Brachiation is a dynamic, coordinated swinging maneuver of body and arms used by monkeys and apes to move between branches. As a unique underactuated mode of locomotion, it is interesting to study from a robotics perspective since it can broaden the deployment scenarios for humanoids and animaloids. While several brachiating robots of varying complexity have been proposed in the past, this letter presents the simplest possible prototype of a brachiation robot, using only a single actuator and unactuated grippers. The novel passive gripper design allows it to snap on and release from monkey bars, while guaranteeing well defined start and end poses of the swing. The brachiation behavior is realized in three different ways, using trajectory optimization via direct collocation and stabilization by a model-based time-varying linear quadratic regulator (TVLQR) or model-free proportional derivative (PD) control, as well as by a reinforcement learning (RL) based control policy. The three control schemes are compared in terms of robustness to disturbances, mass uncertainty, and energy consumption. The system design and controllers have been open-sourced. Due to its minimal and open design, the system can serve as a canonical underactuated platform for education and research.
@article{10106397,dimensions={true},author={Javadi, Mahdi and Harnack, Daniel and Stocco, Paula and Kumar, Shivesh and Vyas, Shubham and Pizzutilo, Daniel and Kirchner, Frank},journal={IEEE Robotics and Automation Letters},title={AcroMonk: A Minimalist Underactuated Brachiating Robot},year={2023},volume={8},number={6},pages={3637-3644},keywords={},doi={10.1109/LRA.2023.3269296},issn={2377-3766},month=jun}
Post-capture detumble trajectory stabilization for robotic active debris removal
Shubham Vyas, Lasse Maywald, Shivesh Kumar, Marko Jankovic, Andreas Mueller, and Frank Kirchner
Recent increase in space debris combined with the increase in the number of satellites launched has created an increased risk of collisions. The effects of the increased risk can be seen in the form of an increased number of near misses in recent years. The use of robotic manipulators has been suggested for Active Debris Removal (ADR) to reduce the risk of potential future collisions that generate more debris in the orbits around Earth. Compared to other ADR methods, robotic manipulators provide increased versatility as they can be reused for On-Orbit Servicing as well as On-Orbit Assembly missions. A robotic ADR operation consists of three phases: Approach, Capture, and Detumble. This paper provides a method for performing feedback-based stabilization of post-capture detumble trajectories of the chaser-debris system. The approach presented here uses Time-Varying Linear Quadratic Regulator (TVLQR) for stabilization along the detumble trajectory. The contributions of this paper are as follows: A quaternion-based linearization method for multibody systems with a free-floating base, TVLQR for stabilizing the optimal detumble trajectory, and a probabilistic Region of Attraction analysis of the resulting closed-loop system. The estimated Region of Attraction could serve as the goal for the capture controller thus allowing for controller composition through ADR phases while guaranteeing stability and successful detumble.
@article{VYAS2022,dimensions={true},title={Post-capture detumble trajectory stabilization for robotic active debris removal},journal={Advances in Space Research},year={2023},volume={72},number={7},pages={2845--2859},issn={0273-1177},doi={10.1016/j.asr.2022.09.033},url={https://www.sciencedirect.com/science/article/pii/S0273117722008742},author={Vyas, Shubham and Maywald, Lasse and Kumar, Shivesh and Jankovic, Marko and Mueller, Andreas and Kirchner, Frank},keywords={Active debris removal, Space robotics, Trajectory stabilization}}
2022
Momentum based classification for robotic active debris removal
Recent spacecraft collisions with debris and various near misses have highlighted the need for pursuing Active Debris Removal (ADR) of space debris. Robotic manipulators provide a versatile way to capture, detumble, and eventually deorbit the debris. This paper explores the classification of space debris and robotic manipulators based on angular momentum. Previous classifications have considered the tumble rates, size, and orbit of the debris. However, a momentum-based classification gives an additional insight into the method selection for debris removal as shown in this paper. A study on the momentum capture capabilities of previously flown robotic manipulators is performed. This gives an impression of the capabilities of the flight-heritage robotic manipulators for their use in ADR missions. Furthermore, an analysis is also performed on the momentum of cylindrical space debris as it closely represents the spent rocket upper stages which could be prime targets for a robotic ADR mission. The change in momentum due to the tumble rate and inertia is analysed for such cylindrical debris and they are then categorized based on their momentum. These analyses provide the data required to perform a matching of the momentum of the debris with the momentum capabilities of the existing robotic manipulators and thus classify the debris based on momentum. The classification is then applied to real debris objects and the results are discussed. The comparison of the momentum of debris and manipulators is also used to provide input for future manipulator development for ADR missions.
