state. The transient behaviors of the microbeam under different shaking frequencies are compared. We deliberately choose the initial conditions to compare our dynamic results with the existing static theory. The paper also analyzes the changing behavior of adhesion length during vibration and an asymmetric pattern of adhesion length change is revealed, which may be used to guide the dynamic de-adhering process. The abnormal behavior of the adhered microbeam vibrating at almost the same frequency under two quite different shaking frequencies is also shown. The Galerkin method is used to discretize the equation of motion and its convergence study is also presented. The model is only applicable in the case that the peel number is equal to 1. Some other model limitations are also discussed.     

Development of power assisted wire suspension system and its application to mould setting

Abstract

In this paper, a power assisted wire suspension system which supports the setting of a mould is presented. The purpose of this system is to eliminate a worker's burden and to assist the skill for unskilled workers. This system measures the swing angle of the rope and the fluctuation of the mould's weight caused by operator's force, and it moves the AC servomotors of both the horizontal and vertical axes work in accordance with the detected swing angle and the force respectively. The effectiveness of this power assisted system is confirmed by experiments for setting of the mould.     

Modelling behaviour of oxide film during vibration diffusion bonding of SiCp/A356 composite in air

Abstract

The vibration liquid phase diffusion bonding of SiC_p/A356 composite in air has been investigated. The surface of specimens to be bonded was treated with and without vibration under the bonding condition. It was found by atomic force microscopy analysis that some of the oxide film could be broken down when ridges on the surface of the matrix were ground down. Dissolution of the base metal by the filler metal occurred with removal of the oxide film during vibration liquid phase bonding, and SiC particles in the base metal entered the bond region. A removal process model for vibration bonding has been established with and without filler metal. Results show that shearing and impacting actions are the two main breaking mechanisms during vibration; the oxide film bulk is generally broken down by shear, and dissolution of the base metal by the filler metal promotes particle segregation from the matrix and their entry into the bond region.     

Real time observation of nucleation and detachment of crystal from chilling surface Part I – effects of vibration

Abstract

The nucleation and detachment of grains from a chilling surface were observed in real time in a model NH₄Cl solution system. The effects of vibration frequency and amplitude on the detachment behaviour and crystallographic morphology of grains were also studied. The results show that partial dendrite arms were broken off under low frequency vibration, whereas the entire dendrite was broken off at its root under high frequency vibration. The higher the frequency and amplitude, the thinner the detached grains. The effect of frequency on the morphology of grains is much greater than that of amplitude, thus increasing vibration frequency is effective in forming fine granular grains, but not amplitude. The amount of detached grains increases with increasing vibration frequency and amplitude up to 1200 Hz and 80 μm; further increase in vibration frequency or amplitude reduced the amount of detached grains.     

The vibration welding of poly(butylene terephthalate) and a polycarbonate/poly(butylene terephthalate) blend to each other and to other resins and blends

Vibration welding is used to assess the weldability of poly(butylene terephthalate) (PBT) and a polycarbonate/poly(butylene terephthalate) blend (PC/PBT) to each other and to other resins and blends: PBT to PC/PBT, PBT to modified poly(phenylene oxide) (M-PPO), PBT to polyetherimide (PEI) and PEI to a 65 wt% mineral-filled polyester blend (65-PF-PEB), PBT to a poly(phenylene oxide)/polyamide blend (PPO/PA), PC/PBT to M-PPO, and PC/PBT to PPO/PA. Based on the tensile strength of the weaker of the two materials in each pair, the following relative weld strengths have been demonstrated: PBT to PC/PBT,98%; PBT to PEI, 95%; 65-PF-PEB to PEI, 92%; and PC/PBT to M-PPO, 73%. PBT neither welds to M-PPO nor to PPO/PA, and PC/PBT does not weld to PPO/PA.     

Vibration welding of glass-filled poly(styrene-co-maleic anhydride)

Vibration welding is used to assess the weldability of 16 wt% glass-filled poly(styrene-comaleic anhydride) (16-GF-SMA). Data are presented on the strengths of butt welds for two specimen thicknesses and T-welds for one specimen thickness. The maximum weld strength of butt joints is shown to be only 35% of the tensile strength of the material. T-joints are shown to have only 61% of the strength of butt joints. The relative butt-weld strengths of 16-GF-SMA are much lower than those measured in other glass filled resins: 71% in a 20-wt% glass-filled modified poly(phenylene oxide); 68 and 60%, respectively, in 15- and 30-wt% glass-filled grades of poly(butylene terephthalate); and 58% in a 40-wt% glass-filled polyamide 6,6.