V. Parenti Castelli

Compliant actuation based on dielectric elastomers for a force-feedback device: modeling and experimental evaluation

Thanks to their large power densities, low costs and shock-insensitivity, Dielectric Elastomers (DE) seem to be a promising technology for the implementation of light and compact force-feedback devices such as, for instance, haptic interfaces. Nonetheless, the development of these kinds of DE-based systems is not trivial owing to the relevant dissipative phenomena that affect the DE when subjected to rapidly changing deformations. In this context, the present paper addresses the development of a force feedback controller for an agonist-antagonist linear actuator composed of a couple of conically-shaped DE films and a compliant mechanism behaving as a negative-rate bias spring. The actuator is firstly modeled accounting for the viscohyperelastic nature of the DE material. The model is then linearized and employed for the design of a force controller. The controller employs a position sensor, which determines the actuator configuration, and a force sensor, which measures the interaction force that the actuator exchanges with the environment. In addition, an optimum full-state observer is also implemented, which enables both accurate estimation of the time-dependent behavior of the elastomeric material and adequate suppression of the sensor measurement noise. Preliminary experimental results are provided to validate the proposed actuator-controller architecture

Parallel Robot with Antagonistic Dielectric Elastomer Actuation for Human-Machine Interaction

The potentialities of a manipulator concept based on isotropic translational parallel mechanisms and agonistic-antagonistic dielectric elastomer actuation are investigated in the context of human-machine interfaces. Static analysis reveals that this manipulator concept is well suited to the development of novel generation of cost-effective interactive robots with low effective inertia and human-like performance and behaviour.

A New Spatial Kinematic Model of the Lower Leg Complex: A Preliminary Study

The importance of the human joint passive motion, i.e., the articulation motion in virtually unloaded conditions, for the study of human diarthrodial joints has been widely recognized. Recently, it has been shown that equivalent mechanisms make it possible to obtain physicalmathematical models that can replicate the articular passive motion well. These models also represent a useful tool for both pre-operation planning and prosthesis design.Although the human ankle joint has been extensively investigated, studies that examine the kinematic behaviour of the tibio-talar joint and also outline the motion of the fibula bone are still lacking. This paper focuses on the 3D kinematic model of the articulation that involves four bones:the tibia, fibula, talus and calcaneus. In particular, a new spatial equivalent mechanism with one degree of freedom is proposed for the passive motion simulation of this anatomical complex. The proposed mechanism is believed to play an important role for future developments of models of the entire human lower limb.

Experimental and Theoretical Analysis of the Gas-Lubricated Porous Rotating Journal Bearing

An experimental and theoretical analysis of the externally gas-pressurized, porous wall, rotating and nonrotating journal bearing is presented. The theoretical results are found to be in good agreement with the experimental ones. The proposed numerical method enables one to design a bearing and to evaluate the influence of journal rotation speed and gas compressibility on its operational performance.

Electro-Elastic Continuum Models for Electrostrictive Elastomers

A continuum finite-deformation model is described for the study of the isothermal electro-elastic deformations of electrostrictive elastomers. The model comprises general balance equations of motion, electrostatics and electro-mechanical energy, along with phenomenological invariant-based constitutive relations. The model is presented in both Eulerian (spatial) and Lagrangian (material) description. Specialization of the considered model is also presented for “Dielectric Elastomers”, which are a specific class of electrostrictive elastomers having dielectric properties independent of deformation.