The ability to realize nonlinear controllers with formal guarantees on dynamic robotic systems has the potential to enable more complex robotic behaviors -- yet, realizing these controllers is often practically challenging. To address this challenge, this paper presents the end-to-end realization of dynamic bipedal locomotion on an underactuated bipedal robot via hybrid zero dynamics and control Lyapunov functions. A compliant model of Cassie is represented as a hybrid system to set the stage for a trajectory optimization framework. With the goal of achieving a variety of walking speeds in all directions, a library of compliant walking motions is compiled and then parameterized for efficient use within real-time controllers. Control Lyapunov functions, which have strong theoretic guarantees, are synthesized to leverage the gait library and coupled with inverse dynamics to obtain optimization-based controllers framed as quadratic programs. It is proven that this controller provably achieves stable locomotion; this is coupled with a theoretic analysis demonstrating useful properties of the controller for tuning and implementation. The proposed theoretic framework is practically demonstrated on the Cassie robot, wherein 3D walking is achieved through the use of optimization-based torque control. The experiments highlight robotic walking at different speeds and terrains, illustrating the end-to-end realization of theoretically justified nonlinear controllers on dynamic underactuated robotic systems.
翻译:实现非线性控制器并正式保障动态机器人系统的能力有可能促成更复杂的机器人行为,然而,实现这些控制器往往在实际中具有挑战性。为了应对这一挑战,本文件展示了通过混合零动态和控制 Lyapunov 功能实现一个低活性双向双向机器人的动态双向移动器的端到端实现。 Cassie 的兼容模型代表了一个混合系统,为轨迹优化框架设置了阶段。为了在所有方向实现各种行走速度的目标,将一个符合要求的行走动作图书馆汇编起来,然后为实时控制器的高效使用而进行参数化。控制 Lyapunov 功能具有很强的理论保证,通过合成来利用步态库的优势,并配以相反的动态动力来获得基于优化的控制器,作为四进式程序。这个控制器的兼容模型被证明可以实现稳定的行走速度;这与一项理论分析相结合,展示了控制器在调控和执行过程中的有用性功能。拟议的逻辑框架在卡西机器人机器人上得到了实际的演示,其中3D行走方式,通过不动到机床压速度,通过机变的机压式系统来展示。