The wrist unit is crucial in humanoid robots, determining their operational dexterity and precision. To address current challenges such as excessive size, limited Degrees of Freedom (DoFs), and insufficient load capacity, we propose a 3-DoF humanoid wrist inspired by the human forearm and wrist anatomy. This paper explores the principles of wrist bionic design and introduces a parallel mechanism actuated by a brushless DC motor (BLDC)-ball screw to achieve flexion/extension (F/E) and radial flexion/ulnar deviation (R/U), as along with pronation/supination (P/S) through an end-coupling design. We conducted an analysis on the inverse kinematic model and singularities of the humanoid wrist. Additionally, the workspace and motion capabilities of the humanoid wrist were evaluated. A prototype based on this design was built to demonstrate its motion and functional performance, verifying the feasibility and practicality of the humanoid wrist. This research provides a more compact design approach for future humanoid wrist development.

One drawback of wheeled robots is their inferiority to conquer large obstacles and perform well on complicated terrains, which limits their application in rescue missions. To provide a solution to this issue, an ant-like six-wheeled reconfigurable robot, called AntiBot, is proposed in this paper. The AntiBot has a Sarrus reconfiguration body, a three-rocker-leg passive suspension, and mechanical adaptable obstacle-climbing wheeled legs. In this paper, we demonstrate through simulations and experiments that this robot can change the position of its center of mass actively to improve its obstacle-crossing capability. The geometric and static stability conditions for obstacle crossing of the robot are derived and formulated, and numerical simulations are conducted to find the feasible region of the robot’s configuration in obstacle crossing. In addition, a self-adaptive obstacle-crossing algorithm is proposed to improve the robot’s obstacle-crossing performance. A physical prototype is developed, and using it, a series of experiments are carried out to verify the effectiveness of the proposed self-adaptive obstacle-crossing algorithm.

The Flexible, fast and lightweight leg mechanism is the key to improve legged robot’s mobility, efficiency and adaptability on complex terrain. Inspired by the motion mechanism of legged animals, we report a concentrated-driven omnidirectional legged locomotion bionic leg – OmniLeg. All the motor actuators are centrally installed in the hip plate of the proposed leg to reduce the rotational inertia. Meanwhile, the special 3-Dimensional dual-parallelogram-linkages transmission mechanism enables it to have the ability of omnidirectional legged locomotion in 3-Dimensional space and makes the posture of leg’s endpoint does not change with the motion of the leg mechanism which simplifying the motion control. In this paper, firstly the theoretical model, including mobility, kinematics model, inverse kinematics model, dimension parameters and workspace model, have been derived, analyzed and verified with the design and control of the real prototype. Next, to demonstrate the ability of omnidirectional legged locomotion intuitively, we manufacture a single-legged omnidirectional mobile robot and design a quadruped robot, and the simulation and experiment result illustrate that the design and analytical mode of OmniLeg is feasible and correct, which could be widely applied in the field of legged robot.

Bionic-based robotic legs enable the legged robots with elegant and agile mobility in multi-terrain environment, just like natural living beings. And the smart design could efficiently improve the performance of a robotic leg. Inspired by the simplified human leg structure, we present a 3-DOF robotic leg—OmniLeg, that is capable of making omnidirectional legged locomotion while keeping constant posture of the foot. Additionally, the concentrated drive mode, in which all the motor actuators are installed in the torso and do not move with the leg, minimizes the inertia of the robotic leg. In this paper, the modular design, the kinematics model, the structural analysis, the workspace, and the performance evaluation of the OmniLeg are discussed. Furthermore, we build a prototype based on the proposed design, and the precision of it is verified by the error calibration experiment which is conducted by tracking the trajectory of the prototype’s endpoint. Then, we present an OmniLeg-based single legged mobile robot. The capability of omnidirectional legged locomotion of the OmniLeg is demonstrated by the experiments.

Bionic amphibious robots have important prospects in scientific,commercial,and military fields.Compared with traditional amphibious robots which use propellers/jets for aquatic medium and wheels/tracks for terrestrial medium,bionic propul-sion method has great advantages in terms of manoeuvrability,efficiency,and reliability,because there is no need to switch between different propulsion systems.To explore the integrated driving technology of amphibious robot,a novel bio-inspired soft robotic fin for amphibious use is proposed in this paper.The bionic fin can swim underwater and walk on land by the same undulating motion.To balance the conflicting demands of flexibility underwater and rigidity on land,the undulating fin adopts a special combination of a membrane fin and a bending spring.A periodic longitudinal wave in horizontal direc-tion has been found generating passively in dynamic analysis.To find the composite wave-driven mechanics,theoretical analysis is conducted based on the walking model and swimming model.A virtual prototype is built in ADAMS software to verify the walking mechanics.The simulation result reveals that the passive longitudinal wave is also periodical and the composite wave contributes to land walking.Finally,an amphibious robot prototype actuated by a pair of undulating fins has been developed.The experiments show that the robot can achieve multiple locomotion,including walking forward/backward,turning in place,swimming underwater,and crossing medium,thus giving evidence to the feasibility of the newly designed undulating fin for amphibious robot.

