HRL Laboratories, LLC, today announced that researchers in its Sensors and Materials Laboratory have developed an active variable stiffness vibration isolator capable of 100x stiffness changes and millisecond actuation times, independent of the static load. According to Principal Investigator Christopher Churchill, “This performance surpasses existing mechanisms by at least 20 times in either speed or useful stiffness change.”
Churchill says that the human body is home to a range of variable stiffness structures that enable efficient load-bearing and nimble activity.
Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness–based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel response from passive structures, is a powerful tool to achieve dynamic stiffness changes when configured with an active component. Using relatively simple hardware and low-power, low-frequency actuation, we show an assembly capable of fast (<10 ms) and useful (>100×) dynamic stiffness control. This approach mitigates limitations of conventional tunable stiffness structures that exhibit either small (<30%) stiffness change, high friction, poor load/torque transmission at low stiffness, or high power active control at the frequencies of interest. We experimentally demonstrate actively tunable vibration isolation and stiffness tuning independent of supported loads, enhancing applications such as humanoid robotic limbs and lightweight adaptive vibration isolators.