Canh Toan Nguyen

A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators

A kind of dielectric elastomer (DE) material, called ‘synthetic elastomer’, has been developed based on acrylonitrile butadiene rubber (NBR) to be used as a dielectric elastomer actuator (DEA). By stacking single layers of synthetic elastomer, a linear actuator, called a multistacked actuator, is produced, and used by mechatronic and robotic systems to generate linear motion. In this paper, we demonstrate the application of the multistacked dielectric elastomer actuator in a biomimetic legged robot. A miniature robot driven by a biomimetic actuation system with four 2-DOF (two-degree-of-freedom) legged mechanisms is realized. Based on the experimental results, we evaluate the performance of the proposed robot and validate the feasibility of the multistacked actuator in a locomotion system as a replacement for conventional actuators.

Printable monolithic hexapod robot driven by soft actuator

Aiming to apply soft actuators in driving a walking robot, the design, fabrication and locomotion of a bio-inspired printable hexapod robot are studied. The robot mimics the insects design and walking posture by driving six legs with alternating tripod gait which provides its locomotive adaptability on flat terrains. The versatile movements of the robots leg are achieved by using soft and multiple degree-of-freedom actuators. The actuators are made by dielectric elastomers with a simple mechanism based on antagonistic configuration. By using 3D printing method, the actuator can be embedded into the frame of the robot and a control system is developed. Finally, the robots locomotion is successfully demonstrated with variable speeds and stride lengths.

Enhancement of transduction performance of a dielectric elastomer actuator based on acrylonitrile butadiene rubber

AbstractThe synthetic elastomer based on acrylonitrile butadiene rubber (NBR) has been recently developed as a kind of dielectric elastomer actuators (DEAs). Its advantages are that its properties can be modified according to the requirements of applications. In this paper, we report a comprehensive study on the effects of plasticizers including diisodecyl phthalate (DIDP), dioctyladipate (DOA), and dioctyl phthalate (DOP) as well as a high dielectric additive, which is, barium titanate (BaTiO3) with respect to the overall performance of the synthetic elastomer. We investigate how the significant parameters representing the actuator performance can be changed according to the composition of the additives and how the actuation performances can be improved. In addition, we address how the environmental conditions such as exposure to the light and the air have influence on the properties of the synthetic elastomer, and a method for extending the lifetime of DEA is also addressed.

Six-axis capacitive force/torque sensor based on dielectric elastomer

The six axis F/T sensor is a primary component for the robotic technologies, but its high unit cost hampers the popularization to the robotic applications. In this paper, we present a six-axis force-torque capacitive sensor based on dielectric elastomer. Dielectric elastomer is compressed and deformed with external forces acting on it. Its deformation results in the variation of capacitance, which can be used as a kind of capacitive sensing scheme. The proposed sensor consists of plastic structure and dielectric elastomer capacitors. Since it takes a simple structure, it is possible to fabricate by using a plastic molding process, which results in extremely lower cost than existing off-the-shelf products. We present the basic structure and design of the sensor with the explanation of its working principle. A fabrication method dedicated to the sensor is developed and finally, a prototype will be demonstrated with calibration procedures.

Highly stretchable dielectric elastomer material based on acrylonitrile butadiene rubber

This study presents a highly stretchable dielectric elastomer material for transducers based on acrylonitrile butadiene rubber (NBR). The material has advantages in that its mechanical and electrical properties can be modified according to the requirements of applications by changing the content of additives such as carbon black (CB), multi-walled carbon nanotubes (MWCNT), and graphite (GP) in the NBR matrix. First, the changes of dielectric permittivity depending on the additives are discussed. Moreover, the electrical resistance is examined in detail by changing the compositions of the additives, and the applicability of the material to the electrodes of transducers is investigated. Finally, the optimal contents of additives for actuators or sensors are discussed.

