Collision-free inverse kinematics of the redundant seven-link manipulator used in a cucumber picking robot

The paper presents results of research on an inverse kinematics algorithm that has been used in a functional model of a cucumber-harvesting robot consisting of a redundant P6R manipulator. Within a first generic approach, the inverse kinematics problem was reformulated as a non-linear programming problem and solved with a Genetic Algorithm (GA). Although solutions were easily obtained, the considerable calculation time needed to solve the problem prevented on-line implementation. To circumvent this problem, a second, less generic, approach was developed which consisted of a mixed numerical-analytic solution of the inverse kinematics problem exploiting the particular structure of the P6R manipulator. Using the latter approach, calculation time was considerably reduced. During the early stages of the cucumber-harvesting project, this inverse kinematics algorithm was used off-line to evaluate the ability of the robot to harvest cucumbers using 3D-information obtained from a cucumber crop in a real greenhouse. Thereafter, the algorithm was employed successfully in a functional model of the cucumber harvester to determine if cucumbers were hanging within the reachable workspace of the robot and to determine a collision-free harvest posture to be used for motion control of the manipulator during harvesting. The inverse kinematics algorithm is presented and demonstrated with some illustrative examples of cucumber harvesting, both off-line during the design phase as well as on-line during a field test

Algoritmos de lagrangiano aumentado para problemas de flujo no lineal

Al abordar la resolución de problemas no lineales mediante tecnicas de Lagrangiano aumentado es usual utilizar algoritmos del tipoPeer Reviewe

Analysis of load displacement in grape harvesters and corresponding effect on dynamic weighing system under laboratory conditions

Harvester bin dynamic weighing systems are affected by a number of sources of variation such as field slopes and load displacement. In grape harvesters, the nature of the material (wine grapes and wine grape juice) and its relative composition can vary significantly. Laboratory tests were carried out using hydrogel spheres and water to simulate field dynamic conditions during harvest. This paper quantifies the sources of variation, submitting an instrumented grape harvester to graduated inclination under shaking conditions. Load displacement is characterized using image analysis from recorded movies on four different pitch axis motions of the machine: front to horizontal, horizontal to rear, rear to horizontal and horizontal to front. Differences in the displacement of the load in relation to the machine inclination and to the load composition have been addressed

Los valles tectónicos recientes de Rubielos de la Cerida (Teruel)

[Resumen] La actividad tectónica cuaternaria y reciente ha dado lugar en este área a un conjunto de depresiones alargadas de orientación submeridiana, enmarcadas por fallas, que constituyen valles tectónicos[Abstract] Quaternary and recent tectonic activity led to a series of elongated depressions in the studied area of roughly N-S orientation, framed by faults, and developping as tectonic valleys

Taphonomy and palaeohistology of ornithischian dinosaur remains from the Lower Cretaceous bonebed of La Cantalera (Teruel, Spain)

The fossiliferous site of La Cantalera-1 (Teruel, Spain) has to date provided remains of more than 30 vertebrate taxa, including dinosaurs, crocodyliforms, pterosaurs, mammals, lizards, turtles, lissamphibians and teleosteans. Located in the lower part of the Blesa Formation (lower Barremian), it is one of the richest vertebrate-bearing deposits from the Lower Cretaceous of the Iberian Peninsula. In this work, taphonomic and palaeohistological studies are carried out on the basis of ornithischian (Ornithopoda and Ankylosauria) dinosaur samples in order to assess the diagenetic processes, to characterize the histological microstructures and, if possible, to make palaeobiological inferences about the state of maturation of the individuals. A variety of techniques are used in the taphonomic study, including scanning electron microscopy (SEM), cathodoluminescence (CL), X-ray diffraction (XRD) and ultraviolet fluorescence (UVF). The bone of the dinosaur samples has been converted into francolite (fluorapatite carbonate); the trabecular cavities are filled with semi-spherical forms of goethite and two different phases of calcite. In addition, the SEM and UVF techniques suggest the activity of coccoid-form bacteria and filaments of bacterial origin (biofilms?) in the bones, which possibly favoured fossilization. The dinosaur remains were subjected to fossil-diagenetic processes in a phreatic environment after a rapid burial, without appreciable seasonality effects. On the other hand, the palaeohistological study of both skeletal and dermal bones found in La Cantalera-1 shows a community of herbivorous dinosaurs composed mostly of immature ornithopods and at least one Polacanthus-like ankylosaur, as suggested by the organizational pattern of structural collagen fibres seen in some samples. The palaeobiological inferences drawn from this study support previous interpretations of a relative abundance of immature ornithischians in La Cantalera-1

