Swimming IPMC thin film soft robot fabricated through malti-layer casting process
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In this paper, we report on a multi-layer casting process of a Nafion membrane to produce a monolithic thin film robot (MTFR). This robot is developed on the basis of the novel concept of a soft robot, which has both a body part and an actuator part and does not require a mechanical and electrical assembly process. A MTFR is made from only one thin film that has thicknesses gradient. The thick parts of the membrane act as bone structures, and the thin parts of the membrane function as actuators. This multi-function structure of the MTFR realizes an assemblyless manufacturing process. To fabricate the monolithic film with a distributed thickness, we propose a multilayer casting process. To demonstrate the potential of a MTFR for use in a biomimetic application, we manufactured anomalocaris-like MTFR and conducted self-sustaining driving experiment in water.Keywords:
Soft Robotics
Thin layers
The UK ATC has developed a novel thermal actuator design as part of an OPTICON project focusing on the development of a Freeform Active Mirror Element (FAME). The actuator uses the well understood concept of thermal expansion to generate the required force and displacement. As heat is applied to the actuator material it expands linearly. A resistance temperature device (RTD) is embedded in the centre of the actuator and is used both as a heater and a sensor. The RTD temperature is controlled electronically by injecting a varying amount of current into the device whilst measuring the voltage across it. Temperature control of the RTD has been achieved to within 0.01°C. A 3D printed version of the actuator is currently being used at the ATC to deform a mirror but it has several advantages that may make it suitable to other applications. The actuator is cheap to produce whilst obtaining a high accuracy and repeatability. The actuator design would be suitable for applications requiring large numbers of actuators with high precision.
Repeatability
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Miniature actuators are the critical components in the robotic applications with high intelligence, high mobility and small scales. Among various types of actuators, linear actuators show advantages in many aspects. A miniature short stroke PM tubular linear actuator for the micro robotic applications is presented in this paper. The actuator is deliberately designed based on the optimal force capability and a proper sensorless control scheme is developed for the driving of the actuator. Experiment both on the prototype of the actuator and the drive system show the validity of the design.
Linear actuator
Rotary actuator
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Various concepts of the degree of controllability (DOC) have been previously developed for the purpose of choosing actuator locations in the control of large flexible spacecraft. A perturbation technique is presented to efficiently account for the actuator mass in the computation of the fuel-optimal, time-optimal, and energy-optimal DOC definitions. Methods are developed for computing each of the three DOCs, when the mass of the actuator is nonnegligible. The energy-optimal DOC is employed to find optimal actuator locations for a large spacecraft under study by the NASA Langley Research Center. The mass of the actuator is seen to have a significant effect on the optimal actuator locations and is shown to spread the actuator locations more evenly for large mass actuators. Results indicate that when the actuator mass is large when compared to the structural mass it should be included in selecting actuator locations.
Plasma actuator
Rotary actuator
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Piezoelectric actuators are being used in increasingly complex structures. An actuator that can be removed and used again would be beneficial in testing actuator placement before the permanent actuator would be attached. Furthermore, an actuator that has similar response characteristics to the permanent actuator would be beneficial in estimating the response characteristics of the actuator before it is attached. A concept for such a removable, reusable actuator has been developed, constructed, and used. This paper describes the differences in authority among three removable, reusable actuators as compared to a permanent actuator. The permanent actuator is bonded to the host structure with only strain gauge cement. This paper also quantifies the changes in authority of the three removable, reusable actuators as they are removed several times from the host structure. When comparing removable and permanent actuators, the stiffer bonding technique typically had greater actuation authority. When comparing authority reduction of removable actuators over ten applications of the actuator, greater reduction occurred with actuators that incorporated a stiffener.
