28 results
(View BibTeX file of all listed publications)
2023
Multi-segmented Adaptive Feet for Versatile Legged Locomotion in Natural Terrain
(Outstanding locomotion paper award)
Chatterjee, A., Mo, A., Kiss, B., Goenen, E. C., Badri-Spröwitz, A.
2023 IEEE International Conference on Robotics and Automation (ICRA 2023), pages: 1162-1169 , IEEE, Piscataway, NJ, IEEE International Conference on Robotics and Automation (ICRA), June 2023 (conference)
Most legged robots are built with leg structures from serially mounted links and actuators and are controlled through complex controllers and sensor feedback. In comparison, animals developed multi-segment legs, mechanical coupling between joints, and multi-segmented feet. They run agile over all terrains, arguably with simpler locomotion control. Here we focus on developing foot mechanisms that resist slipping and sinking also in natural terrain. We present first results of multi-segment feet mounted to a bird-inspired robot leg with multi-joint mechanical tendon coupling. Our one- and two-segment, mechanically adaptive feet show increased viable horizontal forces on multiple soft and hard substrates before starting to slip. We also observe that segmented feet reduce sinking on soft substrates compared to ball-feet and cylinder feet. We report how multi-segmented feet provide a large range of viable centre of pressure points well suited for bipedal robots, but also for quadruped robots on slopes and natural terrain. Our results also offer a functional understanding of segmented feet in animals like ratite birds.
Upside down: affordable high-performance motion platform
Pradhan, N. M. S., Frank, P., Mo, A., Badri-Spröwitz, A.
arXiv, 2023 (conference) Accepted
Parallel robots are capable of high-speed manipulation and have become essential tools in the industry. The proximal placement of their motors and the low weight of their end effectors make them ideal for generating highly dynamic motion. Therefore, parallel robots can be adopted for motion platform designs, as long as end effector loads are low. Traditional motion platforms can be large and powerful to generate multiple g acceleration. However, these designs tend to be expensive and large. Similar but smaller motion platforms feature a small work range with reduced degrees of freedom (DoFs) and a limited payload. Here we seek a medium-sized affordable parallel robot capable of powerful and high-speed 6-DoF motion in a comparably large workspace. This work explores the concept of a quadruped robot flipped upside-down, with the motion platform fixed between its feet. In particular, we exploit the high-power dynamic brushless actuation and the four-leg redundancy when moving the motion platform. We characterize the resulting motion platform by tracking sinusoidal and circular trajectories with varying loads. Dynamic motions in 6 DoFs up to 10 Hz and ± 10 mm amplitude are possible when moving a mass of 300 grams. We demonstrate single-axis end-effector translations up to ± 20 mm at 10 Hz for higher loads of 1.2 kg. The motion platform can be replicated easily by 3D printing and off-the-shelf components. All motion platform-related hardware and the custom-written software required to replicate are open-source.
2022
Mechanical Design, Development and Testing of Bioinspired Legged Robots for Dynamic Locomotion
Eberhard Karls Universität Tübingen, Tübingen , November 2022 (phdthesis)
Diaphragm Ankle Actuation for Efficient Series Elastic Legged Robot Hopping
Bolignari, M., Mo, A., Fontana, M., Badri-Spröwitz, A.
2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE, IROS2022, October 2022 (conference) In press
Robots need lightweight legs for agile locomotion, and intrinsic series elastic compliance has proven to be a major ingredient for energy-efficient locomotion and robust locomotion control. Animals' anatomy and locomotion capabilities emphasize the importance of that lightweight legs and integrated, compact, series elastically actuated for distal leg joints. But unlike robots, animals achieve series elastic actuation by their muscle-tendon units. So far no designs are available that feature all characteristics of a perfect distal legged locomotion actuator; a low-weight and low-inertia design, with high mechanical efficiency, no stick and sliding friction, low mechanical complexity, high-power output while being easy to mount. Ideally, such an actuator can be controlled directly and without mechanical cross-coupling, for example remotely. With this goal in mind, we propose a low-friction, lightweight Series ELastic Diaphragm distal Actuator (SELDA) which meets many, although not all, of the above requirements. We develop, implement, and characterize a bioinspired robot leg that features a SELDA-actuated foot segment. We compare two leg configurations controlled by a central pattern generator that both feature agile forward hopping. By tuning SELDA's activation timing, we effectively adjust the robot's hopping height by 11% and its forward velocity by 14%, even with comparatively low power injection to the distal joint.
