Nature has always inspired human achievements in industry, and biomimetics is increasingly being applied in fluid power technology. Arachnida use hydraulic forces, rather than muscle, for leg extensions during locomotion. Many cold-blooded and soft-bodied organisms rely on a hydrostatic skeleton to transmit force, which involves a hydraulic mechanism. Biological hydraulic transmission differs from engineering hydraulic transmission in many aspects, such as in energy transfer and transformation, the movement mode, environmental friendliness, system pressure level, and energy supplement mode. The existence of a hydraulic mechanism in a biological drive requires 3 features: a power source, cavity, and working medium. The power source is similar to a hydraulic pump, and the cavity is similar to a hydraulic cylinder, both of which are necessary for producing deformation. The working medium is similar to a hydraulic fluid. Under these 3 conditions, a biological flow is generated inside or outside the body to meet the requirements of a biological drive. This paper reviews the biological organisms that employ hydraulic systems, identifies related studies on these biological hydraulic systems, and summarizes the mechanisms involved in using hydraulic pressure to achieve graceful and agile movements. This in-depth study and exploration of biological hydraulic systems can provide a good reference for solving the challenges of using hydraulic systems, such as increasing the energy efficiency, improving reliability, building smart components and systems, reducing the size and weight of compo-nents, reducing the environmental impact of systems, and improving and applying energy storage and redeployment capabilities. This paper also includes a detailed discussion of new ideas and innovative sources for the future development of hydraulic systems. In contrast with the bio-inspired designs used in other engineering fields, very few studies have reported on using bio-inspired methods for hydraulic transmission techniques. The aim of this work is to attract the attention of researchers to help address this gap and to promote the use of biologically-inspired methods to improve engineering fluid power systems.

In this work, we utilized underside of four different plant leaves with different scale of hierarchical surface roughness to fabricate large area self-cleaning antireflective polymer surfaces. A simple and precise two-step soft–lithography replica molding technique was deployed by using polydimethylsiloxane (PDMS) polymer as a replicating material. In the first step, a negative PDMS replica was fab-ricated by using the underside of an original leaf as a template material. In the second step, a positive PDMS replica was fabricated through a negative PDMS replica used as a template. In order to study the non-wetting and light trapping properties, as-replicated polymer surfaces were characterized using Scanning Electron Microscopy (SEM), contact angle goniometer, and UV-Vis spectroscopy. SEM images con-firmed the successful replication of complex hierarchical structures while contact angle measurement studies established retaining high non-wetting properties in polymer replicas. Optical studies suggest near zero reflection in normal mode and less than 5% diffuse reflection when measured using integrated sphere mode. These results have been correlated and explained with the air-liquid fraction and roughness factor as measured using three-dimensional optical profilometer.

The nocturnal scorpion Heterometrus petersii uses Basitarsal Compound Slit Sensilla (BCSS) as mechanoreceptor to detect me-chanical signal (e.g. substrate vibration, cyclic loads caused by walking) without fatigue failure such as initiation of fatigue crack and further propagation of crack-shaped slit. The outstanding perceptive function has been discovered for over half a century. However, it is not yet clear about the microstructure, material composition and micromechanical property which are all important factors that determine the fatigue fracture resistance of the BCSS. Here, the microscopic characteristics of the BCSS were thoroughly studied. The results in-dicate that anti-fatigue resilin and stiff chitinous cuticle form multilayered composite as the main body of the BCSS. Meanwhile, the pre-existing slit as mechanosensory structure is covered by cuticular membrane which has different mechanical property with the epicu-ticle. Theoretical analysis shows that the structure-composition-property synergistic relations of composites confer on the BCSS with extreme fatigue fracture tolerance.

In this paper, the functionalities of microstructures for dragonfly wing during gliding flight are investigated. Three dragonfly-mimic airfoil-shaped wings with hybrid structures were designed and fabricated as: flat wing, zigzag-edged wing and zigzag-edged wing with pillar structure. Based on the wind tunnel experiments, the zigzag-edged wing structure significantly reduces the drag force in the gliding flight. Moreover, the drag reduction is more effective on the combination of the surface pillar and zigzag-edged structure. In addition, the zigzag-edged wing structure has less influence of Karman vortex street, and the surface pillars reduce the frictional drag and stabilized the streamline in the lower vortex region. Overall, the microstructure of the dragonfly wing is an important element in the aerodynamic study. These findings can enhance the knowledge of insect-mimic wing structure and facilitate the application of Micro Air Vehicle (MAV) in the gliding flight. 

The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds’ wing, all test models have S1223 airfoil. Swept models inspired from the bird consist of two parts: the straight part near the root and the swept part near the tip. Aerodynamic forces on each wing were measured from 0? to 24? angles of attack and Reynolds numbers of 4.3×104, 8.6×104, 1.3×105, and 1.7×105. Wind tunnel test results show that wings with an innovative sweep at α > 0 have more lift for Reynolds numbers between 4.3×104 and 8.6×104. Also, innovative sweep increases the stall angle, and the wing did not stall until α = 24? for Reynolds between 1.3×105 and 1.7×105. An increase in lift and having sufficient aero-dynamic performance in low Reynolds numbers for birds’ inspired wing sweep in gliding flight may be the answer to why the wing sweep of birds is not like conventional sweeps.

