Pseudorate sawtooth-pulse-reset control system analysis and design.

Scott, E. D.

doi:10.2514/3.28951

Cited by 15 publications

(4 citation statements)

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“…The target Tg obviously satisfies the above three conditions and is clearly visible to the spacecraft. In contrast, the target T5 is below the horizon and its invisibility is confirmed also by the conditions (16). But, although the target T4 is above the horizon and clearly visible to the spacecraft, the conditions (16) are violated.…”

Section: Conditions Of Visibilitymentioning

confidence: 91%

“…vaeth15 concluded that for the fist two controllers, the required value of hysteresis would be impractical if the situation demands small minimum pulsewidth and large rate gain. To circumvent this obstacle, Scott (1967) 16 introduced a sawtooth-pulse-reset circuit in parallel with a dual time constant feedback lag circuit around the relay with deadband and hysteresis (Schmitt trigger). While the sawtooth-pulse-reset allows the designer to select desired minimum pulsewidth independent of hysteresis, the dual time constant is useful in the case of saturating attitude sensor.…”

Section: Target Acquisitionmentioning

confidence: 99%

“…2, all three conditions (16) are satisfied for the landmark T1 and violated for the landmark T2. Consider now a moving target such as a missile or a booster (T3, T4, T5 in Fig.…”

Section: Conditions Of Visibilitymentioning

confidence: 99%

“…But, although the target T4 is above the horizon and clearly visible to the spacecraft, the conditions (16) are violated. In this circumstance -a moving target above the horizon -the conditions (16) are not useful and, instead, the following condition should be checked: for visibility when target is above horizon o r p I 6 (17) where p is defined via Eq. (7).…”

Section: Conditions Of Visibilitymentioning

confidence: 99%

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Target acquisition, tracking, spacecraft attitude control, and vibration suppression with IPFM reaction jet controllers

Hablani

1992

Astrodynamics Conference

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This paper demonstrates that thrusters, when administered by integral pulse frequency modulation (IPFM) control system, can be used successfully for timdfuel optimal acquisition and precision tracking of moving targets, with low jitter (2 pmd) of the focal plane of flexible spacecraft. The paper first derives roll, pitch, and yaw position, rate and acceleration commands for tracking a moving object with a payload initially on the zenith side of the spacecraft. These commands are then made explicit for landmark tracking. Conditions of visibility of the target to the spacecraft in a given celestial setting are also formulated. A non-iterative, closed-form, single-axis, time/fuel optimal algorithm is developed to slew the spacecraft from one arbitrary state (attitude and rate) to another to acquire a moving target. The formulae for designing the IPFM controller for tracking a given acceleration command profile with a rigid spacecraft are summarized next. Spacecraft flexibility concerns such as mode selection on the basis of spontaneous impulse response, stable or unstable control-structure interaction due to large flexible to rigid inertia ratios or due to symmetric modes having a moment arm from the vehicle mass center, and the elimination of instability using minimum-rise-time lowpass filter are addressed in depth.Extensive numerical results are included which conclusively establish that the IPFM controllers are eminently suitable for precision pointing and tracking and, surprisingly, even for vibration suppression if the flexible to rigid inertia ratio is below unity.

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Section: Conditions Of Visibilitymentioning

confidence: 91%

Section: Target Acquisitionmentioning

confidence: 99%

“…2, all three conditions (16) are satisfied for the landmark T1 and violated for the landmark T2. Consider now a moving target such as a missile or a booster (T3, T4, T5 in Fig.…”

Section: Conditions Of Visibilitymentioning

confidence: 99%

Section: Conditions Of Visibilitymentioning

confidence: 99%

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