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Kinodynamic Motion Planning and Robust Trajectory Tracking for Underactuated Unmanned Surface Vehicles


Основные понятия
The authors develop an algorithm that combines kinodynamic motion planning and prescribed performance control to enable autonomous navigation of an underactuated unmanned surface vehicle while respecting kinodynamic constraints and ensuring robust trajectory tracking in the presence of model uncertainties and disturbances.
Аннотация

The paper presents a two-layer approach to address the problem of motion planning and control for an underactuated unmanned surface vehicle (USV).

The first layer focuses on the trajectory tracking problem. The authors extend the prescribed performance control (PPC) methodology to handle the underactuation and control input constraints of the USV. PPC ensures that the tracking errors, including the distance and orientation errors, evolve strictly within user-defined performance funnels, even in the presence of uncertain dynamics and disturbances.

The second layer addresses the kinodynamic motion planning problem. The authors formulate an optimization problem to generate smooth, collision-free trajectories that satisfy kinodynamic constraints, such as velocity and acceleration limits. The optimization uses B-splines to represent the desired trajectory, leveraging their properties for efficient collision checking and constraint enforcement.

The proposed algorithm is validated through real-world, open-water experiments on a USV, demonstrating its effectiveness in navigating the vehicle while respecting the imposed performance and safety requirements.

Key highlights:

  1. Extension of PPC to handle underactuated USV systems with input constraints.
  2. Optimization-based kinodynamic motion planning using B-splines to generate smooth, collision-free trajectories.
  3. Stability analysis of the closed-loop system under the proposed control scheme and input constraints.
  4. Experimental validation of the algorithm on a physical USV in open-water environments.
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Статистика
The USV has a maximum thrust of FT ≤ FT̄ and a maximum rudder angle of |αr| ≤ ᾱr. The maximum permissible velocity and acceleration are vmax and amax, respectively.
Цитаты
"We extend prescribed performance control (PPC) within the KDF framework to be applicable to the underactuated USV." "We introduce input constraints due to the actuator saturation on the physical surface vehicle and provide conditions on the upper bounds of the dynamics and disturbances to ensure compliant behaviour."

Дополнительные вопросы

How can the proposed framework be extended to handle more complex USV models, such as those with additional degrees of freedom or more sophisticated propulsion systems

The proposed framework can be extended to handle more complex USV models by incorporating additional degrees of freedom or more sophisticated propulsion systems. For models with extra degrees of freedom, such as pitch, roll, or heave, the control design and trajectory planning algorithms would need to be adapted to account for these additional dynamics. This could involve augmenting the state space representation, modifying the control laws to accommodate the new degrees of freedom, and adjusting the trajectory generation process to consider the expanded state space. In the case of USVs with more sophisticated propulsion systems, such as multiple thrusters or variable thrust configurations, the control design would need to be enhanced to effectively manage the increased complexity. This could involve developing control strategies that optimize the utilization of multiple thrusters, account for varying thrust levels, or adapt to different propulsion modes based on the operational requirements of the USV. Additionally, the trajectory planning algorithms would need to consider the capabilities and constraints of the advanced propulsion systems to generate trajectories that can be effectively tracked and executed by the USV.

What are the potential limitations of the B-spline-based trajectory optimization approach, and how could it be further improved to handle more complex environments or dynamic obstacles

The B-spline-based trajectory optimization approach has certain limitations that could be addressed to handle more complex environments or dynamic obstacles. One potential limitation is the reliance on predefined knot spacing, which may not always result in optimal trajectories, especially in complex environments with tight spaces or intricate obstacle configurations. To improve this, the optimization process could be extended to include adaptive knot spacing, allowing the trajectory to be more finely tuned based on the specific environment and obstacle layout. Another limitation is the static nature of the trajectory optimization, which may not adequately account for dynamic obstacles or changing environmental conditions. To address this, the approach could be enhanced with real-time trajectory replanning capabilities that consider dynamic obstacles, unexpected disturbances, or evolving environmental factors. By integrating sensor data and feedback mechanisms, the trajectory optimization process could be made more adaptive and responsive to dynamic changes in the environment. Furthermore, the B-spline-based approach may struggle with highly nonlinear or non-convex environments, where traditional optimization methods may face challenges in finding globally optimal solutions. To overcome this limitation, advanced optimization techniques such as stochastic optimization, reinforcement learning, or evolutionary algorithms could be explored to enhance the trajectory optimization process and improve performance in complex and dynamic environments.

What are the potential applications of the developed kinodynamic motion planning and control algorithms beyond the USV domain, and how could they be adapted to other types of autonomous systems

The developed kinodynamic motion planning and control algorithms have potential applications beyond the USV domain and could be adapted to other types of autonomous systems, such as aerial drones, ground robots, or autonomous vehicles. By modifying the control laws, state space representation, and trajectory planning algorithms to suit the dynamics and constraints of different autonomous systems, the framework can be extended to a variety of applications in robotics and autonomous navigation. For aerial drones, the algorithms could be adapted to handle 3D motion planning, obstacle avoidance in airspace, and dynamic path replanning to navigate complex aerial environments. Ground robots could benefit from the framework by incorporating wheel dynamics, terrain constraints, and navigation in cluttered indoor or outdoor environments. Autonomous vehicles could leverage the algorithms for trajectory planning, collision avoidance, and adaptive control in urban or highway scenarios. By customizing the framework to the specific requirements and dynamics of different autonomous systems, the developed algorithms can be applied to a wide range of applications in robotics, automation, surveillance, exploration, and transportation, contributing to the advancement of autonomous technologies in various domains.
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