Ionic electroactive polymers (IEAPs) are a category of intelligent soft materials exhibiting large displacement under electric excita-tion, based on inner ion or solvent transport. Due to their unique advantages such as flexibility, low driving voltage, large bending dis-placement and aquatic-environment adaptability, IEAPs have been documented as very promising actuators for the applications in bionic robots. This review presents an analysis to the current research status of IEAPs exploited in bionic robots. According to the specific bionic parts, those robots are divided into four classes: imitation of fins, limbs, joints and trunks. Their dimension, weight, voltage amplitude, frequency and maximum speed were summarized to show the optimum design range. The results show that the approach velocity of the current robots were higher (> 35 mm?s?1) when the robot weighted 60 g – 180 g and the body was 90 mm – 130 mm long. For voltage from 1 V – 3 V and frequencies from 0.7 Hz – 1.2 Hz, the speed was relatively higher (> 35 mm?s?1).To some extent, the maximum speed decreases when the area of the IEAP material used in bionic robot increases. For underwater circumstances, IEAP materials are most suitable for designing bionic robots swimming with Body and/or Caudal Fin (BCF). This review provides important guidance for the design of IEAP bionic robots.

This paper proposes a hand exoskeleton system for evaluating hand functions. To evaluate hand functions, the hand exoskeleton system must be able to pull each finger joint, measure the finger joint angle and exerted force on the finger simultaneously. The proposed device uses serially connected 4-bar linkage structures, which have two embedded actuators with encoders and two loadcells per finger, to move each phalanx independently and measure the finger joint angles. A modular design was used for the exoskeleton, to facilitate the removal of unnecessary modules in different experiments and improve convenience. Silicon was used on the surface of the worn part to reduce the skin irritation that results from prolonged usage. This part was also designed to be compatible with various finger thicknesses. Using the proposed hand exoskeleton system, finger independence, multi-finger synergy, and finger joint stiffness were determined in five healthy subjects. The finger movement and force data collected in the experiments were used for analyzing three hand functions based on the physical and physiological phenomena.

A force planning and control method is proposed for a tendon-driven anthropomorphic prosthetic hand. It is necessary to consider grasping stability for the anthropomorphic prosthetic hand with multi degrees of freedom which aims to mimic human hands with dexterity and stability. The excellent grasping performance of the anthropomorphic prosthetic hand mainly depends on the accurate computation of the space position of finger tips and an appropriate grasping force planning strategy. After the dynamics model of the tendon-driven anthropomorphic prosthetic hand is built, the space positions of the finger tips are calculated in real time by solving the dynamic equations based on the Newton iteration algorithm with sufficient accuracy. Then, the balance of internal grasping force on the thumb is adopted instead of force closure of the grasped objects to plan the grasping forces of other fingers based on the method of the linear constraint gradient flow in real time. Finally, a fuzzy logic controller is used to control the grasping force of the prosthetic hand. The proposed force planning and control method is implemented on the tendon-driven anthropomorphic prosthetic hand and the experimental results dem-onstrate the feasibility and effectiveness of the proposed method.

For human assistance device, the particular properties are usually focused on high precision, compliant interaction, large torque generation and compactness of the mechanical system. To realize the high performance of lower extremity augmentation device, in this paper, we introduce a novel control methodology for compact elastic module. Based on the previous work, the elastic module consists of two parts, i.e., the proximal interaction module and the distal control module. To improve the compactness of the exoskeleton, we only employ the distal control module to achieve both purposes of precision force control and human intention recognition with physical human-machine interaction. In addition, a novel control methodology, so-called high precision data-driven force control with disturbance observer is adopted in this paper. To assess our proposed control methodology, we compare our novel force control with several other control methodologies on the lower extremity augmentation single leg exoskeleton system. The experiment shows a satisfying result and promising application feasibility of the proposed control methodology.

