By Anna Tarasova ’19

Many elderly and mobility-impaired individuals are unable or tend to be unwilling to use stairs. While assistive technologies exist, they are frequently costly and unsustainable. The principle of energy recycling has been previously applied to walking assistance mechanisms that take advantage of the continuous braking and propelling of the legs. However, during stair-walking, ascent is a period of constant propulsion and descent of constant braking.  Thus, Dr. Yun Seong Song of the Missouri University of Science and Technology and his team sought to develop “energy-recycling” assistive stairs (ERAS) which collect energy during descent and unload it to aid the user during ascent.

The researchers created ERAS modules for each step of a staircase. A single ERAS consists of a movable tread upheld by a spring that rests on an electromagnetic latch. This latch is modulated by pressure sensor inputs. Each ERAS has pressure sensors to recognize foot placement. When a user steps onto the first step of a descent, the step locks down with the electromagnetic latch and the spring is maximally compressed. This happens with each following step. The energy is thus stored in the loaded springs. When the user steps on the first and then the second step of an ascent, the first step rises to the level of the second step and the second rises to the level of the third, until the last step reaches the level of the landing.

Each ERAS module is customizable to a large variety of stair step shapes and sizes and costs less than $50 to manufacture. The module is made to withstand users of up to 122 kg in weight. The energy consumption of a single module is less than 5 W when the electromagnetic latch is in action. Testing with 9 healthy subjects of weights between 46 and 122 kg was successful in establishing the physical assistance provided by ERAS in practice as well as exposing no potential risks for users. Future studies can evaluate the use of ERAS by individuals who require assistive technology in stair navigation. Overall, ERAS is a promising new technology that may be the affordable and practical alternative to costly elevators and other assistive mechanisms for individuals who are mobility-impaired.

Please refer to the following video for a demonstration: https://www.youtube.com/watch?v=hgwKoo9J410

References

1. Y.S. Song et al., Stair negotiation made easier using novel interactive energy-recycling assistive stairs. PLOS One 12, 1-17 (2017). doi: 10.1371/journal.pone.0179637
2. Image retrieved from: https://upload.wikimedia.org/wikipedia/commons/f/fd/Milan_stairway.jpg