Shape-Deformable and Locomotive MXene (Ti3C2Tx)-Encapsulated Magnetic Liquid Metal for 3D-Motion-Adaptive Synapses

Owing to their unique surface chemistry, room-temperature pseudoliquidity, and high electrical conductivity, gallium-based liquid metals (LMs) exhibit multifunctionality. To grant deformable and self-flowing characteristics to LMs, magnetic particles are incorporated for precisely controlling the LM motion and shape deformability. However, LM surface-adhesion and corrosivity hinders the integration of LMs into complex circuits and devices owing to potential alloying with other metals and contamination of their surroundings. In this study, a highly conductive Ti₃C₂T_x (MXene)-encapsulated magnetic LM (MX–MLM) is developed using a feasible fabrication method. The MX–MLM comprises magnetic particles suspended within its core and self-assembled MXene flakes on the surface to maintain the nonwettability and high electrical conductivity of a liquid droplet. The noncorrosivity and increased magnetism of the MX–MLM enable nonstick magnetic-field-induced locomotion and shape deformation on various surfaces including metals, oxides, and polymers. Furthermore, the MX–MLM exhibits recyclability and magnetic-field-induced self-healing. To demonstrate its functionality, the MX–MLM is employed as a magnetointeractive, shape-deformable, and locomotive top gate electrode in a transistor fabricated using a ferroelectric polymer gate insulator. The device exhibits excellent magnetointeractive synaptic capability for detecting and learning 3D path information.     

实现CPG模型的细胞神经网络的分支分析方法

传统细胞神经网络(CNN)的输出函数是不光滑的,难于研究其状态方程的分支情况.本文提出了用双曲函数近似分段线性输出函数,构成类似CNN系统.首先利用Poincar-éBend ixson定理和数值计算方法证明了新细胞状态方程存在稳定的周期解,然后通过局部分支理论计算出了使状态方程产生分支时偏置量的临界值,最后得出了偏置量的改变会影响状态方程振荡周期的结论,并通过仿真实验表明,在新CNN中得到的结论可以应用到CNN原型系统中,从而为通过CNN产生不同的CPG模式提供了理论依据.     

Vitamin C Mitigates Oxidative Stress and Behavioral Impairments Induced by Deltamethrin and Lead Toxicity in Zebrafish

Environmental contamination from toxic metals and pesticides is an issue of great concern due to their harmful effects to human health and the ecosystems. In this framework, we assessed the adverse effects when aquatic organisms are exposed to toxicants such as deltamethrin (DM) and lead (Pb), alone or in combination, using zebrafish as a model. Moreover, we likewise evaluated the possible protective effect of vitamin C (VC) supplementation against the combined acute toxic effects of the two toxicants. Juvenile zebrafish were exposed to DM (2 μg L⁻¹) and Pb (60 μg L⁻¹) alone and in combination with VC (100 μg L⁻¹) and responses were assessed by quantifying acetylcholinesterase (AChE) activity, lipid peroxidation (MDA), some antioxidant enzyme activities (SOD and GPx), three-dimension locomotion responses and changes of elements concentrations in the zebrafish body. Our results show that VC has mitigative effects against behavioral and biochemical alterations induced by a mixture of contaminants, demonstrating that it can be used as an effective antioxidant. Moreover, the observations in the study demonstrate zebrafish as a promising in vivo model for assessing the neuroprotective actions of bioactive compounds.     

蛇形机器人蜿蜒运动的摩擦机理及推进条件

针对带有从动轮的蛇形机器人,考虑实际结构中从动轮在蛇形机器人关节连杆上的安装位置,建立蛇形机器人蜿蜒运动的动力学模型。提出一种库伦-粘滞混合摩擦力模型,整体的库伦摩擦力特性和临界点处的粘滞摩擦力特性,避免了库伦摩擦力模型本身的非光滑性,以提高动力学模型的求解效率与计算稳定性。基于改进的动力学与摩擦力模型,利用摩擦系数比来表征法向与切向摩擦力的各向异性程度,通过对蜿蜒运动的仿真分析,讨论了摩擦系数比对前向运动速度与推进效率的影响规律,并对运动过程中蛇形机器人各个关节模块的速度和摩擦力变化进行了分析,明确了蛇形机器人蜿蜒运动的摩擦学机理,解释了蛇的蜿蜒抬起运动能够有效减少摩擦阻力而适用于高速运动的原因。最后通过带从动轮的蛇形机器人样机实验,对实现蜿蜒运动的摩擦学推进条件进行了验证。研究对于实现蛇形机器人的结构优化,步态规划与运动控制具有重要的理论意义与实际指导价值。     

Improving the energy efficiency and speed of walking robots

This study analyses the superior performance of gravitationally decoupled actuation in terms of energy efficiency, and hence autonomy. Based on the decoupling concept, a new design is presented for a 3 dof leg, and its performance is validated by including it in a 84 kg hybrid locomotion robot. The proposed leg obtains a straight-line constant-velocity motion of the foot as only one of its 3 motors is operated at constant speed. This feature, together with the hybrid structure, increases the robot’s efficiency and speed when operating on surfaces without obstacles, and drastically simplifies the walking operation control. A series of simulations have been done comparing the energy consumption of the hybrid robot including traditional coupled legs, and including the proposed decoupled legs. They show a superior performance of the later one. A real prototype has been built including the proposed mechanism. It shows a similar performance to that obtained from simulation, and a natural gait in flat terrains,at speeds up to 0.9 m/s.     