Inspired by the structure of the human leg, a bionic leg with the constant posture of the endpoint and capable of omnidirectional legged locomotion is proposed. The structural layout of the bionic leg is introduced. The flexibility of the leg mechanism is analyzed using the condition number of the Jacobian matrix as a performance index. The static model of the leg mechanism is developed based on the virtual work principle. The bearing capacity performance index and the force equilibrium performance index are established by the vector extremum method. Furthermore, the static performance of the leg mechanism is analyzed. In order to verify the applied feasibility and the performance of omnidirectional legged locomotion, the motion simulation of the quadruped robot based on the proposed design is carried out as it moves along seven different directions. A prototype is developed to serve as the foundation for the next phase in the improvement and practical implementation of omnidirectional bionic legs.

Direct ink writing is a versatile bioprinting technology to fabricate soft models, where soft materials are extruded through an orifice and settled on a platform to form multi-layered structures. An extruded filament is the basic unit of the extrusion process which can affect the overall quality of model fabrication. Here, we report a novel method to evaluate the quality of printing via introducing two dimensionless indices, which independently reflect the average width and the width variation of extruded filaments. Different concentrations of Pluronic (R) F127 materials were used to print zigzag multi-layer models to understand the influences of printing parameters on both indices. Results show the dual-index method can semi-quantitatively expose the morphological differ-ences of extrudates under altered printing conditions, providing a potential evaluation tool for the quality assessment of direct ink writing.

The human hand has a fantastic ability to interact with various objects in the dynamic unstructured environment of our daily activities. We believe that this outstanding performance benefits a lot from the unique biological features of the hand musculoskeletal system. In Part I of this article, a bio-inspired anthropomorphic robotic finger was developed, based on which two human-finger-like biomechanical advantages were elaborately investigated, including the anisotropic variable stiffness associated with the ligamentous joints and the enlarged feasible force space associated with the reticular extensor mechanisms. In Part II, the fingertip force-velocity characteristics resulting from the flexible tendon sheath are studied. It indicates that the fingertip force–velocity workspace can be greatly augmented owing to the self-adaptive morphing of the flexible tendon sheaths, showing the average improvement of 41.2% theoretically and 117.5% experimentally compared with the results of 2 mm, 4 mm, and 6 mm size rigid tendon sheaths. Grasping tests and comparisons are then conducted with four three-fingered robotic hands (one with the robotic finger proposed in Part I, one with hinge joints, one with linear extensors, and one with rigid tendon sheaths) and the human hands of six subjects to handle various objects on flat, rough, and soft surfaces. The results show that the novel bio-inspired design in this research could improve the grasping success rates of the robotic hand. Compared with the grasping test results from the robotic hand with the bio-inspired robotic finger proposed in Part I, the overall grasping performance of a robotic hand with hinge joints, linear extensors, and rigid tendon sheaths decreases by 10%, 6%, and 17%, respectively. The results have also shown that with the embedded biomechanical advantages, even without complex control and sensory systems, the robotic fingers can achieve very comparable performance to human fingers in the grasping demonstrations presented, indicating average 94% of the success rate achieved by the human fingers. Successfully demonstrating 14 of 16 grasp types in the Cutkoskey taxonomy further shows the human-finger-like grasping capability of the proposed robotic fingers.

Human-machine intelligent integration of wearable robots such as prostheses and exoskeletons will be a key future robot industry development trend, with significant implications for supporting medical rehabilitation, expanding the boundaries of human sports, and boosting societal welfare. This research presents a novel actuator that replicates the driving principle and structure of human muscles in order to increase the load capacity of wearable robots while lowering their size and weight. Better power density and energy efficiency result in a higher load capacity, more compact construction, lower weight, and longer service life for the actuator system. The hydraulic actuator has a higher driving force and power density than the electric actuator or the new flexible actuator. The bionic hydraulic actuator system has emerged as a significant study area in bionic robotics.

Biomimetic robots have great advantages in terms of flexibility, efficiency, and maneuverability. In this paper, a novel amphibious robot which mimics the undulation motion of stingrays and snakes are proposed. The robot is able to swim underwater and walk on land by a pair of undulating fins. The structure of the robot is designed and the principle of locomotion method are described. The calculation platform is established. And the dynamic mesh method for computational fluid dynamics simulation is outlined. Underwater motion simulation is conducted in surging, steering and in-situ rotation patterns. The results show that the robot is capable of multimodal locomotion by the coordination of two fins.

