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Journal of Bionic Engineering

ISSN 1672-6529

CN 22-1355/TB

Editor-in-Chief : Luquan Ren Published by Science Press and Springer

Table of Content
25 September 2024, Volume 21 Issue 5
 Development of a Bio‑inspired Tailless FWMAV with High‑Frequency Flapping Wings Trajectory Tracking Control
Qingcheng Guo, Chaofeng Wu, Yichen Zhang, Feng Cui, Wu Liu, Xiaosheng Wu & Junguo Lu
Journal of Bionic Engineering. 2024, 21 (5):  2145-2166.  DOI: 10.1007/s42235-024-00554-y
Abstract ( 42 )  
The development of a tailless Flapping Wing Micro Aerial Vehicle (FWMAV) inspired by the hummingbird is presented in this work. By implementing mechanical simplifications, it is possible to use planar machining technology for manufacturing of the FWMAV’s body, greatly reducing assembly errors. Traditionally, studies on flapping wing aircraft are limited to open-loop wing kinematics control. In this work, an instantaneous closed-loop wing trajectory tracking control system is introduced to minimize wings’ trajectory tracking errors. The control system is based on Field-Oriented Control (FOC) with a loop shaping compensation technique near the flapping frequency. Through frequency analysis, the loop shaping compensator ensures the satisfactory bandwidth and performance for the closed-loop flapping system. To implement the proposed controller, a compact autopilot board integrated with FOC hardware is designed, weighing only 2.5 g. By utilizing precise wing trajectory tracking control, the hummingbird-inspired FWMAV demonstrates superior ability to resist external disturbances and exhibits reduced attitude tracking errors during hovering flight compared to the open-loop wing motion
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 Research on Optimization of Stable Damper for Passive Stabilized Double‑wing Flapping Micro Air Vehicle
Yichen Zhang, Qingcheng Guo, Wu Liu, Feng Cui, Jiaxin Zhao, Guangping Wu & Wenyuan Chen
Journal of Bionic Engineering. 2024, 21 (5):  2167-2183.  DOI: 10.1007/s42235-024-00565-9
Abstract ( 21 )  
Passively stabilized double-wing Flapping Micro Air Vehicles (FMAVs) do not require active control and exhibit good electromagnetic interference resistance, with significant research value. In this paper, the dynamic model of FMAV was established as the foundation for identifying flapping damping coefficients. Through a pendulum experiment, we ascertain the flapping damping of the damper using the energy conservation method. Besides, fitting relationships between the damper area, damper mass, and the moment of inertia are developed. The factors influencing the bottom damper damping are determined using correlation coefficients and hypothesis testing methods. Additionally, stable dampers are installed on both the top and bottom of the FMAV to achieve passive stability in simulations. The minimum damper areas for the FMAV were optimized using genetic algorithms, resulting in a minimum top damper area of 128 cm2 and a minimum bottom damper area of 80 cm2. A prototype with a mass of 25.5 g and a wingspan of 22 cm has been constructed. Prototype testing demonstrated that FMAV can take off stably with a 3 g payload and a tilt angle of 5°. During testing, the area-to-mass ratio of the FMAV reached 7.29 cm2/g, achieving passive stability with the world’s smallest area-to-mass ratio.
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 A Hierarchical Control Scheme for Active Power‑assist Lower‑limb Exoskeletons
Jing Deng, Wenzheng Jiang, Haibo Gao, Yapeng Shi & Mantian Li
Journal of Bionic Engineering. 2024, 21 (5):  2184-2198.  DOI: 10.1007/s42235-024-00561-z
Abstract ( 33 )  
Effectively controlling active power-assist lower-limb exoskeletons in a human-in-the-loop manner poses a substantial challenge, demanding an approach that ensures wearer autonomy while seamlessly adapting to diverse wearer needs. This paper introduces a novel hierarchical control scheme comprising five integral components: intention recognition layer, dynamics feedforward layer, force distribution layer, feedback compensation layer, as well as sensors and actuators. The intention recognition layer predicts the wearer’s movement and enables wearer-dominant movement through integrated force and position sensors. The force distribution layer effectively resolves the statically indeterminate problem in the context of double-foot support, showcasing flexible control modes. The dynamics feedforward layer mitigates the effect of the exoskeleton itself on movement. Meanwhile, the feedback compensation layer provides reliable closed-loop control. This approach mitigates abrupt changes in joint torques during frequent transitions between swing and stance phases by decomposed dynamics. Validating this innovative hierarchical control scheme on a hydraulic exoskeleton platform through a series of experiments, the results demonstrate its capability to deliver assistance in various modes such as stepping, squatting, and jumping while adapting seamlessly to different terrains.
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 Contact Force Optimization to Enhance Fault‑tolerant Motion Stability of a Hexapod Robot
Bo You, Shangdong Shi, Chen Chen, Jiayu Li, Nan Li & Liang Ding
Journal of Bionic Engineering. 2024, 21 (5):  2199-2214.  DOI: 10.1007/s42235-024-00577-5
Abstract ( 16 )  
This paper presents a novel method for optimizing the contact force of a hexapod robot to enhance its dynamic motion stability when one of its legs fails. The proposed approach aims to improve the Force Angle Stability Margin (FASM) and adapt the foot trajectory through contact force optimization to achieve safe and stable motion on various terrains. The foot force optimization approach is designed to optimize the FASM, a factor rarely considered in existing contact force optimization methods. By formulating the problem of enhancing the motion stability of the hexapod robot as a Quadratic Programming (QP) optimization problem, this approach can effectively address this issue. Simulations of a hexapod robot using a fault-tolerant gait, along with real field experiments, were conducted to validate the effectiveness and feasibility of the contact force optimization approach. The results demonstrate that this approach can be used to design a motion controller for a hexapod robot with a significantly improved motion stability. In summary, the proposed contact force optimization method offers a promising solution for enhancing the motion stability of hexapod robots with single leg failures and has the potential to significantly advance the development of fault-tolerant hexapod robots for various applications.
