Shaping in Practice: Training Wheels to Learn Fast Hopping Directly in Hardware Dynamic Locomotion Group 2018-02-03 | We show a simple case of using "training wheels", temporary hardware modifications, to shape the reward landscape and make learning easier.Full paper to appear in ICRA 2018, available on arxiv at: arxiv.org/abs/1709.10273
Detailed results Passive knee flexion increases forward impulse... Dynamic Locomotion Group 2025-04-15 | Supplementary video for the publication "Passive knee flexion increases forward impulse of the trailing leg during the step-to-step transition", published April 15 2025.Kiss, B., Buchmann, A., Renjewski, D., Badri-Spröwitz, A., 2025. Passive knee flexion increases forward impulse of the trailing leg during the step-to-step transition. Sci Rep 15, 1–17. doi.org/10.1038/s41598-025-95589-4.Paper online: rdcu.be/ehNx0 (rdcu.be/ehNx0)CAD design files of the EcoWalker-2 robot, control code, data analysis and visualization code, and experimental data are available for non-commercial use at:doi.org/10.17617/3.BJ584MAbstract:During walking, the brain and nervous system coordinate muscle activity to efficiently regulate body movement. Simultaneously, passive structures in the legs interact with the ground, generating reaction forces that contribute to leg and body motion. A well-known example of this active-passive coordination is the human ankle, which plays a crucial role in propelling both the leg and the entire body forward with each step. Human walking efficiency relies on the elastic recoil of the Achilles tendon, facilitated by a “catapult mechanism” that stores energy during stance and releases it during push-off. The catapult release mechanism could include the passive flexion of the knee, as the main part of knee flexion was reported to happen passively after leading leg touch-down. This study is the first to investigate the effects of passive versus active knee flexion initiation, using the bipedal EcoWalker-2 robot with passive ankles. By leveraging the precision of robotic measurements, this study aimed to elucidate the importance of timing of gait events and its impact on momentum and kinetic energy changes of the robot. The EcoWalker-2 walked successfully with both initiation methods, maintaining toe clearance. Passive knee flexion initiation delayed the onset of ankle plantar flexion by 3% of the gait cycle compared to active knee flexion initiation, leading to 87% larger increase in the trailing leg horizontal momentum, and 188% larger magnitude increase in the center of mass momentum vector during the step-to-step transition. The findings highlight the role of knee flexion in the release of the catapult and timing of gait events. These insights contribute to improving the control and mechanics of human-centered robotic and assistive devices. Specifically, enabling passive knee flexion initiation could be beneficial in humanoid robots with passive ankles, and in ankle-knee prostheses and orthoses with passive ankles for saving on control effort, and reducing hardware complexity otherwise required for active knee flexion before the step-to-step transition. Additionally, this approach enhances horizontal momentum gain in the trailing leg during the step-to step transition, with the potential to improve locomotion efficiency.
Robot walking: Passive knee flexion increases forward impulse... Dynamic Locomotion Group 2025-04-15 | Supplementary video for the publication "Passive knee flexion increases forward impulse of the trailing leg during the step-to-step transition", published April 15 2025.Kiss, B., Buchmann, A., Renjewski, D., Badri-Spröwitz, A., 2025. Passive knee flexion increases forward impulse of the trailing leg during the step-to-step transition. Sci Rep 15, 1–17. doi.org/10.1038/s41598-025-95589-4.Paper online: rdcu.be/ehNx0 (rdcu.be/ehNx0)CAD design files of the EcoWalker-2 robot, control code, data analysis and visualization code, and experimental data are available for non-commercial use at:doi.org/10.17617/3.BJ584MAbstract:During walking, the brain and nervous system coordinate muscle activity to efficiently regulate body movement. Simultaneously, passive structures in the legs interact with the ground, generating reaction forces that contribute to leg and body motion. A well-known example of this active-passive coordination is the human ankle, which plays a crucial role in propelling both the leg and the entire body forward with each step. Human walking efficiency relies on the elastic recoil of the Achilles tendon, facilitated by a “catapult mechanism” that stores energy during stance and releases it during push-off. The catapult release mechanism could include the passive flexion of the knee, as the main part of knee flexion was reported to happen passively after leading leg touch-down. This study is the first to investigate the effects of passive versus active knee flexion initiation, using the bipedal EcoWalker-2 robot with passive ankles. By leveraging the precision of robotic measurements, this study aimed to elucidate the importance of timing of gait events and its impact on momentum and kinetic energy changes of the robot. The EcoWalker-2 walked successfully with both initiation methods, maintaining toe clearance. Passive knee flexion initiation delayed the onset of ankle plantar flexion by 3% of the gait cycle compared to active knee flexion initiation, leading to 87% larger increase in the trailing leg horizontal momentum, and 188% larger magnitude increase in the center of mass momentum vector during the step-to-step transition. The findings highlight the role of knee flexion in the release of the catapult and timing of gait events. These insights contribute to improving the control and mechanics of human-centered robotic and assistive devices. Specifically, enabling passive knee flexion initiation could be beneficial in humanoid robots with passive ankles, and in ankle-knee prostheses and orthoses with passive ankles for saving on control effort, and reducing hardware complexity otherwise required for active knee flexion before the step-to-step transition. Additionally, this approach enhances horizontal momentum gain in the trailing leg during the step-to step transition, with the potential to improve locomotion efficiency.
