Details

Autor(en) / Beteiligte

• Wu, Qiyang

Titel

The Development of Soft Robots Capable of Surface Traction Modulation

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2020

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• The author involves a new technology, electrostatic adhesion, into soft robots to realize the climbing-up function. In the elastomer-based work, the electrostatic adhesion is applied to a quadruped soft robot by embedding a thin and compliant adhesion pad (made of PDMS and Ag/AgCl ink) onto each leg of the robot. With the help of the inherent stickiness of PDMS, experiments show the adhesion pad can provide a quite change (up to 3.1 N) of the friction force between robot leg and corresponding substrate. This friction change allows the robot to change its moving pattern under the same control sequence. The robot can move forward, backwards, or stay in the same place with the help of regulating friction forces induced by electrostatic adhesion. A simplified kinematic model is developed for the quadruped robot to explain the important role played by friction forces, and consequently, to show the promising potential of electrostatic adhesion in developing wall-climbing soft robots. In this work, the presence of electrostatic adhesion not only allows the robot to change the moving direction on horizontal plane, but also makes the robot capable of climbing up an inclined slippery surface rather than slide down. However, a vertically 90-degree climbing is not realized on this quadruped robot since the robot’s pneumatic actuation will produce a large falling torque under gravity which will break the attachment of legs to substrate.In order to overcome the problems brought by gravity, the author develops a paper-based soft robot which realizes both horizontal and vertical climbing on a 90-degree vertical-placed substrate. The robot, made from paper and shape memory alloy (SMA), can be controlled to climb walls under certain combinations of activation patterns of electrostatic adhesion and contraction of the SMA. Electrostatic adhesion is applied using a paper structure with embedded interdigitated electrodes. This structure, fully compatible with the paper-based robot, is able to output strong and reliable adhesion forces (the resultant friction force can be as high as 1.65N on specific substrates), and it can be easily turned on and off using a commercial high-voltage converter. The SMA embedded in the robot is employed to deform the robot body and induce contracting displacements while being activated. A bias-spring SMA model applied to this robot is simulated and compared with experimental results, which shows relatively good prediction accuracy. With above structures, we demonstrate the walking and climbing ability of this robot with a locomotion speed of 1 mm/s. The climbing on a vertical wall along both the vertical and horizontal directions is achieved.In addition, an untethered version of the paper-based wall-climbing robot is developed to make the robot closer to perform certain tasks. In order to embed all the electronics, the size of the robot is made larger than tethered version to strengthen its capability of holding weights and fighting against gravity. A tiny microcontroller, Attiny84, is employed to control the activation of SMA and the turning on/off of adhesion pads. Each pad has an individual high-voltage MOSFET to control its adhesion force. With the help of high-voltage MOSFET, the falling torque is much lower than before, and the problem of the small microcontroller’s output power is also solved. With above structures, we demonstrate the walking and climbing ability of this robot with a locomotion speed of 0.6-0.8 mm/s. The climbing on a vertical wall along both the vertical and horizontal directions is also achieved. Meanwhile, since its untethered property, this robot has the potential to perform tasks such as surface detection and video surveillance, which makes soft robot closer to real-life application.