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Often, fluidic soft robots are driven by large pneumatic or low-bandwidth hydraulic systems which struggle to meet performance objectives. This research presents the design of two morphologies of compact, positive displacement hydraulic pumps designed to act as power supplies for fluidic soft robots. These hydraulic pumps were designed to leverage additive manufacturing technology, creating cost-effective, yet volumetrically powerful units. The operational bandwidth of these pumps (> 10Hz) was substantially higher than the natural frequency of most elastomer-based soft robots (1–5Hz), allowing high control authority.

These designs allow for highly scalable pumps, with performance documented in the paper. Due to the 3D printed nature of the pump components, manufacture cost is greatly reduced when compared to machined components. Each was tested driving various soft robotic actuators, demonstrating high-bandwidth, yet precise operation.

With their minimal size, these pumps are candidates for un-tethered mobile soft robots, and their low weight and low noise allows them to be carried on the body for robotic actuators used in mobility rehabilitation.

 

Snakes and their bio-inspired robot counterparts have demonstrated locomotion on a wide range of terrains. However, dynamic vertical climbing is one locomotion strategy that has received little attention in the existing snake robotics literature. We demonstrate a new scansorial gait and robot inspired by the locomotion of the Pacific lamprey. This new gait allows a robot to steer while climbing on flat, near-vertical surfaces. A reduced-order model is developed and used to explore the relationship between body actuation and the vertical and lateral motions of the robot. Trident, the new wall climbing lamprey-inspired robot, demonstrates dynamic climbing on a flat near vertical carpeted wall with a peak net vertical stride displacement of 4.1 cm per step. Actuating at 1.3 Hz, Trident attains a vertical climbing speed of 4.8 cm s⁻¹(0.09 Bl s⁻¹) at specific resistance of 8.3. Trident can also traverse laterally at 9 cm s⁻¹(0.17 Bl s⁻¹). Moreover, Trident is able to make 14% longer strides than the Pacific lamprey when climbing vertically. The computational and experimental results demonstrate that a lamprey-inspired climbing gait coupled with appropriate attachment is a useful climbing strategy for snake robots climbing near vertical surfaces with limited push points.

 

The gaits of undulating animals arise from a complex interaction of their central nervous system, muscle, connective tissue, bone, and environment. As a simplifying assumption, many previous studies have often assumed that sufficient internal force is available to produce observed kinematics, thus not focusing on quantifying the interconnection between muscle effort, body shape, and external reaction forces. This interplay, however, is critical to locomotion performance in crawling animals, especially when accompanied by body viscoelasticity. Moreover, in bioinspired robotic applications, the body's internal damping is indeed a parameter that the designer can tune. Still, the effect of internal damping is not well understood. This study explores how internal damping affects the locomotion performance of a crawler with a continuous, viscoelastic, nonlinear beam model. Crawler muscle actuation is modeled as a traveling wave of bending moment propagating posteriorly along the body. Consistent with the friction properties of the scales of snakes and limbless lizards, environmental forces are modeled using anisotropic Coulomb friction. It is found that by varying the crawler body's internal damping, the crawler's performance can be altered, and distinct gaits could be achieved, including changing the net locomotion direction from forward to back. We will discuss this forward and backward control and identify the optimal internal damping for peak crawling speed. 

Here, we present a multimodal, lamprey-inspired, 3D printed soft fluidic robot/actuator based on an antagonistic pneunet architecture. The Pacific Lamprey is a unique fish which is able to climb wetted vertical surfaces using its suction-cup mouth and snake-like morphology. The continuum structure of these fish lends itself to soft robots, given their ability to form continuous bends. Additionally, the high gravimetric and volumetric power density attainable by soft actuators make them good candidates for climbing robots. Fluidic soft robots are often limited in the forces they can exert due to limitations on their actuation pressure. This actuator is able to operate at relatively high pressures (for soft robots) of 756 kPa (95 psig) with a −3 dB bandwidth of 2.23 Hz to climb at rates exceeding 18 cm/s. The robot is capable of progression on a vertical surface using a compliant microspine attachment as the functional equivalent of the lamprey’s more complex suction-cup mouth. The paper also presents the details of the 3D-printed manufacturing of this actuator/robot. 

Underactuation is a core challenge associated with controlling soft and continuum robots, which possess theoretically infinite degrees of freedom, but few actuators. However, m actuators may still be used to control a dynamic soft robot in an m-dimensional output task space. In this paper we develop a task-space control approach for planar continuum robots that is robust to modeling error and requires very little sensor information. The controller is based on a highly underactuated discrete rod mechanics model in maximal coordinates and does not require conversion to a classical robot dynamics model form. This promotes straightforward control design, implementation and efficiency. We perform input-output feedback linearization on this model, apply sliding mode control to increase robustness, and formulate an observer to estimate the full state from sparse output measurements. Simulation results show exact task-space reference tracking behavior can be achieved even in the presence of significant modeling error, inaccurate initial conditions, and output-only sensing. 

In this paper we present swimming and modeling for Trident, a three-link lamprey-inspired robot that is able to climb on flat smooth walls. We explore two gaits proposed to work for linear swimming, and three gaits for turning maneuvers. We compare the experimental results obtained from these swimming experiments with two different reduced order fluid interaction models, one a previously published potential flow model, and the other a slender cylinder model we developed. We find that depending on the the parameters of swimming chosen, we are able to move forward, backward and sideways with a peak speed of 2.5 cm/s. We identify the conditions when these models apply and aspects that will require additional complexity.