Mart Anton

A Distributed Model of Ionomeric Polymer Metal Composite

This article presents a novel model of an ionomeric polymer metal composite (IPMC) material. An IPMC is modeled as a lossy RC distributed line. Unlike other electro-mechanical models of an IPMC, the distributed nature of our model permits modeling the non-uniform bending of the material. Instead of modeling the tip deflection or uniform deformation of the material, we model the changing curvature. The transient behavior of the electrical signal as well as the transient bending of the IPMC are described by partial differential equations. By implementing the proper initial and boundary conditions we develop the analytical description of the possibly non-uniform transient behavior of an IPMC consistent with the experimental results.

A mechanical model of a non-uniform ionomeric polymer metal composite actuator

This paper describes a mechanical model of an IPMC (ionomeric polymer metal composite) actuator in a cantilever beam configuration. The main contribution of our model is that it gives the most detailed description reported so far of the quasistatic mechanical behaviour of the actuator with non-uniform bending at large deflections. We also investigate a case where part of an IPMC actuator is replaced with a rigid elongation and demonstrate that this configuration would make the actuator behave more linearly. The model is experimentally validated with MuscleSheet™ IPMCs, purchased from BioMimetics Inc.

A linked manipulator with ion-polymer metal composite (IPMC) joints for soft- and micromanipulation

IPMCs are electroactive materials that bend in electric field. This paper describes a linked manipulator using IPMC joints. We argue that this design reduces the control complexity of an IPMC manipulator and increases the precision of the device. The design rationale stems from our theoretical work in material modeling. It suggests that when electrically decoupled short IPMC strips are connected to rigid links, the control of the IPMC manipulator, which is currently vaguely understood and highly non-linear, can be reduced to simple inverse kinematics serial chain manipulator control without the loss in efficiency. We validate our design by comparing the prototype device to a simple IPMC manipulator commonly investigated in the literature. The results show increased precision, reaction time and reachable workspace. We suggest that such a manipulator is suitable for soft and micromanipulation.

Analytical and computational modeling of robotic fish propelled by soft actuation material-based active joints

Soft actuation materials, such as Ionic Polymer-Metal Composites (IPMCs), are gaining increasing interest in robotic applications since they lead to compact and biomimetic designs. In this paper, we propose the use of soft actuation materials as active joints for propelling biomimetic robotic fish. An analytical model is developed to compute the thrust force generated by a two-link tail and the resulting moments in the active joints. The computed joint moments can be combined with internal dynamics of actuation materials to provide realistic kinematic constraints for the joints. Computational fluid dynamics (CFD) modeling is also adopted to examine the flow field, the produced thrust, and the bending moments in joints for the two-link tail. Good agreement is achieved between the analytical modeling and the CFD modeling, which points to a promising two-tier framework for the understanding and optimization of robotic fish with a multi-link tail. We also show that, comparing to a one-link bending tail, a two-link tail is able to produce much higher thrust and more versatile maneuvers, such as backward swimming.

An engineering approach to reduced power consumption of IPMC (ion-polymer metal composite) actuators

Ion-polymer metal composites (IPMC) are electroactive polymer (EAP) materials that behave in electric field similar to biological muscles. Among the shortcomings of an emerging technology like IPMC muscles their energy consumption is one of the most serious. This paper represents a novel open-loop control method for IPMC artificial muscles that significantly reduces their power consumption. We discuss some underlying principles of the ion-conducting polymers and show that our method is consistent with theoretical findings. This method is then experimentally tested and verified to the existing methods. The results confirm that energy consumptions of the muscles can be reduced 3.7 times and peak current consumption up to 2.6 times

