Addressing the trade-off between flight efficiency and environmental adaptability in traditional fixed-wing micro-flapping aircraft, this paper draws inspiration from the dynamic wing deformation mechanisms of birds to design an active folding-wing bionic flapping aircraft based on a single-degree-of-freedom linkage mechanism. This design employs servo-driven tether lines to achieve wing folding. Combined with a lightweight skeleton, the total weight of the aircraft is controlled at 181 g, with power transmission efficiency improved by 18%. The maximum wing folding angle reaches 80 degrees, reducing wing area by 60%. Bench and flight tests demonstrate stable operation at a 3.5 Hz flapping frequency and 120 degrees amplitude. The aircraft can navigate through 70 cm narrow passages, achieving a 103.6% increase in landing speed compared to fixed-wing designs. Wing deployment relies on elastic joints for inertial reset. This single-degree-of-freedom design simplifies control logic, resolves structural redundancy issues in multi-degree-of-freedom mechanisms, enhances the aircraft's maneuverability and adaptability to complex environments, and provides a new approach for the structural design of biomimetic flapping-wing aircraft. It also points to subsequent optimization directions such as lightweighting and intelligent control.

In pursuit of a high folding ratio, existing bio-inspired Flapping-Wing Aerial Vehicles (FWAVs) face a contradiction between the decline in aerodynamic efficiency and the sharp increase in structural complexity. This paper proposes a active-passive cooperative folding strategy based on the flight mechanism of birds. A “non-coplanar three-wing segments + slide rail link” active folding mechanism was constructed to achieve a 60° large-angle spatial contraction. A flexible joint at the leading edge was introduced to utilize the aeroelastic effect to achieve adaptive passive deformation during the flapping cycle, effectively compensating for the additional load loss caused by the folding mechanism. A lightweight on-board control system based on ESP32-C3 was built, integrating MPC and adaptive PID algorithms to solve the nonlinear attitude coupling problem during the morphing process. Experiments show that this configuration maintains a high folding ratio of 3.43 while increasing lift by 12.6

Aiming at the requirement that the brush head must maintain a specific distance from the curved surface during the cleaning operation of complex surfaces such as vases and cultural relics, this paper proposes a fixed-distance control method based on distance feedback from three non-collinear points at the end effector. The method collects distance information through three laser ranging sensors arranged in a triangular distribution, calculates the position deviation by averaging the three-point distances and dynamically adjusts the position of the end effector to maintain the preset working distance. To improve the ranging stability and accuracy of the sensors, moving average, weighted moving average, median filtering, Kalman filtering, and a combined filtering algorithm of moving average + weighted moving average are introduced. Comparative experiments verify that the Kalman filtering algorithm under a sampling period of 180 ms is optimal, reducing the root mean square error (RMSE) of distance measurement to 0.11 mm. To verify the effectiveness of the method, a compact cleaning robotic arm is designed, which realizes the combined motion of low-precision large-angle movement of the arm and high-precision small displacement of the end effector through a single-chip microcomputer and a bus servo control module. Experimental results show that the coordinate deviations of the system are controlled within 1.5 and 2.02 mm in fixed-distance vertical and horizontal motion experiments, respectively; in the irregular curved surface experiment, the maximum deviation is 1.35 mm and the RMSE is 0.61 mm, meeting the precision requirements for complex surface cleaning.

Due to the length of the body, multiple number of wheels and the complexity of controlling, it is difficult for a multi-axle wheeled robot to avoid obstacles autonomously in narrow space. To solve this problem, this article presents window-zone division and gap-seeking strategies for local obstacle avoidance of a multi-axle multi-steering-mode all-wheel-steering wheeled robot. Firstly, according to the influence degree of lidar points on the robot, combining with the human driving characteristics of avoiding obstacles, a window-zone division strategy is proposed. The lidar points are selected and divided according to the degree of emergency. By eliminating irrelevant points, the work of obstacle avoidance calculation is reduced. Thus, this increases the response speed of obstacle avoidance. Based on this, the robot uses a multi-steering-mode to avoid emergency obstacle. Secondly, the gap-seeking theory of normal obstacle avoidance is proposed. It can seek the passable gap among the surrounding lidar points according to the prediction of the robot's driving trajectory corresponding to different steering angles. Thirdly, the on-board control system and the upper computer program of the robot were designed. Thereafter a multi-steering-mode algorithm was designed based on the front and rear wheel steering angles and speed, as well as the travel trajectory forecast-drawing module. Finally, the proposed methods have been implemented on a five-axle all-wheel steering wheeled robot. Some obstacle avoidance experiments are carried out with S-shaped, Z-Shaped, U-Shaped, and Random obstacle distribution. The results show that the proposed strategy can finish all obstacle avoidance successfully.

