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PERCENT REGULATION There are a number of ways to define performance, such as servo bandwidth, accuracy, regulation, etc. Percent regulation, for machine servo drives, can be defined as how much the controlled variable of a servo will reduce as load is applied to the servo. As such, percent regulation is usually applied to type 0 velocity regulators to describe how well the output velocity will be maintained as load is applied to the output of the drive. Percent regulation is often given as the equation Percent regulation ¼ no load speed À full load speed full load speed. | 10 Performance Criteria 10.1 PERCENT REGULATION There are a number of ways to define performance such as servo bandwidth accuracy regulation etc. Percent regulation for machine servo drives can be defined as how much the controlled variable of a servo will reduce as load is applied to the servo. As such percent regulation is usually applied to type 0 velocity regulators to describe how well the output velocity will be maintained as load is applied to the output of the drive. Percent regulation is often given as the equation . no load speed full load speed Percent regulation ------- ------------------- full load speed A general block diagram for a DC servo drive with a position loop is shown in Figure 1. Using block diagram algebra the servo drive block diagram can be redrawn for speed as the controlled variable with the load torque as an input shown in Figure 2. Equations 10.1-1 to 10.1-11 show the calculations for the regulation of a DC drive. Equations 10.1-12 to 10.1-14 rearrange Eq. 10.1-11 for velocity-loop stiffness. Eq. 10.1-15 expresses the velocity stiffness. The position-loop equations are shown in Eq. 10.1-16 to 10.1-27 for the position-loop stiffness. Copyright 2003 by Marcel Dekker Inc. All Rights Reserved Fig. 1 Block diagram for an electric servo. Fig. 2 Block diagram for electric drive stiffness. Velocity Loop Vm Kt 6 1 Kt_ e JsRa Rs 1 x 1 JsRa Rs 1 KtK JsRA Rs 1 10.1-1 V. w__r _ w_ 10.1-2 e hJRa Rs2 JRa s 1 TMTes2 TMs 1 Vm __KaK1 T1S 1 _ A Ke T2S 1 lTMTeS2 TmS 1 6 k- tK K1B S1M 1I 10.1-3 Copyright 2003 by Marcel Dekker Inc. All Rights Reserved Vm_KaK T1S 1 _ A Ke T2s 1 TmTễs2 TmS 1 KaKi Tis 1 Kta s 0 Vm s 0 KaK1 A Ke KaK1Kta Kv - A 10.1-6 Kb - j . Vm _ 1 1 Tl Js 6 1 Kt K8 K1KtaKa T1s 1 Vm __ 1 TL Js - 6 K K1KrAKA ịị s 0 Vm 1 Ra Tl - K 6 Ke K1KtaKa - Kt Ke K1KtaKaKt Velocity-Loop Regulation For these equations .