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 Research on the Virtual–real Interaction System and Interaction Characteristics of a Single‑leg of Quadruped Robots Based on Digital Twin
Yuhan Dou, Hujiang Wang, Bing Wu, Jiandong Cao & Jinzhu Zhang
Journal of Bionic Engineering. 2024, 21 (5):  2215-2231.  DOI: 10.1007/s42235-024-00573-9
Abstract ( 18 )  
Quadruped robots which have flexibility and load-bearing capacity, are regarded as the best mobile platform for remote operation in unstructured and restricted environments. In the process of remote operation of quadruped robots, their status is inevitably influenced by complex environments. To monitor the robot's real-time operation status and make necessary adjustments, this paper focuses on the single-leg of a quadruped robot, proposes a single-leg virtual–real interaction system based on Digital Twin, and studies its virtual–real interaction characteristics. The virtual–reality interaction system contains single-leg physical entity, single-leg virtual model, control system, data service system and communication system, enabling interactive applications for single-leg visual state monitoring and real-time control optimization. This paper creates a high-fidelity model based on the physical entity; provides a system performance analysis method based on the system framework; analyzes virtual–real interaction delay based on communication scheme; conducts stand and jump test based on the single-leg mathematical model and analyzes the interaction characteristics under position/force control. This system provides new insights for real-time monitoring and control optimization of quadruped robots.
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 Hybrid Nonlinear Model Predictive Motion Control of a Heavy‑duty Bionic Caterpillar‑like Robot
Dongyi Li, Kun Lu, Yong Cheng, Huapeng Wu, Heikki Handroos, Songzhu Yang, Yu Zhang & Hongtao Pan
Journal of Bionic Engineering. 2024, 21 (5):  2232-2246.  DOI: 10.1007/s42235-024-00570-y
Abstract ( 30 )  

This paper investigates the motion control of the heavy-duty Bionic Caterpillar-like Robot (BCR) for the maintenance of the China Fusion Engineering Test Reactor (CFETR). Initially, a comprehensive nonlinear mathematical model for the BCR system is formulated using a physics-based approach. The nonlinear components of the model are compensated through nonlinear feedback linearization. Subsequently, a fuzzy-based regulator is employed to enhance the receding horizon optimization process for achieving optimal results. A Deep Neural Network (DNN) is trained to address disturbances. Consequently, a novel hybrid controller incorporating Nonlinear Model Predictive Control (NMPC), the Fuzzy Regulator (FR), and Deep Neural Network Feedforward (DNNF), named NMPC-FRDNNF is developed. Finally, the efficacy of the control system is validated through simulations and experiments. The results indicate that the Root Mean Square Error (RMSE) of the controller with FR and DNNF decreases by 33.2 and 48.9%, respectively, compared to the controller without these enhancements. This research provides a theoretical foundation and practical insights for ensuring the future highly stable, safe, and efficient maintenance of blankets.

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Multi‑modal Bionic Motion Analysis of A Cpg‑controlled Pneumatic Soft Robot
Yu Zhang, Peiyu Huang, Dongjie Li, Jiangyu Zhou, Yu Li, Bo You & Yanhe Zhu
Journal of Bionic Engineering. 2024, 21 (5):  2247-2257.  DOI: 10.1007/s42235-024-00567-7
Abstract ( 16 )  
This paper designs a soft robot with a multi-chamber, multi-airbag mimicking soft biological structure, where the airbags of the same chamber are interconnected with each other. The upper and lower chambers are separated by an intermediate layer (thin plate), which is extended and widened to achieve robot movement and balance. By applying pressure to the different chambers of the soft robot, it is possible to produce a variety of bionic movements of the inchworm and caterpillar. Due to the strong nonlinearity and infinite number of degrees of freedom properties of the material, it is impossible to obtain the analytical solution of the bending morphology and pressure of the soft robot directly. Therefore, a method to establish a mathematical model of soft robot deformation based on the classical stacked plate theory is proposed, and a chain composite model of soft robot bending motion is established based on the large-deflection modeling method. This paper proposes a method to generate a multi-mode soft robot motion control based on the Central Pattern Generator (CPG) using a single controller, which achieves the switching of sine wave-like patterns, half-wave-like patterns, and dragging patterns by adjusting frequency, amplitude and period of parameters. Finally, a pneumatic control platform is built for the validation of the theoretical model and different experimental models of the motion of the robot. And comparation of the different motion modes of the soft robot under similar non-load and load conditions.
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 Expansion of Self‑assembled Structures of Heteroarray NdFeB Semicircular Arc Magnetic Minirobots
Wenguang Yang, Huibin Liu, Qinghao Guo, Wenhao Wang, Haibo Yu & Anqin Liu
Journal of Bionic Engineering. 2024, 21 (5):  2258-2270.  DOI: 10.1007/s42235-024-00544-0
Abstract ( 21 )  
Researching the cooperative operation and functional expansion of multiple minirobot assemblies has the potential to bring about significant advancements in the practical applications of minirobots. In this study, we present a novel assembly system comprised of arc-shaped NdFeB magnetic minirobots. These minirobots can be individually utilized as assembly units, allowing for function expansion and comprehensive capability enhancement. We fabricate four Semicircular Arc Magnetic Minirobots (SAMM) arranged in different configurations and analyze their force and motion characteristics. Furthermore, by using this unit as a base, various expansion structures such as latches, petals, and rings can be assembled through reasonable combinations. We define the comprehensive reinforcement interval by comparatively analyzing changes in the unit’s motion characteristics and operational capabilities. Precise motion manipulation is employed to verify the rationality of the basic unit structure and the feasibility of the assembly scheme. Our proposed self-assembly scheme for magnetic minirobots exhibits great potential and may be used as a paradigm for future research on expanding the functionality of minirobots.
