A study targets the tracking deviation correction (TDC) problem in high-speed landing taxiing (HSLT) exclusively and proposes a hybrid nonlinear control scheme. In the position control, the famous model-independent li...
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A study targets the tracking deviation correction (TDC) problem in high-speed landing taxiing (HSLT) exclusively and proposes a hybrid nonlinear control scheme. In the position control, the famous model-independent line-of-sight (LOS) guidance algorithm is modified such that it is suitable for the airplane control. The LOS algorithm is quite suitable for straight-line tracking control, making it a perfect candidate for position control in TDC. The position tracking error is transformed into the desired yaw angle (YA) such that the underactuation problem is solved, which in turn transforms the position control problem into the Euler angle manipulation one. In the YA control, a linear extended state observer (LESO) is applied to estimate the nonlinear terms such that only few rough model information of the YA plant system is needed. By considering lateral gust, a type of predictive functional controller targeting cascade linear systems is developed such that the input surging can be restrained and the input saturation can be avoided to some extent.
Large navigation and atmospheric uncertainties have historically driven the need for a mid-lift-to-drag-ratio (mid-L/D) vehicle with (L/D)max of 0.6-0.8 for aerocapture at Neptune. Most planetary entry vehicles flown ...
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Large navigation and atmospheric uncertainties have historically driven the need for a mid-lift-to-drag-ratio (mid-L/D) vehicle with (L/D)max of 0.6-0.8 for aerocapture at Neptune. Most planetary entry vehicles flown to date are low-L/D blunt-body aeroshells with L/D less than 0.4. The lack of a heritage mid-L/D aeroshell presents a major hurdle for Neptune aerocapture, as the development of a new entry vehicle incurs significant time and investment. Techniques that may allow Neptune aerocapture to be feasible using heritage low-L/D blunt-body aeroshells are investigated that obviate the need for mid-L/D aeroshells. A navigation study is performed to quantify the delivery errors, and a new guidance algorithm with onboard density estimation is developed to accommodate large atmospheric uncertainties. Monte Carlo simulation results indicate that the reduced navigation uncertainty and improved guidance scheme enable a blunt-body aeroshell with L/D=0.3-0.4 to perform aerocapture at Neptune. The expected heat rate is within the capabilities of existing thermal protection system materials.
The article provides information on the Mars Science Laboratory (MSL) entry, descent and landing (EDL) sequence, which is designed to place a rover on the Mars surface at near-zero velocity.
The article provides information on the Mars Science Laboratory (MSL) entry, descent and landing (EDL) sequence, which is designed to place a rover on the Mars surface at near-zero velocity.
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