In this paper, a sliding mode control-based cooperative guidance strategy for a team of two unmanned aerial vehicles (aircraft), which ensures their survival against pursuers, is proposed. The pursuing interceptors ar...
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In this paper, a sliding mode control-based cooperative guidance strategy for a team of two unmanned aerial vehicles (aircraft), which ensures their survival against pursuers, is proposed. The pursuing interceptors are assumed to employ augmented proportional navigation guidance. The cooperating aircraft maneuver in a way to lure their respective pursuers to an impact angle constrained collision. The problem of controlling impact angle is first transformed to that of tracking line-of-sight angle and its rate, and then the same is achieved by enforcing sliding mode on appropriate chosen switching surface. Furthermore, the allocation of aircraft’s lateral accelerations is performed in a way to minimize the instantaneous aerodynamic drag acting on both unmanned aerial vehicles. Numerical simulations are presented to validate the effectiveness of the proposed guidance strategy under different engagement geometries.
In this paper, a nonlinear impact time constrained three-dimensional guidance strategy to intercept a stationary target is proposed. The guidance strategy is based on non-singular terminal sliding mode control that us...
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In this paper, a nonlinear impact time constrained three-dimensional guidance strategy to intercept a stationary target is proposed. The guidance strategy is based on non-singular terminal sliding mode control that uses an improved time-to-go estimate in the design process, thereby provisioning for the interceptor’s large heading angle errors. Unlike existing approaches in the literature of three-dimensional terminal guidance, the proposed technique does not decouple the nonlinear three-dimensional engagement kinematics to design the guidance commands. Additionally, the proposed technique also considers the effect of autopilot whose dynamics are usually ignored. The stability of the proposed guidance strategy is certified using Lyapunov stability theory. Simulation results show the effective performance of the proposed guidance commands for various engagement conditions. The results in this paper are further backed with a comparison with an existing strategy that vindicates the superior performance of the proposed strategy.
This paper presents the control and stabilization of the rotary inverted pendulum based on a general controller scheme. The proposed scheme has its foundation in classical control theory, and the importance of an inte...
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This paper shows that the torpedo-type Autonomous Underwater Vehicle (AUV) exhibits the non-minimum phase behavior in the depth control operation for a certain range of forward velocity. Contributions in this paper ar...
This paper shows that the torpedo-type Autonomous Underwater Vehicle (AUV) exhibits the non-minimum phase behavior in the depth control operation for a certain range of forward velocity. Contributions in this paper are (i) Transform AUV's 6 DOF dynamic model in a diving plane to the normal form. (ii) A method to determine the range of the forward surge velocity for which zero dynamics is unstable. Understanding the non-minimum phase behavior provides insight into the controller designs in the future, specifically for the identified ranges of the forward surge velocities.
This article studies a fundamental problem of security of cyber-physical systems (CPSs): that of detecting, almost surely, the presence of malicious components in the CPS. We assume that some of the actuators may be m...
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Mechanical systems are most often described by a set of continuous-time, nonlinear, second-order differential equations (SODEs) of a particular structure governed by the covariant derivative. The digital implementatio...
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This work proposes a cooperative strategy that employs deviated pursuit guidance to simultaneously intercept a moving (but not manoeuvring) target. As opposed to many existing cooperative guidance strategies which use...
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It is known in the context of decentralised control that there exist control strategies consistent with the requirements of a given information structure, yet physically unimplementable through any amount of passive c...
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Surfactant-laden thin liquid films overlaid on solid substrates are encountered in a variety of industrial and biological settings. As these films reach submicron thickness, they tend to become unstable owing to the i...
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Surfactant-laden thin liquid films overlaid on solid substrates are encountered in a variety of industrial and biological settings. As these films reach submicron thickness, they tend to become unstable owing to the influence of long-range dispersion forces. In the current study, we investigate how gravitational drainage affects the stability attributes of such thin liquid films. Using scaling arguments, we demonstrate that gravity and dispersion forces can exert their influence simultaneously over a wide range of film thicknesses. In the lubrication limit, we carry out linear stability analysis and nonlinear simulations to understand the evolution of draining thin films. Linear stability indicates the existence of two unstable modes and two cutoff wave numbers, as opposed to a single unstable mode and a unique cutoff wave number observed in stationary films. It is also found that surfactant-laden flowing films are more stable than stationary films with surfactants as well as draining films with clean interfaces. The origin of stabilization is identified as the enhanced surfactant perturbations generated due to drainage. We demonstrate that films exhibiting intermediate levels of surfactant activity and significant drainage exhibit the lowest rates of disturbance growth, leading to extending the time of rupture.
Actuators in real-world systems operate under limited bandwidth and saturation constraints. Mathematically, these limitations manifest as certain types of constraints being imposed on the sequence of control action. W...
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Actuators in real-world systems operate under limited bandwidth and saturation constraints. Mathematically, these limitations manifest as certain types of constraints being imposed on the sequence of control action. While saturation constraints have been studied extensively, bandwidth limitations in the actuators have received very little attention in the control community. While an attempt has been made in the direction of incorporating frequency constraints at the synthesis stage, rate constraints on the control at the design stage has not been studied extensively in the regime of discrete-time. This article tries to fill in that gap by incorporating rate constraints on the control trajectories. We propose a new discrete-time Pontryagin maximum principle (PMP) with rate constraints being imposed on the control and derive a set of first order necessary conditions for optimality. As an illustration, the linear quadratic (LQ) optimal control problem under rate constraints has been considered.
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