A highly sensitive dual mode tactile and proximity sensor using Carbon Microcoils for robotic applications

This paper presents a highly sensitive dual mode tactile and proximity sensor for robotic applications that uses Carbon Microcoils (CMCs). The sensor consists of multiple electrode layers printed on a Flexible Printed Circuit Board (FPCB) and a dielectric substrate into which the CMCs are dispersed. The dielectric layer is simply put on the top of the FPCB. Thus, the sensor provides ease of fabrication and robustness against repetitive external contacts because the dielectric layer protects the electrodes. The electrical properties of the sensor are changed when an object approaches or touches the sensor. The sensor uses a capacitive sensing mode for tactile sensing and an inductive sensing mode for proximity sensing. CMCs amplify the change of the sensor signal because of electrical impedance formed by the CMCs, and thus, the sensitivity of the sensor increases. We fabricate the prototype sensor with the dimensions of 30 × 30 × 0.6 mm3, and with 3 mm spatial-resolution. The sensor detects the applied pressure up to 330 kPa and the distance of an object as much as 150 mm away.

Development of a smart handheld surgical tool with tactile feedback

This paper presents a handheld surgical tool adapting a tactile feedback system. The tool consists of a 3-degree-of-freedom (DOF) force sensor and three tactile displays. The sensor is easily embedded in the tool by adopting the capacitive transduction principle. The sensor measures the direction and magnitude of the 3-DOF force applied to the tool tip. The fingertip grasping the tool is stimulated by the tactile display to transmit the contact force information measured by the sensor. The tactile display is actuated by employing a soft actuator technology based on a dielectric elastomer actuator such as a type of electroactive polymer actuator. In this work, a prototype of the tool is designed and fabricated. Its performance is experimentally validated.

Biomimetic printable hexapod robot driven by soft actuator

This paper presents the preliminary design of a biomimetic printable hexapod robot driven by soft actuators. The robot mimics the insects design with six legs and shows the capability of versatile locomotion on flat terrains by using alternating tripod gait. The soft and multiple degree-of-freedom (multi-DOF) actuators based on dielectric elastomer provide required motions of the robot with a simple mechanism based on antagonistic configuration. The fabrication of the robot is effectively implemented by 3D printing method. In addition, a control system is built to provide various locomotion and walking speeds for the robot and its operation is demonstrated.

Highly sensitive proximity and tactile sensor based on composite with dielectric elastomer and carbon microcoils

This work presents a dual purpose sensor for collecting proximity and tactile information by using a composite with dielectric elastomer (DE) and Carbon Micro Coils (CMC). CMC is a coil-like carbon microstructure with the size of several hundred micrometers, and its electrical characteristics change with the distance between the object or via physical contact. Especially, the impedance change of the composite depending on the distance can be used as the principle for proximity sensing. We present a method to process the materials by using dielectric materials and additives. A prototype of the sensor is fabricated and its feasibility is experimentally validated.

A highly flexible, stretchable and ultra-thin piezoresistive tactile sensor array using PAM/PEDOT:PSS hydrogel

This paper presents a highly flexible, stretchable and ultrathin piezoresistive tactile sensor array, which can be attached to a tactile display actuator array [1] without any influence on its motion. Its operational principal is based on the resistance changing of a tactile cell array prepared by blending a precise conductive polymer — Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) with Polyacrylamide (PAM) hydrogel. Through comparing the characteristics of the blended hydrogel mixed between PAM and PEDOT with different ratios 2.5:1; 3:1; 3.5:1 respectively, the 2.5:1 ratio is the appropriate sample selected as the sensor design. Then, the 12×8 tactile sensor array were fabricated by dropping the conductive hydrogel into the cavity of two electrodes cast on Sylgard 184 substrates (PDMS), which is flexible and thin — around 800μm thickness in total. Finally, a primary measuring circuit using Wheatstone Bridge with a low-pass filter, an amplifier, and a signal processing circuit are also built to demonstrate the sensor s performance successfully.