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robotics Designing the Mechanisms for Automated Machinery Part 6

Tham khảo tài liệu 'robotics designing the mechanisms for automated machinery part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 4.4 Dynamic Accuracy 153 __I s K fJ nlf i FIGURE 4.48 Example of a mechanism described by linear equations. When designing the engineer if it is important must use these approaches choosing the assumptions as required and numerically solve the appropriate equations. It must be mentioned that dynamic errors i p q2 etc. are often serious obstacles in the effort to increase the efficiency accuracy quality and or productivity of newly designed equipment. Let us make a short digression and consider an example relating to the recent history of typewriters and the essence of their dynamics. The classical structure of the typewriter included a carriage that holds the paper and moves it along the typed line providing the correct intervals between the characters. The typebars are fastened onto specially shaped levers that are actuated manually or electrically. The wider the paper sheet or the more copies being typed simultaneously the larger must the mass of the carriage and the dynamic effort of the mechanism be. To compensate it was necessary to limit the typing speed and the dimensions of the parts. These limitations were overcome by the introduction of the IBM concept where the carriage does not move along the lines and thus no inertial forces occur. The line of characters is typed by a small moving golfball element. It is made of light plastic and therefore its mass is much less than that of the carriage in the old concept. The dynamic efforts are thus considerably reduced and do not depend on the paper width and the number of copies. The speed of manual typing is not limited by this concept. However problems can and certainly do appear when this kind of typewriter is attached to a computer which can type much faster. Going back to our subject let US now consider an example of dynamic disturbances in an industrial machine. Figure 4.49 shows an indexing table drive we will deal with these devices in more detail in Chapter 6 . This drive consists of a .