Ecowalker robot on its way to AMAM 2023 (Kobe, June 6-9, 2023) Dynamic Locomotion Group 2023-05-24 | EcoWalker is travelling to #AMAM2023 in Kobe, Japan. We are looking forward meeting you at the AMAM #RobotZoo.Related publication: Kiss, Bernadett, Emre Cemal Gonen, An Mo, Alexandra Buchmann, Daniel Renjewski, and Alexander Badri-Spröwitz. “Gastrocnemius and Power Amplifier Soleus Spring-Tendons Achieve Fast Human-like Walking in a Bipedal Robot.” In Proceedings of IROS2022. arXiv, 2022. doi.org/10.48550/arXiv.2203.01588.
Upside Down: affordable high-performance motion platform Dynamic Locomotion Group 2023-04-03 | We develop a high acceleration motion platform based on the Solo12 quadruped robot: open-dynamic-robot-initiative.github.ioWe open source both (pybullet) simulation model and hardware design: github.com/nayan-pradhan/solo-6dof-motion-platformMore details are in the paper: http://arxiv.org/abs/2303.17974
Slack damper mechanism enables robust and efficient legged hopping Dynamic Locomotion Group 2023-02-26 | Supplementary videos forMo, An, Fabio Izzi, Emre Cemal Gönen, Daniel Haeufle, and Alexander Badri-Spröwitz. “Slack-Based Tunable Damping Leads to a Trade-off between Robustness and Efficiency in Legged Locomotion.” Scientific Reports 13, no. 1 (February 25, 2023): 3290. doi.org/10.1038/s41598-023-30318-3.
Multi-segmented Robot Feet Adapt to Natural Terrain Dynamic Locomotion Group 2023-02-04 | Chatterjee, A., Mo, A., Kiss, B., Gonen, E. C., & Badri-Spröwitz, A. (2022). Multi-segmented Adaptive Feet for Versatile Legged Locomotion in Natural Terrain. Accepted at ICRA2023. arxiv.org/abs/2209.08499
Ecowalker with Xmas lights outfit Dynamic Locomotion Group 2022-12-22 | Bernadett dressed Ecowalker in Xmas lights. Enjoy the holidays!Link to Bernadett's research page https://is.mpg.de/person/kiss More Ecowalker research youtube.com/watch?v=T79pKLQ47XU
SELDA actuated robot leg hopping Dynamic Locomotion Group 2022-07-29 | Diaphragm Ankle Actuation for Efficient Series Elastic Legged Robot Hopping. Bolignari, Mo, Fontana, and Badri-Spröwitz. Accepted at IROS2022. arXiv: arxiv.org/abs/2203.01595
Fast Human-like Walking in a Bipedal Robot Dynamic Locomotion Group 2022-07-29 | Kiss, Gonen, Mo, Buchmann, Renjewski, & Badri-Spröwitz, (2022). Gastrocnemius and Power Amplifier Soleus Spring-Tendons Achieve Fast Human-like Walking in a Bipedal Robot. Accepted at IROS2022, 8pages. arxiv.org/abs/2203.01588
Learning Plastic Matching of Robot Dynamics in Closed-loop Central Pattern Generators Dynamic Locomotion Group 2022-07-18 | Ruppert, F., & Badri-Spröwitz, A. (2022). Learning Plastic Matching of Robot Dynamics in Closed-loop Central Pattern Generators. Nature Machine Intelligence. nature.com/articles/s42256-022-00505-4Animals show agile locomotion performance with reduced control effort and energy efficiency by leveraging compliance in their muscles and tendons. However, it remains a question how biological locomotion controllers learn to leverage the intelligence embodied in their leg mechanics. Here we present a framework to match control patterns and mechanics based on the concept of short-term elasticity and long-term plasticity. Inspired by animals we design robot Morti with passive elastic legs. The quadruped is controlled by a bioinspired closed-loop central pattern generator that is designed to elastically mitigate short term perturbations using sparse contact feedback. By minimizing the amount of corrective feedback in the long term, the robot learns to match the controller to its mechanics and learns to walk within one hour. By leveraging the advantages of its mechanics, the robot improves its energy efficiency by 42% without explicit minimization in the cost function.
