Modeling of Soft Pneumatic Actuators with Different Orientation Angles Using Echo State Networks for Irregular Time Series Data.

Modeling of soft robotics systems proves to be an extremely difficult task, due to the large deformation of the soft materials used to make such robots. Reliable and accurate models are necessary for the control task of these soft robots. In this paper, a data-driven approach using machine learning is presented to model the kinematics of Soft Pneumatic Actuators (SPAs). An Echo State Network (ESN) architecture is used to predict the SPA's tip position in 3 axes. Initially, data from actual 3D printed SPAs is obtained to build a training dataset for the network. Irregular-intervals pressure inputs are used to drive the SPA in different actuation sequences. The network is then iteratively trained and optimized. The demonstrated method is shown to successfully model the complex non-linear behavior of the SPA, using only the control input without any feedback sensory data as additional input to the network. In addition, the ability of the network to estimate the kinematics of SPAs with different orientation angles θ is achieved. The ESN is compared to a Long Short-Term Memory (LSTM) network that is trained on the interpolated experimental data. Both networks are then tested on Finite Element Analysis (FEA) data for other θ angle SPAs not included in the training data. This methodology could offer a general approach to modeling SPAs with varying design parameters.

Underwater Soft Robotics: A Review of Bioinspiration in Design, Actuation, Modeling, and Control.

Nature and biological creatures are some of the main sources of inspiration for humans. Engineers have aspired to emulate these natural systems. As rigid systems become increasingly limited in their capabilities to perform complex tasks and adapt to their environment like living creatures, the need for soft systems has become more prominent due to the similar complex, compliant, and flexible characteristics they share with intelligent natural systems. This review provides an overview of the recent developments in the soft robotics field, with a focus on the underwater application frontier.

Modelling and implementation of soft bio-mimetic turtle using echo state network and soft pneumatic actuators.

Advances of soft robotics enabled better mimicking of biological creatures and closer realization of animals' motion in the robotics field. The biological creature's movement has morphology and flexibility that is problematic deportation to a bio-inspired robot. This paper aims to study the ability to mimic turtle motion using a soft pneumatic actuator (SPA) as a turtle flipper limb. SPA's behavior is simulated using finite element analysis to design turtle flipper at 22 different geometrical configurations, and the simulations are conducted on a large pressure range (0.11-0.4 Mpa). The simulation results are validated using vision feedback with respect to varying the air pillow orientation angle. Consequently, four SPAs with different inclination angles are selected to build a bio-mimetic turtle, which is tested at two different driving configurations. The nonlinear dynamics of soft actuators, which is challenging to model the motion using traditional modeling techniques affect the turtle's motion. Conclusively, according to kinematics behavior, the turtle motion path is modeled using the Echo State Network (ESN) method, one of the reservoir computing techniques. The ESN models the turtle path with respect to the actuators' rotation motion angle with maximum root-mean-square error of [Formula: see text]. The turtle is designed to enhance the robot interaction with living creatures by mimicking their limbs' flexibility and the way of their motion.

Tactile sensing biohybrid soft E-skin based on bioimpedance using aloe vera pulp tissues.

Soft and flexible E-skin advances are a subset of soft robotics field where the soft morphology of human skin is mimicked. The number of prototypes that conformed the use of biological tissues within the structure of soft robots-to develop "Biohybrid Soft Robots"-has increased in the last decade. However, no research was conducted to realize Biohybrid E-skin. In this paper, a novel biohybrid E-skin that provides tactile sensing is developed. The biohybrid E-skin highly mimics the human skin softness and morphology and can sense forces as low as 0.01 newton . The tactile sensing feature is augmented through the use of Aloe Vera pulp, embedded in underlying channel, where the change in its bioimpedance is related to the amount of force exerted on the E-skin surface. The biohybrid E-skin employs high biomimicry as the sensorial output is an oscillating signal similar to signals sent from the human sensing neurons to the brain. After investigating different channel geometries, types of filling tissues, and usage of two silicone materials, their frequency-force behaviour is modelled mathematically. Finally, a functional multichannel prototype "ImpEdded Skin" is developed. This prototype could efficiently detect the position of a tactile touch. This work employs the development of discrete sensing system that exhibits morphological computation that consequently enhances performance.

The effect of water quality on the immunoreactivity of stress-response cells and gonadotropin-secreting cells in the pituitary gland of Nile tilapia, Oreochromis niloticus.

