Repetitive control of digital systems having fast phase change produced in the discretization
Conference proceedings article
ผู้เขียน/บรรณาธิการ
กลุ่มสาขาการวิจัยเชิงกลยุทธ์
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รายละเอียดสำหรับงานพิมพ์
รายชื่อผู้แต่ง: Panomruttanarug B., Longman R.W.
ผู้เผยแพร่: Univelt Inc.
ปีที่เผยแพร่ (ค.ศ.): 2014
Volume number: 150
หน้าแรก: 1921
หน้าสุดท้าย: 1939
จำนวนหน้า: 19
ISBN: 9780877036050
นอก: 0065-3438
eISSN: 0065-3438
ภาษา: English-Great Britain (EN-GB)
บทคัดย่อ
Repetitive control (RC) can be used for active vibration isolation in spacecraft that have vibration sources such as reaction wheels or CMGs. Previous research developed very effective FIR compensator design methods. These designs tune the FIR gains to make the compensator frequency response be close to the inverse of the digital feedback control system frequency response. Then the RC adjusts the command to the feedback control system aiming to converge to complete elimination of the effects of the periodic disturbance. The discrete time equivalents of continuous time systems fed by a zero order hold have somewhat different frequency response characteristics. We investigate the situations in which the phase response of the discrete time system can have sudden changes in phase approaching ฑ 90 deg. A phase error of 90 deg is the ideal stability robustness limit of repetitive control systems. It is the purpose of this paper to determine under what conditions discretization produces such large sudden phase changes in the response, and to determine to what extent such changes cause difficulty in producing stable RC designs. It is shown that fast sample rate with even pole excess produces fast phase changes at Nyquist frequency. Also, slow sample rates can produce arbitrarily steep cliffs in the phase plot. However, the RC design process is found to be able to maintain stability, but with possibly very reduced stability margin.
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