BirdBot at 1.5Hz locomotion frequency, high speed recording Dynamic Locomotion Group 2022-03-18 | BirdBot robot is designed according to the legs of birds like Emus and Ostriches.Robot speed is v=0.75m/s, at a leg length of 0.29m (Froude number Fr=v2/gl=0.18)Publication: Badri-Spröwitz, A., Sarvestani, A. A., Sitti, M., & Daley, M. A. (2022). BirdBot achieves energy-efficient gait with minimal control using avian-inspired leg clutching. Science Robotics. doi.org/10.1126/scirobotics.abg4055The free-access referral link can be found on https://is.mpg.de/publications/bb01More information at https://is.mpg.de/publications/bb01CAD files are available for non-commercial use https://edmond.mpdl.mpg.de/dataset.xhtml?persistentId=doi:10.17617/3.ETFG41
BirdBot, an energy-efficient robot leg inspired by birds legs Dynamic Locomotion Group 2022-03-16 | Publication: Badri-Spröwitz, A., Sarvestani, A. A., Sitti, M., & Daley, M. A. (2022). BirdBot achieves energy-efficient gait with minimal control using avian-inspired leg clutching. Science Robotics. doi.org/10.1126/scirobotics.abg4055The free-access referral link can be found on science.org/stoken/author-tokens/ST-383/fullMore information at https://is.mpg.de/publications/bb01CAD files are available for non-commercial use https://edmond.mpdl.mpg.de/dataset.xhtml?persistentId=doi:10.17617/3.ETFG41
Cheetah-cub MOCAP tracked with traces in Mokka Dynamic Locomotion Group 2021-12-23 | Traces are displayed in Mokka (biomechanical-toolkit.github.io/mokka)Published: Spröwitz, Tuleu, Vespignani, Ajallooeian, Badri, Ijspeert: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013) doi: 10.1177/0278364913489205
Cheetah-cub robot, simulation model at increasing locomotion frequency Dynamic Locomotion Group 2021-12-23 | Eventually published work in Published: Spröwitz, Tuleu, Vespignani, Ajallooeian, Badri, Ijspeert: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013) doi: 10.1177/0278364913489205
Cheetah-cub ground reaction forces individual legs Dynamic Locomotion Group 2021-12-23 | Work with Cheetah-cub robot: ground reaction forces in trot gait, separated by 2x GRF plates. Green vector presents the left hind leg, blue vector presents the front right leg. Red: sum of front and hind leg. Between 32sec and 38sec one stance phase is well recorded. It shows the orientation of the sum of GRFs towards the robot. A slight tendency of the GRF is visible to point behind the COM prior to mid-stance, and in front of the COM between midstance and toe off. This behaviour is consistent with a VPP behaviour off not pointing at the COM.Published by: Spröwitz, Tuleu, Vespignani, Ajallooeian, Badri, Ijspeert: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013) doi: 10.1177/0278364913489205
Cheetah-cub sideview and slowmo Dynamic Locomotion Group 2021-12-23 | Published: Spröwitz, Tuleu, Vespignani, Ajallooeian, Badri, Ijspeert: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013) doi: 10.1177/0278364913489205
Cheetah-cub in side view, with trunk oscillations tracked Dynamic Locomotion Group 2021-12-23 | Published: Spröwitz, Tuleu, Vespignani, Ajallooeian, Badri, Ijspeert: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013) doi: 10.1177/0278364913489205
Scalable Pneumatic and Tendon Driven Robotic Joint Inspired by Jumping Spiders - raw video Dynamic Locomotion Group 2021-12-23 | Spröwitz A., C. Göttler, A. Sinha, C. Caer, M.U. Öztekin, K. Petersen, and M. Sitti., "Scalable pneumatic and tendon driven robotic joint inspired by jumping spiders," 2017 IEEE International Conference on Robotics and Automation (ICRA), 2017, pp. 64-70, doi: 10.1109/ICRA.2017.7988692.Fluidic actuators allow versatile, agile, and powerful motions and are commonly applied in robotics and automation. Likewise, many biological systems use fluidic actuators implemented with tissue for a wealth of tasks and performances. Spiders for example apply a hybrid mechanism of hydraulically actuated joint extension and