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robotics Designing the Mechanisms for Automated Machinery Part 8

Tham khảo tài liệu 'robotics designing the mechanisms for automated machinery part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6.4 Vibrational Transportation 225 acceleration component A v determines the vertical pressure that the body exerts. Obviously when A v is positive directed upwards the pressure Pv can be expressed as Py m g Ay 6.12 and when the vertical component is negative we have Py m g-Ay . 6.13 The horizontal component A h also becomes positive rightward and negative during the cycle of motion. This component engenders horizontal inertial forces ph which equal Ph mAh. 6.14 These forces can be smaller or larger than the frictional force PF. We can now express the frictional force through Expressions 6.12 and 6.13 as follows PF ụm g Ay . 6.15 Obviously horizontal displacement of the body relative to the tray will take place when Ah n g Ay . 6.16 Analysis of these expressions shows that there are several different possibilities for the bodies behavior on the tray. These possibilities can be described qualitatively as follows 1. No motion occurs between the body and the tray. This happens when the value mAh is always smaller than the frictional force. 2. Motion along the tray occurs because Ah Ll g-Ay . 6.17 However the body does not rebound. It is always in contact with the tray because A g. 6.18 3. Motion along the tray occurs because of both a condition 6.17 and b rebounds during the intervals when A v 5 g and there is no contact between the tray and the body. Therefore relative motion of some sort takes place. 4. Relative motion between the tray and the body occurs but the body does not proceed in any definite direction because the values of the frictional coefficient are very low. Balls or rollers on the tray. In practice case 2 is preferable. In this case the body proceeds smoothly along the tray in the direction shown by the arrow. Vibrating transporting trays are used because of their simplicity high reliability high transporting speed simple ways to control this speed and simple means that are adequate for stopping the transported bodies simple mechanical stops are used