28 Mar 2017
2:30 pm – 4:30 pm
Talks: By Professor Fumiya Iida & By Professor Robert J. Full
EPFL, Lausanne Suisse
|Talks: Model-free design optimization of soft robots: Any hope? By Professor Fumiya Iida (Cambridge Univ.), (14:30 – 15:30). BioMotion Science: Leapin’ Lizards, Compressed Cockroaches and Smart Squirrels Inspire Robots By...|
30 Sep – 7 Jan 2016
|The origami robot Tribot from Paik lab is currently at the exhibition in +Ultra Knowledge & Gestaltung in Berlin|
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With the ongoing rise of soft robots there emerges a need for new soft robotic technologies that can cope with hyper-flexibility and stretchability. In this paper, we describe our developments on enabling controllable adhesion, namely electroadhesion, for the use in soft robots. We present a method to manufacture stretchable electroadhesive pads and characterize their performance when stretching the pad more than double its original length. Our results suggest that the normal detachment force per area slightly decreases with the stretching, while the shear detachment force per area increase with the stretch ratio. These results imply that stretchable electroadhesive pads have higher adaptivity to a given task compared to non-stretchable pads, because the stretchable pads are adaptable in terms of their mechanical stiffness as well as their adhesive force.
A novel variable stiffness actuator composed of a dielectric elastomer actuator (DEA) and a low-melting-point-alloy (LMPA) embedded silicone substrate is demonstrated. The device which we call variable stiffness dielectric elastomer actuator (VSDEA) enables functional soft robots with a simplified structure, where the DEA generates a bending actuation and the LMPA provides controllable stiffness between soft and rigid states by Joule heating. The entire structure of VSDEA is made of soft silicones with an elastic modulus of less than 1 MPa providing a high compliance when the LMPA is active. The device has the dimension of 40 mm length × 10 mm width × 1 mm thickness, with mass of 1 g. We characterize VSDEA in terms of the actuation stroke angle, the blocked force, and the reaction force against a forced displacement. The results show the controllable actuation angle and the blocked force up to 23.7 ° and 2.4 mN in the soft state, and 0.6 ° and 2.1 mN in the rigid state. Compared to an actuator without the LMPA, VSDEA exhibits 90× higher rigidity. We develop a VSDEA gripper where the mass of active parts is 2 g, which is able to successfully hold an object mass of 11 g, exhibiting the high performance of the actuator.
Materials with controllable stiffness are of great interest to many fields, including medicine and robotics. In this paper we develop a new type of variable stiffness material based on the combination of a rigid low-melting-point-alloy (LMPA) microstructure embedded in soft poly(dimethylsiloxane) (PDMS). This material can transition between rigid and soft states by controlling the phase of the LMPA through efficient, direct Joule-heating of the LMPA microstructure. The devices tested demonstrate a relative stiffness change of > 25x (elastic modulus is 40 MPa when LMPA is solid and 1.5 MPa when LMPA is liquid) and a fast transition from rigid to soft states (< 1 s) at low power (< 500 mW). Additionally, the material possesses inherent state (soft and rigid) and strain sensing (GF = 0.8) based on resistance changes.
A highly versatile soft gripper that can handle an unprecedented range of object types is developed based on a new design of dielectric elastomer actuators employing an interdigitated electrode geometry, simultaneously maximizing both electroadhesion and electrostatic actuation while incorporating self-sensing. The multifunctionality of the actuator leads to a highly integrated, lightweight, fast, soft gripper with simplified structure and control.
In this paper, we introduce Vision Tape (VT), a novel class of flexible compound-eye-like linear vision sensor dedicated to motion extraction and proximity estimation. This novel sensor possesses intrinsic mechanical flexibility that provides wide-range adaptive shape, allowing adjustable field of view as well as integration with numerous substrates and curvatures. VT extracts Optic Flow (OF) of the visual scene to calculate the motion vector, which allows proximity estimation based on the motion parallax principle. In order to validate the functionality of VT, we have designed and fabricated an exemplary prototype consisting of an array of eight photodiodes attached to a flexible PCB that acts as mechanical and electrical support. This prototype performs image acquisition and processing with an integrated microcontroller at a frequency of 1000 fps, even during bending of the sensor. With this, the effect of VT shape on motion perception and proximity estimation is studied and, in particular, the effect of pixel-to-pixel angle is discussed. The results of these experiments allow estimating an optimal configuration of the sensor for OF extraction. Subsequently, a method that enhances the quality of extracted OF for non-optimal configurations is proposed. The experimental results show that, by applying the proposed method to VT in a suboptimal curvature, the quality of the OF can be increased by up to 176% and proximity estimation by 178%.
Vision Tape is a novel class of flexible compound-eye-like linear vision sensor dedicated to motion extraction and proximity estimation. This novel sensor possesses intrinsic mechanical flexibility that provides wide-range adaptive shape, allowing adjustable field of view as well as integration with numerous substrates and curvatures. Vision Tape extracts Optic Flow of the visual scene to calculate the motion vector, which allows proximity estimation based on the motion parallax principle.