In order to solve the problems of traditional wheeled robots with large turning radius, low obstacle crossing ability, poor flexibility and manoeuvrability, a multimodal mobile robot with a six wheel drive and six wheel steering structure is proposed in this paper. By varying the rotation angle of the robot's six wheels, the robot is able to achieve four basic movement modes: straight travel, translation, steering in situ, and turning around any point. At the same time, the dual rocker arm suspension structure ensures that the robot can always land on six wheels, improving its overall passability and terrain adaptability. Firstly, the robot structure is designed. Then, by establishing a motion model of the six wheel drive and steering robot, the angle and velocity relationships of the six wheels under four different motion modes are established, which will provide a kinematic basis for the design of motion controller. Next, the virtual prototype is modelled in Gazebo software, and simulation tests are conducted for the four basic motion modes as well as the obstacle crossing ability of the robot. The simulation results verify the high flexibility and strong obstacle crossing ability of the robot.

Extrusion-based printing with soft materials is an additive manufacturing technology, which is widely used in biomedical fields such as skin reconstruction, muscle repair, and cartilage regeneration, etc. Constructing high-precision printed structures and maintaining high cellular bioactivity are key issues in the in vitro construction of tissues and organs using extrusion bioprinting. There are some printing paraments such as pressure, height, nozzle type (eg, length and inner diameter), translational speed, etc. can have a huge influence on the structural fidelity. In this work, we put forward a quantitative test method to evaluate the printing accuracy is influenced by pressure and height. The results show that higher pressure can benefit uniformity (the filament width is equal everywhere), and higher height leads to higher uniformity only in low pressure for paste. This study can provide researchers with the tunning suggestions of printing paraments, which may promote the development of printing accuracy in the future.

Exploring human hand fundamental biomechanical features and exploiting them to robotic hands have been proven to be an effective approach to enhancing artificial hands' performance, especially when interacting with various objects in dynamic unstructured environments. In this article, a bioinspired anthropomorphic robotic finger is first proposed, which embeds human finger musculoskeletal features in the design. Based on this design, three human-finger-like biomechanical advantages are systematically investigated and embodied in the bioinspired robotic finger. This article for the first time derives, presents, and experimentally verifies the mathematical models for the variable stiffness of finger ligamentous joints and self-adaptive morphing mechanism of finger flexible tendon sheaths, and validates and compares the influence of the reticular and linear extensor morphologies on fingertip feasible forces in three-dimensional (3-D) space. In this Part I of the article, two of the biomechanical properties, i.e., joint stiffness generated by the ligamentous joint of the finger, and fingertip feasible force space influenced by the reticular extensor mechanism are systematically investigated through theoretical modeling and experimental verification. Correspondingly, two biomechanical advantages were found, i.e., the ligamentous joint of the finger could provide anisotropic variable joint stiffness, enhancing the adaptivity, dexterity, and stability of fingers; and a reticular extensor mechanism could enlarge the fingertip feasible force space in 3-D space by 30.9% theoretically and 146.4% experimentally on average compared with the linear extensor, contributing to enrich force conditions during interactions. The third biomechanical advantage, i.e., fingertip force–velocity workspace can be augmented through the flexible tendon sheath, and grasping tests for a robotic hand designed with the aforementioned advantages are presented in Part II of this article.

Rheology is a science that studies the flow and deformation of materials and the relationships between various factors that cause them to flow and deform. Finding the relationship between stress and strain, or the rate of both, during fluid deformation is the core issue of rheology research. In this study, a composite hydrogel with good conductivity based on polyacrylamide (PAM) and lithium chloride (LiCl) was introduced. This PAM-LiCl conductive hydrogel is also highly stretchable and can be used for flexible actuation technology of robots. Based on the oscillating rheological testing method, the dynamic response of this material under different thermal-mechanical loads was measured, and intrinsic parameters such as shear modulus and yield stress were obtained. Based on the test results, the material ratio and mechanical properties suitable for the preparation of PAM-LiCl conductive hydrogel were obtained, which laid the foundation for the preparation of conductive hydrogel-related materials.

：A muscle-driven robot based on living tissues is deeply integrated with the traditional electromechanical system.Compared with the traditional rigid and the non-biological flexible material driving robot at millimeter scale, muscle-driven robots have the advantages of micro-scale, high power density, biocompatibility, etc.Therefore, they can play an important role in biomedicine, battlefield reconnaissance and other fields, which have attracted widespread interest globally.The current research progress, potential applications, challenges and solutions of muscle-driven robots will be summarized and discussed here.Firstly, the muscle tissue structure and stress mechanism of living cells were described.On this basis, two design ideas of artificial biological muscle-driven robot composed of living cells and non-biological flexible materials and real biological muscle-driven robot directly obtained from living body are summarized.The different control strategies of muscle-driven robots and their advantages and disadvantages are systematically summarized.Finally, its potential application and the main challenges it encounters are discussed and summarized, and the corresponding possible solutions are suggested, which can provide guidance for the development and performance improvements of the follow-up muscle-driven robots.