In the narrow, submarine, unstructured environment, the present localization approaches, such as GPS measurement, dead-reckoning, acoustic positioning, artificial landmarks-based method, are hard to be used for multiple small-scale underwater robots. Therefore, this paper proposes a novel RGB-D camera and Inertial Measurement Unit (IMU) fusion-based cooperative and relative close-range local-ization approach for special environments, such as underwater caves. Owing to the rotation movement with zero-radius, the cooperative localization of Multiple Turtle-inspired Amphibious Spherical Robot (MTASRs) is realized. Firstly, we present an efficient Histogram of Oriented Gradient (HOG) and Color Names (CNs) fusion feature extracted from color images of TASRs. Then, by training Support Vector Machine (SVM) classifier with this fusion feature, an automatic recognition method of TASRs is developed. Secondly, RGB-D camera-
based measurement model is obtained by the depth map. In order to realize the cooperative and relative close-range localization of MTASRs, the MTASRs model is established with RGB-D camera and IMU. Finally, the depth measurement in water is corrected and the efficiency of RGB-D camera for underwater application is validated. Then experiments of our proposed localization method with three robots were conducted and the results verified the feasibility of the proposed method for MTASRs.

Grasping force estimation using surface Electromyography (sEMG) has been actively investigated as it can increase the manipula-bility and dexterity of prosthetic hands and robotic hands. Most of the current studies in this area only focus on finding the relationship between sEMG signals and the grasping force without considering the arm posture. Therefore, regression models are not suitable to predict grasping force in various arm postures. In this paper, a method to predict the grasping force from sEMG signals and various grasping postures is developed. The proposed algorithm uses a tensor algebra to train a multi-factor model relevant to sEMG signals corresponding to various grasping forces and postures of the wrist and forearm in multiple dimensions. The multi-factor model is then decomposed into four independent factor spaces of the grasping force, sEMG signals, wrist posture, and forearm posture. Moreover, when a participant executes a new posture, new factors for the wrist and forearm are interpolated in the factor spaces. Thus, the grasping force with various postures can be predicted by combining these factors. The effectiveness of the proposed method is verified through experiments with ten healthy subjects, demonstrating the higher performance of proposed grasping force prediction method than the previous algorithm.

In this study, mechanical properties of bionic porous structures with diagonal-symmetrical and midline-symmetrical unit cells were studied when the porosities were same. Three typical unit cells (Diamond (DO), Rhombic Dodecahedron (RD), and Octet Truss (OT)) were selected, in which DO has diagonal-symmetrical shape, while RD and OT share midline-symmetrical structure. Based on the same porosity, corresponding models were designed, and Ti6Al4V samples were manufactured by electron beam melting. Then, using Me-chanical Properties Testing (MPT) and Finite Element Analysis (FEA) methodologies, mechanical properties and transmissions of dif-ferent porous structures were evaluated. Besides, composition and details before and after printing were analyzed with Energy Dispersive Spectrometer (EDS), X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). MPT results showed that midline-symmetrical shape would have superior compressive performance than diagonal-symmetrical shape, but opposite trend for the torsion performance, which were in line with FEA prediction. Furthermore, effective modulus of DO, RD and OT were 2.59 GPa, 4.89 GPa, and 1.77 GPa, approximating the mechanical properties of human bones. Additionally, manufacturing defects and discrepancies between FEA and MPT were found. This study would provide great helps for unit cell selection and initial mechanical properties matching for optimum bone implants.

Polymer composites reinforced with the biofibers are found to have improved applications in many fields and also they can reduce the environmental effect. In this work, caryota – a new natural fiber for polymer composites is fabricated and their tensile, flexural and impact properties are estimated to be used in economical and lightweight load carrying structures. Laminates at different weight fraction (wt%) of 10 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt% and 45 wt% are manufactured using a compression molding technique. Results asserted that the unidirectional arrangement having 40 wt% fiber posses good properties. Also the dynamic characteristics such as natural frequency and damping study are carried out for different wt% of unidirectional caryota fiber reinforced composite laminates by ex-perimental modal analysis. From this study, it has been asserted that by using the caryota fiber reinforced polyester composites, the tra-ditional synthetic fiber can be replaced especially in automobile sector. If the caryota fiber reinforced composite material is applied properly, then its application fields will be improved.

In this paper, a novel cable-driven parallel robot, CUBE, is introduced for the assistance of patients in rehabilitation exercising of both upper and lower limbs. The system is characterized by a lightweight structure that is easy to set-up and operate, for both clinical and home usage for both pre-determined and customized exercises, with control over the position of the end-effector while locking its rotation around the horizontal axes. Its cable-driven design makes it inherently safe in human/robot interactions also due to the extremely low inertia. While a novel end-effector design makes the device wearable both on the upper and lower limbs without having to disassemble any part of the structure. The design is presented with its kinematic analysis. Then, the manufacturing through 3D-printing and commercial components of a first prototype is reported. Finally, the system is validated through motion tests along simple trajectories and two different spatial exercises.

