tailieunhanh - Indexes of Performance

The state of the art of the machine industry has experienced a rapidly accelerating evolution since the outset of the first industrial revolution. Modern machines are required to perform to varying requirements of accuracy, productivity, and surface finish requirements. It is the purpose of this discussion to establish some guidelines of machine system design to attain the desired performance requirements of accuracy, surface finish, etc. Modern industrial machines are considered as a total system comprised of the control, drive, and machine | 9 Indexes of Performance The state of the art of the machine industry has experienced a rapidly accelerating evolution since the outset of the first industrial revolution. Modern machines are required to perform to varying requirements of accuracy productivity and surface finish requirements. It is the purpose of this discussion to establish some guidelines of machine system design to attain the desired performance requirements of accuracy surface finish etc. Modern industrial machines are considered as a total system comprised of the control drive and machine. There are two kinds of performance criteria. One referred to as indexes of performance . relates to specifying servo drive stability in relation to design parameters. The second performance characteristics relates to parameters such as drive stiffness resolution maximum acceleration and the effects of friction. To some extent the performance characteristics are a function or the end result of the indexes of performance that are selected. DEFINITION OF INDEXES OF PERFORMANCE FOR SERVO DRIVES During World War II the growth of feedback control theory was given a stimulus that has continued for five decades. As the state of the art improved control system performance could be predicted with increased accuracy. However as the state of the art in feedback control theory Copyright 2003 by Marcel Dekker Inc. All Rights Reserved increased in reliability it also increased in complexity. There is a need to specify performance in relation to design parameters. An accepted technique to relate performance . is an attempt to optimize performance using constraints of design criteria. Some in common use are A. From the frequency response 1. Phase margin 2. Gain margin 3. Gain margin versus control loop bandwidth B. From the step response 1. Percent overshoot 2. Rise time 3. Delay time 4. Settling time These are given for the frequency response and step response because these two methods of analysis are