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A flexure frame mechanism is a device historically used to amplify the displacement of an actuator with limited travel, such as a piezoelectric stack actuator. Conversely, these mechanisms may be used as a generator to amplify the force applied to piezoelectric transducers. This in turn can greatly increase the harvested power. Previous studies have used a variety of methods to analyse the amplification factor of a flexure frame mechanism operating as an actuator in displacement mode, as opposed to a generator in force amplification mode. The effects on the performance of such a device when operating in force amplification mode are not as well understood. In this study, an analysis of the force amplification of a flexure frame mechanism is conducted. A model of the force amplification factor based on the material properties and geometry of the device is developed for use as an optimisation and design tool. The analytical findings are compared against finite element analysis simulation and experimental results for validation. The effect of the stiffness of the central piezoelectric stack and the maximum stresses developed in the frame are determined to be critical parameters in determining the effectiveness of the mechanism as an energy harvester. [ABSTRACT FROM AUTHOR]

This paper proposes a double-chamber valveless pump actuated by a cantilever ionic polymer-metal composite (IPMC), whose deflection is measured by inductive sensors. While IPMCs are regarded as a promising actuator for portable devices, their unique electrochemical and mechanical properties such as dehydration, hysteresis, and back-relaxation constraint are from real-life applications. To address these drawbacks, two adaptive control schemes, PID with iterative feedback tuning and repetitive control, were implemented and evaluated to compare tracking performance. The following contributions are presented based on the proposed IPMC pump: validation a double-chamber configuration addresses the back-relaxation problem of IPMC and compensates the nonlinearity of inductive sensors, demonstration of a compact configuration utilizing a contactless inductive sensor, controlling IPMC for over 2 h using repetitive control that favors tracking of periodic signal in terms of control effort, tracking error, and computational memory consumption. The pump has a maximum flow rate of 780 μL/min when the IPMC operates at a maximum deflection of 1.7 mm, which validates its suitability for use in drug delivery applications. [ABSTRACT FROM PUBLISHER]

Ionic polymer metal composites (IPMCs) are actuators that lend themselves well to microfluidic applications due to their lightweight, flexibility, ability to tailor their geometry, as well as the capability to be miniaturized and implanted into microelectro-mechanical systems devices. The major issue with implementing IPMCs into such devices is the ability to control their actuation and, hence, their reliability over a long period of time. This paper presents a novel iterative feedback tuning (IFT) algorithm that tunes the system online using experimental data during normal system operation. The controller adaptively tunes the highly nonlinear and time varying IPMC for a newly proposed micropump. This demonstrates the ability of the system to have a reliable performance over a long period of time without the need of any offline tuning or system identification. The system was run for 20 controller updates. This corresponds to 10 and 20 min of operation for the 0.1 and 0.05 Hz reference inputs, respectively. 100 and 300 μm amplitudes were tested to demonstrate the ability of the system to adaptively tune to different input signals. Experimental results show the newly proposed IFT algorithm has successfully tuned the controller to achieve up to 92% better performance when compared with a conventional model-based tuned controller. [ABSTRACT FROM PUBLISHER]

Soft compliant grasping is essential in delicate manipulation tasks typically required in manufacturing and/or medical applications to prevent stress concentration at the point of contact. In comparison with their rigid counterparts, the intrinsic compliance of soft grippers offers simpler control and planning of the grasping action, especially where robots are faced with a number of objects varying in shape and size. However, quantitative analysis is rarely utilized in the design and fabrication of soft grippers, due to the fact that significant and complex deformation occurs once the soft gripper is in contact with external objects. In this paper, we demonstrate the design of a soft gripper using our novel bimorph-like pneumatic bending actuators. The gripper was modelled through finite element analysis to reflect its gripping capability during interaction with certain targeted objects. The proposed systematic design and analytical model was validated via experiments. The system’s gripping capability was evaluated with objects of different weight and dimension. In addition, compliance testing has proved that the proposed soft gripper is able to grip objects of 60 g from the side, without causing exceeding concentration stress on the targeted object. [ABSTRACT FROM AUTHOR]