muscle-based joint flexion to produce movement in two of their seven leg joints. Here, we present a novel spider-inspired joint mechanism employing both pneumatics and electrically-actuated tendons capable of strong, dynamic, and rapid joint movement. The implementation of the joint is closely inspired by those seen in real spiders, with a foldable structured membrane that effectively transfers all the energy from pressure to torque as the leg unfolds. To evaluate the mechanism we derived static joint models and a simple jumping model, and conducted equivalent experimental tests with a prototype of a single jumping leg robot. Besides applications in robot locomotion, the implementation and modeling of the spider-inspired joint mechanism can be utilized to further explore dynamics and functional biomechanics in spiders. In the future, we hope to use this platform to answer questions related to the impressive jumping and locomotion performances of real arachnids, and explore what morphological traits lie behind efficient spider locomotion at different size scales.Work at Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
Series Elastic Behavior of Biarticular Muscle-Tendon Structure in a Robotic Leg - Robustness Dynamic Locomotion Group 2021-11-05 | We are researching the advantages of biarticular elastic connectivity in a three-segmented robot leg. The biarticular leg shows, to the best of our knowledge, the lowest achieved relative cost of transport documented for dynamically hopping and running robots; the biart-leg hops with a cost of transport that is 64% lower than an average natural runner of comparable weight.Published article:frontiersin.org/articles/10.3389/fnbot.2019.00064
FootTile sensor for legged robots dropping into mud Dynamic Locomotion Group 2021-10-29 | We develop the FootTile sensor for rugged sensing of center of pressure and ground reaction forces in natural substrates and outdoor terrains.Here shown high speed video footage of four FootTiles mounted to an elastic leg dropping into a soft ground (mud). In our paper below we compare externally measured ground reaction forces with the FootTile-measured forces.arxiv.org/abs/2005.09025Ruppert, Felix, and Alexander Badri-Spröwitz. “FootTile: A Rugged Foot Sensor for Force and Center of Pressure Sensing in Soft Terrain.” In 2020 IEEE International Conference on Robotics and Automation (ICRA), 4810–16. IEEE, 2020. doi.org/10.1109/ICRA40945.2020.9197466.
FootTile sensor dropping into seeds granular media Dynamic Locomotion Group 2021-10-29 | We develop the FootTile sensor for rugged sensing of center of pressure and ground reaction forces in natural substrates and outdoor terrains.Here shown high speed video footage of four FootTiles mounted to an elastic leg dropping into a soft, granular substrate (seeds). In our paper below we compare externally measured ground reaction forces with the FootTile-measured forces.arxiv.org/abs/2005.09025Ruppert, Felix, and Alexander Badri-Spröwitz. “FootTile: A Rugged Foot Sensor for Force and Center of Pressure Sensing in Soft Terrain.” In 2020 IEEE International Conference on Robotics and Automation (ICRA), 4810–16. IEEE, 2020. doi.org/10.1109/ICRA40945.2020.9197466.
Series Elastic Behavior of Biarticular Muscle-Tendon Structure in a Robotic Leg - Stepdown Dynamic Locomotion Group 2021-10-28 | We are exploring the advantages of biarticular elastic connectivity in the mid-segment of a three-segmented leg. The biarticular leg shows, to the best of our knowledge, the lowest achieved relative cost of transport documented for dynamically hopping and running robots; the biart-leg hops with a cost of transport that is 64% lower than an average natural runner of comparable weight.Published article:frontiersin.org/articles/10.3389/fnbot.2019.00064
Oncilla robot Multimedia Extension 4 Dynamic Locomotion Group 2021-10-26 | Publication:frontiersin.org/articles/10.3389/frobt.2018.00067/fullOncilla robot walking in front of EPFL.