蛇形机器人的机构设计及运动分析

蛇形机器人以其独特的身体结构和运动形式能够适应各种复杂环境。为了验证蛇形机器人的运动能力,设计了一种前进中可做周期性运动的蛇形机器人,重点讨论了其关节机构的设计和运动原理;通过建立蛇形机器人运动的数学模型,并结合其运动的周期性,详细分析了三连杆模型的运动步态特性。研究结果表明,三连杆运动步态提高了蛇形机器人的运动能力。     

壁虎在垂直的不同材料表面的运动与附着行为研究

用动物全空间运动行为-反力测试系统测试记录了大壁虎(gekko gecko)在垂直的玻璃、有机玻璃、铝和不锈钢表面的运动行为和运动反力。分析了壁虎在垂直的不同材料表面的运动附着能力与材料表面特性之间的关系。大壁虎在玻璃、有机玻璃、铝表面上采用对角步态向上爬行,运动与附着能力依次降低,在不锈钢表面不能爬行与附着。在玻璃表面的爬行速度是铝表面爬行速度的两倍。壁虎主要通过提高步频来提高速度。在运动与附着能力较弱的表面,壁虎对壁面的运动反力较小,通过降低爬行速度、提高占空比、增加腿的附着时间来保证运动的稳定与安全,并通过轴向力克服身体重力向上爬行,通过侧向力和法向力使身体稳定地附着在壁面上。壁虎在垂直表面的运动与附着能力随着接触面材料表面能的增加而提高。     

基于强化学习的双足机器人的实时避障位置控制

为了提高双足机器人的实时控制能力，提出一种基于强化学习的双足机器人的实时避障位置控制方法。以机器人的双足步行稳定性为控制目标函数，构建双足机器人的实时路径动力学模型，以机器人质心运动的加速度和惯性力矩为被控对象，采用等效碰撞子模型进行双足机器人的实时避障路径规划，采用碰撞子模型和摆动子模型相结合的方法，进行双足机器人行走路径的纠偏参量反馈调节，采用模糊强化学习跟踪方法，进行双足机器人的误差增益控制，实现双足机器人的实时避障位置控制。仿真结果表明，采用该方法进行双足机器人控制的实时避障性能较好，纠偏能力较强，提高了机器人的自适应控制能力。     

Does swimming activity influence gas bubble trauma in fish?

Total dissolved gas (TDG) supersaturation from sources such as hydroelectric dams can cause harmful bubble growth in the tissues of aquatic animals, known as gas bubble trauma (GBT). Locomotion is known to exacerbate bubble growth in tissues during decompression under certain conditions (such as in diving animals), possibly because of increased bubble nucleation. As with decompression sickness, GBT is caused by the supersaturation of tissues with gas, and thus we hypothesize that locomotion promotes bubble nucleation in the tissues of fish exposed to TDG supersaturation. Many previous laboratory studies have tested the effects of TDG on fish exposed to low-velocity, non-directional flow, whereas fish in field conditions are exposed to higher-velocity flows and are likely more active. Therefore, it is important to understand the effects of locomotion on GBT to apply laboratory results to active fish in field conditions. We exposed rainbow trout (Oncorhynchus mykiss) to either control (100% TDG) or TDG supersaturation (123% TDG) in either static or flowing water conditions (1.8 Bl/s) and recorded time to 50% loss of equilibrium (LOE). We observed no statistically significant difference in time to 50% LOE between flow conditions. Given the lack of statistically significant difference between static and flowing water, our findings indicate that results from GBT experiments on rainbow trout in non-directional flow are applicable to more active individuals.     

MARCEL: Mobile active rover chassis for enhanced locomotion

To extend planetary exploration beyond the current limitations of wheeled vehicles while preserving reliability, simplicity, and efficiency, actuation can be judiciously incorporated into the locomotion system. Based on a static analysis, we propose a new four-wheeled chassis concept for planetary rovers that can traverse more challenging terrain with the help of two internal active joints. These joints are arranged as follows: a vertical pivot articulates the chassis around its center while a bogie allows the rear wheels to rotate around the longitudinal axis of the vehicle. We also introduce a control method that uses a two-stage procedure to produce an interpretable controller based on a policy devised by reinforcement learning. This way, we eliminate the black box made of a neural network and facilitate the transfer from simulation to reality. The resulting controller efficiently harnesses the internal mobility of the chassis to climb over obstacles in a sequenced manner while relying only on proprioceptive data provided by the chassis. A rover prototype named MARCEL has been built and tested experimentally. Contrary to any state-of-the-art six-wheeled passive chassis, the proposed locomotion system and its associated control has proven to be able to overcome solid step obstacles as tall as the diameter of the wheels with a $90^{\circ }$ edge and a friction coefficient as low as 0.5. This simple but capable design will enable future missions to explore more challenging areas while providing better guarantees in the face of unforeseen difficulties that could arise.