Flapping-Wing Aerial Vehicles (FWAVs) have received extensive attention due to their high maneuverability and high efficiency in low Reynolds number flow conditions. Among them, FWAVs with foldable wings effectively improves flight performance by imitating the deformation characteristics of the wings during the flight of birds .This paper proposes a new type of passive deformation mechanism. Through the elastic joint installed on the wing, the automatic folding of the wing along the vertical direction during the upward flapping process is achieved, thereby reducing the effective area of the outer section of the wing, lowering air resistance and increasing net lift. When the flapping motion reaches the highest position, the wing can naturally unfold by utilizing the inertial force. Through dynamic modeling and simulation optimization, this study successfully developed a prototype with a weight of 152.72g. Compared with similar designs, the overall mass was significantly reduced. Verified through bench experiments and multiple sets of flight experiments, the results show that when the flapping frequency is 4 Hz and the flapping amplitude is 80°, the designed FWAV can achieve stable flight, and the maximum folding Angle of the wing reaches 45°. Compared with the rigid wing, its average lift has increased by 16%, and the relative error between the predicted lift of the model and the measured lift is less than 10%, with power consumption reduced by 42.9%. The research results of this paper provide important references and practical basis for the realization of the passive folding deformation mechanism in bio-inspired FWAVs.

In recent years, flapping-wing aircrafts have made remarkable progress in hover control, obstacle avoidance navigation, and wing surface contraction through the application of bionics. However, they still lack effective active deceleration and smooth landing capabilities. This paper proposes and designs a bionic flapping-wing aircraft that can autonomously decelerate through a slider-crank mechanism, based on the biomechanical characteristics of birds’ active posture adjustment before landing. This aircraft can effectively simulate the high-resistance gliding strategy adopted by birds before landing, which involves changing the flapping direction of the wing surfaces, and integrates a controllable torsion adjustment mechanism to achieve dynamic switching of flight states. System experiments have verified that the developed aircraft can significantly reduce its flight speed to 57% of the normal cruising speed during the deceleration and landing phase while ensuring flight stability, thereby significantly enhancing the controllability and safety of the landing process.

Vibration energy harvesting technology promotes the development of self-powered sensors. In response to the existing issues in piezoelectric energy harvesting, this paper designs a multi-directional multi-modal multi-stable piezoelectric vibration energy harvester (MDMMMS-PVEH). The device consists of a support base and four multi-modal and multi-stable structures. By adopting an inclined beam array design, it achieves multi-directional vibration energy capture. Meanwhile, a composite beam-magnetic coupling multi-stable design is employed to achieve wideband response and high power density energy output. Firstly, theoretical analysis and simulation parameter optimization were conducted on the prototype. The COMSOL software was used to analyze the cantilever beam structure, calculating the natural frequencies and vibration modes of different beams. Then, the simulation optimization of the inclined beam angle affecting multi-directional energy collection was carried out, determining the optimal inclination angle to be 45 degrees. The open-circuit voltage values of the beam structure were analyzed, and the arrangement of permanent magnets was also simulated. Finally, a prototype was developed and an experimental system was set up for testing. The experimental results show that the prototype can collect multi-dimensional vibration energy in the low-frequency range. Compared with the non-magnetic coupling, when excited in the Z-axis direction, the open-circuit voltage of the prototype increased by 36.1% and 61.2% at 12 Hz and 26 Hz excitation frequencies, respectively, and the maximum power density reached 21.50 mW cm-3, providing a solution for self-powered technology in the Internet of Things era.

Ornithopter is a research hotspot of unmanned aerial vehicles. In this paper, an ornithopter inspired by birds is designed. The fin deflection mechanism is adopted. During the upstroke phase, the fins are passively unfolded to reduce the resistance when the wing moves upward; while during the downstroke phase, the wings are passively closed to increase the effective wing area and the resistance during the downstroke, so as to increase the lift generated by the ornithopter during the flapping process. The wingspan of the ornithopter is 1.2 meters, and its weight is 180 grams. The inner wing is designed with a cambered wing and can carry a load of 150 grams. Through the lift test experiment of the ornithopter with and without the deflection mechanism, the results show that the lift of the cambered wing is increased by 41.99% +/- 2.63% compared with that of the flat wing, and the lift of the wing deflection mechanism is increased by 5.26% +/- 1.47%. Indoor and outdoor flight experiments are carried out, and the ornithopter can achieve the expected flight goals with good flight performance. This study provides new insights for improving the performance of ornithopter.

