Planar Micro-Positioning Device Based on a 3D Digital Electromagnetic Actuator

In this paper, a novel micro-positioning device based on a 3D digital actuator is presented. The proposed system allows realizing planar motions of micro-objects, which could be implemented in several applications where micro-positioning tasks are needed such as micro-component manufacturing/assembly, biomedicine, scanning microscopy, etc. The device has three degrees of freedom, and it is able to achieve planar motions of a mobile plate in the xy-plane at two different levels along the z-axis. It consists of a hexagonal mobile part composed of a permanent magnet that can reach twelve discrete positions distributed between two z-axis levels (six at each level). Two different approaches are presented to perform positioning tasks of the plate using the digital actuator: the stick-slip and the lift-mode approaches. A comparison between these two approaches is provided on the basis of the plate displacement with respect to different current values and conveyed mass. It was observed that for a current of 2 A, the actuator is able to displace a mass of 1.15 g over a distance of 0.08 mm. The optimal positioning range of the planar device was found to be ±5.40 mm and ±7.05 mm along the x- and y-axis, respectively.

Kinematic geometry of hyperbolic dual spherical motions and Euler–Savary’s equation

In this paper, differential properties of the one-parameter hyperbolic dual spherical kinematics are developed with explicit expressions independent of coordinates systems. We calculate Euler–Savary equations of spherical kinematics in the dual Lorentzian 3-space [Formula: see text]. Then from E. Study’s map new proofs are directly attained for the Disteli’s formulae and their spatial equivalents are examined in detail. Lastly for spherical and planar motions, the point trajectories theoretical expressions of the point trajectories are investigated with a certain value of acceleration and velocity, which are regarded as different forms of Euler–Savary equation form.

Model-based dynamic feedback control of a planar soft robot: trajectory tracking and interaction with the environment

Leveraging the elastic bodies of soft robots promises to enable the execution of dynamic motions as well as compliant and safe interaction with an unstructured environment. However, the exploitation of these abilities is constrained by the lack of appropriate control strategies. This work tackles for the first time the development of closed-loop dynamic controllers for a continuous soft robot. We present two architectures designed for dynamic trajectory tracking and surface following, respectively. Both controllers are designed to preserve the natural softness of the robot and adapt to interactions with an unstructured environment. The validity of the controllers is proven analytically within the hypotheses of the model. The controllers are evaluated through an extensive series of simulations, and through experiments on a physical soft robot capable of planar motions.

Patrones de desplazamiento del eje instantáneo de rotación del movimiento de elevación humeral

En este trabajo se presentan los resultados de un estudio experimental para la descripción de las trayectorias descritas por el eje instantáneo de rotación (EIR) toracohumeral para movimientos cíclicos de elevación-descenso. Se ha desarrollado una técnica de análisis de movimientos mediante videofotogrametría que permite la medida del EIR del movimiento relativo húmero tórax con un error inferior a 1 cm y de forma muy reproducible [1,2]. Esto permite registrar el movimiento continuo del EIR como un axoide, cuyo desplazamiento mediolateral está relacionado con las velocidades de rotación de las articulaciones esternoclavicular, acromioclavicular y glenohumeral, y cuya posición vertical se asocia a la elevación de articulación glenohumeral [3] Se ha realizado un estudio con 45 sujetos sanos y 15 sujetos con patologías del hombro, analizando el movimiento cíclico de elevación-descenso del húmero en los planos frontal y escapular. La ubicación y forma de los axoides es sensible a los efectos de la carga y del estado funcional del sujeto. Así el efecto de la carga se manifiesta en un desplazamiento medial de la trayectoria del EIR, asociado a un movimiento más acusado de las articulaciones esternoclavicular, acromioclavicular frente al movimiento sin carga. Por otra parte, el efecto de la patología afecta a la trayectoria del EIR sólo a partir de cierto nivel de limitación funcional. Los patrones correspondientes a pacientes con limitaciones leves no muestran diferencias importantes frente a los sujetos sanos. Los resultados obtenidos muestran que el EIR puede ser de utilidad en la valoración funcional biomecánica del hombro, al ofrecer información sobre la coordinación de las diferentes articulaciones que lo constituyen REFERENCIAS [1] A.Page, J.A. Gálvez, H. de Rosario, V. Mata., J. Prat. Optimal average path of the instantaneous shelical axis in planar motions with one functional degree of freedom. Jnl. Biomech, vol. 43, pp 375-378, 2010. doi: 10.1016/j.jbiomech.2009.09.023. [2] A.Page, H. de Rosario, J.A. Gálvez, V. Mata. Representation of planar motion of complex joints by means of rolling pairs. Application to neck motion. Jnl. Biomech, vol. 44, pp 747-750, 2011. doi: 10.1016/j.jbiomech.2010.11.019. [3] M. Cáceres, P. Serra, J. Lopez, & A. Page. Reliability of the Shoulder Instantaneous Helical Axis measurement during the scaption movement. Gait & Posture, vol. 49, pp 268, 2016.