Gastrocnemius and Power Amplifier Soleus Spring-Tendons Achieve Fast Human-like Walking in a Bipedal Robot
Kiss, B., Gonen, E. C., Mo, A., Buchmann, A., Renjewski, D., Badri-Spröwitz, A.
2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE, IROS2022, October 2022 (conference) In press
Legged locomotion in humans is governed by natural dynamics of the human body and neural control. One mechanism that is assumed to contribute to the high efficiency of human walking is the impulsive ankle push-off, which potentially powers the swing leg catapult. However, the mechanics of the human’s lower leg with its complex muscle-tendon units spanning over single and multiple joints is not yet understood. Legged robots allow testing the interaction between complex leg mechanics, control, and environment in real-world walking gait. We developed a 0.49 m tall, 2.2 kg anthropomorphic bipedal robot with Soleus and Gastrocnemius muscle-tendon units represented by linear springs, acting as mono- and biarticular elastic structures around the robot’s ankle and knee joints. We tested the influence of three Soleus and Gastrocnemius spring-tendon configurations on the ankle power curves, the coordination of the ankle and knee joint movements, the total cost of transport, and walking speed. We controlled the robot with a feed-forward central pattern generator, leading to walking speeds between 0.35 m/s and 0.57 m/s at 1.0 Hz locomotion frequency, at 0.35 m leg length. We found differences between all three configurations; the Soleus spring-tendon modulates the robot’s speed and energy efficiency likely by ankle power amplification, while the Gastrocnemius spring-tendon changes the movement coordination between knee and ankle joints during push-off.
Power to the springs: Passive elements are sufficient to drive push-off in human walking
Buchmann, A., Kiss, B., Badri-Spröwitz, A., Renjewski, D.
In Robotics in Natural Settings , pages: 21-32, Lecture Notes in Networks and Systems, 530, (Editors: Cascalho, José M. and Tokhi, Mohammad Osman and Silva, Manuel F. and Mendes, Armando and Goher, Khaled and Funk, Matthias), Springer, Cham, 25th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machine (CLAWAR 2022), August 2022 (inproceedings)
For the impulsive ankle push-off (APO) observed in human
walking two muscle-tendon-units (MTUs) spanning the ankle joint play
an important role: Gastrocnemius (GAS) and Soleus (SOL). GAS and
SOL load the Achilles tendon to store elastic energy during stance followed by a rapid energy release during APO. We use a neuromuscular
simulation (NMS) and a bipedal robot to investigate the role of GAS and
SOL on the APO. We optimize the simulation for a robust gait and then
sequentially replace the MTUs of (1) GAS, (2) SOL and (3) GAS and SOL
by linear springs. To validate the simulation, we implement NMS-3 on
a bipedal robot. Simulation and robot walk steady for all trials showing
an impulsive APO. Our results imply that the elastic MTU properties
shape the impulsive APO. For prosthesis or robot design that is, no
complex ankle actuation is needed to obtain an impulsive APO, if more
mechanical intelligence is incorporated in the design.
2021
Control Mechanisms for Postural Stability and Trunk Motion in Bipedal Running. A Numerical Study for Humans, Avians, and Bipedal Robots
Drama, Ö.
Universität Stuttgart, Stuttgart, May 2021 (phdthesis)
A little damping goes a long way
Heim, S., Millard, M., Mouel, C. L., Badri-Spröwitz, A.
In Integrative and Comparative Biology, 61(Supplement 1):E367-E367, Oxford University Press, Society for Integrative and Comparative Biology Annual Meeting (SICB Annual Meeting 2021) , March 2021 (inproceedings)
Effects of tendon-network mechanisms on avian terrestrial locomotion
Contreras, F. B., Daley, M., Badri-Spröwitz, A.
In Integrative and Comparative Biology, 61(Supplement 1):E89-E90, Oxford University Press, Society for Integrative and Comparative Biology Annual Meeting (SICB Annual Meeting 2021), January 2021 (inproceedings)
Developing a mechanical model for intraspinal mechanosensing in avians
Mo, A., Kamska, V., Contreras, F. B., Daley, M., Badri-Spröwitz, A.
In Integrative and Comparative Biology , 61(Supplement 1):E618-E619, Oxford University Press, Society for Integrative and Comparative Biology Annual Meeting (SICB Annual Meeting 2021), January 2021 (inproceedings)
Associating functional morphology of the lumbosacral organ and locomotion modalities in avians
Kamska, V., Contreras, F. B., Daley, M., Badri-Spröwitz, A.