A multilink manipulator with IPMC joints

IPMC (Ionic Polymer Metal Composite) is a class of electroactive polymers (EAP) that bend when electric field is applied to the material. From our theoretical studies of the material it appears that IPMC can be modelled as a lossy transmission line. From simulations it appears that IPMC reaction time depends on length of the strip used. Also the shorter the transmission line the less complex it is to model. We have also mechanically modeled an IPMC. It appears that the output force does not depend on length on IPMC but on width. Also the shape unpredictability is the larger the longer the strip is. Based on these results the concept of a short IPMC with rigid extension was created. From simulations and experiments it was seen that there exists a certain length of IPMC at which output force and deflection angle remain close to those of a long IPMC while precision increases. Also, the material becomes easier to model and its short-term stability appears to be sufficient to be controlled. A manipulator was built to verify IPMC compatibility as links, tested for accuracy and compared with a long sheet of IPMC. The manipulator appeared to be 314% more accurate and twice as fast compared to the long strip of an IPMC and thus confirming the usability of the described design.

Validating Usability of Ionomeric Polymer-Metal Composite Actuators for Real World Applications

Ionomeric polymer-metal composites (IPMC) are electroactive polymer (EAP) materials that bend when electrically stimulated. As IPMC is a relatively new material, proper control methods have not yet evolved. In this paper the usability of IMPC actuators in real world applications is examined from the point of view of precision control. We propose a classical inverted pendulum control problem as a testbed. We suggest that if the pendulum can be balanced, then we have proven the usability of IPMC actuators for precise control tasks. In this paper we describe an inverted pendulum system driven by an IPMC actuator with PC-based control and a camera in the feedback loop. We report the preliminary experimental results in controlling the pendulum and discuss further improvements. To our knowledge this is the first attempt to control a system or manipulate an object with IMPC actuators in a feedback loop

A distributed model of IPMC

This paper presents a distributed model of an IPMC (Ionomeric Polymer-Metal Composite). Unlike other electromechanical models of an IPMC, the distributed nature of our model permits modelling the non-uniform bending of the material. Instead of modeling solely the tip deflection of the material, we model the changing curvature. Our model of the IPMC describes the actuator or sensor as a distributed one-dimensional RC transmission line. The behavior of the IPMC at its each particular position in time-domain is described by a system of Partial Differential Equations. (PDE). The parameters of the PDE-s have a clear physical interpretation: the conductivity of the electrodes, the pseudocapacitance of the arising double-layer at the boundary of the electrodes, the electric current caused by electrode reactions etc. The electromechanical coupling between the electrical parameters and the bending motion is implemented by means of distribution of electric current along the material in a time domain. The distributed nature of the model permits predicting the non-uniform bending of the IPMC actuators in time domain or to reconcile the output of an IPMC-based position sensor with its shape. Taking into account several nonlinear parameters, the model is consistent with the experimental results even when the inflexion of the actuator or sensor is large or the water electrolysis appears.

Empirical model of a bending IPMC actuator

We study ionomeric polymer-metal composite (IPMC) actuators in situations where the strip of actuator acts either on maximum mechanical power or maximum amplitude of actuation. We apply a modified equivalent circuit of IPMC muscle which takes into account the surface resistance change while material bends. In case of series of bending acts, the first actuation of IPMC actuator is performed by a relaxed actuator, it bends over its full length. During the next movements the most of the energy is caught by fore-part of actuator. The explanation of that effect is given.

Linear modeling of elongated bending EAP actuator at large deformations

This paper describes a linear dynamic model of an elongated bending Electroactive Polymer (EAP) actuator applicable with deformations of any magnitude. The model formulates relation of a) voltage applied to the EAP sheet, b) current passing through the EAP sheet, c) force applied by the actuator and d) deformation of the actuator. In this model only the geometry of EAP piece and four empirical parameters of the EAP material: a) bending stiffness, b) electromechanical coupling term, c) electrical impedance and d) initial curvature are considered. The contribution of this paper is introducing a model that can be used to characterize the properties of different EAP materials and compare them. The advantage of the model is its simplicity and ability to provide insights in to the behavior of bending EAPs. Additionally, due to linearity of the model, the real-time control is feasible. Experiments, using Ionomeric Polymer-Metal Composite (IPMC) sheet from Environmental Robotics Inc., where carried out to verify the model. The experimental results confirm the model is valid.