Spider-leg inspires new, rotary diaphragm actuator Dynamic Locomotion Group 2021-06-25 | title:A Novel Spider-Inspired Rotary-Rolling Diaphragm Actuator with Linear Torque Characteristic and High Mechanical Efficiencyauthors:Jonas Hepp and Alexander Badri-Spröwitzpublication (open access):liebertpub.com/doi/10.1089/soro.2020.0108abstract:We present a novel, fluid-driven rotary-rolling diaphragm actuator with direct rotary output. Its working principle is inspired by the spider leg's hydraulically operated joints and the diaphragm design of rolling diaphragm actuators. The new actuator is fully sealed, shows minimal output torque losses, and minimum friction during operation. Stiction and Coulomb friction are avoided by design. Our proposed mechanism can be used as a compliant actuator in soft robots, or as a stiff transmission device, depending on the fluid and working pressure. The rotary-rolling diaphragm is the defining component of the actuator. The diaphragm is based on silicone rubber, reinforced by a fabric with anisotropic tensile strength characteristics. The diaphragm is custom-designed to follow the actuator's toroidal shape and to ensure the smooth unrolling behavior throughout the stroke. Our actuator outputs a constant torque throughout its stroke compared with monolithic, rotary soft robot actuators with a change in torque. Our design offers a high mechanical efficiency of 95%, compactness, a wide working range of 100°, and a low mechanical complexity from a single chamber.
Video2 Hybrid Parallel Compliance Allows Robots to Operate With Sensorimotor Delays and Low Control Dynamic Locomotion Group 2021-06-23 | Supplementary video file 2 for manuscriptHybrid Parallel Compliance Allows Robots to Operate With Sensorimotor Delays and Low Control FrequenciesPublished inFront. Robot. AI, 16 June 2021DOIdoi.org/10.3389/frobt.2021.645748AbstractAnimals 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 ms, or control frequencies as low as 20 Hz, 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 m) for a 2 kg quadruped robot with 100 Hz control frequency and a sensorimotor delay of 35 ms.
Video1 Hybrid Parallel Compliance Allows Robots to Operate With Sensorimotor Delays and Low Control Dynamic Locomotion Group 2021-06-23 | Supplementary video file 1 for manuscriptHybrid Parallel Compliance Allows Robots to Operate With Sensorimotor Delays and Low Control FrequenciesPublished inFront. Robot. AI, 16 June 2021DOIdoi.org/10.3389/frobt.2021.645748AbstractAnimals 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 ms, or control frequencies as low as 20 Hz, 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 m) for a 2 kg quadruped robot with 100 Hz control frequency and a sensorimotor delay of 35 ms.
3D Anatomy of the Quail Lumbosacral Spinal Canal - Implications for Putative Mechanosensory Function Dynamic Locomotion Group 2020-12-21 | Publication (online first): Kamska, Viktoriia, Monica Daley, and Alexander Badri-Spröwitz. “3D Anatomy of the Quail Lumbosacral Spinal Canal—Implications for Putative Mechanosensory Function.” Integrative Organismal Biology, 2020. academic.oup.com/iob/advance-article/doi/10.1093/iob/obaa037/5943883Birds are diverse and agile vertebrates capable of aerial, terrestrial, aquatic, and arboreal locomotion. Evidence suggests that birds possess a novel balance sensing organ in the lumbosacral spinal canal, a structure referred to as the “lumbosacral organ” (LSO), which may contribute to their locomotor agility and evolutionary success. The mechanosensing mechanism of this organ remains unclear. Here we quantify the 3D anatomy of the lumbosacral region of the common quail, focusing on establishing the geometric and biomechanical properties relevant to potential mechanosensing functions. We combine digital and classic dissection to create a 3D anatomical model of the quail LSO and estimate the capacity for displacement and deformation of the soft tissues. We observe a hammock-like network of denticulate ligaments supporting the lumbosacral spinal cord, with a close association between the accessory lobes and ligamentous intersections. The relatively dense glycogen body has the potential to apply loads sufficient to pre-stress denticulate ligaments, enabling external accelerations to excite tuned oscillations in the LSO soft tissue, leading to strain-based mechanosensing in the accessory lobe neurons. Considering these anatomical features together, the structure of the LSO is reminiscent of a mass-spring-based accelerometer.
A little damping goes a long way - SICB2021 presentation Dynamic Locomotion Group 2020-12-21 | SICB2021 presentation: sicbannualmeeting.pathable.co/meetings/virtual/BfMMXF2jpiCp7zebAFull publication: Heim, Steve, Matthew Millard, Charlotte Le Mouel, and Alexander Badri-Spröwitz. “A Little Damping Goes a Long Way: A Simulation Study of How Damping Influences Task-Level Stability in Running.” Biology Letters 16, no. 9 (September 30, 2020): 20200467. doi.org/10.1098/rsbl.2020.0467.