The present experiments investigated the effect of water quality characteristics on the condition factor, the ovarian activity, cortisol level, and the immunoreactivity of stress-response cells (adrenocorticotropic hormone; ACTH- and melanin stimulating hormone; MSH- and somatolactin; SL- secreting cells) and gonadotropin (GTH)-secreting cells in the pituitary gland of Nile tilapia, Oreochromis niloticus. After 3 months of exposure to mixtures of water from different sources (Tap and Lake Manzalah waters), with high levels of minerals and heavy metals, water quality affected the number, size, and immunostaining of stress-response-immunoreactive (ir) cells and GTH-ir cells, which showed a dramatic decrease in their size. The integrated optical density (IOD) of immunoreactivity of MSH- and GTH- cells was significantly increased; however, it was significantly decreased for ACTH- and SL- cells. Also, high levels of cortisol were observed in females exposed to waters with high concentrations of minerals and heavy metals. In parallel, low values of gonadosomatic index (GSI%) and the ovarian histology revealed a decrease of maturing follicles concomitant with an increase of atretic follicles in females exposed to Lake Manzalah polluted water. Taken together, the increased activity of stress-response-ir pituitary cells, serum cortisol level and ovarian atretic follicles in response to elevated concentrations of minerals and heavy metals, supports the possible role of ACTH, MSH, and SL in the adaptive stress response of fish. Therefore, minerals and heavy metals must be considered when discussing tilapia aquaculture status.

Effect of stress during handling, seawater acclimation, confinement, and induced spawning on plasma ion levels and somatolactin-expressing cells in mature female Liza ramada.

The present experiments were designed to determine the effect of different stress factors; handling, seawater acclimation, confinement, and induced spawning on plasma cortisol, hydro mineral balance as well as changes in size, number and integrated intensity of somatolactin (SL)-expressing cells in Liza ramada mature females confined to fresh water ponds. The plasma levels of cortisol, PO(4)(3-), Na(+), and K(+) were higher, while Ca(2+) and Mg(2+) were lower than controls during transportation without anesthesia. By using clove oil (5 mg L(-1)) as an anesthetic during transportation, the plasma cortisol, PO(4) (3-), Na(+), and K(+) were similar to controls, while Ca(2+) and Mg(2+) were higher. During seawater acclimation, the plasma cortisol and minerals were significantly higher except Na(+) which was lower than controls. In addition, during induction of spawning, the plasma levels of cortisol, PO(4)(3-), Na(+), K(+), and Mg(2+) were significantly higher than controls. The SL-producing cells are located in the pars intermedia (PI) bordering the neurohypophysis. The stress affected the number, size, and immunostaining of SL-expressing cells. During seawater acclimation, the size and the integrated intensity of SL immunoreactivity were lower, but the number of these cells was higher than controls. Furthermore, the number, size, and the integrated intensity of SL immunoreactivity were significantly lower than controls during handling and after spawning, which was opposite to confinement. The response of SL-expressing cells in PI in parallel with changes in cortisol and hydro mineral balance induced by stress support the possible role of SL in the adaptive response of fish to stress.

Induced spawning and embryonic development of Liza ramada reared in freshwater ponds.

The possibility of inducing and synchronizing spawning can be very useful to facilitate fish farming, particularly in species that achieve ovarian development in captivity without ovulation occuring. The present study was undertaken to observe the morphological and normal embryonic development of thin-lipped mullet, Liza ramada, after spawning induction of fish reared in freshwater fish farms. The use of pregnyl (HCG) as a priming injection at a dose of 20,000 IU/kg body weight followed by a second injection of 40,000 IU HCG/kg body weight 24 h later, proved to be effective in inducing final oocyte maturation, ovulation and spawning in L. ramada at 52-60 h after hormonal injection. The mean number of the ovulated eggs for each female was 700 +/- 80.3 eggsg(-1) body weight. The mean rates of buoyancy, fertilization and hatching were 46 +/- 7.1, 55 +/- 8.4 and 60 +/- 6.6, respectively. Fertilized eggs were kept under normal environmental conditions in seawater at 20-21 degrees C. The first cleavage occurred at 40 min, epiboly began at 5 h, the embryonic body was formed at 24 h and hatching occurred at 48 h after spawning. Newly hatched larvae were approximately 2.5 mm (total length) and similar to those of the other mullet species in terms of external features except no pigment spots were present over the yolk. The mouth and foregut opened on the 5th day after hatching; at which the total length of larvae was 3.5 mm; the hindgut and anus had developed prior to hatching. The induced ovulation technique using acute injections of hormones is an important step in the development of the mullet culture.

Involvement of corticotropin-releasing factor and adrenocorticotropic hormone in the ovarian maturation, seawater acclimation, and induced spawning of Liza ramada.

In the present study, we investigated the distribution and activities of corticotropin-releasing factor (CRF) and adrenocorticotropic hormone (ACTH) immunoreactive (ir) cells in the brain and pituitary of Liza ramada during ovarian maturation, seawater acclimation, and induction of spawning. Using immunohistochemistry, we detected that CRF-ir cell bodies exist in different brain regions: medulla oblongata (MO), midbrain tegmentum, habenula, nucleus preopticus (NPO), and in a ventral hypothalamic region corresponding to the nucleus lateralis tuberis (NLTP). In the pituitary gland, we detected some ACTH-producing cells in the rostral pars distalis (RPD) containing CRF immunoreactivity. The synthetic and secretory activity of CRF-ir cells in the NPO and MO as well as ACTH-ir cells in the pituitary were enhanced during ovarian maturation. During seawater acclimation, CRF-ir cells in the NPO and MO and ACTH-ir cells in the pituitary showed dramatic increases in their synthetic activity. These cells showed dramatic increase in their secretory activity during spawning induced by human chorionic gonadotropin (HCG) injection in L. ramada. Finally, hormonally induced ovulation was accompanied with elevation of plasma cortisol and depletion of CRF and ACTH immunoreactivity within the brain and the pituitary gland, respectively. Taken together, our findings suggest that mature breeders of L. ramada may respond to stress resulting from ovarian maturation, and seawater acclimation as well as induced spawning. Mechanisms include enhancement of the synthetic and/or secretory activity of CRF-ir cells in the NPO and MO as well as ACTH-ir cells in the pituitary gland along with a rise in plasma cortisol during ovulation, supporting the possible role of these hormones during stress and reproduction in L. ramada.

