This paper presents an angular momentum-based controller for crouch-to-stand motion of a powered pediatric lower-limb orthosis. The control law is developed using an underactuated triple pendulum model representing the legs of an orthosis-dummy system where the hip and knee joints are actuated but the ankle joint is unpowered. The control law is conceived to drive the angular momentum of the system to zero, thereby bringing the system to a statically balanced upright configuration. The parameters of the dynamic model of the orthosis-dummy system are experimentally identified and used to synthesize the momentum-based controller. Control parameters are selected using closed-loop pole placement of the linearized system via numerical optimization to ensure local closed-loop stability with adequate damping and satisfactory response time without too large controller gains. The controller is applied in simulation to determine the region of viable initial conditions resulting in no knee hyperextension or loss of balance, as determined from a zero-moment point analysis. The controller is then implemented in experiment showing feasibility of the control strategy in practice. Results are compared against a similarly-synthesized linear-quadratic regulator.

本文提出了一种基于角动量的控制器，用于电动小儿下肢矫形器的蹲伏站立运动。控制法则是使用欠驱动的三重摆模型开发的，该模型代表了矫正假人系统的腿，其中髋关节和膝关节被致动，但踝关节未受力。控制律的构想是将系统的角动量驱动为零，从而使系统达到静态平衡的竖立配置。矫形假人系统的动力学模型的参数通过实验确定，并用于合成基于动量的控制器。通过数值优化使用线性化系统的闭环极点布置来选择控制参数，以确保局部闭环稳定性，足够的阻尼和令人满意的响应时间而不会获得太大的控制器增益。将该控制器应用于仿真中，确定可行的初始条件区域，该区域不会导致膝关节过度伸展或失去平衡，这是通过零力矩点分析确定的。然后在实验中实施该控制器，以表明该控制策略在实践中的可行性。将结果与类似合成的线性二次调节器进行比较。然后在实验中实施该控制器，以表明该控制策略在实践中的可行性。将结果与类似合成的线性二次调节器进行比较。然后在实验中实施该控制器，以表明该控制策略在实践中的可行性。将结果与类似合成的线性二次调节器进行比较。