This paper deals with the inherent instability observed in the speed of a planing type craft. In the case of displacement craft, the systems governing the speed are stable hence closed-loop control is trivial. In the case of planing craft, however, there may exist instability in their speed. By using the Qualitative Theory of Dynamical Systems (QTDS), this paper shows that there may exist a set of speeds in which planing craft are not able to achieve adequate stability. This instability problem cannot be acceptable in many applications (such as that examined in this paper, an Unmanned Surface Vehicle, USV, of planing craft type). The observed instability is explained by means of the appearance of bifurcations which bring new attractors to the state space, such as equilibrium points or limit cycles. This paper proposes a novel solution to manage the vessel instability behavior. This is done by way of increasing the droop characteristic in the propulsion thrust with respect to speed. By increasing the droop, the system becomes more robust. The key advantage of this approach is that it is achieved by way of modifying the propulsion controller rather than by changing the hydrodynamic profile of the vessel, the mass distribution or by adding extra control surface (i.e., flaps). Resulting in a more cost-effective control system. Furthermore, due to this method acting on propulsion and its control, it is compatible with the other methods aforementioned. Stability analysis is undertaken. This analysis is very general, because it considers a wide range of controller and propulsion systems. Open-loop control and analysis into different types of propulsion is also presented. The effect of each propulsion type on stability is explained. In addition, the effect in the control loop of the electro-mechanical actuators inaccuracy (dead-zone) has also been analyzed. The paper explains that this inaccuracy, though small, can make the speed oscillate in planing craft. A practical implementation of this analysis is validated by way of sea trials with a real planing craft.

本文讨论了在滑行式飞行器的速度中观察到的固有不稳定性。对于排水船，控制速度的系统是稳定的，因此闭环控制很简单。但是，在刨船的情况下，其速度可能会不稳定。通过使用动力学系统的定性理论（QTDS），本文显示出可能存在一组速度，其中刨削工艺无法达到足够的稳定性。这种不稳定性问题在许多应用中都是无法接受的（例如本文所研究的滑行飞行器类型的无人水面载具USV）。观察到的不稳定性是通过分叉的出现来解释的，分叉的出现将新的吸引子带入状态空间，例如平衡点或极限环。本文提出了一种管理船舶失稳行为的新颖解决方案。这是通过相对于速度增加推进推力的下垂特性来实现的。通过增加下垂，系统变得更强大。这种方法的主要优势在于，它是通过修改推进控制器而不是通过改变容器的流体动力学曲线，质量分布或通过添加额外的控制表面（即襟翼）来实现的。从而形成了更具成本效益的控制系统。此外，由于该方法作用于推进及其控制，因此与上述其他方法兼容。进行稳定性分析。这种分析非常笼统，因为它考虑了广泛的控制器和推进系统。还介绍了对不同类型推进力的开环控制和分析。解释了每种推进方式对稳定性的影响。此外，机电执行器在控制回路中的影响不准确（死区）也进行了分析。本文解释说，这种误差虽然很小，但可以使刨削速度在振荡。该分析的实际实施是通过使用真正的刨床进行海试来验证的。