In Integrative and Comparative Biology, 61(Supplement 1):E437-E437, Oxford University Press, Society for Integrative and Comparative Biology Annual Meeting (SICB Annual Meeting 2021), January 2021 (inproceedings)
Tackling sensorimotor delays and low control update frequencies during drop impacts with hybrid parallel leg compliance
Ashtiani, M. S., Sarvestani, A. A., Badri-Spröwitz, A.
The 9.5th international symposium on Adaptive Motion of Animals and Machines. Ottawa，Canada (Virtual Platform). 2021-06-22/25. Adaptive Motion of Animals and Machines Organizing Committee., pages: 3, Adaptive Motion of Animals and Machines Organizing Committee, Adaptive Motion of Animals and Machines, 2021 (conference)
2020
Simulating the response of a neuro-musculoskeletal model to assistive forces: implications for the design of wearables compensating for motor control deficits
Stollenmaier, K., Rist, I., Izzi, F., Haeufle, D. F.
In 2020 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob 2020), pages: 779-784, IEEE, Piscataway, NJ, 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob 2020), October 2020 (inproceedings)
Models of the human arm may help to estimate design parameters like peak torque and power of wearable assistive devices by predicting required forces to compensate for motor control impairments. This work focuses on the idea of compensating hypermetria (overshoot)-a motor control deficit that may occur in neurodegenerative diseases-by a simple assistive device. As musculoskeletal dynamics play an important role in the interaction between an assistive device and the neuro-musculoskeletal system, we hypothesized that their consideration in the model might influence the predicted design parameters. To test this, we simulated two-degree-of-freedom point-to-point arm movements. By introducing inconsistent neuronal control parameters, we induced hypermetria. We implemented mechanical and low-level assistive torque strategies in simulation which lead to a reduction of hypermetria. We found that-depending on the type of assistance-the predicted torques and powers can differ by more than a factor of 10 between musculoskeletal and torque-driven arm models. We conclude that the magnitude of torque and power required to reduce hypermetria by simple wearable assistive devices may be significantly underestimated if muscle-tendon characteristics are not considered.
Beyond Basins of Attraction: Quantifying Robustness of Natural Dynamics
Heim, S., Badri-Spröwitz, A.
May 2020 (talk)
FootTile: a Rugged Foot Sensor for Force and Center of Pressure Sensing in Soft Terrain
Ruppert, F., Badri-Spröwitz, A.
In 2020 IEEE International Conference on Robotics and Automation (ICRA 2020), pages: 4810-4816, IEEE, Piscataway, NJ, IEEE International Conference on Robotics and Automation (ICRA 2020) , 2020 (inproceedings)
In this paper, we present FootTile, a foot sensor for reaction force and center of pressure sensing in challenging terrain. We compare our sensor design to standard biomechanical devices, force plates and pressure plates. We show that FootTile can accurately estimate force and pressure distribution during legged locomotion. FootTile weighs 0.9g, has a sampling rate of 330 Hz, a footprint of 10×10 mm and can easily be adapted in sensor range to the required load case. In three experiments, we validate: first, the performance of the individual sensor, second an array of FootTiles for center of pressure sensing and third the ground reaction force estimation during locomotion in granular substrate. We then go on to show the accurate sensing capabilities of the waterproof sensor in liquid mud, as a showcase for real world rough terrain use.
Viability in State-Action Space. Connecting Morphology, Control, and Learning
Eberhard Karls Universität Tübingen, Tübingen, February 2020 (phdthesis)
2019
Trunk Pitch Oscillations for Joint Load Redistribution in Humans and Humanoid Robots
Drama, Ö., Badri-Spröwitz, A.
Proceedings of 2019 IEEE-RAS 19th International Conference on Humanoid Robots, pages: 531-536, IEEE, Humanoids, October 2019 (conference)
Creating natural-looking running gaits for humanoid robots is a complex task due to the underactuated degree of freedom in the trunk, which makes the motion planning and control difficult. The research on trunk movements in human locomotion is insufficient, and no formalism is known to transfer human motion patterns onto robots. Related work mostly focuses on the lower extremities, and simplifies the problem by stabilizing the trunk at a fixed angle. In contrast, humans display significant trunk motions that follow the natural dynamics of the gait. In this work, we use a spring-loaded inverted pendulum model with a trunk (TSLIP) together with a virtual point (VP) target to create trunk oscillations and investigate the impact of these movements. We analyze how the VP location and forward speed determine the direction and magnitude of the trunk oscillations. We show that positioning the VP below the center of mass (CoM) can explain the forward trunk pitching observed in human running. The VP below the CoM leads to a synergistic work between the hip and leg, reducing the leg loading. However, it comes at the cost of increased peak hip torque. Our results provide insights for leveraging the trunk motion to redistribute joint loads and potentially improve the energy efficiency in humanoid robots.