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 Development and Performance Analysis of Pneumatic Variable Stiffness Imitation Dolphin Tail Actuator
Yu Zhang, Ning Wang, Wenchuan Zhao, Linghui Peng & Jun Luo
Journal of Bionic Engineering. 2024, 21 (5):  2271-2290.  DOI: 10.1007/s42235-024-00574-8
Abstract ( 16 )  
It has been demonstrated that the flexibility of the structure can enhance the kinematic performance of the underwater bionic robotic fish. Furthermore, the thrust of the underwater robotic fish can be further enhanced by changing the stiffness of the tail when the motion frequency of the propulsion system increases. This paper proposes a novel actuator, the pneumatic variable stiffness imitation dolphin tail actuator (PVSA), which combines soft robotics with the structural characteristics and movement mode of a biological dolphin. The PVSA comprises a pneumatic bi-directional bending soft actuator and a pull-wire-driven variable stiffness mechanism. The soft actuator is capable of mimicking the dorsoventral movement of dolphins by changing the pressure difference between the cavities, thereby achieving bending deformation. The variable stiffness mechanism is based on the stiffness mechanism of particle interference and the structural characteristics of vertebrate endoskeleton, with the objective of achieving variable stiffness. The parameters of the PVSA are optimised using numerical simulations and experimental studies, and then designed underwater experiments are conducted to investigate the effects of amplitude, stiffness and frequency on the propulsive performance of the PVSA. The results demonstrate that the PVSA is capable of enhancing thrust by adjusting its own stiffness and movement frequency. The development of the PVSA provides a reference for the research of related underwater bionic propulsion technology.
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Performance‑based Assistance Control for Upper Limb Robotic Mirror Therapy
Sixian Fei, Qing Sun, Yichen Zhang, Huanian Cai, Shuai Guo & Xianhua Li
Journal of Bionic Engineering. 2024, 21 (5):  2291-2301.  DOI: 10.1007/s42235-024-00568-6
Abstract ( 21 )  
As an effective therapy for treating unilateral neglect, Mirror Therapy (MT) is employed in the upper limb motor function rehabilitation of hemiplegic patients. However, traditional MT has a serious limitation—the Impaired Limb (IL) doesn’t actually move. In this study, a novel performance-based assistance strategy suitable for Robotic Mirror Therapy (RMT) based on MT is proposed. A guiding assistance based on the progress difference HL and IL is constructed in trajectory guidance, and a multi-stiffness region correction force field based on trajectory tracking error is designed to constrain IL’s deviation from the intended path in trajectory correction assistance. To validate the presented strategy, a series of experiments on a RMT system based on the end-effector upper limb rehabilitation robot are conducted. The results verify the performance and feasibility of this strategy.
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Soft Actuator with Integrated and Localized Sensing Properties through Parameter-Encoded 4D Printing
Yang Li, Xinyu Yang, Jianyang Li, Qingping Liu, Bingqian Li & Kunyang Wang
Journal of Bionic Engineering. 2024, 21 (5):  2302-2312.  DOI: 10.1007/s42235-024-00552-0
Abstract ( 18 )  
4D printed smart materials is mostly relying on thermal stimulation to actuate, limiting their widely application requiring precise and localized control of the deformations. Most existing strategies for achieving localized control rely on heterogeneous material systems and structural design, thereby increasing design and manufacturing complexity. Here, we endow localized electrothermal, actuation, and sensing properties in electrically-driven soft actuator through parameter-encoded 4D printing. We analyzed the effects of printing parameters on shape memory properties and conductivity, and then explored the multi-directional sensing performance of the 4D printed composites. We demonstrated an integrated actuator-sensor device capable of both shape recovery and perceiving its own position and obstacles simultaneously. Moreover, it can adjust its sensing characteristics through temporary shape programming to adapt to different application scenarios. This study achieves integrated and localized actuation-sensing without the need for multi-material systems and intricate structural designs, offering an efficient solution for the intelligent and lightweight design in the fields of soft robotics, biomedical applications, and aerospace.
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Highly Bendable Ionic Electro‑responsive Artificial Muscles Using Microfibrillated Cellulose Fibers Combined with Polyvinyl Alcohol
Congqing Deng, Shanqi Zheng, Ke Zhong & Fan Wang
Journal of Bionic Engineering. 2024, 21 (5):  2313-2323.  DOI: 10.1007/s42235-024-00571-x
Abstract ( 28 )  
For promising applications such as soft robotics, flexible haptic monitors, and active biomedical devices, it is important to develop ultralow voltage, highly-performant artificial muscles with high bending strains, rapid response times, and superior actuation endurance. We report a novel highly performant and low-cost artificial muscle based on microfibrillated cellulose (MFC), ionic liquid (IL), and polyvinyl alcohol (PVA), The proposed MFC–IL–PVA actuator exhibits excellent electrochemical performance and actuations characteristics with a high specific capacitance of 225 mF/cm2, a large bending strain of 0.51%, peak displacement up to 7.02 mm at 0.25 V ultra-low voltage, outstanding actuation flexural endurance (99.1% holding rate for 3 h), and a wide frequency band (0.1–5 Hz). These attributes stem mainly from its high specific surface area and porosity, tunable mechanical properties, and the strong ionic interactions of cations and anions with MFC and PVA in ionic liquids. Furthermore, bionic applications such as bionic flytraps, bionic butterflies with vibrating wings, and smart circuit switches have been successfully realized using this technology. These specific bionic applications demonstrate the versatility and potential of the MFC–IL–PVA actuator, highlighting its important role in the fields of bionic engineering, robotics, and smart materials. They open up new possibilities for innovative scientific research and technological applications.