Morfología de vertientes y neotectónica en el Macizo de Javalambre (provincia de Teruel)

[Resumen] El modelado actual de las vertientes del macizo de Javalambre es consecuencia de tres tipos principales de procesos que actúan a partir de su elevación a comienzos del Plioceno -superior: (a) la dinámica periglaciar, (b) una etapa de activida~ tect6nica ocurrida hacia el Pleistoceno medio-superior, y (c) deslizamientos gravitacionales, translacionales y rotacionales producidos a favor de un sustrato plástico en las áreas de mayor incisión de la red -fluvial.Abstract] The present slope form in Javalambre area results from three principal types of processes which are active after its elevation in the early Upper Pliocene: (a) periglacial dynamics, (b) a tectonic phase in Middle-Upper Pleistocene, and (c) gravitational, translational and rotational landslides generated over plastic rocks in zones with a intensive fluvial incisio

Flor de levaduras: Análisis morfológico del crecimiento en medio sólido.

La contaminación con levaduras es un factor muy relevante en el detrimento de la calidad de algunos alimentos. Cuando las levaduras se desarrollan en medio sólido lo hacen en forma de colonias superficiales. El análisis de imagen es una técnica idónea para el análisis objetivo de las diferencias morfológicas que se observan durante el crecimiento de las levaduras en medio sólido. En este trabajo se escogen los parámetros matemáticos que permitan establecer un procedimiento cuantitativo capaz de caracterizar el tránsito de una morfología circular a otra lobulada, programándolos empleando como base las librerías de análisis de imagen Matlab. El procedimiento propuesto se valida con un amplio diseño experimental: periodo de crecimiento y número de colonias por placa

New version of a laboratory impact device for firmness sensing of fruits.

Results of previous studies conducted by different researchers have shown that impact techniques can be used to evaluate firmness (Delwiche et al., 1989; Delwiche et al.;1996; Jaren et al., 1992; Ruiz Altisent et al., 1996). To impact the fruit with a small spherical impactor of known mass and radius of curvature and measure the acceleration of the impactor is a technique described by Chen et al. (1985) and used by several researchers for sensing fruit firmness (Jaren et al., 1992; Correa et al.; 1992). The advantages of this method vs. a force sensor that measures the force as a function of time is that the measured impact-acceleration response is independent of the fruit mass and is less sensitive to the variation in the radius of curvature of the fruit (Chen et al., 1996). Ruiz Altisent et al. (1993) developed and used a 50 g impactor with a 19 mm diameter spherical tip, dropping from different height for fruits (apples, pears, avocados, melons, peaches ...). Another impact device for firmness sensing of fruits was developed by Chen and Ruiz Altisent (1996). They designed and fabricated an experimental low-mass impact sensor for high-speed sensing of fruit firmness. The impactor consisted of a semi-spherical impacting tip attached to the end (near the centre of percussion) of a pivoting arm. Impact is done by swinging the impactor to collide with the fruit. It has been implemented for on-line use. In both devices a small accelerometer is mounted behind the impacting tip. Lateral impactor and vertical impactor have been used in laboratory and the results from non-destructive impact tests have contributed to standardise methods to measure fruit firmness: Barreiro (1992) compared impact parameters and results of Magness-Taylor penetration tests for apples, pears, apricots [and peaches; Agulheiro (1994) studied the behaviour of the impact parameters during seven weeks of cold storage of two melon varieties; Ortiz (1998) used low energy impact and NIR procedures to segregate non crispy, non firm and soft peaches. Steinmetz (1996) compared various non-destructive firmness sensors, based on sound, impact and micro-deformation