NYQUIST STABILITY CRITERION Welcome to the Frank H 奈奎斯特稳定判据欢迎弗兰克H.ppt

Typical slewing response. In practice, step rate is often increased beyond the slew rate, in a time interval shorter than what is specified for acceleration and then decelerated to the slew rate by pulse subtraction at the end. -In transient operation, non uniform stepping sequences might be necessary depending on the complexity of the motion trajectory and the required accuracy.  -The Electrical Time Constant is given by L/R. Electrical Time constant =L/(R + R’). Static Position Error : Damping in Stepper Motors - Mechanical damping. Electrical Damping. Electronic Damping. -Advantages and disadvantages. Feedback Control of Stepper Motor Why Feedback? Open loop operation is adequate for low speed and steady state operation. Actual response can not be measured. In open loop control significant errors can not be measured. Models of Stepper Motor Simple Model Under steady state operation most of its parameters remains constant. Modified Model Under transient and high speed operation assumed constant in the torque source model will vary with time as well as rotor position. Selection of stepper motor Main requirement of particular application. eg. Speed, acceleration, required accuracy and resolution and load characteristics, such as size, resistance torques. Compute operating torque and stepping rate for particular application. Using torque versus stepping rate curves select suitable motor. Applications Printing Disk drives Robotics Automotives Medical and Metallurgical lens drives Advantages Position error is noncumulative. High accuracy is possible. Easy to adopt to digital controlled applications. No serious stability problem occurs. Torque and power requirements can be optimized and response can be controlled by electronic switching. Disadvantages Low torque Limited speed High vibration Conclusion References:-Control sensors and actuators by Clarence W. deSilva.-/jasstep.htm Thank you !!!