We have created an inchworm robot capable of the two-anchor crawl gait on level ground and inclined plane. The main novelty is in the design of the inchworm: (1) three-part body that is 3D printed and actuated by two servo motors to allow a looping and lengthening action, (2) passive friction pads to anchor the feet, each of which may be disengaged using a servo motor actuated lever arm, and (3) modular body and electronics. The robot is about 2 feet (61 cm) in length, has a mass of about 4 kg, and uses an open-loop controller to achieve steady crawling gait. The inchworm robot achieved a speed of 2.54 cm?s?1 on level ground as well as on an incline plane of 19?. The energy usage as measured by the Mechanical Cost of Transport (a non-dimensional number defined as the energy used per unit weight per unit distance moved) is 3.34. Our results indicate that simple robotic designs that copy the basic features of natural organisms provide a promising alternative over conventional wheeled robots.

Biped locomotion has excellent environment adaptability due to natural selection and evolution over hundreds of millions years. However, the biped walking stability mechanism is still not clear. In this paper, an experimental analysis of walking stability in human walking is carried out by using a motion capture system. A new stability analysis method is proposed based on Zero Moment Point (ZMP) and Sliding Time Window (STW). The influences of ground friction coefficient, ground slope angle and contact area of support polygon on human walking stability are investigated. The experiment is carried out with 12 healthy subjects, and 53 passive reflective markers are pasted to each subject to obtain moving trajectory and to calculate lower limb joint variation during walking. Experimental results show that ground friction coefficient, ground slope angle and contact area have significant effects on the stride length, step height, gait cycle and lower limb joint angles. When walking with small stability margin, subjects modulate gait to improve the stability, such as shortening stride length, reducing step height, and increasing the gait cycle. These results provide insights into the stability mechanism of human walking, which is beneficial for locomotion control of biped robots.

In bio-inspired design activities, nature is a basis of knowledge. Over the last twenty years, many solutions to measure and analyze human or animal gaits have been developed (VICON system, X-ray radiography...). Although, these methods are becoming more and more accurate, they are quite expensive, long to set up and not easily portable. In this paper, a method called the bio-inspired topological skel-eton is proposed in order to complement the classic videography process and to enable animal gait analysis. A new predictive kinematic model with closed-loops of an unguligrade quadruped is suggested. This kinematic model includes three segments per leg and takes into account the scapula movements. The proposed method allows us to improve the accuracy of the kinematic input data measured from a single video including an additional artefact. To show the benefits of this method, joint parameters that are difficult to measure are derived symbolically from the kinematic model and compared with experimental data.

It has been well demonstrated that there are two kinds of surface morphologies, including binary structures (namely micro-and nanostructures) and less common unitary structures (such as micro-line structures), which play crucial roles in endowing the plant leaves with superhydrophobic properties. In this work, five superhydrophobic plant leaves in nature are introduced, by means of the combination of surface morphology and wettability with the aid of Scanning Electron Microscopy (SEM) and contact angle measurement. The results indicate that either the binary structures or the unitary structures enable the construction of a superhydrophobic surface, and the latter shows likely better mechanics compared with the former according to the corresponding theory. This research aims at introducing two different types of corresponding morphologies of superhydrophobic plant leaves.

It is found that many biological organisms exhibit superior adhesion characteristics in wet environments. It has been observed that the foot pads of tree frogs and katydids are consist of a number of closely arranged polygons, most of them are hexagonal. In this paper, the common structure of two kinds of biological foot pad was extracted to model the bionic surface structure of friction plates. The friction plate prototypes were also prepared. Through the multivariate orthogonal regression design, the optimum parameter combination of the friction performances of the prototypes of the bionic plates has been obtained. The hexagonal circumcircle size is 10 mm, the groove width is 1 mm, and the hexagonal diagonal angle is 90?. Then the maximum static friction coefficient, dynamic friction coefficient and wear amount of the optimal friction plate were tested and compared with the control group friction plates. The comparative analysis of the experiment findings demonstrated that the bionic structure with hexagonal ring grooves can significantly improve the friction performance of the friction plates.