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 Intelligent Optimization of Particle‑Jamming‑Based Variable Stiffness Module Design Using a Grey‑box Model Based on Virtual Work Principle
Hao Huang, Zhenyun Shi, Ziyu Liu, Tianmiao Wang & Chaozong Liu
Journal of Bionic Engineering. 2024, 21 (5):  2324-2339.  DOI: 10.1007/s42235-024-00563-x
Abstract ( 14 )  
Soft grippers are favored for handling delicate objects due to their compliance but often have lower load capacities compared to rigid ones. Variable Stiffness Module (VSM) offer a solution, balancing flexibility and load capacity, for which particle jamming is an effective technology for stiffness-tunable robots requiring safe interaction and load capacity. Specific applications, such as rescue scenarios, require quantitative analysis to optimize VSM design parameters, which previous analytical models cannot effectively handle. To address this, a Grey-box model is proposed to analyze the mechanical response of the particle-jamming-based VSM by combining a White-box approach based on the virtual work principle with a Black-box approach that uses a shallow neural network method. The Grey-box model demonstrates a high level of accuracy in predicting the VSM force-height mechanical response curves, with errors below 15% in almost 90% of the cases and a maximum error of less than 25%. The model is used to optimize VSM design parameters, particularly those unexplored combinations. Our results from the load capacity and force distribution comparison tests indicate that the VSM, optimized through our methods, quantitatively meets the practical engineering requirements.
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 Honeycomb Inspired Independent-cell Droplet-based Electricity Generator Array
Shixu Wang, Xu Wang, Chenguang Lu, Wenna Ge, Quanmao Wei & Yahua Liu
Journal of Bionic Engineering. 2024, 21 (5):  2340-2348.  DOI: 10.1007/s42235-024-00559-7
Abstract ( 19 )  
The transistor-inspired Droplet-based Electricity Generator (DEG) significantly enhances the energy collection efficiency from single-position droplets. However, the design of the DEG arrays combining high output performance and large-scale integration under multi-position droplet impacts remains a challenge. Inspired by the unique structure of the honeycomb, we developed an Independent-Cell Droplet-based Electricity Generator (IC-DEG) array that allows for high-efficiency and stable droplet energy harvesting under multi-position droplet impacts. Each independent cell is a transistor-inspired Tubular Droplet-based Electricity Generator (T-DEG), which ensures the high electrical output of the IC-DEG array. The honeycomb-like arrangement improves the space utilization, accelerates the detachment of droplets, and avoids electrical interference among independent cells, all of which further enhance the IC-DEG array performance. The average peak open-circuit voltage of the IC-DEG array is 265.2 V, and 96.6% of peak voltages exceed 200 V, almost double that of a traditional planar array. Moreover, the average droplet detachment time of the IC-DEG array is 44.8 ms, 41.4% shorter than the traditional planar array. The enhanced performance of the IC-DEG array is further demonstrated by the high speed of charging capacitors and the capability of driving electronic devices. This study provides a promising design concept for large-scale droplet energy harvesting devices.
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 Glass Sponge-inspired Auxetic Mechanical Metamaterials for Energy Absorption
Chao Xu, Qiwei Li, Lu Zhang, Qingping Liu & Luquan Ren
Journal of Bionic Engineering. 2024, 21 (5):  2349-2365.  DOI: 10.1007/s42235-024-00576-6
Abstract ( 18 )  
The Auxetic Structure (AS) exhibits significant densification strain due to its concave cell architecture, functioning as an effective energy-absorbing metamaterial. However, its limited plateau stress hampers further enhancement of energy absorption. The deep-sea Glass Sponge (GS) has high plateau stress due to its diagonal braces. Inspired by GS, the Glass-Sponge-Auxetic Structure (GSAS) is proposed, featuring concave cells reinforced by diagonal braces to achieve both high plateau stress and densification strain. Different structural configurations incorporating various brace arrangements and thicknesses for GSAS are designed and compared through finite element analysis. An optimal GSAS is achieved with a 0.5 mm strut thickness and an asymmetric arrangement of crossing and uncrossing braces. The GSAS is fabricated using Ti6Al4V through selective laser melting and compared with AS, GS, body-centered cube, and honeycomb in compression tests. The unique bending-stretching deformation and non-simultaneous fracturing pattern results in simultaneous high plateau stress and densification strain, and the highest energy absorption and specific energy absorption. Compared to AS, these values are enhanced by 156% and 75%, respectively. The exceptional energy absorption capability of GSAS presents promising prospects in fields such as automobile collision avoidance and vibration damping, with its customizable cell numbers offering the potential for more specific applications.
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 Efficiency Enhancement in Hammer Mills through Biomimetic Pigeon Wing Sieve Design
Jindong Wang, Zhanyang Wu, Yi Chen, Yuhong Xie & Zhongrong Zhou
Journal of Bionic Engineering. 2024, 21 (5):  2366-2378.  DOI: 10.1007/s42235-024-00551-1
Abstract ( 13 )  
Hammer mill is widely used in the feed processing industry. During its operation, the material is thrown against the inner wall of the sieve after being broken by the hammer. Limited by the annular structure sieve, the grinded material tends to produce a “air- material circulation layer” on the inner wall of the sieve, leading to problems such as low grinding efficiency and high grinding energy consumption. Considering the disruptive characteristics of the special profile structure of a pigeon’s wing on the airflow field, we extract the geometric characteristics of the coupling element and optimize the related structural parameters. Based on the principles of bionics, a new wing sieve is then designed, and its efficient grinding mechanism is studied. Compared to the commercial sieve, the experimental results indicate the bio-inspired sieve can significantly improve the material productivity and grinding quality.