@article{VYAS2022649,dimensions={true},title={Momentum based classification for robotic active debris removal},journal={Journal of Space Safety Engineering},volume={9},number={4},pages={649-655},year={2022},month=dec,issn={2468-8967},doi={10.1016/j.jsse.2022.09.008},url={https://www.sciencedirect.com/science/article/pii/S2468896722001136},author={Vyas, Shubham and Jankovic, Marko and Kirchner, Frank},keywords={Space debris, Active debris removal, Space robotics, Space debris classification}}
Torque-limited simple pendulum: A toolkit for getting familiar with control algorithms in underactuated robotics
Felix Wiebe, Jonathan Babel, Shivesh Kumar, Shubham Vyas, Daniel Harnack, Melya Boukheddimi, Mihaela Popescu, and Frank Kirchner
@article{Wiebe2022,dimensions={true},doi={10.21105/joss.03884},url={https://doi.org/10.21105/joss.03884},year={2022},month=jun,publisher={The Open Journal},volume={7},number={74},pages={3884},author={Wiebe, Felix and Babel, Jonathan and Kumar, Shivesh and Vyas, Shubham and Harnack, Daniel and Boukheddimi, Melya and Popescu, Mihaela and Kirchner, Frank},title={Torque-limited simple pendulum: A toolkit for getting familiar with control algorithms in underactuated robotics},journal={Journal of Open Source Software}}
Conference Papers
2023
LQR for Free-Floating Robots: Theory and Experiments
Shubham Vyas, Lasse Shala, and Anton Bredenbeck
In Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA), Oct 2023
Space robots have been suggested as a prime candidate for On-Orbit Servicing (OOS) and Active Debris Removal (ADR) missions. In this paper, we present the results of employing LQR-based controllers for various free-floating robotic systems. LQR-based controllers have been used frequently as they provide an optimal controller for linear systems. Previous work has shown that the LQR controller for the linearized equations of motion for free-floating robots without gravity is globally asymptotically stable and locally optimal. The linearized equations of motion for 3 different systems are presented along with results from experiments for fixed-point stabilization and trajectory tracking. These systems vary between having continuous actuation using propellers, and binary-pulsed thrusters, along with either a single floating rigid body or a multi-body floating system. LQR controllers allow for trajectory tracking during different phases of OOS or ADR missions. Along with trajectory stabilization, recent works have demonstrated the estimation of the Region of Attraction (RoA) of such controllers for trajectory stabilization. This can be used in the future for sequential controller composition of controllers to guarantee stability through phase transitions. Furthermore, the estimated RoA allows for quick go/no-go decision-making during operations when unaccounted/unmodelled disturbances are observed.
@inproceedings{vyasnastra2023,dimensions={true},author={Vyas, Shubham and Shala, Lasse and Bredenbeck, Anton},booktitle={Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA)},title={LQR for Free-Floating Robots: Theory and Experiments},year={2023},month=oct}
PERSIM: Perception for Planetary Prospection and Internal Simulation
Raúl Domínguez, Mariela De Lucas Alvarez, Siddhant Kadwe, Christoph Hertzberg, Siddhant Shete, Leon Cedric Danter, Marko Jankovic, Shubham Vyas, Jonas Eisenmenger, Pierre Willenbrock, André Felmet, Vikram Unnithan, and
1 more author
In Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA), Oct 2023
For planetary robotics autonomous prospecting, robust, long-term navigation becomes crucial. The goal of the research project PerSim is to develop technology to address some of the challenges of active perception for resource identification and long-term navigation strategies in an integrated architecture. The fist assessment addressed autonomous selection of regions for inspection, combined arm-base approach, close range data acquisition and categorization of the acquired spectral data using Deep Learning. Furthermore, autonomous navigation including potential failure prediction and avoidance are also scoped. The following targets are pursued in the second assessment: an internal simulation to enhance the system safety and provide means for autonomous on- board safe testing, an episodic memory representation to serve as basis for the implementation of long term adaptation and finally a repertoire of behaviors to enable different motion modalities. The paper provides insights on the approaches and initial results.
