Research
Research Projects:
A Soft Robotic Gripper With Gecko-Inspired Adhesive
Elastomer actuators, compliant mechanisms for robots that are driven by internal fluid pressure, can be used to create robust and versatile grippers. We apply gecko-inspired adhesives, a micron-scale pattern of wedges that mimics the behavior of gecko’s toes, to extend and enhance this versatility. We show that these grippers made from elastomer actuators and gecko-inspired adhesives are capable of high strength grasps, manipulation of large objects, a wider grasp choice, and fast actuation. We present a novel design, modeling, and manufacturing framework for elastomer actuators to take advantage of the gecko-inspired adhesives. Using this modeling approach we can create a fluidic elastomer actuator that conforms to and evenly distributes pressure across a surface. These developments are applicable to industrial automation and we demonstrate the gripper on a robotic arm lifting 25 lbs. The gripper weighs 48.7 g and uses only $7.25 of raw materials.
Glick, P., Suresh, S.A., Ruffatto III, D., Cutkosky, M., Tolley, M.T., Parness, A., (2018) "A soft robotic gripper with gecko-inspired adhesive" IEEE Robotics and Automation Letters, no. 99, pp. 1-1.
Robust capture of unknown objects with a highly under-actuated gripper
Capturing large objects of unknown shape and orientation remains a challenge for most robotic grippers. This problem is especially important for potential satellite servicing missions in space where targets can be large, delicate, and in uncontrolled orbits. Highly under-actuated grippers that can conform to large arbitrarily-shaped objects show promise for this application. However, prior work shows two primary limitations to these highly under-actuated grippers: the grip force of each link tends to decrease as the number of links increases, and the stability of an under-actuated linkage depends on the grasp configuration. In this project we developed a highly under-actuated gripper that addresses these issues. Our approach uses a gecko-inspired adhesive to provide an adhesion-controlled friction that helps stabilize the gripper and improves grasp performance without the need of large normal forces. The under-actuated linkages conform around arbitrary shapes, maintaining performance across disparate target geometries. With these high-friction interfaces, we show highly under-actuated linkages successfully grasp in many configurations without strict stability. The gripper is capable of holding over 30 N and consists of two tendon driven linkages that are each 65 cm long.
More from our collaborators can be found here (https://www-robotics.jpl.nasa.gov/index.cfm , https://neurobionics.engin.umich.edu/)
Related Publications:
Glick P. E., Van Crey N., Tolley M. T., Ruffatto D. (2020), "Robust capture of unknown objects with a highly under-actuated gripper", IEEE International Conference on Robotics and Automation, pp. 3996-4002.
Eversion and Retraction of a Soft Robot Towards the Exploration of Coral Reefs
Coral reefs represent only 1% of the seafloor, but are home to more than 25% of all marine life. Reefs are declining worldwide. Yet, critical information remains unknown about basic biological, ecological, and chemical processes that sustain coral reefs because of the challenges to access their narrow crevices and passageways. A robot that grows through its environment would be well suited to this challenge as there is no relative motion between the exterior of the robot and its surroundings. We design and develop a soft growing robot that operates underwater and take a step towards navigating the complex terrain of a coral reef.
Related Publications:
Luong J.*, Glick P.*, Ong A.*, deVries M. S., Sandin S., Hawkes E. W., Tolley M. T. (2019) "Eversion and Retraction of a Soft Robot Towards the Exploration of Coral Reefs", in IEEE-RAS International Conference on Soft Robotics (RoboSoft), April 2019, pp. 801-807.
Long Duration Surface Anchoring with a Hybrid Electrostatic and Gecko-Inspired Adhesive
Many scenarios require access to locations that are difficult to reach; however, mobile and untethered robots for these applications operate on a limited reserve of energy. Researchers often design robots specifically to be able to wait for periods of time in low-power states, conserving energy and protecting hardware during periods of inactivity. In this work, we introduce a temporary anchor using a low-power hybrid electrostatic/geckoinspired adhesive for robots such as quadrotors and wall-climbing systems to allow access to remote areas while providing the ability to safely hold a position for an extended duration. This work presents a self-contained electrostatic and gecko-inspired adhesive anchor mechanism which is particularly well suited for long duration payload placement. We model the capacity of the device and demonstrate carrying an 11.9 N load applied 12 mm off of a rough drywall surface with an adhesive area of 32 cm2 . Furthermore, to reduce the power consumption of the adhesive we introduce the concept of power-cycling, and reduce power consumption by an order of magnitude while still maintaining over 85 percent adhesion strength.
