Multivehicle Motion Planning and Control

A reliable guidance system is of utmost importance for autonomous vehicles operating in diverse mobility scenarios, including path-following, target tracking, interception, formation flying, and obstacle avoidance. The development of such a system is vital due to its wide-ranging applicability and the high level of autonomy required. Our focus lies in designing an automated flight control system, which serves as a critical necessity in numerous significant applications. These applications include but are not limited to waypoint navigation, path-following, surveillance, localization, mapping, and autonomous landing. By emphasizing the design of an advanced flight control system, we aim to address the complex demands of these applications, ensuring optimal performance, precise navigation, and successful execution of tasks in various operational environments.

Guidance and Control for Autonomous Path-following

In a path-following problem, the control objective is to enable the autonomous vehicle to converge to and follow the desired path without needing any temporal constraints. In a way, this feature makes it more flexible than trajectory tracking or target capture scenarios where spatiotemporal constraints are accounted for. Specifically, for the path-following problem, we currently focus on developing a simple and robust path-following controller that enables an autonomous vehicle to follow the desired path without needing the information of the path's curvature.

A schematic of path-following.
UAV following a path in strong wind from various initial conditions.

Selected Publications:

Target Enclosing Guidance

There are several situations where it is required for a vehicle (referred to as the "pursuer") to approach and maintain a specific shape or pattern around a region, object, or another vehicle (referred to as the "target"). This behavior is referred to as "target enclosing" and involves the pursuer orbiting the target while preserving the desired shape. One of the most commonly encountered types of target enclosing is circumnavigation or standoff tracking, where the pursuer keeps a fixed distance from the target by orbiting it. Instead of assuming a specific shape or geometry for the target, our research is focused on providing flexibility in enclosing targets of various shapes, sizes, and mobility. Our research addresses the challenges that include dealing with uncertainties in target motion, handling occlusions or sensor limitations, addressing control constraints, and ensuring robustness and stability of the enclosing behavior.

Target enclosing behavior.
Target circumnavigation.
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Fig: Enclosing a target in various geometrical shapes.

Selected Publications:

Relational Maneuvering for Flexible Formation

We present a novel formation strategy for a leader-follower unmanned aerial vehicle (UAV) system, drawing inspiration from the behavior of human pilots. In our approach, the formation geometry is not restricted to remain fixed as the vehicles maneuver. This means that the position and orientation of the follower UAV in relation to the leader UAV can change while adhering to certain constraints. Our strategy aims to maintain a desired fixed relative distance between the follower and leader UAVs, allowing for variations in their orientation. This flexibility in orientation helps reduce control effort for the follower UAV and offers tactical advantages. We term this approach as a "flexible relational maneuvering scheme" since the follower UAV is not constrained to a predetermined set of feasible positions, as is typical in close-proximity two-ship formations in air-to-air combat. Our approach seeks to replicate the behavior of human pilots in UAVs by implementing anticipatory maneuvers when the leader UAV executes aggressive turns.

Leader-follower relation maneuvering for (fixed-bearing angle) flexible formation.

Selected Publications: