Acoustic transmission, or sound, can effectively communicate information over distances through various media. We focus on generating acoustic transmission using pneumatically driven resonators for wireless tactile sensing without the need for any electronics at the end-effector or contact point. We explore the relationship between emitted frequency and the geometry of the resonance chamber. When a normal compressive force is applied to the end cap, the compliant resonant cavity deforms, leading to an increase in frequency measurable by an external microphone. Prior work uses tube resonators with fipple attachments. In the present work, we study whether a different smaller audible cylindrical resonator with air blown across the entryway can be utilized instead. We test the utility of the Helmholtz resonator model in predicting the experimental frequency response. Resonance is often modeled for rigid cavities, presenting unique challenges in predicting resonance for the design of soft resonating taxels.

Sandy environments present challenges for robotic space rovers and systems due to reduced traction, limiting mobility and tugging force. This paper presents an anchoring method that utilizes a winching system to create a sand mound in front of a mobile agent dragged through the media. The proposed controller is designed to consistently achieve realtime capture of close-to-maximal lateral sand mound resistive force, even when applied to varied uneven terrains, like holes or waves. Notably, tugging is non-reversible, so suitable peaks should be captured before breakdown and without necessarily knowing the global optimum a priori. The controller logic tracks both tugging force and agent pitch gradients to detect terrain conditions and peak force trends. Results show that the controller captures an average 92 % of the maximum forces, within the previously winched workspace tested, across three different granular media with four varying structured terrain features. The controller achieves higher resistive force peaks on terrains with geometric features, as opposed to flat sand. We conclude that sand mounding through tugging is a viable means to generate robotic resistive forces for unknown sandy terrains, a simple yet effective anchoring mechanism.

The disposal of waste electrical and electronic equipment (WEEE) presents a sustainability challenge, particularly for waste printed circuit boards (PCBs). PCBs are challenging to sort out from other waste materials in part because traditional industrial end-effectors struggle to reliably grip these irregularly shaped objects with unmodeled surface-mounted components. Vision-based separators, while effective for object categorization, face challenges with identifying precise grasp points on PCB surfaces. This paper studies regrasping control to enhance suction cup grasping performance on PCBs, addressing issues arising from uneven surfaces and intricate features that interfere with suction sealing. We categorize PCBs into two recycling levels – with large surface features intact or removed – and conduct experiments on both stationary and conveyor belt setups with realistic vision-based grasp planners. Results show that jumping regrasping improves pick-and-place success rate. Haptically driven jumping – using the Smart Suction Cup – is especially useful for unprocessed waste PCBs with large surface mount parts. The proposed method offers a promising solution to enhance the efficiency and reliability of robotic grasping in recycling applications.

Squirrels exhibit agile leaping between tree branches, often using non-prehensile gripping with compliant and passively adaptive fingers. We aim to test the utility of such gripping in agile robotic maneuvering. In the present study, we first examine the parametric design of a squirrel-inspired underactuated gripper for passive landing on impact. We fix the geometry of the gripper and vary the joint stiffness and contact conditions. We find that stiffer fingers with soft foam pads enlarge the landing sufficiency region. Specifically, friction appears to enlarge horizontal error tolerance, while joint stiffness and pad damping allow for higher impact speeds. Thus, these features should be considered in the design of future agile robot hands and feet that include high impact landings on rods with pose inaccuracy.

The Smart Suction Cup is a tactile sensing and gripping system designed to enhance pick-and-place operations in industrial settings. While previous research has primarily focused on utilizing this technology for haptic search in cases of initial grasp failure, this study introduces a novel application: following contours. This function is already established as an important function for object recognition and grasp planning – substantiated by numerous works using other tactile sensors. Here, we explore contour following for a flow-based tactile sensor because it is not susceptible to visual occlusions nor tactile sensor wear. Experimental validation demonstrates the Smart Suction Cup’s ability to track edges at different speeds and navigate various planar contours, showcasing rapid and robust tracking of edges. Notably, the Smart Suction Cup can reliably operate at a speed of 3 cm/s. This is one step towards the adoption of the Smart Suction Cup for real-world applications.

