Autonomous atmospheric entry on mars: Performance improvement using a novel adaptive control algorithm

Abstract

Upcoming landing missions to Mars will require on-board guidance and control systems in order to meet the scientific requirement of landing safely within hundreds of meters to the target of interest. More specifically, in the longitudinal plane, the first objective of the entry guidance and control system is to bring the vehicle to its specified velocity at the specified altitude (as required for safe parachute deployment), while the second objective is to reach the target position in the longitudinal plane. This paper proposes an improvement to the robustness of the constant flight path angle guidance law for achieving the first objective. The improvement consists of combining this guidance law with a novel adaptive control scheme, derived from the so-called Simple Adaptive Control (SAC) technique. Monte-Carlo simulation results are shown to demonstrate the accuracy and the robustness of the proposed guidance and adaptive control system.

Modified Simple Adaptive Control for a two-link space robot

“…The reference model, which is modeled by a set of second order uncoupled linear equations of the form Eqs. (14) to (17). (21) where the first and second terms on the right-hand side of Eq.…”

“…with the MSAC adaptation law originally proposed by Ulrich and de Lafontaine for SISO systems [14]. Extending the MSAC algorithm for the control of a MIMO system, i.e.…”

“…(14) to (17), pp Γ , pi Γ , dp Γ and di Γ are control parameters to be adjusted and where p δ and d δ are small positive control coefficients necessary to avoid divergence of the integral control gains. Indeed, with the δ -terms, the integral adaptive gains could increase indefinitely as long as a tracking error exists.…”

“…In fact, the SAC theory does not provide any means of efficiently selecting the several coefficients of the weighting matrices, although Kaufman gives some hints [13]. To overcome this design complexity, Ulrich and de Lafontaine [14] derived a modified version of the SAC algorithm for SISO systems, referred to as the Modified SAC (MSAC) adaptation law. Since the MSAC algorithm depends only on the error between the reference model outputs and the plant outputs, its computational efficiency is greatly improved over the original SAC methodology, making it a suitable candidate control algorithm for space robots.…”

Simple Adaptive Control for Spacecraft Proximity Operations

“…33 In the last few decades, the SAC methodology and variations thereof have been used in many successful linear and nonlinear applications, such as nonminimum phase autopilots, 34 atmospheric entry vehicles, 35,36 spacecraft underactuated attitude control, 37 flexible-joint robot manipulators, 38 and flexible structures with collocated and noncollocated sensors. 39…”