Electromechanical Dynamics (Part 1).0061

Electromechanical Dynamics (Part 1).0061 - linear ideal...

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Lumped Electromechanical Elements Fig. 2.2.6 A linear ideal torsional spring: (a) physical system; (b) circuit. It is always possible, although in many cases not convenient, to define reference positions for measuring xz and xa such that 1 = 0. We can also have linear ideal torsional springs in rotational systems. The mathematical and circuit representations are analogous to those of a transla- tional spring and are evident in Fig. 2.2.6. The torque is a linear function of the relative angular displacement of the two ends T = K(0 2 - 01 - 4). (2.2.4) Note that the K in (2.2.3) has different dimensions than the K in (2.2.4). 2.2.1b The Mechanical Damper The mechanical damper is analogous to electrical resistance in that it dissipates energy as heat. An ideal damper is a device that exhibits no mass or spring effect and exerts a force that is a function of the relative velocity between its two nodes. A
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Unformatted text preview: linear ideal damper has a force proportional to the relative velocity of the two nodes. In all cases a damper produces a force that opposes the relative motion of the two nodes. A linear damper (often called a viscous damper) is usually constructed in such a way that friction forces result from the viscous drag of a fluid under laminar flow conditions.* Two examples of viscous dampers, one for linear and one for rotary motion, are shown in Fig. 2.2.7 along with the mechanical circuits. Note that the forcef (or torque T) is the force (or torque) that must be applied by an external agent to produce a positive relative velocity of the two nodes. For the linear-motion damper the terminal relation is d f = B -(x, -x) (2.2.5) dt * For more detail on viscous laminar flow see Chapter 14. A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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This note was uploaded on 02/10/2012 for the course MECE 4371 taught by Professor Liu during the Fall '11 term at University of Houston.

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