Comparison of Legged Single-Robot and Multi-Robot Planetary Analog Exploration Systems

The development of ongoing and future planetary exploration missions calls for novel, effective robotic exploration technologies. Inspired by the recent developments in terrestrial robotic teams, we investigate the design and deployment of heterogeneous robotic teams and the accompanying operation concepts in planetary analog missions. Specifically, we describe a single-robot and a multi-robot system we developed for analog exploration missions using legged robots. We focus on the field trials using these systems at the ESA/ESRIC Space Resources Challenge. We show a performance comparison of our approaches, including payload utilization, mapping performance, redundancy, and human-robot interaction metrics. Furthermore, we present our lessons learned on developing and testing single-robot and multi-robot exploration systems. Our work shows that a heterogeneous robotic team allows higher payload utilization and a safer redundancy concept than single-robot approaches. However, a higher level of autonomy per robot is required to scale up the multi-robot approach

A certified model reduction approach for robust parameter optimization with PDE constraints

We investigate an optimization problem governed by an elliptic partial differential equation with uncertain parameters. We introduce a robust optimization framework that accounts for uncertain model parameters. The resulting non-linear optimization problem has a bi-level structure due to the min-max formulation. To approximate the worst-case in the optimization problem we propose linear and quadratic approximations. However, this approach still turns out to be very expensive, therefore we propose an adaptive model order reduction technique which avoids long offline stages and provides a certified reduced order surrogate model for the parametrized PDE which is then utilized in the numerical optimization. Numerical results are presented to validate the presented approach

Concept Study of a Small-Scale Dynamic Legged Robot for Lunar Exploration

When it comes to the exploration of the lunar surface, many high-reward targets, such as the craters at the lunar south pole or the Aristarchus Plateau, lie in hard-to-reach areas due to steep slopes, crater rims, and unstructured terrain. Therefore, such high-risk high-reward targets are currently out of human and robotic reach. Legged robots present a promising approach to exploring hard-to-access targets on the Moon. Legged robot prototypes have shown impressive locomotion capabilities in sloped, unstructured terrain in analog environments. However, despite their success in locomotion validation tests, we currently lack a target- and mission-specific analysis and design of the locomotion pattern, the thermal requirements, and the power system. We have set our goal to develop a small-scale, legged, technology demonstration robot. In this paper, we present our conceptual work on such a robot, targeting a traverse distance of 200 m and a payload capability of 1.5 kg. Our study showcases a basic locomotion study that identifies a feasible gait and its power requirements on representative terrain. We then lay our major focus on a thermal and power model considering the environment, the robot, and task schedule with sufficient accuracy to fulfill our self-defined mission success criteria. We also investigate the influence of the system’s emissivity and absorptivity on the regulation of the robot’s temperature. The simulation results suggest feasibility for missions at latitudes of 24°S and 75°S using a small-scale dynamic legged robot. However, it becomes clear that further research is required to validate the accuracy of the model. Research in solar panel degradation due to dust perturbation in legged robots will be necessary as the solar panel degradation shows a significant impact on the mission duration. Furthermore a precise soil-robot view factor needs to be determined. The determination of a realistic multi layer insulation concept for SpaceHopper in a lunar environment will be necessary to validate the assumptions draw based on the results the simulations

Traversing Steep and Granular Martian Analog Slopes With a Dynamic Quadrupedal Robot

Celestial bodies, such as the Moon and Mars are mainly covered by loose, granular soil, which is a notoriously challenging terrain to traverse with wheeled robots. Here, we present experimental work on traversing steep, granular slopes with the dynamically-walking quadrupedal robot SpaceBok. To adapt to the challenging environment, we developed passive-adaptive, planar feet and optimized studs to reduce sinkage and increase traction. Single-foot experiments revealed that a surface area of 110 cm2 per foot reduces sinkage to an acceptable level for the 22 kg robot, even on highly collapsible soil. Implementing several 12 mm studs increases traction by 22% to 66% on granular media compared to stud-less designs. Together with a terrain-adapting walking controller, we validate — for the first time — static and dynamic locomotion on Mars analog slopes of up to 25° (the maximum of the testbed). We evaluated the performance between point- and planar feet and static and dynamic gaits for safety, velocity, and energy consumption. We show that dynamic gaits are energetically more efficient than static ones, but are riskier on steep slopes. Our tests also revealed that energy consumption with planar feet increases drastically as slope inclination approaches the soil’s angle of repose. Point feet are less affected by slippage due to their excessive sinkage but, in turn, are prone to instabilities and tripping. Based on our findings, we present safe and energy-efficient, global, path-planning strategies for negotiating steep Martian topography.ISSN:2771-398

Scientific exploration of challenging planetary analog environments with a team of legged robots

The interest in exploring planetary bodies for scientific investigation and in situ resource utilization is ever-rising. Yet, many sites of interest are inaccessible to state-of-the-art planetary exploration robots because of the robots’ inability to traverse steep slopes, unstructured terrain, and loose soil. In addition, current single-robot approaches only allow a limited exploration speed and a single set of skills. Here, we present a team of legged robots with complementary skills for exploration missions in challenging planetary analog environments. We equipped the robots with an efficient locomotion controller, a mapping pipeline for online and postmission visualization, instance segmentation to highlight scientific targets, and scientific instruments for remote and in situ investigation. Furthermore, we integrated a robotic arm on one of the robots to enable high-precision measurements. Legged robots can swiftly navigate representative terrains, such as granular slopes beyond 25°, loose soil, and unstructured terrain, highlighting their advantages compared with wheeled rover systems. We successfully verified the approach in analog deployments at the Beyond Gravity ExoMars rover test bed, in a quarry in Switzerland, and at the Space Resources Challenge in Luxembourg. Our results show that a team of legged robots with advanced locomotion, perception, and measurement skills, as well as task-level autonomy, can conduct successful, effective missions in a short time. Our approach enables the scientific exploration of planetary target sites that are currently out of human and robotic reach

Scientific Exploration of Challenging Planetary Analog Environments with a Team of Legged Robots

The interest in exploring planetary bodies for scientific investigation and in situ resource utilization is ever-rising. Yet, many sites of interest are inaccessible to state-of-the-art planetary exploration robots because of the robots’ inability to traverse steep slopes, unstructured terrain, and loose soil. In addition, current single-robot approaches only allow a limited exploration speed and a single set of skills. Here, we present a team of legged robots with complementary skills for exploration missions in challenging planetary analog environments. We equipped the robots with an efficient locomotion controller, a mapping pipeline for online and postmission visualization, instance segmentation to highlight scientific targets, and scientific instruments for remote and in situ investigation. Furthermore, we integrated a robotic arm on one of the robots to enable high-precision measurements. Legged robots can swiftly navigate representative terrains, such as granular slopes beyond 25°, loose soil, and unstructured terrain, highlighting their advantages compared with wheeled rover systems. We successfully verified the approach in analog deployments at the Beyond Gravity ExoMars rover test bed, in a quarry in Switzerland, and at the Space Resources Challenge in Luxembourg. Our results show that a team of legged robots with advanced locomotion, perception, and measurement skills, as well as task-level autonomy, can conduct successful, effective missions in a short time. Our approach enables the scientific exploration of planetary target sites that are currently out of human and robotic reach.ISSN:2470-947