Preliminary design of eddy current brake to improve sustainable mobility

In recent years, the need to reduce CO2 emissions has developed a change in the transport sector. E-mobility is emerging as a zero-emissions way of travel, but not only the combustion engine produces emission. In fact, a significant part of the vehicle's total pollution is produced by tires and conventional brakes. The eddy current brake is a possible alternative to the well-known mechanical brake to obtain zero-emissions braking with low maintenance. This type of brake converts the vehicle's kinetic energy into thermal energy through the magnetic generation of the eddy currents, which generate Lorentz braking forces. This paper proposes a preliminary design of a zero-emission eddy current brake with a first geometry variation to increase the brake performance, that has been evaluated with an analytical approach and EMS by EMWorks, a 3D finite element method magnetic software able to calculate brake torque and electromagnetic effects

A methodology for the development of a Hinged Ankle-Foot Orthosis compatible with natural joint kinematics

This work presents a new concept to design Hinged Ankle-Foot Orthoses (HAFOs), based on the definition of a special mechanical articulation able to mimic the physiological behavior of the human ankle joint. Current commercial braces typically do not take into account the natural variability of the ankle joint axis. As the hinge location as well as the rotation axis variability are both relevant for the overall function of the device, and strongly depend on the subject-specific characteristics, a methodology for the development of a HAFO with a floating axis of rotation, based on the in-vivo kinematic analysis of the ankle joint, is here proposed. The kinematic analysis was performed by calculation of the instantaneous and mean helical axes over the collected stereo-photogrammetric data of joint motion. This procedure was tested on a healthy subject, leading to the design and fabrication of a first customized prototype of the orthosis. The performance of this HAFO was experimentally verified by motion analysis. All relevant results are presented, and further possible future improvements of the procedure are discussed

A methodology for the customization of hinged ankle-foot orthoses based on in vivo helical axis calculation with 3D printed rigid shells

This study aims to develop techniques for ankle joint kinematics analysis using motion capture based on stereophotogrammetry. The scope is to design marker attachments on the skin for a most reliable identification of the instantaneous helical axis, to be targeted for the fabrication of customized hinged ankle-foot orthoses. These attachments should limit the effects of the experimental artifacts, in particular the soft-tissue motion artifact, which affect largely the accuracy of any in vivo ankle kinematics analysis. Motion analyses were carried out on two healthy subjects wearing customized rigid shells that were designed through 3D scans of the subjects’ lower limbs and fabricated by additive manufacturing. Starting from stereophotogrammetry data collected during walking and dorsi-plantarflexion motor tasks, the instantaneous and mean helical axes of ankle joint were calculated. The customized shells matched accurately the anatomy of the subjects and allowed for the definition of rigid marker clusters that improved the accuracy of in vivo kinematic analyses. The proposed methodology was able to differentiate between subjects and between the motor tasks analyzed. The observed position and dispersion of the axes were consistent with those reported in the literature. This methodology represents an effective tool for supporting the customization of hinged ankle-foot orthoses or other devices interacting with human joints functionality

Comparison among different modular SMA actuated flexible fingers

Four prototypes of a flexible finger, each made up of three actuator modules based on shape memory alloy (SMA) wires, are experimentally studied in this research. A module is basically composed by few simple components: a plastic body, made of different materials, and SMA wires. The bending of the module is performed with the heating and cooling of the SMA wires and the central rod exerts bias force, necessary to the stretching of the wire to the original shape. To evaluate the actuator workspace different tests were performed, and the results of three prototypes are compared. Finally a more complex prototype in which the antagonist wires can be deactivated during the working cycle was designed and preliminary tests were performed, obtaining encouraging results

Three-Fingered Gripper with Flexure Hinges Actuated by Shape Memory Alloy Wires

A three-fingered gripper with flexure hinges actuated by shape memory alloy (SMA) wires was designed and prototyped. The aim of the work was the manipulation of small, almost cylindrical objects, e.g. test tubes, by a device having small overall dimensions. A parametric study of four different, but similar, fingers was conducted with the aim of obtaining a solution with a good amplification ratio and a gripping force almost constant during closure. The use of flexure hinges simplifies the design, but limits the finger range of motion. Moreover, it was possible to find a configuration with sufficient work space. Once the finger geometry was defined, the whole hand was then designed with the aim of producing a compact hand contained in a cylindrical volume (d 65 x h 65 mm), and the first prototype was built. Preliminary tests demonstrated its good dimensioning and the success of some technological solutions. The experimental transmission ratio was almost the same as the theoretical one. Some drawbacks have been highlighted, such as a reduced range of motion and incomplete backstroke; future studies will deal with them