Flapping-wing vehicles have attracted extensive attention due to their high maneuverability and high efficiency under low Reynolds number flow conditions. Among them, the foldable flapping-wing vehicle effectively improves flight performance by imitating the deformation of wings during the flight of living organisms. Therefore, Inspired by the active contraction and deformation of wings in birds and bats during flapping, this study designed and tested two types of active folding wing mechanisms based on the lever principle (lever type and lever-scissors combination type). The key flight parameters (flapping-wing frequency, amplitude, and elevation Angle) were optimized through fluid-structure coupling simulation. Force measurement experiments and flight tests show that when the flapping frequency is 5 Hz, the flapping amplitude is 120°, and the takeoff elevation Angle is 16°, both mechanisms can achieve rapid folding (<0.3 s), with wing folding rates of 1.92 and 2.06 respectively. And it significantly increases the dive acceleration in the folded state, indicating the effectiveness of independently controlling the folding wing motion in enhancing the maneuverability of flapping-wing vehicles.

This paper presents a design scheme for a bionic jumping take-off flapping-wing aircraft. By mimicking the mechanical mechanism of bird jumping, this scheme enables the autonomous take-off of the aircraft. The aircraft features a skeletal structure that combines a lightweight carbon fiber frame with 3D-printed nylon components. It has a wingspan of 1.2 meters and an overall weight of 0.172 kilograms. The flapping motion of the wings is driven by high-torque servos. The jumping mechanism uses a torsion spring as an energy storage element, and the instantaneous energy release is achieved through servo control. To verify the effectiveness of the jumping take-off, high-platform jumping and high-platform jumping take-off experiments were designed. The experimental results show that when the wings are at the Lower Flapping Limit Position (LFLP) and the take-off ramp is inclined downward by 24 degrees, the aircraft can successfully jump and take off from a 4-meter-high ramp and achieve stable flight over a distance of more than 15 meters. This study reveals the crucial role of the flapping-wing attitude (especially the forward tilt angle of the fuselage) in the conversion of initial kinetic energy and its relationship with the take-off ability. Compared with the traditional horizontal take-off method, this design significantly reduces the space required for take-off, providing an effective solution for the autonomous take-off of small flapping-wing aircraft in complex environments.

The variability of vibration direction and the randomness of frequency in the environment pose a serious challenge to the development of efficient energy harvesting devices. Based on this, a multidirectional wide-band piezoelectric vibration energy harvester (MWB-PVEH) based on magnetic coupling effect is proposed in this paper. The MWB-PVEH consists of three piezoelectric cantilever beams with orthogonal orientations and their terminal permanent magnets. The prototype realizes the mutual excitation of multi-directional vibration through the magnetic coupling between the piezoelectric cantilever beams in different directions, and simultaneously makes the piezoelectric cantilever beams in each direction show staggered resonance frequency distribution. Thus, the combination of broadband response and multi-directional energy collection is realized, which effectively improves the energy collection efficiency under various vibration conditions. In order to verify the feasibility of the device, theoretical analysis, simulation research and experimental tests are carried out respectively. The experimental results show that in the low frequency range (0-30Hz), the prototype can generate three resonant peaks (12.8 Hz, 15 Hz and 19.1 Hz), which significantly broadens the working frequency band of the energy harvester. Under the excitation rate of 0.5 g, Z-direction and 12.8 Hz, the total output power of MWB-PVEH is 3.14mW and the power density is 6.54mW/cm3.

The internal inspection of smooth and clean cavity structural parts such as glass components can only be carried out by negative pressure adsorption wall climbing robots. Due to the complexity of the internal structure of these structural parts, robots are required to avoid obstacles and transition between different surfaces. However, due to the large number of joints, it is very difficult to achieve these actions and the cost is high. In this paper, we propose a method to realize the robot's space motion by controlling the robot's stride length and steering angle. Firstly, the normal climbing and traversing climbing movements are designed, the key control points (target points) are found to realize these movements, and the geometric relationship of each joint angle is derived. Secondly, we analyze the relationship between stride length and joint angle, as well as the relationship between the distance to transition the wall and stride length, and further deduce the equations of space movement, and design the equations and program of iterative calculation. With it, the robot can automatically detect the distance, adjust the stride length, and automatically transition during the climbing process. Real-world experiments have confirmed that the robot can perform straight and turning motions on horizontal, vertical and inverted surfaces, transition from one wall to another, and avoid obstacles on both horizontal and vertical surfaces. This paper reduces the difficulty of the wall-climbing robot control, and enhances the movement flexibility and application potential in the narrow environment.

