A fluidic relaxation oscillator for reprogrammable sequential actuation in soft robots

•A simple, compact elastomeric valve is used to control soft-robotic actuators•Up five actuators are activated in different patterns•The pattern can be changed on the fly by mechanical reprogramming•We demonstrate a four-legged robot that requires nothing but pump walk Soft robotics an emerging research field fueled vision of adaptative behavior unpredictable environments and safe cooperation with humans. robots possess so-called embodied intelligence, for example, soft grippers conform arbitrarily shaped objects. However, higher-level adaptivity remains elusive. To bring this goal step closer reality, we introduce valve. Fluidic circuits our valves transform continuous flow air into timed pulses activate up sequences. We select which sequence executed, excitingly, system switch between sequences response physical cue. real-life applicability controlling walker. As such, work leads way toward fully autonomous interact their environment, triggering drug release inside body or changing gait move past obstacles, without any electronics. Despite exciting developments robotics, systems remain could enable embedded using In work, simple intentional hysteresis, analogous electronic relaxation oscillator. By integrating actuator, inflow cyclic activation. Importantly, show various physically reprogram activation order varying (initial) conditions fluidic circuit. Moreover, feasibility approach under more realistic building robot. Our paves environment behavior, e.g., trigger targeted change obstacles. compliant enough deformed interactions while being stiff perform meaningful action. Prime examples starfish-like wrap around object knowing its shape yet strong lift significant weight.1Bao G. Fang H. Chen L. Wan Y. Xu F. Yang Q. 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The typical use one manually operated motor-controlled syringes14Marchese Tedrake Dynamics trajectory optimization spatial manipulator.Int. Robot Res. 2016; 35: 1000-1019https://doi.org/10.1177/0278364915587926Crossref (131) (electro-)mechanical valves.4Polygerinos Due weight components, they typically not placed robot, tethers needed. Similarly, provide ability externally actuation when Recently, efforts made replace only elements. Making properties actuators, valves, channels, methods point all bodies.15Wehner Truby R.L. Fitzgerald D.J. Lewis J.A. integrated design strategy entirely soft, 536: 451-455https://doi.org/10.1038/nature19100Crossref (1210) Scholar,16Drotman Jadhav Sharp Chan Electronics-free pneumatic soft-legged robots.Sci. 2021; 6: eaay2627https://doi.org/10.1126/SCIROBOTICS.AAY2627Crossref (52) Analogously electronics, identify innovations component level well circuit level, it clear advances both levels needed improve complexity robots. So far, mostly low-level functions demonstrated, where actions triggered supplied time-varying pressure inputs. For sequential has achieved connecting series tubes optimized diameter length.17Vasios Gross A.J. Soifer J.T. Harnessing viscous simplify 2020; 7: 1-9https://doi.org/10.1089/soro.2018.0149Crossref (44) Besides combining components linear response, combination nonmonotonic pressure-volume relation designed actuate given sequence.18Overvelde Kloek D’haen J.J.A. Jonas J.A.D. Amplifying harnessing snap-through instabilities.Proc. U.S.A. 112: 10863-10868https://doi.org/10.1073/pnas.1504947112Crossref (141) Scholar,19Gorissen Milana E. Baeyens Broeders Christiaens Collin Hardware sequencing nonlinear robots.Adv. 2019; 31: 1804598https://doi.org/10.1002/adma.201804598Crossref (33) friction exploited peristaltic motion20Glozman Hassidov Senesh Shoham self-propelled earthworm-like endoscope actuated supply line.IEEE Trans. Biomed. 