D. Ruffatto III, P. E. Glick, M. T. Tolley and A. Parness, (2018) "Long Duration Surface Anchoring with a Hybrid Electrostatic and Gecko-Inspired Adhesive" IEEE Robotics and Automation Letters
An electrostatic gripper for flexible objects
We present a gripper designed to controllably grasp and manipulate soft goods in space. The 8-fingered gripper has 50 cm2 of active electrodes operating at 3 kV . The gripper generates electrostatic adhesion forces up to 3.5 N (700 Pa) on Ge-coated polyimide film and 1.2 N (240 P a) on MLI blanket, a film composite used for satellite thermal insulation. Extremely low-force gripper engagement (0.08 N) and release (0.04 N) of films is ideal for micro-gravity. Individual fingers generate shear adhesion forces on the same films up to 4.76 N (5.04 kP a) using electrostatic adhesive and 45.0 N (47.6 kP a) with a hybrid electrostatic / gecko adhesive. To simulate a satellite servicing task, the gripper was mounted on a 7-DoF robot arm and performed a supervised grasp, manipulate, and release sequence on a hanging, Al-coated PET film.
E. W. Schaler, D. Ruffatto, P. Glick, V. White and A. Parness, "An electrostatic gripper for flexible objects" 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Vancouver, BC, 2017, pp. 1172-1179.
The second generation prototype of a Duct Climbing Tensegrity robot, DuCTTv2
Duct exploration and maintenance is a task well suited for small agile robots, which must be capable of navigating complex and irregular systems of ducts. Previously, we presented a tensegrity robot, DuCTT (Duct Climbing Tetrahedral Tensegrity), which demonstrated the plausibility of such a robot for duct exploration but was never able to successfully demonstrate climbing. Here we present DuCTTv2, redesigned from the ground up to address issues with actuator power, cable routing, compliance and synchronized control present in our first prototype. These improvements allow the prototype to be the first tensegrity robot to demonstrate duct climbing, and does so with an average climb speed of 1.4 cm/s. We also demonstrate initial tests of the prototypes ability to bend and translate its two segments relative to one another, which will allow it to navigate T-junctions and sharp corners commonly found in duct systems. Testing of the prototype is conducted to demonstrate the new faster and more robust control of motion, and analysis of dynamic simulations is presented.
J. M. Friesen, P. Glick, M. Fanton, P. Manovi, A. Xydes, T. Bewley, V. Sunspiral "The second generation prototype of a Duct Climbing Tensegrity robot, DuCTTv2" 2016 IEEE International Conference on Robotics and Automation (ICRA), Stockholm, 2016, pp. 2123-2128.
Robust and Efficient Multistage Braking System for Cable Driven Robots
We present a Multistage Braking System (MBS), optimized for the needs of NASA's SUPERball tensegrity robot, which addresses a range of issues common to cable driven robotic drivetrains. The system works to reduce power consumption, provide constant motor protection, and dissipate large but infrequent impact forces. The Spherical Underactuated Planetary Exploration Robot ball (SUPERball) from NASA Ames Research Center's Dynamic Tensegrity Robotics Lab is designed to land at terminal velocity on other planets as tensegrity structures can withstand significant impact shocks. Furthermore, SUPERball may experience subsequent impact events as its mission may include exploring treacherous terrain such as ledges and canyons. However, the drivetrain still must be protected from residual forces reflected into the gearboxes and motors. Thus, SUPERball must balance the ability to withstand occasional but extreme landing forces with efficient and robust locomotion. Using the presented MBS, comprised of a Bi-Directional Self-Locking Clutch (BDSLC) for routine locomotion and a Retractable Jaw Clutch (RJC) for large impact events, SUPERball will be able to traverse previously inaccessible extraterrestrial locations with a lower average power consumption.
M. Fanton, P. Glick, J. Bruce, K. Caluwaerts, J. Friesen, V. Sunspiral, "Robust and Efficient Multistage Braking System for Cable Driven Robots" 2016 International Symposium on Artificial Intelligence, Robotics, and Automation in Space (i-SAIRAS), Beijing.