Suction cups are an important gripper type in industrial robot applications, and the prior literature focuses on using vision-based planners to improve grasping success in these tasks. Vision-based planners can fail due to adversarial objects or lose generalizability for unseen scenarios, without retraining learned algorithms. In this article, we propose haptic exploration to improve suction cup grasping when visual grasp planners fail. We present the smart suction cup, an end effector that utilizes internal flow measurements for tactile sensing. We show that model-based haptic search methods, guided by these flow measurements, improve grasping success by up to 2.5× as compared with using only a vision planner during a bin-picking task. In characterizing the smart suction cup on both geometric edges and curves, we find that flow rate can accurately predict the ideal motion direction even with large postural errors. The smart suction cup includes no electronics on the cup itself, such that the design is easy to fabricate and haptic exploration does not damage the sensor. This work motivates the use of suction cups with autonomous haptic search capabilities in especially adversarial scenarios.

We present SunBot, a robotic system for the study and implementation of fish-inspired tearing manipulations. Various fish species–such as the sunburst butterflyfish-feed on prey fixed to substrates, a maneuver previously not demonstrated by robotic fish which typically specialize for open water swimming and surveillance. Biological studies indicate that a dynamic “head flick” behavior may play a role in tearing off soft prey during such feeding. In this work, we study whether the robotic tail is an effective means to generate such head motions for ungrounded tearing manipulations in water. We describe the function of SunBot and compare the forces that it applies to a fixed prey in the lab while varying tail speeds and ranges of motion. A simplified dynamic template model for the tail-driven head flick maneuver matches peak force magnitudes from experiments, indicating that inertial effects of the fish's body play a substantial role. Finally, we demonstrate a tearing scenario and evaluate a free-swimming trial of SunBot – this is important to show that the actuator that enables swimming also provides the new dual purpose of forceful tearing manipulation.

Wrist-driven orthotics have been designed to assist people with C6-7 spinal cord injury, however, the kinematic constraint imposed by such a control strategy can impede mobility and lead to abnormal body motion. This study characterizes body compensation using the novel Tenodesis Grasp Emulator, an adaptor orthotic that allows for the investigation of tenodesis grasping in subjects with unimpaired hand function. Subjects perform a series of grasp-and-release tasks in order to compare normal (test control) and constrained wrist-driven modes, showing significant compensation as a result of the constraint. A motor-augmented mode is also compared against traditional wrist-driven operation, to explore the potential role of hybrid human-robot control. We find that both the passive wrist-driven and motor-augmented modes fulfill different roles throughout various tasks tested. Thus, we conclude that a flexible control scheme that can alter intervention based on the task at hand holds the potential to reduce compensation in future work.

Despite significant progress in the realm of upper-limb prosthetic design, end-users still abandon modern myoelectric prostheses, with haptic feedback listed as a primary need. The passive scheme of cable-driven body-powered prostheses provides kinesthetic sensory information to the user but can also lead to discomfort and fatigue due to the large loads applied to the body during operation. In order to investigate the role of this kinesthetic feedback on grasp force control, we design a body-powered prosthesis emulator capable of varying the amount of displayed force feedback along a continuous scale. Using this experimental test bed, we collect data from 9 participants while they perform a grasp and lift task. Analysis shows that, with increasing amounts of force feedback, people produce lower and steadier grasp forces but also become more prone to dropping held objects. These results suggest that the use of moderate amounts of feedback provides significant grasp performance benefits while also mitigating some of the shortcomings of cable-driven prostheses. These findings support the continued study of the incorporation of kinesthetic feedback into novel prosthetic designs.