2010; 57: 1264-1272https://doi.org/10.1109/TBME.2010.2040617Crossref expand number possible state transitions.21Ben-Haim Salem Or Gat Single-input elastic via interaction bistability viscosity.Soft 259-265https://doi.org/10.1089/soro.2019.0060Crossref (14) Another example band-pass let low flows block high flows, allows setting individually time-controlled source.22Napp Araki Nagpal Simple passive addressable actuation.in: Proc. - IEEE Int. Conf. Autom.2014: 1440-1445https://doi.org/10.1109/ICRA.2014.6907041Crossref (31) Finally, following principles from digital transistors arranged states three drive lines23Mahon S.T. Buchoux Sayed M.E. Teng extreme environments: removing control.in: RobotSoft 2019 2019: 782-787https://doi.org/10.1109/ROBOSOFT.2019.8722755Crossref (24) eight outputs inputs.24Bartlett Becker K.P. demultiplexer large arrays actuators.Soft Matter. 16: 5871-5877https://doi.org/10.1039/c9sm02502bCrossref (21) key limitation above-mentioned rely inputs therefore operate. knowledge, there two breakthrough results originate generate signals itself. first three-dimensional (3D)-printed octopus-inspired employs micro-fluidic oscillator25Mosadegh Kuo C.H. Tung Y.C. Torisawa Y.S. Bersano-Begey Tavana Takayama Integrated regulation oscillatory switching microfluidic devices.Nat. Phys. 433-437https://doi.org/10.1038/nphys1637Crossref (216) alternate groups actuators.15Wehner second robot16Drotman uses ring oscillators26Preston Rothemund Jiang H.J. Nemitz M.P. Rawson Suo Digital logic devices.Proc. 116: 7750-7759https://doi.org/10.1073/pnas.1820672116Crossref (94) that, provided constant pressure, cyclical, actuator chambers each.27Drotman Karimi Dezonia 3D printed legged capable navigating unstructured terrain.in: Autom.2017: 5532-5538https://doi.org/10.1109/ICRA.2017.7989652Crossref (119) implements bistable actuator28Rothemund Ainla Belding Preston Kurihara actuators.Sci. eaar7986https://doi.org/10.1126/SCIROBOTICS.AAR7986Crossref (187) circuits.29Preston Sanchez Lee W.K. oscillator.Sci. 1-10https://doi.org/10.1126/scirobotics.aaw5496Crossref (72) applications, programmable moving previous robots, employed oscillators demonstrated maximum degrees freedom each. More importantly, fundamentally support sequence, reprogramming actuators’ “rewiring” system.16Drotman overcome limitations, extremely directly actuators. contrast straightforward fabrication, highly shows harness most basic arrangement forms oscillates air, no external timing required. oscillator cyclically bending behind then connect parallel analyze instability alternating Supported model describes including parallel, experimentally novel limited imperfections due production tolerances, how allowed imperfection scales freedom. repeatedly stimulus. integrate conditions. proposed enables new kinds brings concept realization. With aim start developing transforms pulsatile flow. do so fabricating (Figure 1A ), fluid consists curved membrane contains slits meet at apex. thickness T = 0.75 mm, angle ?=75?, radius a0 2.5 length L mm 1B). These values result ?popen?60kPa, ?pclose?5kPa, Ropen?2kPa/ standard liter per minute (SLPM). fabricated casting (Dragon Skin 20, Smooth-On) 3D-printed mold, after machined laser cutter. It holder create robust, self-contained unit 1B; experimental procedures). exhibits translates hysteresis 1C). Upon applying increasing membrane, will undergo several stages, shown Figure 1D. (1) very pressures, completely closed finite width laser-cut slits, some opening. (2) closes pass (3) reaching critical difference ?popen, snaps inverted state, opening letting through. open acts restriction. (4) decreasing does snap back same point, instead, (5) lower ?pclose. Next, apply Q 1 SLPM measure before, rate through, Interestingly, observe containing outflow (Figures 1E 1G; Video S1). Note repeatable, small deviation 500 cycles overlaid 1H, even dynamics occur during unstable transitions. find valve, cycle