Wall Climbing Robots (WCRs) represent the proliferation in the field of robotics. Research on wall-climbing robots has led to significant advancements in various capabilities, particularly in abilities such as navigation on curved surfaces and transitioning between different walls. This systematic review offers a detailed analysis of the current advancements in wall-climbing robots, highlighting their promising applications in real-life scenarios such as inspection and maintenance. We discussed and evaluated the different methods of adhesion and locomotion, considering their effectiveness across different scenarios and key factors impacting their performance. The control strategies employed in wall-climbing robots and their perception abilities were also examined in this review. Possible challenges ahead for wall-climbing robots include the optimization of their robustness and adaptability to complex environments, which are crucial for optimizing the robot's efficiency.

Flapping wing vehicles mimic the wing flapping of flying creatures such as birds, bats and insects, and are characterized by simplicity, lightness, good concealment, high maneuverability and diversified flight attitudes. Currently, the development of wing-fluttering vehicles mainly focuses on wing-fluttering configurations, while there is little research on mimicking the large-scale active folding of wings of birds and bats. Here, we developed two types of large-scale folding wing vehicles with light mass and actively folded wings respectively, based on the property that the wings of flying organisms can be actively folded and contracted in a large scale, and tested their flight capabilities. The test results show that the latter vehicle, which combines the flapping wing mechanism and the active folding mechanism, has good flight performance and is able to accomplish the airborne folding of the wings on the basis of the flapping wing flight.

In nature, birds and bats dynamically alter their wing shapes to suit various flight environments and tasks. This paper focuses on the design and validation of a biomimetic flapping-wing aerial vehicle, named FlexiWing, which features a unique mechanism for active wing deformation. This mechanism allows the wings to adjust their shapes flexibly in response to flight demands, significantly enhancing attitude control and maneuverability.' 'This study began with an in-depth exploration of biomimetic principles, focusing particularly on how birds and bats achieve precise control during flight through active wing deformation. Subsequently, we present a detailed account of the design and fabrication process of the active folding biomimetic flapping-wing aerial vehicle, including the design of mechanical mechanisms and material selection. Utilizing lightweight nylon materials and hollow carbon fiber rods, we successfully constructed a mechanically foldable wing structure. To achieve precise control over the aircraft's movement, an embedded control system was designed, comprising an onboard embedded flight controller and ground-based equipment. The onboard controller uses a high-performance ESP32-C3 processor and a JY901 inertial measurement unit to acquire real-time attitude information of the aircraft. The control system incorporates Wi-Fi communication technology, enabling operators to send commands via a remote control or personal computer to manage flight modes and attitudes. Ultimately, a series of flight experiments were conducted to validate the performance of FlexiWing. The results demonstrate that FlexiWing exhibits remarkable maneuverability and stability, capable of achieving high-precision attitude control through active wing folding, making it adaptable to complex environments and tasks.'

Existing magnetically driven soft robots mainly rely on external electromagnetic, leading to a substantial energy consumption due to the requirement of a large external magnetic field. Moreover, the precise control of these soft robots relies on electric current, making them highly susceptible to disturbances and deviations induced by minute variations in the current. To overcome these challenges, we propose and evaluate a novel approach employing a miniature walking soft robot empowered by its internal electromagnets. The overall robot size is 18 mm x 6 mm x 12 mm (length x heightx width). This design enables the robot to achieve precise and stable motion using a 240-mA current with a 6 V low voltage. In addition, the incorporation of specially designed sheet-leg mechanism with varying degrees of friction facilitates the transformation of linear motion into an effective forward gait. This paper outlines the principles and control strategies of the robot, illustrates the robot fabrication process, at the same time verifies the structural integrity through experimental validation. Further evaluations include comprehensive analysis of the robot's gait and speed. The results show that the robot attains a speed of 2.86 mm s-1. This study marks a stride towards the realization of a fully autonomous, unrestrained, cost-effective, and energy-conserving magnetic soft robot.

