Development of Hanger-Rope Inspection Robot for Suspension Bridges

This paper describes the development of a hanger-rope inspection robot for suspension bridges. The inspection robot inspects the hanger rope by going up and down the rope installed vertically downward from the main cable of a suspension bridge. The going-up-and-down mechanism of the robot consists of a drive roller driven by a motor and a non-excitation electromagnetic brake, and the robot can safely descend after climbing the rope at high speed. The developed robot is small in size and light in weight, and an inspection worker can easily install the robot on the rope. In addition, the robot can be wirelessly controlled with ease from the controller. First, this paper describes the hanger-rope inspection strategy of the suspension bridge. Then, the developed prototype 2 robot is introduced. Next, the result of the hanger-rope inspection in an actual suspension bridge and the problems are clearly revealed by experiment. Finally, the newly developed prototype 3 robot is introduced, and the result of the going-up-and-down experiment is described.

Ovality Defect Control for Round Casting Based on Mechanical Deformation Analysis

Deformation of round castings due to thermal and/or mechanical strain may lead to the occurrence of their ovality defects during continuous casting. Presently, ovality defect from thermal deformation have been effectively controlled in actual casting process with the application of more advanced equipments and more sophisticated control strategies. But the control of ovality defect from larger mechanical deformation still cannot satisfy the need of caster design or higher qualified rate of castings. It is shown that excessive hot pressure while strand passes through tension leveler, is the main reason to generate larger mechanical deformation. With consideration of the characteristics of round caster and the requirement of safety production, a theoretical calculated model based on mechanical deformation analysis has been developed in the paper to eliminate ovality defect specially from the over large hot pressure. Calculation analysis suggests that groove design of drive roller and range of round section sizes should be the important consideration for the determination of hot pressure, and there always exists an optimum value for hot pressure when the machine equipments of round caster have been designed and installed. The model can provide a useful guideline for casting engineers to design the groove of drive roller and to determine reasonable safe hot pressure. Reliability of the model analysis has been verified by industrial application on a newly built round caster.

Nondimensional Analysis on the Mitigation of Hard Surface Roughness Induced Torque on Hard Cylinders by Introduction of a Soft Interfacial Layer for Precision Positioning Applications

It is widely known that surface roughness and other geometric imperfections can impose a limit on the positioning precision of actuators. The case of a hard cylinder rolling on a hard layer is investigated here, as it is applicable to friction drives. It is proposed that a soft interfacial layer between the drive roller and drive rail can mitigate the effects of geometric imperfections on positioning accuracy. Positioning accuracy is characterized by way of a 'roughness torque', which is the maximum torque that the roller sustains due to roughness of the rail. It is assumed that lower roughness torque values lead to greater positioning accuracy. Finite element analysis and an analytic approach are employed to investigate the situation.

Probability of Load-Carrying Ability of Two-Profile Chain Drives

The analysis of the available calculation methods of chain-drives load-carrying ability is given according to the criterion of the tolerance unit pressure in a single profile chain joint [p]0. It is shown, that the values of [p]0 were determined according to the deterministic ideas without consideration of the distribution law of both random varieties of contact step of inner and outer rings and lengths of drive strands of the first and second profile of the chain drive. Probability task of determination of the tolerance unit pressure in two profile chain joints [p0]q is solved, when the structural, technological and physical-mechanical characteristic of the chain, that is, the lengths of drive strand of a chain-drive, accuracy of contact steps and stiffness of a drive roller chain are considered. The measurement procedure and the empirical dependencies for determination of drive roller chains deformation and stiffness are presented. As a result, the dependencies for the determination of [p0]q as the basic criterion according to which selection of a chain dimension-type, as well as characteristics used for the comparative estimation of a drive chain quality of different manufacturers when certain probability estimations are taken into consideration, were obtained.

Device Developed to Measure Drive Roller

A new device has been developed to measure the distance from the drive roller to the cage for studying sensor measurement of distance. In one application, it uses a laser, and in another, a strain gauge.