{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T22:45:30Z","timestamp":1792017930579,"version":"4.4.0"},"reference-count":87,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2021,6,16]],"date-time":"2021-06-16T00:00:00Z","timestamp":1623801600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Robot. AI"],"abstract":"<jats:p>Animals locomote robustly and agile, albeit significant sensorimotor delays of their nervous system and the harsh loading conditions resulting from repeated, high-frequent impacts. The engineered sensorimotor control in legged robots is implemented with high control frequencies, often in the kilohertz range. Consequently, robot sensors and actuators can be polled within a few milliseconds. However, especially at harsh impacts with unknown touch-down timing, controllers of legged robots can become unstable, while animals are seemingly not affected. We examine this discrepancy and suggest and implement a hybrid system consisting of a parallel compliant leg joint with varying amounts of passive stiffness and a virtual leg length controller. We present systematic experiments both in computer simulation and robot hardware. Our system shows previously unseen robustness, in the presence of sensorimotor delays up to 60\u00a0ms, or control frequencies as low as 20\u00a0Hz, for a drop landing task from 1.3 leg lengths high and with a compliance ratio (fraction of physical stiffness of the sum of virtual and physical stiffness) of 0.7. In computer simulations, we report successful drop-landings from 3.8 leg lengths (1.2\u00a0m) for a 2\u00a0kg quadruped robot with 100\u00a0Hz control frequency and a sensorimotor delay of 35\u00a0ms.<\/jats:p>","DOI":"10.3389\/frobt.2021.645748","type":"journal-article","created":{"date-parts":[[2021,6,16]],"date-time":"2021-06-16T04:35:21Z","timestamp":1623818121000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":25,"title":["Hybrid Parallel Compliance Allows Robots to Operate With Sensorimotor Delays and Low Control Frequencies"],"prefix":"10.3389","volume":"8","author":[{"given":"Milad Shafiee","family":"Ashtiani","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alborz","family":"Aghamaleki Sarvestani","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alexander","family":"Badri-Spr\u00f6witz","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2021,6,16]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1109\/TMECH.2020.3019686","article-title":"Parallel Compliance Design for Increasing Robustness and Efficiency in Legged Locomotion-Theoretical Background and Applications","author":"AhmadSharbafi","year":"2020","journal-title":"IEEE\/ASME Trans. 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