Existing gripping devices limit the way of gripping the object, and the object may slide due to insufficient friction, when the manipulator grips the object, the object may slip phenomenon, which leads to the manipulator can not complete the gripping work normally. In order to solve this problem, this paper proposes a robotic slipping sensor to detect the slipping state of the object and its slipping distance, the sensor through the friction of two different materials and electrostatic induction phenomenon of triboelectricity and the peak voltage signal to determine whether the contact object produces the phenomenon of slipping and its slipping distance. This design integrates two rectangular copper foils and two polytetrafluoroethylene (PTFE) films together to form a triboelectricity nanogenerator in independent layer mode, which judges the slip distance of an object by the peak voltage signal generated by the object's slip, which is flexible and can be combined with a robot to make the robot more flexible and convenient in its work. In order to verify the performance of this sensor, horizontal slip test and vertical slip test were conducted. In the horizontal slip test and vertical slip test, the peak voltage signal output from the TENG sensor has a linear relationship with the slip distance of the object. The sensor and the object contact slip process ends after 100ms, the oscilloscope will output the peak voltage signal, so that according to the size of the peak voltage signal to determine the object in the range of 0-10cm slip distance, for judging whether the object appears to slip phenomenon and the occurrence of the phenomenon of the slip distance it produces provides a flexible program.

The classic vibration energy collector has functional restrictions, and it can only collect vibration energy in one or two dimensions. At the same time, it has issues with low output power in the low-frequency vibration region and a limited reaction frequency range. This research proposes a segmented nonlinear broadband piezoelectric-magnetic coupled energy collector capable of collecting vibration energy in different directions. The collector is equivalent to current state-of-the-art research in that it can collect vibration energy in three dimensions while also having a wide collection frequency and a high power density. The collection consists of a hemispherical support structure and four fundamental piezoelectric beam collision components. The rationality of the collision segmentation nonlinear principle is first clarified through theoretical calculation and analysis, and then the collision design is applied between the ends of different cantilever beams to broaden the captured energy frequency band, while parallel piezoelectric beams use a 45 degrees tilt treatment to fully utilize the geometrical properties of the tilted beams for multidirectional energy collection. In addition, the collector introduces a magnetic coupling effect to create a bistable structure via magnetic contact. Comsol 5.6 software is used to model and simulate the planned 45 degrees tilted beam structure, which clarifies the piezoelectric beam's linear intrinsic frequency characteristics and multi-directional geometric aspects. To further verify the collector's validity, a physical model is built and a vibration experiment apparatus is created. The experimental results demonstrate that the collector's effective bandwidth range is up to 6.3 Hz under 1 g acceleration excitation, representing a 125.0% increase in bandwidth when compared to the cantilever beam with a linear array. At 14 Hz frequency, the collector produces a maximum total output power of 19.52 mW and a power density of up to 3211uW cm-3 when excitation is provided in the Z-direction.

Aiming at the problems of high environmental vibration frequency, low output power and short life of the energy harvesters, a noncontact magnetically coupled piezo-electromagnetic rotary energy harvester is proposed in this paper. It consists of a base, a top cover, a rotating body, a cantilever beam, a permanent magnet, a coil, a hollow tube and a clamp. The novel hybrid harvester can produce both piezoelectric and electromagnetic energy at the same time, and in addition, it can efficiently generate electricity at low ambient vibration. Moreover, the piezoelectric material is protected from direct collision by noncontact magnetic coupling excitation. In order to conduct a comprehensive study on the performance of the piezoelectric-electromagnetic rotary energy harvester, we set up a rotating test platform to carry out systematic test verification, and to determine the distance between the permanent magnet and the rotating body and the number of permanent magnets on the rotating body. The test results show that when four permanent magnets are uniformly pasted on the rotating body and the rotating speed is 775 r/min, the piezoelectric and electromagnetic output power are 3.4 mW and 2.69 mW, respectively, and the total hybrid output power is 6.09 mW.

In order to upgrade aircraft’s endurance and satisfy its needs for special tasks such as surveillance and reconnaissance,a new lightweight bird-like grabbing structure,inspired by birds,was designed so that the aircraft can take a rest by grabbing branches. A three-dimensional grabbing model was established with SolidWorks 2016 to analyze the working principle and movements of the structure which was driven by steering engine. This design,which is simple in structure and easy to control,can be installed onto different types of aircraft.