Actuators2015, 4(1), 2-16; doi:10.3390/act4010002 - published 16 February 2015 Show/Hide Abstract
Abstract: The tension in the warp yarns is a critical variable in the weaving process. If the warp tension is too high or too low the weaving process will be interrupted. A parameter that directly affects the warp tension is the vertical warp stop motion position. The position of the warp stop motion must be set for every produced new article. The setting procedure is performed completely manual. In this paper we present a mechatronic modification of an air jet-weaving machine to adjust the vertical warp stop motion position with the help of actuators. The parameters for the automated movement are determined and an open loop control, which uses a PLC, is proposed.
Actuators2014, 3(4), 285-292; doi:10.3390/act3040285 - published 9 December 2014 Show/Hide Abstract
Abstract: A paper actuator was fabricated from poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) by a wet process without organic solvents. The paper actuator had a capacitor structure, with a cationic polymer as an insulating layer sandwiched between two PEDOT:PSS films as the electrodes. The thickness of the paper actuator was approximately 36 mm. We measured its displacement as a function of applied voltage and frequency; the maximum displacement was 2.2 mm at 1.5 V and 1 Hz.
Actuators2014, 3(3), 270-284; doi:10.3390/act3030270 - published 11 August 2014 Show/Hide Abstract
Abstract: The fundamental objective in developing variable stiffness actuators is to enable the actuator to deliberately tune its stiffness. This is done through controlling the energy flow extracted from internal power units, i.e.,themotors of a variable stiffness actuator (VSA). However, the stiffness may also be unintentionally affected by the external environment, over which, there is no control. This paper analysis the correlation between the external loads, applied to different variable stiffness actuators, and their resultant output stiffness. Different types of variable stiffness actuators have been studied considering springs with different types of nonlinearity. The results provide some insights into how to design the actuator mechanism and nonlinearity of the springs in order to increase the decoupling between the load and stiffness in these actuators. This would significantly widen the application range of a variable stiffness actuator.
Actuators2014, 3(3), 245-269; doi:10.3390/act3030245 - published 28 July 2014 Show/Hide Abstract
Abstract: The current smallest self-contained modular robot uses a shape memory alloy, which is inherently inefficient, slow and difficult to control. We present the design, fabrication and demonstration of a module based on dielectric elastomer actuation. The module uses a pair of bowtie dielectric elastomer actuators in an agonist-antagonist configuration and is seven times smaller than previously demonstrated. In addition, we present an intuitive model for the bowtie configuration that predicts the performance with experimental verification. Based on this model and the experimental analysis, we address the theoretical limitations and advantages of this antagonistic bender design relative to other dielectric elastomer actuators.
Actuators2014, 3(3), 226-244; doi:10.3390/act3030226 - published 9 July 2014 Show/Hide Abstract
Abstract: Soft robotics requires technologies that are capable of generating forces even though the bodies are composed of very light, flexible and soft elements. A soft actuation mechanism was developed in this work, taking inspiration from the arm of the Octopus vulgaris, specifically from the muscular hydrostat which represents its constitutive muscular structure. On the basis of the authors’ previous works on shape memory alloy (SMA) springs used as soft actuators, a specific arrangement of such SMA springs is presented, which is combined with a flexible braided sleeve featuring a conical shape and a motor-driven cable. This robot arm is able to perform tasks in water such as grasping, multi-bending gestures, shortening and elongation along its longitudinal axis. The whole structure of the arm is described in detail and experimental results on workspace, bending and grasping capabilities and generated forces are presented. Moreover, this paper demonstrates that it is possible to realize a self-contained octopus-like robotic arm with no rigid parts, highly adaptable and suitable to be mounted on underwater vehicles. Its softness allows interaction with all types of objects with very low risks of damage and limited safety issues, while at the same time producing relatively high forces when necessary.