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 Research on the Influencing Factors of Peristalsis Amplitude Based on an in Vitro Bionic Rat Stomach Model
Wentao Liang, Keyong Zhao, Peng Wu, Changyong Li, Xiaodong Chen, Renpan Deng & Zhigang Lei
Journal of Bionic Engineering. 2024, 21 (5):  2379-2394.  DOI: 10.1007/s42235-024-00566-8
Abstract ( 12 )  
The In Vitro Bionic Digestion Model (IVBDM) are used to simulate the digestion process of food or pharmaceuticals in corresponding digestion tracts for obtaining the digestion data, which are expected to replace in vivo experiments with animals in the early stages of functional food or drug development, and thus have broad applications prospects. However, little is known so far about how the factors including the Young’s modulus of the model, the level, location and direction of the applied load, affect the peristalsis amplitude of the IVBDM. Based on an In Vitro Bionic Rat Stomach Model (IVBRSM), simulation and experimental analysis were conducted to examine the factors effecting the peristalsis amplitude of the IVBRSM. It is shown that Young’s modulus of the model significantly affects the peristalsis amplitude, with lower Young’s modulus resulting in larger amplitude. Load level, location, and direction also influence the peristalsis amplitude. Additionally, IVBRSM size and wall thickness play a role, with larger models requiring higher load levels or lower Young’s modulus for the same peristalsis amplitude. Simulation data correlate well with experimental results. These findings contribute to the understanding of the peristalsis state of IVBRSM under different conditions and can guide the design and fabrication of such in vitro bionic digestion models.
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 Dynamic Color Regulation of the Lycaenid Butterfly Wing Scales
Mingxia Sun, Weihao Meng, Haiwei Yin, Lingjie Fan, Lei Shi, Gregory S. Watson, Jolanta A. Watson, Jingxia Wang, Lei Jiang & Aiping Liang
Journal of Bionic Engineering. 2024, 21 (5):  2395-2408.  DOI: 10.1007/s42235-024-00560-0
Abstract ( 18 )  
Butterfly coloration originates from the finely structured scales grown on the underlying wing cuticle. Most researchers who study butterfly scales are focused on the static optic properties of cover scales, with few works referring to dynamic optical properties of the scales. Here, the dynamic coloration effect of the multiple scales was studied based on the measurements of varying-angle reflection and the characterization of scale flexibility in two species of Lycaenid, Plebejus argyrognomon with violet wings and Polyommatus erotides with blue wings. We explored the angle-dependent color changeability and the color-mediating efficiency of wing scales. It was found that the three main kinds of flexible scales (cover, ground and androconia scales) were asynchronously bent during wing rotation, which caused the discoloration effect. The three layers of composite scales broaden the light signal when compared to the single scale, which may be of great significance to the recognition of insects. Specifically, the androconia scales were shown to strongly contribute to the overall wing coloration. The cover scale coloration was ascribed to the coherence scattering resulted from the short-range order at intermediate spatial frequencies from the 2D Fourier power spectra. Our findings are expected to deepen the understanding of the complex characteristics of biological coloration and to provide new inspirations for the fabrication of biomimetic flexible discoloration materials.
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Gait Characteristics and Adaptation Strategies of Ants with Missing Legs
Ming Zeng, Chang Meng, Bin Han, Yuanhao Li, Hanshen Yu, Huijia Fu & Shutong Zhong
Journal of Bionic Engineering. 2024, 21 (5):  2409-2423.  DOI: 10.1007/s42235-024-00572-w
Abstract ( 17 )  
This paper systematically studies the movement behavior changes of Camponotus japonicus under one or two leg injuries. Firstly, a linear motion channel matching the size of the ants’ legs was designed, and the movements of ants with different leg injuries were captured using high-speed cameras, constructing a comprehensive video dataset of ants’ movements with missing legs. Secondly, stable and reliable motion position information for keypoints on the ants’ bodies and legs was obtained by utilizing low-annotation biometric keypoint detection technology. Finally, by analyzing the filtered gait data, information about the changes in the step locational points areas, phase differences, and duty factors of the injured ants’ remaining legs was obtained. Comparative analysis of the ants’ gait characteristics revealed some common adjustment patterns when the ants were in the injured states. Additionally, the study found that the loss of a foreleg had a significant impact on the ants’ movement. When two legs were missing, the loss of both legs on the same side had a greater effect on movement, whereas symmetric opposite-side leg loss conditions had a lesser impact. The research will provide an important reference for the subsequent design of gait adjustment algorithms for biomimetic multi-legged robots under damaged conditions.
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Boosted Spider Wasp Optimizer for High‑dimensional Feature Selection
Elfadil A. Mohamed, Malik Sh. Braik, Mohammed Azmi Al-Betar & Mohammed A. Awadallah
Journal of Bionic Engineering. 2024, 21 (5):  2424-2459.  DOI: 10.1007/s42235-024-00558-8
Abstract ( 14 )  
With the increasing dimensionality of the data, High-dimensional Feature Selection (HFS) becomes an increasingly difficult task. It is not simple to find the best subset of features due to the breadth of the search space and the intricacy of the interactions between features. Many of the Feature Selection (FS) approaches now in use for these problems perform significantly less well when faced with such intricate situations involving high-dimensional search spaces. It is demonstrated that meta-heuristic algorithms can provide sub-optimal results in an acceptable amount of time. This paper presents a new binary Boosted version of the Spider Wasp Optimizer (BSWO) called Binary Boosted SWO (BBSWO), which combines a number of successful and promising strategies, in order to deal with HFS. The shortcomings of the original BSWO, including early convergence, settling into local optimums, limited exploration and exploitation, and lack of population diversity, were addressed by the proposal of this new variant of SWO. The concept of chaos optimization is introduced in BSWO, where initialization is consistently produced by utilizing the properties of sine chaos mapping. A new convergence parameter was then incorporated into BSWO to achieve a promising balance between exploration and exploitation. Multiple exploration mechanisms were then applied in conjunction with several exploitation strategies to effectively enrich the search process of BSWO within the search space. Finally, quantum-based optimization was added to enhance the diversity of the search agents in BSWO. The proposed BBSWO not only offers the most suitable subset of features located, but it also lessens the data’s redundancy structure. BBSWO was evaluated using the k-Nearest Neighbor (k-NN) classifier on 23 HFS problems from the biomedical domain taken from the UCI repository. The results were compared with those of traditional BSWO and other well-known meta-heuristics-based FS. The findings indicate that, in comparison to other competing techniques, the proposed BBSWO can, on average, identify the least significant subsets of features with efficient classification accuracy of the k-NN classifier.