Immunohistochemical localization of inhibin and activin-like proteins in the brain, pituitary gland, and the ovary of thin-lipped grey mullet, Liza ramada (Risso).

Inhibin and activin, dimeric protein hormones originally isolated from mammalian gonads, are involved in the regulation of vertebrate reproduction. In the present study, we investigated the localization of inhibin and activin subunits (alpha, beta(A), and beta(B)) immunoreactivity in the brain, pituitary, and ovary of female Liza ramada using immunohistochemistry. We demonstrate that activin beta(A) subunit immunoreactivity is found in most of the brain regions: telencephalon (Tel), midbrain tegmentum (MT), and cerebellum (C). In the pituitary gland, activin beta(A) subunit immunoreactivity is observed in nerve fibers that are in close contact with somatotrophs and gonadotrophs. Strong immunostaining of activin beta(B) subunit is detected in melanotropin (MSH)-producing cells in pars intermedia (PI), which are in close contact with gonadotrophs. In the ovary, the cytoplasm as well as follicle cells of previtellogenic oocytes exhibited strong immunoreactivity of activin beta(A). However, the activin beta(A) and beta(B) immunoreactivity is decreased when the oocytes entered the vitellogenic stage (recrudescence). The progress in the accumulation of yolk within oocytoplasm is accompanied by a decrease in the activin beta(A) and beta(B) immunoreactivity and eventually the immunoreactivity disappears completely when the oocytes become fully mature. Interestingly, the vitellogenic oocytes of female L. ramada obtained from fresh water (captivity) contain only weak immunoreactivity of activin beta(A) compared to that of saline water (natural habitat). Moreover, immunoreactivity of activin beta(B) is observed in the phagocytic granulosa cells during resorption of oocytes (atresia) within the ovary of female reared in captivity. The immunostaining of inhibin alpha in the ovary is similar to that of activin beta(B) but the reaction intensity is weaker. However, the mature oocytes show a positive reaction for inhibin alpha. These results provide evidence for the presence of inhibin and activin-like molecules within L. ramada and reveal the distribution of these molecules in L. ramada brain-hypophysial-gonadal system. Our observations add some new informations to our current understanding of activin system in fish and suggest that inhibin and activin may play an important role for L. ramada reproduction in the event of oocyte growth and maturation.

Immunohistochemical localization of gonadotropin releasing hormones in the brain and pituitary gland of the Nile perch, Lates niloticus (Teleostei, Centropomidae).

In the present study we investigated the distribution of gonadotropin-releasing hormones (GnRH) in the brain of Lates niloticus and their association with different pituitary cell types using immunohistochemical techniques. We found immunoreactive (ir) chicken GnRH-II (cGnRH-II) and mammalian GnRH (mGnRH) as the main components of the GnRH-ir system within the brain of the Nile perch. The results indicate that mGnRH and cGnRH are localized in different neurons: mGnRH-ir perikaria were observed in the preoptic region particularly in the organum vasculosum laminae terminalis (OVLT) and in the nucleus lateralis tuberis pars posterior (NLTP) of the mediobasal hypothalamus. These cell bodies are located along a continuum of ir-fibers that could be traced from the olfactory nerve to the pituitary. mGnRH-ir fibers were detected in many parts of the brain (olfactory bulbs, ventral telencephalon, hypothalamus, and mesencephalon) and in the pituitary. cGnRH-ir cell bodies are restricted to the optic tract, but few scattered fibers could be detected in different parts of the brain. The pituitary exhibited very few cGnRH-II ir fibers, contrasting with an extensive mGnRH innervation. Moreover, mGnRH-ir fibers were targeting the three areas of the pituitary gland: rostral pars distalis (RPD), proximal pars distalis (PPD), and pars intermedia (PI). Double immunolabeling studies showed GnRH-ir fibers in close proximity with prolactin (PRL)- and adrenocorticotropic hormone (ACTH)-producing cells in the RPD, growth hormone (GH)-producing cells in the PPD, gonadotropins (GTHs)-producing cells in the PPD in the external border of the PI, and with somatolactin (SL)- and alpha-melanocyte stimulating hormone (alpha-MSH)-producing cells in the PI. Our results showed direct morphological evidence for a close association of GnRH-ir fibers with the different adenohypophysial cell types. These results suggest a multiple role of GnRH in the regulation of various pituitary hormones' release.