Taking advantage of the lateral line organ, fish can navigate, feed, and avoid predators and obstacles by sensing surrounding flow fields. The lateral line organ provides an important reference for the development of new underwater detection technology. Inspired by the lateral line organ, in this paper, for the sake of localizing the target dipole source in three-dimensional underwater space, an artificial lateral line consisting of nine underwater pressure sensors forming a cross-shaped sensor array is applied. Combined with the method of gener-alized regression neural network, which is suitable for solving nonlinear pattern recognition problems, a corresponding experimental platform has been built to sample data for training the neural network from a 12 cm by 12 cm by 24 cm cuboid space. The experimental results indicate that the cross-shaped artificial lateral line can localize the target dipole source two body-lengths away. The well-performing perceptual distance is below 13 cm away from the sensing array. Moreover, decreasing the data sampling interval and in-creasing the number of sensors utilized can help improve the positioning accuracy.

Bone cements are often used for bone repair and fixation. The main objective of formulating a bone cement is to achieve structure and properties similarity to bone. In addition, bioactivity of a bone cement provides a major advantage that helps achieving better binding and interaction with the surrounding tissues. In the current study, gypsum was used as a matrix for a composite that comprises highly crys-talline prestine and acid-treated wollastonite (CaSiO3) fibers. Composites made by mixing their powder precursors with deionized water at room temperature, were investigated for their composition using X-ray diffraction (XRD) and Thermogravimetric Analysis (TGA), for their microstructure using Scanning Electron Microscopy (SEM), for their compressive strengths and modulus of elasticity, and for setting time measurements. In addition, cement composites were evaluated for their preliminary bioactivity in a protein-free Simulated Body Fluid (SBF) for up to 14 days. Results show the improvement of mechanical properties and bioactivity of the composites using acid-treated wollastonite fibers. This was attributed to the formation of hydrated silica layer on the surface of the acid-treated fibers which improved the binding with the gypsum matrix and provided nucleating sites for the deposition of bone-like apatite spherolites from SBF media.

Health and sustainability are the major concerns that drive researchers to find novel materials to replace artificial hazardous materials. In this investigation, the mechanical properties of Cissus quadrangularis Stem Fiber (CQSF) reinforced with unsaturated polyester composite were optimized by varying the fiber length and content. To substantiate the findings, chemical property, thermal property, microstructure, and water absorption property were analyzed. Progressive enhancement of mechanical properties was observed with increasing the fiber content and fiber length up to 30 wt.% and 40 mm. However, beyond that limit, there was a decline in the strength due to improper bonding of fiber with matrix. Optimal values of mechanical property for CQSF composite were obtained at 30 wt.% fiber content and 40 mm fiber length, which are comparable with that of common artificial fiber-reinforced polymer composites.

Tissue-engineered bone scaffolds provide temporary mechanical support for bone tissue growth. Mechanical stimuli are transferred to seeded cells through the scaffold structure to promote cell proliferation and differentiation. This paper presents a numerical investigation specifically on bone and cartilage tissue differentiation with the aim to provide a theoretical basis for scaffold design and bone defect repair in clinics. In this study, the scaffold structures were established on the basis of cancellous bone microarchitectures. For finite element simulations, inlet velocity and compressive strain were applied under in vitro culture conditions. The influences of this scaffold mor-phology and macro-level culture conditions on micro-mechanical stimuli at scaffold surfaces were investigated. Correlations between the microarchitectural parameters and the mechanical parameters, as well as the cell differentiation parameters were analyzed. Highly het-erogeneous stress distributions were observed on the scaffolds with irregular morphology. Cell differentiation on the scaffold was more sensitive to the inlet velocity than the axial strain. In addition, cartilage differentiation on the scaffolds with structures comprising more plate-like trabeculae was more pronounced than on those with more rod-like trabeculae. This paper is helpful to gain more insight into the mechanical environments under in vitro culture conditions that approximate the in vivo mechanical environments of Bone Marrow Stromal Cells (BMSCs).