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 Improved Runge Kutta Optimization Using Compound Mutation Strategy in Reinforcement Learning Decision Making for Feature Selection
Jinpeng Huang, Yi Chen, Ali Asghar Heidari, Lei Liu, Huiling Chen & Guoxi Liang
Journal of Bionic Engineering. 2024, 21 (5):  2460-2496.  DOI: 10.1007/s42235-024-00555-x
Abstract ( 18 )  
Runge Kutta Optimization (RUN) is a widely utilized metaheuristic algorithm. However, it suffers from these issues: the imbalance between exploration and exploitation and the tendency to fall into local optima when it solves real-world optimization problems. To address these challenges, this study aims to endow each individual in the population with a certain level of intelligence, allowing them to make autonomous decisions about their next optimization behavior. By incorporating Reinforcement Learning (RL) and the Composite Mutation Strategy (CMS), each individual in the population goes through additional self-improvement steps after completing the original algorithmic phases, referred to as RLRUN. That is, each individual in the RUN population is trained intelligently using RL to independently choose three different differentiation strategies in CMS when solving different problems. To validate the competitiveness of RLRUN, comprehensive empirical tests were conducted using the IEEE CEC 2017 benchmark suite. Extensive comparative experiments with 13 conventional algorithms and 10 advanced algorithms were conducted. The experimental results demonstrated that RLRUN excels in convergence accuracy and speed, surpassing even some champion algorithms. Additionally, this study introduced a binary version of RLRUN, named bRLRUN, which was employed for the feature selection problem. Across 24 high-dimensional datasets encompassing UCI datasets and SBCB machine learning library microarray datasets, bRLRUN occupies the top position in classification accuracy and the number of selected feature subsets compared to some algorithms. In conclusion, the proposed algorithm demonstrated that it exhibits a strong competitive advantage in high-dimensional feature selection for complex datasets.
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 Improving PID Controller Performance in Nonlinear Oscillatory Automatic Generation Control Systems Using a Multi‑objective Marine Predator Algorithm with Enhanced Diversity
Yang Yang, Yuchao Gao, Jinran Wu, Zhe Ding & Shangrui Zhao
Journal of Bionic Engineering. 2024, 21 (5):  2497-2514.  DOI: 10.1007/s42235-024-00548-w
Abstract ( 19 )  
Power systems are pivotal in providing sustainable energy across various sectors. However, optimizing their performance to meet modern demands remains a significant challenge. This paper introduces an innovative strategy to improve the optimization of PID controllers within nonlinear oscillatory Automatic Generation Control (AGC) systems, essential for the stability of power systems. Our approach aims to reduce the integrated time squared error, the integrated time absolute error, and the rate of change in deviation, facilitating faster convergence, diminished overshoot, and decreased oscillations. By incorporating the spiral model from the Whale Optimization Algorithm (WOA) into the Multi-Objective Marine Predator Algorithm (MOMPA), our method effectively broadens the diversity of solution sets and finely tunes the balance between exploration and exploitation strategies. Furthermore, the QQSMOMPA framework integrates quasi-oppositional learning and Q-learning to overcome local optima, thereby generating optimal Pareto solutions. When applied to nonlinear AGC systems featuring governor dead zones, the PID controllers optimized by QQSMOMPA not only achieve 14% reduction in the frequency settling time but also exhibit robustness against uncertainties in load disturbance inputs.
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 MAPFUNet: Multi‑attention Perception‑Fusion U‑Net for Liver Tumor Segmentation
Junding Sun, Biao Wang, Xiaosheng Wu, Chaosheng Tang, Shuihua Wang & Yudong Zhang
Journal of Bionic Engineering. 2024, 21 (5):  2515-2539.  DOI: 10.1007/s42235-024-00562-y
Abstract ( 20 )  
The second-leading cause of cancer-related deaths globally is liver cancer. The treatment of liver cancers depends heavily on the accurate segmentation of liver tumors from CT scans. The improved method based on U-Net has achieved good performance for liver tumor segmentation, but these methods can still be improved. To deal with the problems of poor performance from the original U-Net framework in the segmentation of small-sized liver tumors and the position information of tumors that is seriously lost in the down-sampling process, we propose the Multi-attention Perception-fusion U-Net (MAPFUNet). We propose the Position ResBlock (PResBlock) in the encoder stage to promote the feature extraction capability of MAPFUNet while retaining the position information regarding liver tumors. A Dual-branch Attention Module (DWAM) is proposed in the skip connections, which narrows the semantic gap between the encoder's and decoder's features and enables the network to utilize the encoder's multi-stage and multi-scale features. We propose the Channel-wise ASPP with Attention (CAA) module at the bottleneck, which can be combined with multi-scale features and contributes to the recovery of micro-tumor feature information. Finally, we evaluated MAPFUNet on the LITS2017 dataset and the 3DIRCADB-01 dataset, with Dice values of 85.81 and 83.84% for liver tumor segmentation, which were 2.89 and 7.89% higher than the baseline model, respectively. The experiment results show that MAPFUNet is superior to other networks with better tumor feature representation and higher accuracy of liver tumor segmentation. We also extended MAPFUNet to brain tumor segmentation on the BraTS2019 dataset. The results indicate that MAPFUNet performs well on the brain tumor segmentation task, and its Dice values on the three tumor regions are 83.27% (WT), 84.77% (TC), and 76.98% (ET), respectively.
