This paper present a novel dual-speed actuator adapted to robotics. In many applications, robots have to bear large loads while moving slowly and also have to move quickly through the air with almost no load. This lead to conflicting requirements for their actuators. Multiple gear ratios address this issue by allowing an effective use of power over a wide range of torque-speed load conditions. Furthermore, very different gear ratios also lead to drastic changes of the intrinsic impedance, enabling a non-back-drivable mode for stiff position control and a back-drivable mode for force control. The proposed actuator consists of two electric motors coupled to a differential; one has a large gear ratio while the other is almost direct-drive and equipped with a brake. During the high-force mode the brake is locked, only one motor is used, and the actuator behaves like a regular highly-geared servo-motor. During the high-speed mode the brake is open, both motor are used at the same time, and the actuator behaves like a direct drive motor. A dynamic model is developed and novel controllers are proposed for synergic use of both motors. The redundancy of motors is exploited for maintaining full control of the output during mode transitions, allowing for fast and seamless switching even when interacting with unknown environments. Results are demonstrated with a proof-of-concept linear actuator.

翻译：本文提出了一种适用于机器人技术的新型双速执行器。在许多应用中，机器人需要承载大负载缓慢移动，同时也需要在几乎无负载状态下快速空载运动。这对其执行器提出了相互矛盾的要求。多档变速比通过允许在广泛的扭矩-速度负载条件下有效利用功率来解决这一问题。此外，差异极大的变速比还会导致固有阻抗的剧烈变化，从而能够实现用于刚性位置控制的非反向驱动模式以及用于力控制的反向驱动模式。所提出的执行器由两个耦合至差速器的电动机组成：其中一个具有大变速比，另一个几乎是直接驱动并配备制动器。在高力模式下，制动器锁定，仅使用一个电机，执行器表现如同常规高减速比伺服电机。在高速模式下，制动器打开，两个电机同时使用，执行器表现如同直接驱动电机。本文建立了动态模型，并提出了用于协同使用两个电机的新型控制器。利用电机的冗余性，可在模式切换期间保持对输出的完全控制，从而实现即使在未知环境中交互时也能快速无缝切换。通过一个概念验证线性执行器展示了实验结果。