With the development of science and technology, the modern high-tech war has put forward a higher demand for soldiers. Soldiers often carry loads beyond safety standards, which can reduce combat effectiveness and cause non-combat diseases. Aiming at the complex and changeable battlefield environment, this paper designed a light passive knee exoskeleton for walking assistance. It has the advantages of simple structure and comfortable wearing, and can realize the functions of assist, reduce the load of knee joint and auxiliary support. Through the optimal design of the six-bar mechanism, the trajectory matching of the ICR of the man-machine joint was realized and the joint was self-locked in the standing state. In order to verify the assistance effect of the exoskeleton, the human-machine coupling model was established in the OpenSim biomechanical analysis software to simulate and calculate the changes of some muscle forces before and after wearing the exoskeleton, and the prototype was completed to detect the changes of EMG signals before and after wearing the exoskeleton. Simulation and experimental results show that the exoskeleton can significantly reduce the acting force on extensor knee muscle and calf plantarflexion muscle during the gait of the wearer.

Stable, quiet, and efficient propulsion methods are essential for underwater robots to complete their tasks in a complex marine environment. However, with a single propulsion method, such as propeller propulsion and bionic propulsion, it is difficult to achieve high efficiency and high mobility at the same time. Based on the advantages of the high-efficiency propulsion of a bionic undulating fin and the stable control of the propeller, an underwater robot based on the hybrid propulsion of a quadrotor and undulating fin is proposed in this paper. This paper first introduces the mechanical implementation of the underwater robot. Then, based on kinematic modeling and theoretical derivation, the underwater motion and attitude of the robot are analyzed and the 6-DOF dynamic equation of the robot is established. Finally, the underwater motion performance of the robot is verified through field experiments. The experimental results show that the robot can realize the heave motion, surge motion, and in-situ steering motion independently and can hover stably. When the undulating frequency is 6 Hz, the maximum propulsion speed of the robot can reach up to 1.2 m/s (1.5 BL/s).

Mobile robots can replace rescuers in rescue and detection missions in complex and unstructured environments and draw the interest of many researchers. This paper presents a novel six-wheeled mobile robot with a reconfigurable body and self-adaptable obstacle-climbing mechanisms, which can reconfigure itself to three locomotion states to realize the advantages of terrain adaptability, obstacle-crossing ability, and portability. Design criteria and mechanical design of the proposed mobile robot are first presented, based on which the geometry of the robot is modeled and the geometric constraint, static conditions, and motion stability condition for obstacle crossing of the robot are derived and formulated. Numerical simulations are then conducted to verify the geometric passing capability, static passing capability, and motion stability and to find feasible structure parameters of the robot in obstacle crossing. Further, a physical prototype of the proposed mobile robot is developed and integrated with mechatronic systems and remote control. Using the prototype, field experiments are carried out to verify the feasibility of the proposed design and theoretical derivations. The results show that the proposed mobile robot satisfies all the criteria set and is feasible for applications in disastrous rescuing scenarios.

Limited load capacity is the bottleneck for the practical application of mobile multi-joint legged robots. And improving the efficiency of the drive system is a key factor in improving the load capacity. To improve the efficiency of mobile robots, in this paper, a new kind of actuator that imitates the driving mechanism of human muscles is innovatively designed and validated through experiments. The proposed actuator consists of a single power source and multiple plunger pistons, and imitates the configuration of a human muscle, to improve the efficiency and load capacities. The design proposed here represents a new class of driving methods. The actuator selects the most appropriate combination of the effective areas of plunger pistons like the human muscles, to ensure that the maximal output force aligns with the load force. To validate that the new actuator can improve the efficiency of hydraulic systems of mobile robots, a robotic arm incorporating a prototype of the new actuator was designed. The proposed system was validated through a series of experiments. The experiments show that the bionic actuator can adjust the flow rate of the system input by adjusting the number and size of the motion units involved in the work, and with the change in load force, it changes the output force by recruiting different motion units, which indicates good controllability. The results reported herein reveal that the application of bionics to the design of robotic actuator can significantly improve the efficiency and overall performance of the robots, and this biomimetic approach can be applied to a variety of robots.

In view of the shortcomings of traditional teaching in the Mechanical Design Fundamentals course, the teaching resources are integrated, the teaching content, teaching methods, and assessment methods are reformed, scientific research results are introduced into course teaching, and the task-driven teaching practice is applied. These measures have improved classroom activity, stimulated independent learning, and laid the foundation for the cultivation of students’ engineering literacy and innovative ability.