1、Lessons Learned Entry: 0358Lesson Info:a71 Lesson Number: 0358a71 Lesson Date: 1994-12-13a71 Submitting Organization: JPLa71 Submitted by: H.K. Bouvier / J.O. BlosiuSubject: Magellan Solar Array Drive Jitter Abstract: A jitter in the solar array drive control loop during Venus mapping operations was
2、 caused by a deficiency, at oblique sun angles, in the algorithm that is used in Flight Software (FSW) to determine whether a solar panel position correction is required. Conduct thorough reviews to verify math models of hardware and to understand the implications of simplification of math models on
3、 performance in flight. Use finer resolution display scales to identify subtle instabilities.Description of Driving Event: During Venus mapping operations at high (over 64 degrees) incidence angles of the sun to the solar panels, a jitter occurred in the solar array drive control loop. This jitter e
4、xcited a structural resonance in the solar panels, causing severe vibration. The problem was caused by a deficiency, at oblique sun angles, in the algorithm that is used in Flight Software (FSW) to determine whether a solar panel position correction is required. The deficiency was caused by not acco
5、unting for high sun incidence angles (geometrical effects) in setting the minimum step size software parameter. As a result, the algorithm continually determined that a correction was required - first in one direction, then in the reverse, then in the first direction, etc.The jitter was actually pre
6、sent in simulations performed by the flight team before the incident occurred on the spacecraft, but was not recognized because of the plotting scale used.Once recognized, the problem was solved by switching the solar array control to an open-loop mode, i.e., not using the sun sensors, while the cel
7、estial geometry was unfavorable.A complete description of the problem can be found in the references.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Keyword(s): AACS, Mathematical ModelsReference(s): PFR #52242, ISA 8775, ISA 9049, ISA 853
8、6Lesson(s) Learned: Stability analyses for all geometries are an important part of attitude control hardware and software development and testing.Recommendation(s): 1. Because of the difficulties involved in ground testing spacecraft attitude and articulation control systems in a one G field, it is
9、extremely important to conduct thorough reviews to verify math models of hardware and to understand the implications of simplification of math models on performance in flight. These reviews should involve hardware, analysis, software and systems engineers.2. Finer resolution display scales should be
10、 used around worst-case conditions to identify subtle instabilities.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Safety & Mission Assurancea71 SoftwareAdditional Info: Provided by IHSNot for Resa
11、leNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1992-01-16a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
