Energy-efficient tunable-stiffness soft robots using second moment of area actuation

The optimal stiffness for soft swimming robots depends on swimming speed, which means no single stiffness can maximise efficiency in all swimming conditions. Tunable-stiffness would produce an increased range of high-efficiency swimming speeds for robots with flexible propulsors and enable soft control surfaces for steering underwater vehicles. We propose and demonstrate a method for tunable soft robotic stiffness using inflatable rubber tubes to stiffen a silicone foil through pressure and second moment of area change. We achieved double the effective stiffness of the system for an input pressure change from 0 to 0.8 bar and 2 J energy input. We achieved a resonant amplitude gain of 5 to 7 times the input amplitude and tripled the high-gain frequency range compared to a foil with fixed stiffness. These results show that changing second moment of area is an energy effective approach to tunable-stiffness robots.

对于软体游泳机器人而言，最佳刚度取决于游泳速度，这意味着没有单一的刚度能够在所有游泳条件下使效率最大化。可调节刚度将为具有柔性推进器的机器人提高高效游泳速度的范围，并为水下航行器的转向提供柔性控制面。我们提出并展示了一种利用充气橡胶管通过压力和截面二次矩变化来调节软体机器人刚度的方法。当输入压力从0变化到0.8巴且输入能量为2焦耳时，我们使系统的有效刚度提高了一倍。与固定刚度的箔片相比，我们实现了共振振幅增益为输入振幅的5到7倍，并且使高增益频率范围增加了两倍。这些结果表明，改变截面二次矩是一种对可调节刚度机器人有效的能量方法。