A closed-loop NC system, illustrated in Figure 6.27(h). uses servomotors and feedback
measurements to ensure that the worktable is moved to the desired position. A common
feedback sensor used for NC (and also for industrial robots) is the optical encoder, shown
in Figure 6.28. An optical encoder consists of a light source and a photodetector on either
side of a disk. The disk contains slots uniformly spaced around the outside of its face. These slots allow the light source to shine through and energize the photodetector. The disk is connected, either directly or through a gear box, to a rotating shaft whose angular position and velocity are to be measured. As the shaft rotates, the slots cause the light source to be seen by the photocell as a series of flashes. The flashes are converted into an equal number of electrical pulses. By counting the pulses and computing the frequency of the pulse train, worktable position and velocity can be determined.
(Mikell P. Groover, Automation, Production Systems, and Computer-Integrated Manufacturing (2nd Edition)Systems, pg.183)
Closed loop positioning systems : (New)(Better)(Control system)
A closed loop positioning system has one or more feedback loops that has continuously compare the system's response with input command or sttings to correct errors in motor and/or load speed, load position, or motor torque. Feedback sensors provide the electronic signals for correcting deviations from the desired input commands. Closed loop systems are also called servosystems.
Each motor in a servosystem requires its own feedback sensors, typically encoders, resolvers, or tachometers, that close loop around the motor and load. Variations in velocity, positions, and torque are typically caused by variations in load conditions, but changes in ambient temperature and humidity can also affect load conditions.
(Mechanisms and Mechanical Devices Sourcebook, Neil Sclater, p.22)
Pick and place robots : (Previous)
Pick and place robots are typically stationary, pedestal-mounted robots. Therefore their work envelope is limited. To increase the work envelope and serve more machines, a (pick-and-place) robot can be installed on a gantry crane.
(Shimon Y. Nof, Handbook of industrial robotics, p960)
Pick and place robots : (New)(Better)(Robot Type)
A Pick and place robot is the simplest version accounting for about one-third of all U.S. installations. The name comes from the usual application in materials handling, picking something from one spot and placing it at another. Freedom of movement is usually limited to two or three directions-- in and out, left and right, and up and down. The control system is electro-mechanical.
(Technology, regions, and policy, John Rees, p.174)
Band Saw: (Previous)(Better)
The modern woodworker need tools that are simple yet versatile. These tools should do a large variety of jobs without expensive or complex jigs. There is no operation more basic to woodworking than sawing, and the versatile band saw can do all types of sawing. It will cut wood thick or thin and square or round. It will cuth both curves and straight lines. It will resaw thin veneer and make tight scroll-saw-type cuts. A skilled user can quickly turn a humble log into four perfectly matched Quenn Anne chair legs,. And with a simple band saw jig, he can cut through dove tails for a box or a drawer presicely and efficiently with aminimum of setup. In fact, a band sawn dovetail box can be finished before a router jig can be properly adjusted fort he same operation. The band saw dovetail jig doesn’t cost any thing either, just a little time and some scrap wood.
There are many reasons why a band saw should be the first power tool a person should learn to operate. To use a term coined in computer jargon, the band saw is user friendly. It is quiet and easy to use. Women often comment that it reminds them of a sewing machine. It can ben also be used for a wide range of functions.
(Mark Duginske, Band Saw Handbook, page 5)
Band Saw: (New)(Metal and wood cutting machine)
The band saw is designed to cut circles, areas and other regular or irregular curves. The band saw uses a thin band of steel with saw teeth cut intoone edge as its blade. The band is made into a continuous loop and mounted on two large wheels, one above the other.the saw blade is positioned vertically and passes through a table that can be angled to enable beveled cuts. The saw blade can be purchased in a variety of widths and tooth settings that will dictate theintricacies of the cut, among other things. The tighter the curve, the thinner the blade needs to be.
(The stagecraft handbook, Daniel A. Ionazzi, p.42)
Kelvin Model : (New)(Better)(Plastic Deformation Model)
Spring and damper are arranged in a parallel fashion, Fig. 17.