@inproceedings{persimastra2023,dimensions={true},author={Domínguez, Raúl and Alvarez, Mariela De Lucas and Kadwe, Siddhant and Hertzberg, Christoph and Shete, Siddhant and Danter, Leon Cedric and Jankovic, Marko and Vyas, Shubham and Eisenmenger, Jonas and Willenbrock, Pierre and Felmet, André and Unnithan, Vikram and Kirchner, Frank},booktitle={Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA)},title={PERSIM: Perception for Planetary Prospection and Internal Simulation},year={2023},month=oct}
Linear Model Predictive Control for a planar free-floating platform: A comparison of binary input constraint formulations
Franek Stark, Shubham Vyas, Georg Schildbach, and Frank Kirchner
In Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA), Oct 2023
This work develops a first Model Predictive Controller for ESA’s 3-dof free-floating platform. The challenges of the platform are the on/off thrusters, which cannot be actuated continuously and which are subject to certain timing constraints. This work compares penalty-term, Linear Complimentarity Constraints, and classical Mixed Integer formulations in order to develop a controller that natively handles binary inputs. Furthermore, linear constraints are proposed which enforce the timing constraints. Only the Mixed Integer formulation turns out to work sufficiently. Hence, this work develops a new Mixed Integer Model Predictive Controller on the decoupled model of the platform. Feasibility analysis and simulation results show that for a short enough prediction horizon, this controller can (sub)optimally stabilize and control the system under consideration of the constraints in real-time.
@inproceedings{mimpcastra2023,dimensions={true},author={Stark, Franek and Vyas, Shubham and Schildbach, Georg and Kirchner, Frank},booktitle={Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA)},title={Linear Model Predictive Control for a planar free-floating platform: A comparison of binary input constraint formulations},year={2023},publisher={ESA},month=oct}
AUV Trajectory Optimization with hydrodynamic forces for icy moon exploration
Lukas Rust, Shubham Vyas, Bilal Wehbe, and Frank Kirchner
In Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA), Oct 2023
To explore oceans on ice-covered moons in the solar system, energy-efficient Autonomous Underwater Vehicles (AUVs) with long ranges must cover enough distance to record and collect enough data. These usually underactuated vehicles are hard to control when performing tasks such as vertical docking or the inspection of vertical walls. This paper introduces a control strategy for DeepLeng to navigate in the ice-covered ocean of Jupiter’s moon Europa and presents simulation results preceding a discussion on what is further needed for robust control during the mission.
@inproceedings{deeplengastra2023,dimensions={true},author={Rust, Lukas and Vyas, Shubham and Wehbe, Bilal and Kirchner, Frank},booktitle={Proceedings of the 17th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA)},title={AUV Trajectory Optimization with hydrodynamic forces for icy moon exploration},year={2023},publisher={ESA},month=oct}
2022
Trajectory Optimization and Following for a Three Degrees of Freedom Overactuated Floating Platform
A. Bredenbeck, S. Vyas, M. Zwick, D. Borrmann, M.A. Olivares-Mendez, and A. Nüchter
In Proceedings of the 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Oct 2022
Space robotics applications, such as Active Space Debris Removal (ASDR), require representative testing before launch. A commonly used approach to emulate the microgravity environment in space is air-bearing based platforms on flat-floors, such as the European Space Agency’s Orbital Robotics and GNC Lab (ORGL). This work proposes a control architecture for a floating platform at the ORGL, equipped with eight solenoid-valve-based thrusters and one reaction wheel. The control architecture consists of two main components: a trajectory planner that finds optimal trajectories connecting two states and a trajectory follower that follows any physically feasible trajectory. The controller is first evaluated within an introduced simulation, achieving a 100 percent success rate at finding and following trajectories to the origin within a Monte-Carlo test. Individual trajectories are also successfully followed by the physical system. In this work, we showcase the ability of the controller to reject disturbances and follow a straight-line trajectory within tens of centimeters.