This paper deals with an optimization approach to design a cable driven parallel robot intended for upper limb rehabilitation tasks. The cable driven parallel robots have characteristics that make them best candidate for rehabilitation exercise purposes such as large workspace, re-configurable architecture, portability and cost effectiveness. Here, both the cable tensions that are needed to move a wristband as well as the workspace need to be carefully optimized for fulfilling the prescribed operation tasks. A specific case of study is addressed in this work by referring to LARM wire driven exercising device (LAWEX), which is applied to upper limbs exercises. To that end, a motion capture system is used to collect quantitative data on the prescribed workspace of a human upper limb. A specific optimi-zation problem is settled up for considering combining two optimization goals, namely, the smallest robot size reaching a prescribed workspace and the minimum cable tension distributions. A sequence of optimization steps is defined using Genetic Algorithms (GAs) applied to LAWEX robot. The proposed objective function is based on a mathematical formulation of the power of a point with respect to bounding surfaces in combination with a performance index to show the distributions of the minimum cable tensions. 

The first objective of this paper is to study the influence of the orthotic device on the maximum values of stresses in knee cartilages by using Ansys Workbench 14.5 software and applying the Finite Element Analysis (FEA) on a virtual assembly composed by an orthotic device and osteoarthritic knee (OAK). The second objective consists into quantifying and investigating the nonlinear motion of the human knee joint for OAK patients, with and without the orthotic device mounted on OAK, using tools of dynamics stability analysis. The short Lyapunov Exponents (LEs) are calculated, as measures of human knee and ankle joints stability, based on the experimental time series collected by using the biometrics acquisition system during walking on horizontal and inclined treadmills from a sample of healthy sub-jects and a sample of patients suffering by OAK disease. The values of LEs obtained for OAK patients are larger on the inclined treadmill than on horizontal treadmill and are larger than those obtained for healthy knees, being associated with more divergence and less stability. The results confirm that the influence of an orthotic device mounted on OAK on its stability is significant, the values obtained for LEs being smaller than those calculated for OAK, and closer to the values of normal knees of patients and of healthy subjects.

Technological advances are increasing the range of applications for artificial intelligence, especially through its embodiment within humanoid robotics platforms. This promotes the development of novel systems for automated screening of neurological conditions to assist the clinical practitioners in the detection of early signs of mild cognitive impairments. This article presents the implementation and the experimental validation of the first robotic system for cognitive assessment, based on one of the most popular platforms for social robotics, Softbank “Pepper”, which administers and records a set of multi-modal interactive tasks to engage the user cognitive abilities. The robot intelligence is programmed using the state-of-the-art IBM Watson AI Cloud services, which provide the necessary capabilities for improving the social interaction and scoring the tests. The system has been tested by healthy adults (N = 35) and we found a significant correlation between the automated scoring and one of the most widely used Paper-and-Pencil tests. We conclude that the system can be considered as a screening instrument for cognitive assessment.

This paper investigates the walking performance of a thermal walker on various inclined surfaces. The thermal walker can walk only by ground heat energy using bimetal sheets. The walking performance on slopes is analyzed using a simplified walker model. The ana-lytical result is compared with the two sets of walking experiments, on slopes with either pitch or roll inclinations. The analyses and the experiments are done with different Center-of-Mass (CoM) positions of the legs, which considerably influence the walking performance. It was found that, on up/down slopes, the stride of the thermal walker changes almost linearly with the slope angle. When the CoM was close to the center of the walker body, the walker walked backward on upward slopes. With CoM largely shifted backward, the walker could walk up slopes but did not walk down slopes well. On the other hand, when walking along a contour line of a slope, the stride decreased as the slope angle increased. The smaller leg swing distances would be caused by the change of leg swing time on such slopes.

Intermittent Pneumatic Compression (IPC) devices can be used to analyze the mechanisms underlying several vascular phenomena, such as hyperaemia. Commercial devices have limited dynamics and do not allow the delivery of customizable compressive pressure patterns, making the analysis of such phenomena difficult, which may require the application of long stimulations with low amplitude as well as fast compressions with higher pressure level. To overcome these issues, a novel pneumotronic device aimed to the investigation of the physiological effects induced by limb compressions is conceived and presented in this work. The design requirements of the system, capable of delivering customizable compressive patterns in the range 0 mmHg – 200 mmHg, are outlined. The final prototype architecture is described, and a mathematical model of the entire system, also including the interaction between the device and the limb tissues, is proposed. The performance of the device was evaluated in several conditions by means of simulations, whose results were compared to the data collected from experimental trials in order to validate the model. The outcomes of both experimentation and simulation trials proved the effectiveness of the solution proposed. A possible employment of this device for the investigation of the rapid compression-induced hyperaemia is presented. Other potential applications concern the wide range of intermittent-pneumatic compression treatments.