frequency tuned range f? 0.3 5 Hz Qin 0.2 4.5 (and 17 minimizing capacitance C0 sensor), S1. higher inflow, stops oscillating open. Details durability obtained performing experiment lasting 10 h S2. eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiJiYWM5NTQ2YjA4YmVkMTAwZmYxYWJmNTE2MDA5NDk4NSIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjcxMzE5Njc2fQ.etILQkZVHwSMCR8L2IOiB26xsk5RnlGqB_NVQ4GtLK45pA2_Cpcg3R91bN8r5WMkoG4ye6Sy_JHOp0SGo0fv4qa1NVw6O7bBtnD-ZqLUZ-oW7ONssUlJheR2yE-9dbA_G2sZ8qOqyH9aa3l_cX-OyUB-wl6X7ivmcq_TAiqUOXEiWHKz298Q7Rb6C4-a4Bv_3stGipxMRhf6HLt14kDdUkkqgobAMrxDN5TogpvPOlbuGB9og8XAh5q7XuxDq3TC0QQDuLa0hYghaRFfEsPoeP9x5WpXvcoBnsUBBN-gzAgGtugcTvrOyy21J2IBkmPfefV_fKJ0ZHByEeqZCPsDkQ Download .mp4 (3.34 MB) Help files hysteretic flowA hysteric outflow. dome-shaped domain. slit opens buckled state. explain analogy fluidics described voltage current30Oh K.W. Ahn Furlani E.P. Design pressure-driven networks electric analogy.Lab Chip. 2012; 515-545https://doi.org/10.1039/c2lc20799kCrossref (449) 1F; Using analogy, voltage-controlled resistance Ropen Rclosed?Ropen (note definition opposite electronics indicates valve), respectively. deformation compressibility contained before capacitor C0. provides energy storage required oscillate. simulate current source. oscillator, characterized periodic, relatively slow fast pressure. effect witnessed Pearson-Anson oscillator,31Pearson S.O. Anson H.S.G. neon tube means producing intermittent currents.Proc. Soc. Lond. 1921; 34: 204-212https://doi.org/10.1088/1478-7814/34/1/341Crossref (17) hysteresis. explains why rates, caused drag force prevents snapping back. (current source, capacitor, switch) accurately capture system, seen 1G comparison experiments. here, always circuits, fixed volume air. using, water, although case chamber capacitance. should note simulations, did dynamic effects visible Figures 1H closing. affect descriptive power since effective time sufficiently separated. couple 2A ; S2). fabricate modified PneuNet based was previously robot,2Tolley Scholar,32Ilievski chemists.Angew. Chem. Ed. 50: 1890-1895https://doi.org/10.1002/anie.201006464Crossref (858) limit amount inflate actuator33Mosadegh Polygerinos Keplinger Wennstedt Gupta U. Shim Pneumatic rapidly.Adv. Funct. 24: 2163-2170https://doi.org/10.1002/adfm.201303288Crossref (938) S3). clamp hold place inflow. port tube. furthermore front able vary compressed prior each (C0) add needles act restriction (R) reduce leaves vented atmosphere 2A). eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiIwZTkwMzg2NGVlODdhZjgzYzI1ZGQ3MmE4YjdiNDI4YSIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjcxMzE5Njc2fQ.NnYTM1NhmHqPu9_aBzgdXp7C_hmoS2v4kcWkxNPGWlnpk4zv2VAUYl8LmmPuOvIt8BXmf8eXl8TdoSSrq4AQXn-b5EMTeu3ORF8A3LOeL70J00jvz2YSGq-_OLNdMJKVLKwkXhN1Tqs_gd5XDP0qc7X6OmBzWcYkxxqybJ1plyJxfldJPhI5Kene_1CkQZ4mIsKoClF5E3dQLDCANTW_p3P7ABEz2DHKqJIpKmnxPVamBDKVscH5HkDyKcQGVzSZNNfkEFx4Nc----KzhO1JJmudHAv1SwINiOo8dg5dMTglfV1J5CVEiKm63FC4wcmZ_03HeLgqWNhjfV2c3HM1vA (4.02 Cyclic actuatorDifferent combinations C0/Cact R/Ropen pact,max?20kPa. determine parameters desired profile (i.e., minimum frequency), numerical study considering equivalent schematic 2B (experimental Given (nonlinear) S3) still choose (Qin), size (C0), (R). 2C resulting f (normalized initial Cact,0) R Ropen) SLPM. analysis S4 rates. tune activation, lead pressurization. illustrate this, consider parameter pact,max 20 kPa, indicated line 2C. value cause excessive fatigue. Along line, regimes. At C0), deflation occurs rapidly inflation chamber, empties again. Therefore, zero part 2D, 3). contrast, initially faster actuator. equilibrium pact,min>0, longer goes undeformed 1). boundary regimes, deflating cycle. dashed approximates pact,max, set equal pact,min kPa. now unique {C0/Cact,0,R/Ropen} kPa 2). locomotion. if contain next focus simultaneous them val