Research ArticleSOFT ROBOTS

New soft robots really suck: Vacuum-powered systems empower diverse capabilities

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Science Robotics  30 Aug 2017:
Vol. 2, Issue 9, eaan6357
DOI: 10.1126/scirobotics.aan6357
  • Fig. 1 V-SPAs blend multiple material and operational domains for diverse potential applications.

    Existing work explored the use of vacuum and foam materials separately for the development of soft robotic systems to leverage the unique attributes of robustness, safety, and manufacturability offered by different fabrication and actuation methods. This work explores a new approach that leverages foam and vacuum power simultaneously with an actuator called the V-SPA to take advantage of a new construction technique that enables rapid production of soft robotic systems using minimal resources and opens the possibility for fully vacuum-powered systems that enable soft robots with expanded capabilities.

  • Fig. 2 V-SPA Module step response characterization.

    Three V-SPAs were characterized with a step input while measuring the angular response with an inertial measurement unit (IMU). The average (red curve) step response at maximum vacuum with no load is shown in (A), and the step-down profile is shown in (B). A single SD is also shown in light gray shading, for 30 cycles (10 cycles for each of three actuators) comprising the average response. The metrics found from the average step response for variable loads are shown in (C) and variable pressure in (D), and the trends were plotted with a third-order polynomial fit.

  • Fig. 3 Architecture of V-SPA Module and integrated soft modular device network.

    (A) Each module contains three main components: actuators (V-SPA), control valves, and electronics. (B) Each actuator in the module is paired to a valve and dedicated channel of a communication IC. A common pneumatic supply line provides fluid power to every module simultaneously, whereas a common electrical bus similarly provides electrical power. (C) Control commands are assembled into data packets by a main controller and relayed by the IC through each module connected in series. Each module has three independent channels (X, Y, and Z) that can be addressed to control up to three embedded valves in open loop.

  • Fig. 4 Versatility of vacuum-powered soft hyper-redundant robot.

    The workspace and repeatability of the five-module soft hyper-redundant robot is depicted in (A) along with a depiction of the maximum reach for up to nine modules. To measure the range of motion along three primary directions determined by the actuators in each module, three markers were placed on the top of the distal module, and a centroid was calculated to track the center of the module as the robot end point. A top view of the distal module centroid 3D trajectory is shown through a 10-cycle repeatability test. A variety of module types shown in (B) can be readily integrated with the hyper-redundant robot. The configurations in (C) combining various modules are all validated experimentally in subsequent sections.

  • Fig. 5 Diverse locomotion modes of modular continuum robot.

    A series of frames captured from video is shown for each of the four different gait modes: wave gait with five V-SPA Modules (A), wave gait with three V-SPA Modules (B), rolling gait (C), and vertical climbing with suction cup modules (D).

  • Fig. 6 Granular cellular matrix jamming enables active stiffness tuning of vacuum-driven soft structures.

    (A) The addition of a jamming module enables stiffening of a continuum robot composed of three V-SPA Modules. The stiffness was measured using a vertical material testing machine, configured with a grounded pulley to redirect vertical motion of a cable to the horizontal direction. Tensile force and displacement measured in the vertical direction were thereby mapped to the direction perpendicular to the initially vertical axis of the actuator structure. (B) The cable was attached at the top of the distal module, and the assembly was rotated in increments of 60° to six total positions for measurements in multiple radial directions, with five loading cycles performed in each position. The measured stiffness shown in (C) increased in every direction when the jamming module was activated, in comparison with its inactive state. Error bars represent 1 SD.

  • Fig. 7 Fabrication of V-SPAs.

    A four-step process is shown for V-SPA fabrication. (1) Foam core shapes and paper divider plates were cut using a computer numerical control (CNC) CO2 laser. (2) Actuator cores and dividers were assembled on a mounting post of a preform structure using cyanoacrylate gel. (3) Two coats of silicone rubber were applied to the outer surface of the foam core assembly, including the space between the bottom foam and base plate. A vent hole is included through the mounting post and base plate to reduce the formation of bubbles caused by expanding internal air in the foam core when a heating oven is used to speed curing. Layer cure was allowed between coats. (4) The actuator was removed from the preform using a razor to separate the attached foam and finally glued to a vacuum distribution manifold.

  • Table 1 Physical properties and performance of V-SPA Module.

    Performance metrics were estimated from an angular displacement step response test recorded relative to gravity using an IMU fixed to the upper stage of the module and with 86.2% vacuum supply.

    PropertiesValueUnit
    Size (D × H)45 × 45(mm)
    Total module weight45.0(g)
      V-SPAs (×3)11.1(g)
      Solenoid valves (×3)12.0(g)
      PCBs8.5(g)
      Acrylic and epoxy
    layers
    8.5(g)
      Central conduit
    (tubes, connectors,
    wires)
    4.9(g)
    Blocked torque166.9(N∙mm)
    Specific torque
    (relative to actuator
    mass)
    45.1(N∙mm/g)
    Angular velocity, ω (no
    load)
    3.5(°/s)
    Step rise time, tr1.5(s)
    Step decay time, td2.4(s)
    Bandwidth0.2(Hz)
    Maximum angular
    stroke, α (no load)
    27.3(°)
    Specific power (relative
    to actuator mass)
    5.0(W/kg)
    Specific energy
    (relative to actuator
    mass)
    1.2(J/kg)

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/2/9/eaan6357/DC1

    Fig. S1. Anatomy of a V-SPA.

    Fig. S2. Fabrication and testing of jamming module.

    Fig. S3. Single wire module networking with serial LED driver IC.

    Movie S1. Binary control of 3-DoF V-SPA array without modular interface.

    Movie S2. Binary workspace of V-SPA Module.

    Movie S3. Continuum robot repeatability test.

    Movie S4. Vacuum suction manipulation with continuum robot.

    Movie S5. Vacuum suction climbing with payload.

    Movie S6. Vacuum robot locomotion.

    Reference (51)

  • Supplementary Materials

    Supplementary Material for:

    New soft robots really suck: Vacuum-powered systems empower diverse capabilities

    Matthew A. Robertson and Jamie Paik*

    *Corresponding author. Email: jamie.paik{at}epfl.ch

    Published 30 August 2017, Sci. Robot. 2, eaan6357 (2017)
    DOI: 10.1126/scirobotics.aan6357

    This PDF file includes:

    • Fig. S1. Anatomy of a V-SPA.
    • Fig. S2. Fabrication and testing of jamming module.
    • Fig. S3. Single wire module networking with serial LED driver IC.
    • Legends for movies S1 to S6
    • Reference (51)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Binary control of 3-DoF V-SPA array without modular interface.
    • Movie S2 (.mp4 format). Binary workspace of V-SPA Module.
    • Movie S3 (.mp4 format). Continuum robot repeatability test.
    • Movie S4 (.mp4 format). Vacuum suction manipulation with continuum robot.
    • Movie S5 (.mp4 format). Vacuum suction climbing with payload.
    • Movie S6 (.mp4 format). Vacuum robot locomotion.

    Files in this Data Supplement:

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