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Multi‑strategy Hybrid Coati Optimizer: A Case Study of Prediction of Average Daily Electricity Consumption in China
Gang Hu, Sa Wang & Essam H. Houssein
Journal of Bionic Engineering. 2024, 21 (5):  2540-2568.  DOI: 10.1007/s42235-024-00549-9
Abstract ( 33 )  
The power sector is an important factor in ensuring the development of the national economy. Scientific simulation and prediction of power consumption help achieve the balance between power generation and power consumption. In this paper, a Multi-strategy Hybrid Coati Optimizer (MCOA) is used to optimize the parameters of the three-parameter combinatorial optimization model TDGM(1,1,r,ξ,Csz) to realize the simulation and prediction of China’s daily electricity consumption. Firstly, a novel MCOA is proposed in this paper, by making the following improvements to the Coati Optimization Algorithm (COA): (i) Introduce improved circle chaotic mapping strategy. (ii) Fusing Aquila Optimizer, to enhance MCOA's exploration capabilities. (iii) Adopt an adaptive optimal neighborhood jitter learning strategy. Effectively improve MCOA escape from local optimal solutions. (iv) Incorporating Differential Evolution to enhance the diversity of the population. Secondly, the superiority of the MCOA algorithm is verified by comparing it with the newly proposed algorithm, the improved optimization algorithm, and the hybrid algorithm on the CEC2019 and CEC2020 test sets. Finally, in this paper, MCOA is used to optimize the parameters of TDGM(1,1,r,ξ,Csz), and this model is applied to forecast the daily electricity consumption in China and compared with the predictions of 14 models, including seven intelligent algorithm-optimized TDGM(1,1,r,ξ,Csz), and seven forecasting models. The experimental results show that the error of the proposed method is minimized, which verifies the validity of the proposed method.
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 A Modified Genetic Algorithm for Combined Heat and Power Economic Dispatch
Deliang Li & Chunyu Yang
Journal of Bionic Engineering. 2024, 21 (5):  2569-2586.  DOI: 10.1007/s42235-024-00569-5
Abstract ( 17 )  
Combined Heat and Power Economic Dispatch (CHPED) is an important problem in the energy field, and it is beneficial for improving the utilization efficiency of power and heat energies. This paper proposes a Modified Genetic Algorithm (MGA) to determine the power and heat outputs of three kinds of units for CHPED. First, MGA replaces the simulated binary crossover by a new one based on the uniform and guassian distributions, and its convergence can be enhanced. Second, MGA modifies the mutation operator by introducing a disturbance coefficient based on guassian distribution, which can decrease the risk of being trapped into local optima. Eight instances with or without prohibited operating zones are used to investigate the efficiencies of MGA and other four genetic algorithms for CHPED. In comparison with the other algorithms, MGA has reduced generation costs by at least 562.73$, 1068.7$, 522.68$ and 1016.24$, respectively, for instances 3, 4, 7 and 8, and it has reduced generation costs by at most 848.22$, 3642.85$, 897.63$ and 3812.65$, respectively, for instances 3, 4, 7 and 8. Therefore, MGA has desirable convergence and stability for CHPED in comparison with the other four genetic algorithms.
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 Reconstructing 3D Biomedical Architectural Order at Multiple Spatial Scales with Multimodal Stack Input
Chaojing Shi, Guocheng Sun, Kaitai Han, Mengyuan Huang, Wu Liu, Xi Liu, Zijun Wang & Qianjin Guo
Journal of Bionic Engineering. 2024, 21 (5):  2587-2601.  DOI: 10.1007/s42235-024-00557-9
Abstract ( 21 )  
Microscopy, crucial for exploring biological structures, often uses polarizing microscopes to observe tissue anisotropy and reconstruct label-free images. However, these images typically show low contrast, and while fluorescence imaging offers higher contrast, it is phototoxic and can disrupt natural assembly dynamics. This study focuses on reconstructing fluorescence images from label-free ones using a complex nonlinear transformation, specifically aiming to identify organelles within diverse optical properties of tissues. A multimodal deep learning model, 3DTransMDL, was developed, employing the Stokes vector to analyze the sample’s retardance, phase, and orientation. This model incorporates isotropy and anisotropy to differentiate organelles, enhancing the input with structures' varied optical properties. Additionally, techniques like background distortion normalization and covariate shift methods were applied to reduce noise and overfitting, improving model generalization. The approach was tested on mouse kidney and human brain tissues, successfully identifying specific organelles and demonstrating superior performance in reconstructing 3D images, significantly reducing artifacts compared to 2D predictions. Evaluation metrics such as SSIM, PCC, and R2 score confirm the model's efficacy, with improvements observed in multi-modality input setups. This advancement suggests potential applications in molecular dynamics, aiming for further enhancements in future studies.
