An official website of the United States government
Conventional soft robots are designed with constant, passive stiffness properties, based on desired motion capabilities. The ability to encode two fundamentally different stiffness characteristics promises to enable a single robot to be optimized for multiple divergent tasks simultaneously and this has been previously proposed with a variety of approaches including jamming-based designs. In this paper, we propose phase-changing metallic spines of various geometries to independently control specific directional stiffness parameters of soft robots, changing how they respond to their actuation inputs and external loads. We fabricate spine-like structures using a low melting point alloy (LMPA), enabling us to switch on and off the effects of the stiff metal structure of the overall robot's stiffness during use. Changing soft robot morphology in this manner will enable these robots to adapt to environments and tasks that require divergent motion and force/moment application capabilities.
more »
« less
This content will become publicly available on May 20, 2026
Informed Repurposing of Quadruped Legs for New Tasks
Redesigning and remanufacturing robots are infeasible for resource-constrained environments like space or undersea. This work thus studies how to evaluate and repurpose existing, complementary, quadruped legs for new tasks. We implement this approach on 15 robot designs generated from combining six pre-selected leg designs. The performance maps for force-based locomotion tasks like pulling, pushing, and carrying objects are constructed via a learned policy that works across all designs and adapts to the limits of each. Performance predictions agree well with real-world validation results. The robot can locomote at 0.5 body lengths per second while exerting a force that is almost 60% of its weight.
more »
« less
- Award ID(s):
- 1944789
- PAR ID:
- 10615227
- Publisher / Repository:
- IEEE
- Date Published:
- Format(s):
- Medium: X
- Location:
- Atlanta, GA
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
This paper will investigate the effects of pennate angle on fluidic artificial muscle (FAM) bundles for a robot arm motion. Rising interest in soft fluidic actuators exists due to their prospective inherent compliance and safe human-robot interaction. The high force-to-weight ratio, innate flexibility, inexpensive construction, and muscle-like force-contraction behavior of McKibben FAMs make them an attractive type of soft fluidic actuator. Multi-unit architectures found in biological muscles tissues and geometric fiber arrangements have inspired the development of hierarchical actuators to enhance the total actuator performance and increase actuator functionality. Parallel, asymmetric unipennate, and symmetric bipennate are three muscle fiber arrangement types found in human skeletal muscle tissues. Unique characteristics of the pennate muscle tissue, with muscle fibers arranged obliquely from the line of muscle motion, enable passive regulation of effective transmission between the fibers and muscle. Prior studies developed an analytical model based on idealized assumptions to leverage this pennate topology in optimal fiber parameter design for FAM bundles under spatial bounds. The findings showed FAMs in the bipennate topology can be designed to amplify the muscle output force, contraction, and stiffness as compared to that of a parallel topology under equivalent spatial and operating constraints. This work seeks to extend upon previous studies by investigating the effects of pennate angle on actuation and system hydraulic efficiency for a robot arm with a more realistic FAM model. The results will progress toward tailoring actuator topology designs for custom compliant actuation applications.more » « less
-
Motivated by a high demand for automated inspection of civil infrastructure, this work presents an efficient design and development of a tank-like robot for structural health monitoring. Unlike most existing magnetic wheeled mobile robot designs, which may be suitable for climbing on flat steel surface, our proposed tank-like robot design uses reciprocating mechanism and roller-chains to make it capable of climbing on different structural shapes (e.g., cylinder, cube) with coated or non-coated steel surfaces. The developed robot is able to pass through the joints and transition from one surface to the other (e.g., from flat to curving surfaces). Taking into account several strict considerations (including tight dimension, efficient adhesion and climbing flexibility) to adapt with various shapes of steel structures, a prototype tank-like robot integrating multiple sensors (hall-effects, sonars, inertial measurement unit, Eddy current and cameras), has been developed. Rigorous analysis of robot kinematics, adhesion force, sliding failure and turn-over failure has been conducted to demonstrate the stability of the proposed design. Mechanical and magnetic force analysis together with sliding/turn-over failure investigation can serve as an useful framework for designing various steel climbing robots in the future. The robot is integrated with cameras and Eddy current sensor for visual and in-depth fatigue crack inspection of steel structures. Experimental results and field deployments confirm the adhesion, climbing, inspection capability of the developed robot.more » « less
-
This paper describes the control, and evaluation of a new human-scaled biped robot with liquid cooled viscoelastic actuators (VLCA). Based on the lessons learned from previous work from our team on VLCA, we present a new system design embodying a Reaction Force Sensing Series Elastic Actuator and a Force Sensing Series Elastic Actuator. These designs are aimed at reducing the size and weight of the robot’s actuation system while inheriting the advantages of our designs such as energy efficiency, torque density, impact resistance and position/force controllability. The robot design takes into consideration human-inspired kinematics and range-of-motion, while relying on foot placement to balance. In terms of actuator control, we perform a stability analysis on a Disturbance Observer designed for force control. We then evaluate various position control algorithms both in the time and frequency domains for our VLCA actuators. Having the low level baseline established, we first perform a controller evaluation on the legs using Operational Space Control. Finally, we move on to evaluating the full bipedal robot by accomplishing unsupported dynamic walking.more » « less
-
Having a well-rounded fixed leg design for a quadruped inevitably limits performance across diverse tasks, while tunability enables specialization and leads to better performance. This paper introduces a sub-500-gram quadruped robot with a rich leg design space. Made with laminate design and fabrication techniques, its legs have a range of tunable design parameters, including leg length, transmission ratio, and passive parallel and series stiffness. The legs are also straightforward to model, low-cost, and fast to manufacture. We propose methods to span the leg’s feasible design space and construct simulation environments for training a locomotion policy with reinforcement learning to remove the need for manual controller design and tuning. This policy not only works across leg designs but also exploits the unique dynamics of each leg for better locomotion. A curation process is employed to select designs given performance goals, which is more interpretable than optimization and provides insights for design improvements and discoveries of design principles. Thanks to the tight integration of design, fabrication, simulation, and control, our proposed pipeline produces leg designs with performance that aligns with the simulation, while the learned locomotion policy can be used successfully on the real robot. The fast longitudinal running design reaches a maximum speed of 0.7 m/s or 5.4 body lengths per second, and the low cost of transport (COT) design has a COT of 0.3.more » « less