@inproceedings{antoniros2022,dimensions={true},author={Bredenbeck, A. and Vyas, S. and Zwick, M. and Borrmann, D. and Olivares-Mendez, M.A. and Nüchter, A.},booktitle={Proceedings of the 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},title={Trajectory Optimization and Following for a Three Degrees of Freedom Overactuated Floating Platform},year={2022},pages={4084-4091},doi={10.1109/IROS47612.2022.9981294},issn={2153-0866},month=oct}
Trajectory Optimization and Following for a Three Degrees of Freedom Overactuated Floating Platform
A. Bredenbeck, S. Vyas, Willem Suter, M. Zwick, D. Borrmann, M.A. Olivares-Mendez, and A. Nüchter
In Proceedings of the 16th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA), Jun 2022
The recent increase in yearly spacecraft launches and the high number of planned launches have raised questions about maintaining accessibility to space for all interested parties. A key to sustaining the future of space-flight is the ability to service malfunctioning - and actively remove dysfunctional spacecraft from orbit. Robotic platforms that autonomously perform these tasks are a topic of ongoing research and thus must undergo thorough testing before launch. For representative system-level testing, the European Space Agency (ESA) uses, among other things, the Orbital Robotics and GNC Lab (ORGL), a flat-floor facility where air-bearing based platforms exhibit free-floating behavior in three Degrees of Freedom (DoF). This work introduces a representative simulation of a free-floating platform in the testing environment and a software framework for controller development. Finally, this work proposes a controller within that framework for finding and following optimal trajectories between arbitrary states, which is evaluated in simulation and reality.
@inproceedings{antonastra2022,dimensions={true},author={Bredenbeck, A. and Vyas, S. and Suter, Willem and Zwick, M. and Borrmann, D. and Olivares-Mendez, M.A. and Nüchter, A.},booktitle={Proceedings of the 16th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA)},title={Trajectory Optimization and Following for a Three Degrees of Freedom Overactuated Floating Platform},year={2022},eprint={2206.03993},archiveprefix={arXiv},primaryclass={cs.RO},month=jun}
Robot Dance Generation with Music Based Trajectory Optimization
Melya Boukheddimi, Daniel Harnack, Shivesh Kumar, Rohit Kumar, Shubham Vyas, Octavio Arriaga, and Frank Kirchner
In Proceedings of the 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Oct 2022
Musical dancing is an ubiquitous phenomenon in the human society. Providing robots the ability to dance has the potential to make the human robot co-existence more acceptable in our society. Hence, dancing robots have generated a considerable research interest in the recent years. In this paper, we present a novel formalization of robot dancing as planning and control of optimally timed actions based on beat timings and additional features extracted from the music. We showcase the use of this formulation in three different variations: with input of human expert choreography, imitation of a predefined choreography, and automated generation of a novel choreography. Our method has been validated on four different musical pieces, both in simulation and on a real robot, using the upper-body humanoid robot RH5 Manus.
@inproceedings{dancerobotiros2022,dimensions={true},author={Boukheddimi, Melya and Harnack, Daniel and Kumar, Shivesh and Kumar, Rohit and Vyas, Shubham and Arriaga, Octavio and Kirchner, Frank},booktitle={Proceedings of the 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},title={Robot Dance Generation with Music Based Trajectory Optimization},year={2022},volume={},number={},pages={3069-3076},keywords={},doi={10.1109/IROS47612.2022.9981462},issn={2153-0866},month=oct}
Quaternion based LQR for Free-Floating Robots without Gravity
Shubham Vyas, Bilal Wehbe, and Shivesh Kumar
In Proceedings of the 6th CEAS Conference on Guidance, Navigation and Control (EuroGNC), May 2022
Quaternions are commonly used for rotation representation as they avoid the singularities found in the Euler angles representation and are more compact than using rotation matrices (for storage, operations, and constraints required). However, it is difficult to use quaternions in linear control approaches due to the inherent unit length constraint of the representation. Quaternion-based linear control has been previously used for single rigid body control such as quadrotors and satellite attitude control. In this paper, we provide an analytical method for linearizing multibody freefloating robotic systems without gravity using a quaternion-based rotation representation for the floating base. This linearization is then used for deriving a Linear Quadratic Regulator (LQR) based controller. The LQR is optimal in the local neighbourhood of the linearization and is globally asymptotically stable for such systems. The utility of this method is demonstrated using two examples from different robotic domains: space and underwater robotics.