Effective Viscous Damping Enables Morphological Computation in Legged Locomotion Dynamic Locomotion Group 2020-09-22 | Mo, An, Fabio Izzi, Daniel F. B. Haeufle, and Alexander Badri-Spröwitz. “Effective Viscous Damping Enables Morphological Computation in Legged Locomotion.” Frontiers in Robotics and AI 7 (2020). doi.org/10.3389/frobt.2020.00110.abstract: Muscle models and animal observations suggest that physical damping is beneficial for stabilization. Still, only a few implementations of physical damping exist in compliant robotic legged locomotion. It remains unclear how physical damping can be exploited for locomotion tasks, while its advantages as sensor-free, adaptive force- and negative work-producing actuators are promising. In a simplified numerical leg model, we studied the energy dissipation from viscous and Coulomb damping during vertical drops with ground-level perturbations. A parallel spring- damper is engaged between touch-down and mid-stance, and its damper auto-decouples from mid-stance to takeoff. Our simulations indicate that an adjustable and viscous damper is desired. In hardware we explored effective viscous damping and adjustability, and quantified the dissipated energy. We tested two mechanical, leg-mounted damping mechanisms: a commercial hydraulic damper, and a custom-made pneumatic damper. The pneumatic damper exploits a rolling diaphragm with an adjustable orifice, minimizing Coulomb damping effects while permitting adjustable resistance. Experimental results show that the leg-mounted, hydraulic damper exhibits the most effective viscous damping. Adjusting the orifice setting did not result in substantial changes of dissipated energy per drop, unlike adjusting the damping parameters in the numerical model. Consequently, we also emphasize the importance of characterizing physical dampers during real legged impacts to evaluate their effectiveness for compliant legged locomotion.
Trunk Pitch Oscillations for Energy Trade-offs in Bipedal Running Birds and Robots Dynamic Locomotion Group 2020-06-06 | Video attachment for manuscript: Drama, Özge, and Alexander Spröwitz. “Trunk Pitch Oscillations for Energy Trade-Offs in Bipedal Running Birds and Robots.” Bioinspiration & Biomimetics 15, no. 3 (2020): 036013. doi.org/10.1088/1748-3190/ab7570arxiv.org/abs/1909.09378
Beyond Basins of Attraction: Quantifying Robustness of Natural Dynamics Dynamic Locomotion Group 2020-05-28 | ICRA 2020 talk for publication:Heim, Steve, and Alexander Spröwitz. “Beyond Basins of Attraction: Quantifying Robustness of Natural Dynamics.” IEEE Transactions on Robotics 35, no. 4 (August 2019): 939--952. Preprint on arXiv arxiv.org/abs/1806.08081
FootTile: a Rugged Foot Sensor for Force and Center of Pressure Sensing in Soft Terrain (presenter) Dynamic Locomotion Group 2020-05-28 | Presentation slides with voice over for ICRA2020 submissionRuppert, Felix, and Alexander Badri-Spröwitz. “FootTile: A Rugged Foot Sensor for Force and Center of Pressure Sensing in Soft Terrain,” 2020. http://arxiv.org/abs/2005.09025.
FootTile: a Rugged Foot Sensor for Force and Center of Pressure Sensing in Soft Terrain Dynamic Locomotion Group 2020-05-14 | title: FootTile: a Rugged Foot Sensor for Force and Center of Pressure Sensing in Soft Terrainauthors: Felix Ruppert and Alexander Badri-Spröwitz
ATRIAS robot walking outside. Dynamic Locomotion Group 2020-02-06 | Cooperation work with research group Dr. Jonathan Hurst (OSU, Portland, USA), and Dr. Monica Daley (RVC, London, UK). ATRIAS robot, walking at the RVC. Related publications: (1) Renjewski, Daniel, Alexander Spröwitz, Andrew Peekema, Mikhail Jones, and Jonathan Hurst. “Exciting Engineered Passive Dynamics in a Bipedal Robot.” IEEE Transactions on Robotics 31, no. 5 (September 16, 2015): 1244--1251. (2) Hubicki, Christian, Jesse Grimes, Mikhail Jones, Daniel Renjewski, Alexander Spröwitz, Andy Abate, and Jonathan Hurst. “ATRIAS: Design and Validation of a Tether-Free 3D-Capable Spring-Mass Bipedal Robot.” The International Journal of Robotics Research 35, no. 12 (October 1, 2016): 1497–1521.
YaMoR modular robot, tripod configuration, random CPG parameter gait initialisation. Dynamic Locomotion Group 2020-02-06 | YaMoR modular robot, tripod configuration, random CPG parameter gait initialisation. From publication: Spröwitz, Alexander, Rico Moeckel, Jerome Maye, and Auke Jan Ijspeert. “Learning to Move in Modular Robots Using Central Pattern Generators and Online Optimization.” The International Journal of Robotics Research 27, no. 3–4 (March 1, 2008): 423–43. doi.org/10.1177/0278364907088401.