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The Chaos Sparrow Search Algorithm: Multi‑layer and Multi‑pass Welding Robot Trajectory Optimization for Medium and Thick Plates
Song Mu, Jianyong Wang & Chunyang Mu
Journal of Bionic Engineering. 2024, 21 (5):  2602-2618.  DOI: 10.1007/s42235-024-00556-w
Abstract ( 14 )  
The welding of medium and thick plates has a wide range of applications in the engineering field. Industrial welding robots are gradually replacing traditional welding operations due to their significant advantages, such as high welding quality, high work efficiency, and effective reduction of labor intensity. Ensuring the accuracy of the welding trajectory for the welding robot is crucial for guaranteeing welding quality. In this paper, the author uses the chaos sparrow search algorithm to optimize the trajectory of a multi-layer and multi-pass welding robot for medium and thick plates. Firstly, the Sparrow Search Algorithm (SSA) is improved by introducing tent chaotic mapping and Gaussian mutation of the inertia weight factor. Secondly, in order to prevent the welding robot arm from colliding with obstacles in the welding environment during the welding process, maintain the stability of the welding robot, and ensure the continuous stability of the changes in each joint angle, joint angular velocity, and angular velocity of the joint angle, a welding robot model is established by improving the Denavit–Hartenberg parameter method. A multi-objective optimization fitness function is used to optimize the trajectory of the welding robot, minimizing time and energy consumption. Thirdly, the optimization and convergence performance of SSA and Chaos Sparrow Search Algorithm (CSSA) are compared through 10 benchmark test functions. Based on the six sets of test functions, the CSSA algorithm consistently maintains superior optimization performance and has excellent stability, with a faster decline in the convergence curve compared to the SSA algorithm. Finally, the accuracy of welding is tested through V-shaped multi-layer and multi-pass welding experiments. The experimental results show that the CSSA algorithm has a strong superiority in trajectory optimization of multi-layer and multi-pass welding for medium and thick plates, with an accuracy rate of 99.5%. It is an effective optimization method that can meet the actual needs of production.
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 Single Solution Optimization Mechanism of Teaching‑Learning‑Based Optimization with Weighted Probability Exploration for Parameter Estimation of Photovoltaic Models
Jinge Shi, Yi Chen, Zhennao Cai, Ali Asghar Heidari & Huiling Chen
Journal of Bionic Engineering. 2024, 21 (5):  2619-2645.  DOI: 10.1007/s42235-024-00553-z
Abstract ( 18 )  
This article presents a novel optimization approach called RSWTLBO for accurately identifying unknown parameters in photovoltaic (PV) models. The objective is to address challenges related to the detection and maintenance of PV systems and the improvement of conversion efficiency. RSWTLBO combines adaptive parameter w, Single Solution Optimization Mechanism (SSOM), and Weight Probability Exploration Strategy (WPES) to enhance the optimization ability of TLBO. The algorithm achieves a balance between exploitation and exploration throughout the iteration process. The SSOM allows for local exploration around a single solution, improving solution quality and eliminating inferior solutions. The WPES enables comprehensive exploration of the solution space, avoiding the problem of getting trapped in local optima. The algorithm is evaluated by comparing it with 10 other competitive algorithms on various PV models. The results demonstrate that RSWTLBO consistently achieves the lowest Root Mean Square Errors on single diode models, double diode models, and PV module models. It also exhibits robust performance under varying irradiation and temperature conditions. The study concludes that RSWTLBO is a practical and effective algorithm for identifying unknown parameters in PV models.
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 Fast and Accurate Pupil Localization in Natural Scenes
Zhuohao Guo, Manjia Su, Yihui Li, Tianyu Liu, Yisheng Guan & Haifei Zhu
Journal of Bionic Engineering. 2024, 21 (5):  2646-2657.  DOI: 10.1007/s42235-024-00550-2
Abstract ( 16 )  
The interferences, such as the background, eyebrows, eyelashes, eyeglass frames, illumination variations, and specular lens reflection pose challenges for pupil localization in natural scenes. In this paper, we propose a novel method comprising improved YOLOv8 and Illumination Adaptive Algorithm (IAA), for fast and accurate pupil localization in natural scenes. We introduced deformable convolution into the backbone of YOLOv8 to enable the model to extract the eye regions more accurately, thus avoiding the interference of background outside the eye on subsequent pupil localization. The IAA can reduce the interference of illumination variations and lens reflection by adjusting automatically the grayscale of the image according to the exposure. Experimental results verified that the improved YOLOv8 exhibited an eye detection accuracy (IOU0.5) of 90.2%, while the IAA leads to a 9.15% improvement on 5-pixels error ratio ????5 with processing times in the tens of microseconds on GPU. Experimental results on the benchmark database CelebA show that the proposed method for pupil localization achieves an accuracy of 83.05% on ????5 and achieves real-time performance of 210 FPS on GPU, outperforming other advanced methods.
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 An Intrusion Detection System on The Internet of Things Using Deep Learning and Multi‑objective Enhanced Gorilla Troops Optimizer
Hossein Asgharzadeh, Ali Ghaffari, Mohammad Masdari & Farhad Soleimanian Gharehchopogh
Journal of Bionic Engineering. 2024, 21 (5):  2658-2684.  DOI: 10.1007/s42235-024-00575-7
Abstract ( 16 )  
In recent years, developed Intrusion Detection Systems (IDSs) perform a vital function in improving security and anomaly detection. The effectiveness of deep learning-based methods has been proven in extracting better features and more accurate classification than other methods. In this paper, a feature extraction with convolutional neural network on Internet of Things (IoT) called FECNNIoT is designed and implemented to better detect anomalies on the IoT. Also, a binary multi-objective enhance of the Gorilla troops optimizer called BMEGTO is developed for effective feature selection. Finally, the combination of FECNNIoT and BMEGTO and KNN algorithm-based classification technique has led to the presentation of a hybrid method called CNN-BMEGTO-KNN. In the next step, the proposed model is implemented on two benchmark data sets, NSL-KDD and TON-IoT and tested regarding the accuracy, precision, recall, and F1-score criteria. The proposed CNN-BMEGTO-KNN model has reached 99.99% and 99.86% accuracy on TON-IoT and NSL-KDD datasets, respectively. In addition, the proposed BMEGTO method can identify about 27% and 25% of the effective features of the NSL-KDD and TON-IoT datasets, respectively.
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