@inproceedings{vyaseurognc2022,dimensions={true},author={Vyas, Shubham and Wehbe, Bilal and Kumar, Shivesh},booktitle={Proceedings of the 6th CEAS Conference on Guidance, Navigation and Control (EuroGNC)},title={Quaternion based LQR for Free-Floating Robots without Gravity},year={2022},address={Berlin, Germany},month=may}
2020
Underwater Demonstrator for Autonomous In-Orbit Assembly of Large Structures
Christian Ernst Siegfried Koch, Marko Jankovic, Sankaranarayanan Natarajan, Shubham Vyas, Wiebke Brinkmann, Vincent Bissonnette, Thierry Germa, Alessio Turetta, and Frank Kirchner
In Proceedings of the International Symposium on Artificial Intelligence, Robotics and Automation in Space (i-SAIRAS), Oct 2020
The PULSAR project aims to develop key- technologies to enable the autonomous assembly of large structures in space. Similar to industrial applications, the assembly process relies on robotic systems capable of assembling modular elements to form a complex structure. However, the in-space assembly provides exceptional challenges necessitat- ing innovation in fields such as free-floating manipulation and autonomous robotics. This paper provides details on the PULSAR project and, more specifical- ly, on a hardware-in-the-loop demonstrator dLSAFFE, developed to show the assembly process of a large telescope mirror in a micro-gravity environment.
@inproceedings{koch2020underwater,dimensions={true},year={2020},booktitle={Proceedings of the International Symposium on Artificial Intelligence, Robotics and Automation in Space (i-SAIRAS)},month=oct,title={Underwater Demonstrator for Autonomous In-Orbit Assembly of Large Structures},author={Koch, Christian Ernst Siegfried and Jankovic, Marko and Natarajan, Sankaranarayanan and Vyas, Shubham and Brinkmann, Wiebke and Bissonnette, Vincent and Germa, Thierry and Turetta, Alessio and Kirchner, Frank}}
2015
Design and Development of an Earth Based Experimental Setup for Testing Algorithms on Space Robots
Francis James, Shubham Vyas, Puneeth Bandikatla, P. Mithun, and S. V. Shah
In Proceedings of the 2015 Conference on Advances In Robotics, Jul 2015
In space robots, coupling between the base and the arms causes the floating base to translate and rotate when the arms execute a maneuver, which is typically not seen in earth based robots. Since it is difficult to test developments in space robotics primarily due to the high cost and lack of access to robots in space, it is necessary to have physical systems that can mimic space conditions for experimental validation on earth. Among several options, the use of air bearings to build floating-base robots is one of the most effective. We describe the development of one such system that replicates zero gravity conditions for planar robots. Although similar systems exist elsewhere, the planar dual-arm space robot we have built is distinctive by being relatively lightweight, compact and modular. The setup can be used to test a wide range of experiments such as visual servoing, reactionless maneuvering and object grasping in space. In this paper, the approach taken during the development of both the hardware and software for the experimental setup are discussed. A few results obtained by numerical simulations as well as experimentation are also presented.
@inproceedings{surilshah2015,dimensions={true},author={James, Francis and Vyas, Shubham and Bandikatla, Puneeth and Mithun, P. and Shah, S. V.},title={Design and Development of an Earth Based Experimental Setup for Testing Algorithms on Space Robots},year={2015},isbn={9781450333566},publisher={Association for Computing Machinery},address={New York, NY, USA},url={https://doi.org/10.1145/2783449.2783487},doi={10.1145/2783449.2783487},booktitle={Proceedings of the 2015 Conference on Advances In Robotics},articleno={38},numpages={6},location={Goa, India},series={AIR '15},month=jul}
