Shiquan Wang

Ocean One: A Robotic Avatar for Oceanic Discovery

The promise of oceanic discovery has long intrigued scientists and explorers, whether with the idea of studying underwater ecology and climate change or with the hope of uncovering natural resources and historic secrets buried deep in archaeological sites. This quest to explore the oceans requires skilled human access, yet much of the oceans are inaccessible to human divers; nearly ninetenths of the ocean floor is at 1 km or deeper [1]. Accessing these depths is imperative since factors such as pollution and deep-sea trawling threaten ecology and archaeological sites. While remotely operated vehicles (ROVs) are inadequate for the task, a robotic avatar could go where humans cannot and still embody human intelligence and intentions through immersive interfaces.

A compliant underactuated hand with suction flow for underwater mobile manipulation

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.

A robotic device using gecko-inspired adhesives can grasp and manipulate large objects in microgravity

A load-sharing robotic device can grasp, manipulate, and release objects in microgravity using space-qualified dry adhesives. Grasping and manipulating uncooperative objects in space is an emerging challenge for robotic systems. Many traditional robotic grasping techniques used on Earth are infeasible in space. Vacuum grippers require an atmosphere, sticky attachments fail in the harsh environment of space, and handlike opposed grippers are not suited for large, smooth space debris. We present a robotic gripper that can gently grasp, manipulate, and release both flat and curved uncooperative objects as large as a meter in diameter while in microgravity. This is enabled by (i) space-qualified gecko-inspired dry adhesives that are selectively turned on and off by the application of shear forces, (ii) a load-sharing system that scales small patches of these adhesives to large areas, and (iii) a nonlinear passive wrist that is stiff during manipulation yet compliant when overloaded. We also introduce and experimentally verify a model for determining the force and moment limits of such an adhesive system. Tests in microgravity show that robotic grippers based on dry adhesion are a viable option for eliminating space debris in low Earth orbit and for enhancing missions in space.

A palm for a rock climbing robot based on dense arrays of micro-spines

We present a new palm design that features a dense array of micro-spines for the JPL Robosimian human-scale climbing robot. A linearly-constrained spine mechanism is introduced and analyzed using adhesion and stiffness models. This mechanism achieves a spine density of 19/cm2 and a mean adhesion of 67N (207kPa) on coarse concrete surfaces. The models are validated on two different surfaces with two sets of experiments. A 120×100mm palm consisting of 12 spine tiles and a pulley differential system for load sharing are designed and tested on 9 different surfaces. The mean shear adhesion goes up to 710N (183kPa) on concrete blocks. Design considerations include scaling efficiency and maximal single-spine force. Desirable properties for load sharing in the palm design are discussed.

The Ocean One hands: An adaptive design for robust marine manipulation:

Underactuated, compliant, tendon-driven robotic hands are suited for deep-sea exploration. The robust Ocean One hand design utilizes elastic finger joints and a spring transmission to achieve a variety of pinch and wrap grasps. Compliance in the fingers and transmission determines the degree of load-sharing among contacts and the hands’ ability to secure irregularly shaped objects. However, it can also decrease external grasp stiffness and acquisition reliability. SimGrasp, a flexible dynamic hand simulator, enables parametric studies of the hand for acquisition and pull-out tests with varying transmission spring rates. In the present application, we take advantage of achieving different stiffnesses by reversing the direction of tendon windup using a torsional spring-loaded winch. With this provision, the hand can be relatively soft for handling delicate objects and stiff for tasks requiring strength. Two hands were field-tested as part of the Ocean One humanoid platform, which acquired a vase from the La Lune shipwreck site at a 91 m depth in the Mediterranean Sea.

Design and modeling of linearly-constrained compliant spines for human-scale locomotion on rocky surfaces

We present a new spine solution for the locomotion of human-scale robots on steep, rocky surfaces, known as linearly-constrained spines. The spine stiffness is low in the normal direction but high with respect to lateral and bending loads. The solution differs from previous spine arrays used for small robots in having a much higher spine density and less spine scraping over asperities. We present theoretical and empirical results to demonstrate that this solution is capable of shear stresses of over 200kPa, enabling human-scale robots to apply forces parallel to steep rock surfaces for climbing, bracing, etc. The analysis includes the effects of spine geometry, stiffness, backlash and three-dimensional loading angle to predict the overall forces possible in three dimensions of both single and opposed configurations of spine arrays. Demonstrated applications include a gripper for a “smart staff” aimed at helping humanoid robots to negotiate steep terrain and a palm that provides over 700N in shear for the RoboSimian quadruped.

SupraPeds: Smart staff design and terrain characterization

We present a light, actuated smart staff with 5DOF tip force sensing which can be used by a humanoid robot operating in challenging terrain. The staff has an extension mechanism that employs mechanical multiplexing to achieve a high extension ratio in a stiff and compact package. The tip force sensor uses two metal diaphragms to achieve decoupling of axial and radial forces and the ability to tune the maximum range of forces in each direction independently. With the force sensor, the robot can characterize the coefficient of friction and orientation of a surface with simple motion primitives. Two sets of experiments were conducted with the smart staff manipulated by a 7 DOF robot arm. Using the sensor, the robot was able to determine the orientations of sloped surfaces within two degrees in two orthogonal directions.

Suction helps in a pinch: Improving underwater manipulation with gentle suction flow

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.

Stochastic models of compliant spine arrays for rough surface grasping

This paper presents models of arrays of compliantly supported spines that attach to rough surfaces. The applications include climbing and perching robots. Surfaces are characterized in terms of asperity distributions, which lead to stochastic models of spine force capabilities over a range of loading directions. Models cover unidirectional spine arrays and pairs of opposed arrays that withstand normal forces pulling away from a surface. Experiments on a variety of surfaces confirm the predicted behavior. For opposed spine arrays, the overall load capability also depends on the preloading strategy for applying internal forces. Insights from the analysis guide the design of spine array mechanisms to allow, for example, a small aerial platform to attach to walls and ceilings.

Bioinspired Grippers for Natural Curved Surface Perching

Perching and climbing as animals do is useful to aerial robots for extending mission life and for interacting with the physical world because flight is energetically costly. This paper presents the design and modeling of a claw or spine based gripper for perching on rough, curved surfaces. Drawing inspiration from the opposed grip techniques found in animals, we focus on the design considerations associated with surface geometry and preload. A model elucidates the relationship between these variables, and a mechanism demonstrates the effectiveness of the opposed grip technique.