The Dorsal Grasper, an assistive wearable grasping device, incorporates supernumerary fingers and an artificial palm with the forearm and back of the hand, respectively. It enables power wrap grasping and adduction pinching with its V-shaped soft fingers. Designed with C6/C7 spinal cord injury in mind, it takes advantage of active wrist extension that remains in this population after injury. We propose that allowing the operator to actively participate in applying grasp forces on the object, using the back of the hand, enables intuitive, fast and reliable grasping relevant for the execution of activities of daily living. Functional grasping is tested in three normative subjects and a person with C6 SCI using the Grasp and Release Test. Results indicate that this device provides promising performance on a subset of objects that complements the existing compensatory strategies used by people with C6/C7 SCI. We find that the addition of the artificial palm is important for increasing maximum grip strength, by increasing contact friction and protecting the opisthenar.

We present a novel robot end-effector for gripping and haptic exploration. Tactile sensing through suction flow monitoring is achieved with a new suction cup design that contains multiple chambers for air flow. Each chamber connects with its own remote pressure transducer, which enables both absolute and differential pressure measures between chambers. By changing the overall vacuum applied to this smart suction cup, it can perform different functions such as gentle haptic exploration (low pressure) and monitoring breaks in the seal during strong astrictive gripping (high pressure). Haptic exploration of surfaces through sliding and palpation can guide the selection of suction grasp locations and help to identify the local surface geometry. During suction gripping, a trained LSTM network can localize breaks in the suction seal between four quadrants with up to 97% accuracy and detects breaks in the suction seal early enough to avoid total grasp failure.

The ocean is a harsh and unstructured environment for robotic systems; high ambient pressures, saltwater corrosion and low-light conditions demand machines with robust electrical and mechanical parts that are able to sense and respond to the environment. Prior work shows that the addition of gentle suction flow to the hands of underwater robots can aid in the handling of objects during mobile manipulation tasks. The current paper explores using this suction flow mechanism as a new modality for tactile sensing; by monitoring orifice occlusion we can get a sense of how objects make contact in the hand. The electronics required for this sensor can be located remotely from the hand and the signal is insensitive to large changes in ambient pressure associated with diving depth. In this study, suction is applied to the fingertips of a two-fingered compliant gripper and suction-based tactile sensing is monitored while an object is pulled out of a pinch grasp. As a proof of concept, a recurrent neural network model was trained to predict external force trends using only the suction signals. This tactile sensing modality holds the potential to enable automated robotic behaviors or to provide operators of remotely operated vehicles with additional feedback in a robust fashion suitable for ocean deployment.

Gentle suction flow at the fingertips of a compliant hand can enhance object acquisition and increase the robustness of pinch grasps under water. The approach adds a low-pressure pump and flexible tubes that terminate at the distal phalanges. The light flow rate does not create a powerful suction force, nor does it stir up significant sediment. The method works on porous and rough objects in addition to smooth objects as it does not require forming a seal. It changes contact conditions - normal force and coefficient of friction - and enlarges the acquisition region when grasping free objects under water. A simple hydrodynamic model matches empirical force measurements adequately for incorporation in a dynamic simulation to explore the effects of flow rate and object mass. Simulations and experiments show that effects of fingertip suction flow are most pronounced for acquiring objects on the order of 1 kg or less and when pinching large objects. Gentle suction flow is an effective, versatile, and convenient addition for robots that must grasp and manipulate objects under water.

Pinching is an important capability for mobile robots handling small items or tools. Successful pinching requires force-closure and, in underwater applications, gentle suction flow at the fingertips can dramatically improve the handling of light objects by counteracting the negative effects of water lubrication and enhancing friction. In addition, monitoring the flow gives a measure of suction-engagement and can act as a binary tactile sensor. Although a suction system adds complexity, elastic tubes can double as passive spring elements for desired finger kinematics.

Fingertip suction is investigated using a compliant, underactuated, tendon-driven hand designed for underwater mobile manipulation. Tendon routing and joint stiffnesses are designed to provide ease of closure while maintaining finger rigidity, allowing the hand to pinch small objects, as well as secure large objects, without diminishing strength. While the hand is designed to grasp a range of objects, the addition of light suction flow to the fingertips is especially effective for small, low-friction (slippery) objects. Numerical simulations confirm that changing suction parameters can increase the object acquisition region, providing guidelines for future versions of the hand.