YaMoR modular robot, tripod gait, optimized CPG parameters. Dynamic Locomotion Group 2020-02-06 | YaMoR modular robot, tripod gait, optimized CPG parameters.From publication: Spröwitz, Alexander, Rico Moeckel, Jerome Maye, and Auke Jan Ijspeert. “Learning to Move in Modular Robots Using Central Pattern Generators and Online Optimization.” The International Journal of Robotics Research 27, no. 3–4 (March 1, 2008): 423–43. doi.org/10.1177/0278364907088401.
YaMoR modular robots in snake configuration, optimised central pattern generator parameters. Dynamic Locomotion Group 2020-02-06 | YaMoR modular robot, snake configuration, optimiaed CPG parameters. From publication: Spröwitz, Alexander, Rico Moeckel, Jerome Maye, and Auke Jan Ijspeert. “Learning to Move in Modular Robots Using Central Pattern Generators and Online Optimization.” The International Journal of Robotics Research 27, no. 3–4 (March 1, 2008): 423–43. doi.org/10.1177/0278364907088401.
YaMoR modular robot, snake configuration, random CPG parameter gait initialisation. Dynamic Locomotion Group 2020-02-06 | YaMoR modular robot, quadruped configuration, random CPG parameter gait initialisation. From publication: Spröwitz, Alexander, Rico Moeckel, Jerome Maye, and Auke Jan Ijspeert. “Learning to Move in Modular Robots Using Central Pattern Generators and Online Optimization.” The International Journal of Robotics Research 27, no. 3–4 (March 1, 2008): 423–43. doi.org/10.1177/0278364907088401.
YaMoR modular robot, quadruped configuration, optimised CPG parameters Dynamic Locomotion Group 2020-02-06 | YaMoR modular robot, quadruped configuration, optimised CPG parameters.From publication: Spröwitz, Alexander, Rico Moeckel, Jerome Maye, and Auke Jan Ijspeert. “Learning to Move in Modular Robots Using Central Pattern Generators and Online Optimization.” The International Journal of Robotics Research 27, no. 3–4 (March 1, 2008): 423–43. doi.org/10.1177/0278364907088401.
YaMoR modular robot, learning to locomote. Dynamic Locomotion Group 2020-02-06 | YaMoR modular robot, quadruped configuration, random CPG parameter gait initialisation. From publication: Spröwitz, Alexander, Rico Moeckel, Jerome Maye, and Auke Jan Ijspeert. “Learning to Move in Modular Robots Using Central Pattern Generators and Online Optimization.” The International Journal of Robotics Research 27, no. 3–4 (March 1, 2008): 423–43. doi.org/10.1177/0278364907088401.
Biarticular Muscle-Tendon Structure in Hopping Robotic Leg Dynamic Locomotion Group 2019-08-08 | We investigate the role of lower leg muscle-tendon structures in providing serial elastic behavior to the hip actuator. We present a leg design with physical elastic elements in leg angle and virtual leg axis direction, and its impact onto energy efficient legged locomotion. The biarticular leg shows, to the best of our knowledge, the lowest achieved relative cost of transport documented for all dynamically hopping and running robots: 64% lower than a comparable-sized, running animal (tCOT=1.2).Accepted for publication in Frontiers in Neurorobotics (07/2019)frontiersin.org/articles/10.3389/fnbot.2019.00064/abstract
Shaping in Practice: Training Wheels to Learn Fast Hopping Directly in Hardware Dynamic Locomotion Group 2018-01-12 | Learning instead of designing robot controllers can greatly reduce engineering effort required, while also emphasizing robustness. Despite considerable progress in simulation, applying learning directly in hardware is still challenging, in part due to the necessity to explore potentially unstable parameters. We explore the of concept shaping the reward landscape with training wheels; temporary modifications of the physical hardware that facilitate learning. We demonstrate the concept with a robot leg mounted on a boom learning to hop fast. This proof of concept embodies typical challenges such as instability and contact, while being simple enough to empirically map out and visualize the reward landscape. Based on our results we propose three criteria for designing effective training wheels for learning in robotics.Steve Heim, Felix Ruppert, Alborz A. Sarvestani, and Alexander Spröwitz, "Shaping in Practice: Training Wheels to Learn Fast Hopping Directly in Hardware", accepted for ICRA2018, Brisbane, AustraliaEdition, FX and composition: Alejandro Posada Boada
