REG NASA-LLIS-1609--2005 Lessons Learned - Fin Actuator System Logic Circuit Separation from High Current.pdf

1、Lessons Learned Entry: 1609Lesson Info:a71 Lesson Number: 1609a71 Lesson Date: 2005-06-02a71 Submitting Organization: DFRCa71 Authored by: Jonathan BrownSubject: Fin Actuator System/Logic Circuit Separation from High Current Abstract: Following the recommendations from the X43A Flight 1 MIB, the Peg

2、asus actuator system was redesigned to accommodate the need for greater hinge torque. The analog-based legacy actuator system was redesigned for digital drive of the power output stage to the actuators, an additional actuator was incorporated to provide the necessary torque including margins, and th

3、e power supply was increased to provide the required 80+ amps, instead of the previous 40 amp capability. Multiple failures during qualification testing, and the subsequent technical investigations, proved the lack of understanding between the ideal circuit operation and the impact of system impleme

4、ntation. Low-inductance ground and power planes/paths within (sub)systems are essential for proper operation. Description of Driving Event: Following the recommendations from the X43A Flight 1 MIB, the Pegasus actuator system was redesigned to accommodate the need for greater hinge torque. The analo

5、g-based legacy actuator system was redesigned for digital drive of the power output stage to the actuators, an additional actuator was incorporated to provide the necessary torque including margins, and the power supply was increased to provide the required 80+ amps, instead of the previous 40 amp c

6、apability. Multiple failures during qualification testing, and the subsequent technical investigations, proved the lack of understanding between the ideal circuit operation and the impact of system implementation. Lesson(s) Learned: Instantaneous currents associated with digital switching of power c

7、omponents can far exceed the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-steady-state values. These high current transients strain the ground and power planes, adequate for lower slew rate analog systems, but leading to increased noise levels and

8、 deleterious ground bounce in digital circuits. Recommendation(s): Low inductance cabling, kept to minimum length, is mandatory. As a general rule, keep logic circuit power and grounds separated from high current drive circuits, preferably all the way back to the power supply (battery). Minimum grou

9、nd return inductance must be a design goal. Utilizing heavier copper traces on printed circuit boards, 2 oz. versus 1 oz. copper, especially for ground planes should be considered; ensure that sufficient number of connector pins are used to minimize potential voltage drops; and recognize that the nu

10、mber of feed-throughs, or vias, on a printed circuit board, and their hole-size and plating will have an effect on the inductance of the trace or plane. Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics Res

11、earcha71 Space OperationsAdditional Key Phrase(s): a71 Accident Investigationa71 Flight Equipmenta71 Hardwarea71 Safety & Mission Assurancea71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2006-04-18a71 Approval Name: dkruhma71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-