The task of self-balancing is one of the most important tasks when developing humanoid robots. This paper proposes a novel external balance mechanism for humanoid robot to maintain sideway balance. First, a dynamic model of the humanoid robot with balance mechanism and its simplified model are introduced. Secondly, a backstepping-based control method is utilized to split the system into two sub-systems. Then, a minimum observer-based controller is used to control the first sub-system. Since the second sub-system has unknown parameters, a model reference adaptive controller (MRAC) is used to control it. The proposed design divides the walking and balancing into two separated tasks, allowing the walking control can be executed independently of the balancing control. Furthermore, the use of the balance mechanism ensures the humanoid robot's hip movement does not exceed the threshold of a human when walking. Thus, making the overall pose of the humanoid robot looks more natural. An experiment is carried out on a commercial humanoid robot known as UXA-90 to evaluate the effectiveness of the proposed method.

翻译：自我平衡是开发人造机器人时最重要的任务之一。 本文为人造机器人提出了一个新的外部平衡机制, 以保持侧面平衡。 首先, 引入了具有平衡机制及其简化模型的人类机器人动态模型。 其次, 使用后步控制方法将系统分割成两个子系统。 然后, 使用最低限度的观察控制器来控制第一个子系统。 由于第二个子系统有未知参数, 使用一个示范参考适应控制器来控制它。 拟议的设计将行走和平衡分为两个任务, 允许行走控制可以独立于平衡控制。 此外, 使用平衡机制可以确保人造机器人的臀部运动不会超过人行走时的门槛。 因此, 使人类机器人的总体面貌看起来更加自然。 在一个名为 UXA-90 的商业性人类机器人上进行了实验, 以评价拟议方法的有效性 。