Scalable Pneumatic and Tendon Driven Robotic Joint Inspired by Jumping Spiders Dynamic Locomotion Group 2017-05-30 | Scalable Pneumatic and Tendon Driven Robotic Joint Inspired by Jumping Spiders; A. Spröwitz, C. Göttler, A. Sinha, C. Caer, M.U. Öztekin, K. Petersen, and M. Sitti. Accepted for ICRA 2017.Fluidic actuators allow versatile, agile, and powerful motions and are commonly applied in robotics and automation. Likewise, many biological systems use fluidic actuators implemented with tissue for a wealth of tasks and performances. Spiders for example apply a hybrid mechanism of hydraulically actuated joint extension and muscle-based joint flexion to produce movement in two of their seven leg joints. Here, we present a novel spider-inspired joint mechanism employing both pneumatics and electrically-actuated tendons capable of strong, dynamic, and rapid joint movement. The implementation of the joint is closely inspired by those seen in real spiders, with a foldable structured membrane that effectively transfers all the energy from pressure to torque as the leg unfolds. To evaluate the mechanism we derived static joint models and a simple jumping model, and conducted equivalent experimental tests with a prototype of a single jumping leg robot. Besides applications in robot locomotion, the implementation and modeling of the spider-inspired joint mechanism can be utilized to further explore dynamics and functional biomechanics in spiders. In the future, we hope to use this platform to answer questions related to the impressive jumping and locomotion performances of real arachnids, and explore what morphological traits lie behind efficient spider locomotion at different size scales.Work at Max Planck Institute for Intelligent Systems, Stuttgart, Germany.Video cut and animation by C. Göttler.
Bobcat robot, a bounding quadruped robot with an active spine. Dynamic Locomotion Group 2016-07-26 | Bobcat robot applies its active spine control to efficiently bound. Short flight phases are visible in this gait. An open loop central pattern generator controllers provides the feed forward locomotion patterns. Published in: Khoramshahi , M.; Spröwitz, A.; Tuleu, A.; Ahmadabadi, M. N.; Ijspeert, A. J.: Benefits of an active spine supported bounding locomotion with a small compliant quadruped robot. In: Proceedings of the 2013 IEEE International Conference on Robotics and Automation (ICRA), pp. 3329-3334. Karlsruhe, May 06, 2013 - May 10, 2013. IEEE, New York, NY (2013)
Cheetah-cub in slow motion running in the hallway Dynamic Locomotion Group 2016-07-26 | Slow motion video of Cheetah-cub running in the hallway. Published in: Slow motion video of Cheetah-cub running in the corridor. Published in: Spröwitz, A.; Tuleu, A.; Vespignani, M.; Ajallooeian, M.; Badri, E.; Ijspeert, A. J.: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013)
Cheetah-cub leg design, spring loaded pantograph legs Dynamic Locomotion Group 2016-07-26 | Work at Biorob / EPFL; the video shows the spring loaded pantograph leg design of Cheetah-cub robot. Trough gravity-compensating springs in the legs, no motor actuation is required during standing and stance phase. Published in: Spröwitz, A.; Tuleu, A.; Vespignani, M.; Ajallooeian, M.; Badri, E.; Ijspeert, A. J.: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013)
Cheetah-cub step down perturbation Dynamic Locomotion Group 2016-07-26 | Work at Biorob / EPFL; Cheetah-cub runs successful over a step-down perturbation, and self-stabilizes afterwards. The applied locomotion controller is a feed-forward Central Pattern Generator. Published in: Spröwitz, A.; Tuleu, A.; Vespignani, M.; Ajallooeian, M.; Badri, E.; Ijspeert, A. J.: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013)
Cheetah-cub level running Dynamic Locomotion Group 2016-07-26 | Work at Biorob / EPFL; 1st part: Video sideview at Cheetah-cub running over force plates, round, non-segmented feet are mounted, and considerable forward sliding is visible. 2nd part: Cheetah-cub simulated in Webots. Published in: Spröwitz, A.; Tuleu, A.; Vespignani, M.; Ajallooeian, M.; Badri, E.; Ijspeert, A. J.: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013)
Cheetah-cub running in hallway Dynamic Locomotion Group 2016-07-26 | Work at Biorob / EPFL with Cheetah-cub running with 5.1 body length per second (1.04m/s) in the hallway. Gait is trot gait. There are no 3d constraints, the power cable is held loosely and used for steering only.Published in: Spröwitz, A.; Tuleu, A.; Vespignani, M.; Ajallooeian, M.; Badri, E.; Ijspeert, A. J.: Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot. The International Journal of Robotics Research 32 (8), pp. 932-950 (2013)