Rotary actuator
Strain gauge
Pneumatic actuator
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Soft Robotics
Soft sensor
Fluidics
Pneumatic actuator
Contact force
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This paper demonstrates the effect of dynamic load conditions on the design and performance of actuators. Actuators have both active and passive properties that determine their overall performance. The interaction between the active and passive components of an actuator, and hence the performance, will depend on both the objective (i.e., the actuator used in a control system or as a source) and the dynamics of the structure to which the actuator is attached. It is shown that it is mainly the active properties of an actuator which are affected by the load conditions of the structure. Changes in the active properties due to varying load conditions are demonstrated for various actuator types. By altering the passive properties of an actuator (i.e., mass and stiffness) it is possible to enhance the performance of the actuator used in a particular application. It is shown that the optimal actuator design depends on both the dynamics of the structure to which the actuator is attached and the performance objective. It will be demonstrated that actively changing the passive properties of an actuator allows significant enhancement of performance.
Plant
Plasma actuator
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Existing actuator controls are typically designed based on optimizing performance and robustness to system uncertainties, without considering the operational lifetime of the actuator. It is often desirable, and sometimes necessary, to trade off performance for extended actuator operational lifetime. This paper introduces the concept of incorporating the actuator lifetime as a controlled parameter. We describe preliminary methods for speed/position tracking control of an electromechanical actuator (EMA) while maintaining a desired minimum lifetime of the actuator motor
Robustness
Position tracking
Rotary actuator
Plant
Position (finance)
Pneumatic actuator
Valve actuator
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Active microvibration control systems have been developed and applied in a practical manner. Various types of actuator, for example an air actuator, a linear moving actuator, a piezoelectric (PZT) actuator and a giant-magnetostrictive (GMS) actuator, have been used. In general, all actuators have both merits and demerits, so an optimal actuator should be selected based on the objective performance and the conditions of usage. We developed an active 6-DOF microvibration control system using GMS actuators. It has been speculated that the GMS actuator is suitable as a displacement actuator for an active microvibration control. The reasons for this are that it has better durability and reliability compared with a PZT actuator, and also its response to an input signal is much faster than an air actuator. However, the demerits of the GMS actuator come to light through practical application of the system. The displacement property tends to decrease with increase in the magnitude of forced axial load, and it cannot generate a sufficient displacement in a low frequency range.
Plant
Rotary actuator
Pneumatic actuator
SIGNAL (programming language)
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The emerging field of soft robotics often relies on soft actuators powered by pressurized fluids to obtain a variety of movements. Strategic incorporation of soft actuators can greatly increase the degree of freedom of soft robots thereby bestowing them with a range of movements. Balloon actuators are extensively used to achieve various motions such as bending, twisting, and expanding. A detailed understanding of how material properties and architectural designs of balloon actuators influence their motions will greatly enable the application of these soft actuators. In this study, we developed a framework involving experimental and theoretical analyses, including computational analysis, delineating material and geometrical parameters of balloon actuators to their bending motions. Furthermore, we provide a simple analytical model to predict and control the degree of bending of these actuators. The described analytical tool could be used to predict the actuating function of balloon actuators and thereby help generate optimal actuators for functions which require control over the extent and direction of actuation.
Soft Robotics
Pneumatic actuator
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IPMCs are one of the most promising smart actuators to replace traditional actuators for some specific applications particularly in the micro-nano scales. IPMC actuator’s shape and configuration have a dramatic effect on the actuation parameters. While the behaviour of IPMCs as a single fixed end strip actuator (cantilever) has been widely studied since the early 80’s, its behaviour in other configurations is relatively unknown. This paper presents work carried out in order to reconfigure these actuators for some new applications. The first configuration is when both ends of an IPMC actuator strip are fully constrained, in both the actuator plane and the normal direction. In this case the displacement and force measurements at the mid point of the strip are presented. The results of a series of experiments show the behaviour of the actuator in this configuration and using these results some models have been proposed. The second configuration is when only one end of the strip is fixed and the other end is constrained in the normal direction with respect to the plane of the actuator strip. A series of experiments were also carried out to explore the IPMC actuator behaviour in terms of maximum displacement and force generated in this configuration. The behaviour of the IPMC actuator in these two configurations is also investigated by studying the internal stresses in the IPMC structure.
STRIPS
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