Compliance in actuation has been exploited to generate highly dynamic maneuvers such as throwing that take advantage of the potential energy stored in joint springs. However, the energy storage and release could not be well-timed yet. On the contrary, for multi-link systems, the natural system dynamics might even work against the actual goal. With the introduction of variable stiffness actuators, this problem has been partially addressed. With a suitable optimal control strategy, the approximate decoupling of the motor from the link can be achieved to maximize the energy transfer into the distal link prior to launch. However, such continuous stiffness variation is complex and typically leads to oscillatory swing-up motions instead of clear launch sequences. To circumvent this issue, we investigate decoupling for speed maximization with a dedicated novel actuator concept denoted Bi-Stiffness Actuation. With this, it is possible to fully decouple the link from the joint mechanism by a switch-and-hold clutch and simultaneously keep the elastic energy stored. We show that with this novel paradigm, it is not only possible to reach the same optimal performance as with power-equivalent variable stiffness actuation, but even directly control the energy transfer timing. This is a major step forward compared to previous optimal control approaches, which rely on optimizing the full time-series control input.
翻译:动作中的合规性已被利用来产生高度动态的动作,例如利用联合弹簧中储存的潜在能量进行抛射,以利用联合弹簧中储存的潜在能量。然而,能源储存和释放的时机尚不成熟。相反,对于多链接系统来说,自然系统动态甚至可能对实际目标起作用。随着采用不固定的硬性激励器,这一问题已经部分得到解决。有了适当的最佳控制战略,发动机与链接的大致脱钩可以实现最大程度的能量转移,进入发射前的分解连接。然而,这种持续的僵化变异非常复杂,通常导致悬浮不定的回旋动作,而不是明确的发射顺序。相反,为了回避这一问题,我们调查如何将速度最大化与一个专用的新动作概念脱钩,这标志着双重阻断作用的动作。有了这样的战略,发动机与联合机制的连接可以实现最大程度的脱钩,从而最大限度地将能量传输到发射前的分解点。我们发现,根据这个新模式,这种恒定的僵化的回旋移动动作通常不只可能达到最优化的状态,而要与前置最佳的节制。