Ji-Hong Li, a prominent researcher in the field of marine vessel control systems, has introduced a novel approach to address the challenges of trajectory tracking for underactuated marine vessels. This innovative method leverages control barrier functions (CBF) and quadratic programming (QP) to overcome the singularity issues that arise in traditional control strategies.
In his research, Li tackles the inherent complexities of marine vessel dynamics, which are characterized by a two-input-three-output second-order tracking model. By introducing two polar coordinate transformations, Li simplifies this model to a two-input-two-output feedback form. However, this transformation does not conform to the strict-feedback structure, which can lead to singularities when designing stabilizing functions for virtual inputs in recursive controller design. Additionally, the polar coordinate transformation itself can introduce singularities, further complicating the control process.
To mitigate these issues, Li employs a control barrier function (CBF) based approach. This method formulates the trajectory tracking problem as a quadratic program (QP), which is then solved using a QP optimizer. The use of CBF ensures that the control inputs remain within safe operating limits, thereby preventing singularities and ensuring stable performance. This approach not only addresses the singularity problems but also enhances the overall robustness and reliability of the control system.
The effectiveness of Li’s proposed method is demonstrated through numerical simulations. These simulations showcase the ability of the CBF-based QP approach to achieve precise trajectory tracking while avoiding the pitfalls of singularities. The results highlight the potential of this method to be applied in real-world scenarios, where underactuated marine vessels often face complex and dynamic environments.
The practical applications of this research are significant for the marine sector. By improving the control systems of underactuated marine vessels, this method can enhance the safety, efficiency, and performance of maritime operations. From autonomous shipping to offshore exploration, the ability to accurately track trajectories while avoiding singularities can lead to more reliable and cost-effective solutions. Li’s work represents a significant advancement in the field of marine vessel control, offering a robust and innovative approach to trajectory tracking that can be widely adopted in the industry. Read the original research paper here.