The positive side of damping
Heim, S., Millard, M., Le Mouel, C., Sproewitz, A.
Proceedings of AMAM, The 9th International Symposium on Adaptive Motion of Animals and Machines, August 2019 (conference)
Quantifying the Robustness of Natural Dynamics: a Viability Approach
Heim, S., Sproewitz, A.
Proceedings of Dynamic Walking , Dynamic Walking , 2019 (conference)
Das Tier als Modell für Roboter, und Roboter als Modell für Tiere
Badri-Spröwitz, A.
In pages: 167-175, Springer, 2019 (incollection)
2018
Learning from Outside the Viability Kernel: Why we Should Build Robots that can Fail with Grace
Heim, S., Sproewitz, A.
Proceedings of SIMPAR 2018, pages: 55-61, IEEE, 2018 IEEE International Conference on Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR), May 2018 (conference)
Impact of Trunk Orientation for Dynamic Bipedal Locomotion
Drama, Ö.
Dynamic Walking Conference, May 2018 (talk)
Impact of trunk orientation for dynamic bipedal locomotion
My research revolves around investigating the functional demands of bipedal running, with focus on stabilizing trunk orientation. When we think about postural stability, there are two critical questions we need to answer: What are the necessary and sufficient conditions to achieve and maintain trunk stability?
I am concentrating on how morphology affects control strategies in achieving trunk stability. In particular, I denote the trunk pitch as the predominant morphology parameter and explore the requirements it imposes on a chosen control strategy.
To analyze this, I use a spring loaded inverted pendulum model extended with a rigid trunk, which is actuated by a hip motor. The challenge for the controller design here is to have a single hip actuator to achieve two coupled tasks of moving the legs to generate motion and stabilizing the trunk. I enforce orthograde and pronograde postures and aim to identify the effect of these trunk orientations on the hip torque and ground reaction profiles for different control strategies.
Shaping in Practice: Training Wheels to Learn Fast Hopping Directly in Hardware
Heim, S., Ruppert, F., Sarvestani, A., Sproewitz, A.
In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA) 2018, pages: 5076-5081, IEEE, International Conference on Robotics and Automation, May 2018 (inproceedings)
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.
2017
Scalable Pneumatic and Tendon Driven Robotic Joint Inspired by Jumping Spiders
Sproewitz, A., Göttler, C., Sinha, A., Caer, C., Öztekin, M. U., Petersen, K., Sitti, M.
In Proceedings 2017 IEEE International Conference on Robotics and Automation (ICRA), pages: 64-70, IEEE, Piscataway, NJ, USA, IEEE International Conference on Robotics and Automation (ICRA), May 2017 (inproceedings)
Linking Mechanics and Learning
Heim, S., Grimminger, F., Drama, Ö., Spröwitz, A.
In Proceedings of Dynamic Walking 2017, 2017 (inproceedings)
Is Growing Good for Learning?
Heim, S., Spröwitz, A.
Proceedings of the 8th International Symposium on Adaptive Motion of Animals and Machines AMAM2017, 2017 (conference)
2011
Oncilla Robot—A Light-weight Bio-inspired Quadruped Robot for Fast Locomotion in Rough Terrain
Spröwitz, A., Kuechler, L., Tuleu, A., Ajallooeian, M., D’Haene, M., Moeckel, R., Ijspeert, A. J.
Symposium on adaptive motion of animals and machines (AMAM 2011), January 2011 (conference)
On the hardware level, we are proposing and testing a bio-inspired quadruped robot design (Oncilla robot), based on light-weight, compliant, and three-segmented legs. Our choice of placing the compliance such that it is spanning two joints enforces a non-linear spring stiffness. Based on the SLIP-model assumption, we compare progressive and de- gressive stiffness profiles against a linear-leg stiffness. To facilitate fast and throughout testing also of control approaches we have created a robot model of Oncilla robot in simulation (in Webots [1], a physics-based simulation environment). Here we are presenting new simulation results based on open-loop-central pattern generator (CPG) control and PSO- optimization of the CPG parameters. Our quadruped robot is equipped with passive compliant elements in its legs, and we apply two different strategies to make use of the legs’ compliance during stance phase. This enables us to find stable trot gait patterns propelling the robot up to 1 m/s (more than four times the robot’s leg length), depending on the applied stance phase leg-strategy. Different trot gait patterns emerge, and resulting trot gaits are variable in stability (tested as robustness against external perturbations) and speed.