In this paper, two nonlinear methods for stabilizing the orientation of a Four-Wheel Independent Drive and Steering (4WIDS) robot while in the air are analyzed, implemented in simulation, and compared. AGRO (the Agile Ground Robot) is a 4WIDS inspection robot that can be deployed into unsafe environments by being thrown, and can use the reaction torque from its four wheels to command its orientation while in the air. Prior work has demonstrated on a hardware prototype that simple PD control with hand-tuned gains is sufficient, but hardly optimal, to stabilize the orientation in under 500ms. The goal of this work is to decrease the stabilization time and reject disturbances using nonlinear control methods. A model-based Feedback Linearization (FL) was added to compensate for the nonlinear Coriolis terms. However, with external disturbances, model uncertainty and sensor noise, the FL controller does not guarantee stability. As an alternative, a second controller was developed using backstepping methods with an adaptive compensator for external disturbances, model uncertainty, and sensor offset. The controller was designed using Lyapunov analysis. A simulation was written using the full nonlinear dynamics of AGRO in an isotropic steering configuration in which control authority over its pitch and roll are equalized. The PD+FL control method was compared to the backstepping control method using the same initial conditions in simulation. Both the backstepping controller and the PD+FL controller stabilized the system within 250 milliseconds. The adaptive backstepping controller was also able to achieve this performance with the adaptation law enabled and compensating for offset noisy sinusoidal disturbances.

中文翻译：

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比较使用车轮反作用扭矩的敏捷地面机器人空中定向的反馈线性化和自适应反步控制

在本文中，用于稳定四轮独立驱动和转向 (4WIDS) 机器人在空中时的方向的两种非线性方法进行了分析，在仿真中实现并进行了比较。AGRO（敏捷地面机器人）是一种 4WIDS 巡检机器人，可以通过投掷部署到不安全的环境中，并且可以在空中使用四个轮子的反作用力来控制其方向。先前的工作已经在硬件原型上证明，具有手动调整增益的简单 PD 控制足以在 500 毫秒内稳定方向，但几乎不是最佳选择。这项工作的目标是使用非线性控制方法减少稳定时间并抑制干扰。添加了基于模型的反馈线性化 (FL) 以补偿非线性科里奥利项。然而，在外界的干扰下，模型不确定性和传感器噪声，FL 控制器不保证稳定性。作为替代方案，使用反步法开发了第二个控制器，该控制器具有针对外部干扰、模型不确定性和传感器偏移的自适应补偿器。控制器是使用李雅普诺夫分析设计的。模拟是在各向同性转向配置中使用 AGRO 的全非线性动力学编写的，其中对其俯仰和滚转的控制权是均衡的。在仿真中使用相同的初始条件将 PD+FL 控制方法与反步控制方法进行比较。反推控制器和 PD+FL 控制器都在 250 毫秒内稳定了系统。