Viscoelastic deformation results from the paralel overlapping of spring and damper deformation: Elongation is delayed, but completely reversiblr upon relaxation. This is called entropy or rubber elasticity
(Polymers - Opportunities and Risks I: General and Environmental Aspects, 1. cilt, Peter Eyerer, p.83-84)
Burger model : (Previous)(Better)
Burger model is a four-unit and four-parameter (E1, E2, n1 and n2) model, which can reflect instant elastic deformation, viscoelastic deformation and viscosity flowing deformation of asphalt mixture under repeated loading. The disadvantage of this model is its incapacity of reflecting deformation characteristics of asphalt mixtures in the entire process of loading and unloading. In order to solve this problem, the four-unit and five-parameter modified Burger model was built, which can better describe the deformation regulation of asphalt mixtures in high temperature.
(Rafiqul A., Pavements and Materials: Testing and Modeling in Multiple Length Scales, 2010, p. 196)
Burger model : (New)(Plastic Deformation Model)
Voigt-Kelvin series arrangement with Maxwell model, see Fig. 19.
The Burger model provides a correct graphic description of the elongation time behavior of most plastics in a first approximation. The spring 1 results in spontaneous elastic load application and creep recovery (delayed viscoelastic reverse deformation) after relaxation, damper 2 results in residual elongation.
(Polymers - Opportunities and Risks I: General and Environmental Aspects, 1. cilt, Peter Eyerer, p.83-85)
Band Saw: (New)(Metal and wood cutting machine)
The band saw is designed to cut circles, areas and other regular or irregular curves. The band saw uses a thin band of steel with saw teeth cut intoone edge as its blade. The band is made into a continuous loop and mounted on two large wheels, one above the other.the saw blade is positioned vertically and passes through a table that can be angled to enable beveled cuts. The saw blade can be purchased in a variety of widths and tooth settings that will dictate theintricacies of the cut, among other things. The tighter the curve, the thinner the blade needs to be.
(The stagecraft handbook, Daniel A. Ionazzi, p.42)
Kelvin Model : (Previous)
The classical Kelvin-Voigt viscoelastic solid (see Kelvin [6], Voigt [8]) can be viewed as a mixture
of a linearized elastic solid and a linearly viscous °uid that co-exist. The one-dimensional model
is represented as a linear spring in parallel with a linearly viscous dashpot. A generalization of the
mechanical analog is to consider a non-linear spring in parallel with a non-linearly viscous dashpot.
Such a one-dimensional model can be appropriately generalized to obtain a three dimensional
(On Kelvin-Voigt model and its generalizations, M. Bulicek, J. Malek, K. R. Rajagopal)
model.
Kelvin Model : (New)(Better)(Plastic Deformation Model)
Spring and damper are arranged in a parallel fashion, Fig. 17.
Viscoelastic deformation results from the paralel overlapping of spring and damper deformation: Elongation is delayed, but completely reversiblr upon relaxation. This is called entropy or rubber elasticity
(Polymers - Opportunities and Risks I: General and Environmental Aspects, 1. cilt, Peter Eyerer, p.83-84)
Burger model : (Previous)(Better)
Burger model is a four-unit and four-parameter (E1, E2, n1 and n2) model, which can reflect instant elastic deformation, viscoelastic deformation and viscosity flowing deformation of asphalt mixture under repeated loading. The disadvantage of this model is its incapacity of reflecting deformation characteristics of asphalt mixtures in the entire process of loading and unloading. In order to solve this problem, the four-unit and five-parameter modified Burger model was built, which can better describe the deformation regulation of asphalt mixtures in high temperature.
(Rafiqul A., Pavements and Materials: Testing and Modeling in Multiple Length Scales, 2010, p. 196)
Burger model : (New)(Plastic Deformation Model)
Voigt-Kelvin series arrangement with Maxwell model, see Fig. 19.
The Burger model provides a correct graphic description of the elongation time behavior of most plastics in a first approximation. The spring 1 results in spontaneous elastic load application and creep recovery (delayed viscoelastic reverse deformation) after relaxation, damper 2 results in residual elongation.
(Polymers - Opportunities and Risks I: General and Environmental Aspects, 1. cilt, Peter Eyerer, p.83-85)
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