混沌神经动力学行为在多自由度机器人上的应用研究

本文把混沌神经动力学行为应用到了一个多自由度的机器人手臂,利用一种简单的神经编码方法使高维的神经网络模式转化成了低维的运动参数。虽然只在神经网络中嵌入了三种简单的姿势动作,但是在混沌神经动力学行为出现时,机器人手臂呈现出复杂的组合运动。利用这一点,提出了一个简单的控制算法用来解决病态问题(不一定有解或者确定的解无法保证的问题)。实装实验进一步表明,尽管只有粗略甚至不确定的光源信息,利用提出的算法机器人手臂可以成功的寻找到光源。     

基于DSP的机器人末端力控制系统设计

工业机器人的运动分为自由运动和受力约束运动两种不同的运动类型。受力约束运动不仅要进行精确的位置控制,而且要对接触力进行精确控制。文章对机械臂的末端力控制系统进行了研究。采用了高精度电动滑台作为力控制系统的执行机构,在电动滑台末端增加了柔性单元,从而克服了系统柔性不足的缺点,并且依据Lyapunov稳定性理论确定系统的二阶参数,使用Narendra提出的稳定自适应设计方法构建了电动滑台的数学模型。对机械臂末端柔顺系统的系统设计及算法进行了研究,消除了外界噪声对系统的干扰,解决了力控制的基本控制策略问题,优化了力控制时系统的响应特性。     

Contact-impact formulation for multi-body systems using component mode synthesis

The efficiency and accuracy are two most concerned issues in the modeling and simulation of multi-body systems involving contact and impact. This paper proposed a formulation based on the component mode synthesis method for planar contact problems of flexible multi-body systems. A flexible body is divided into two parts： a contact zone and an un-contact zone. For the un-contact zone, by using the fixed-interface substructure method as reference, a few low-order modal coordinates are used to replace the nodal coordinates of the nodes, and meanwhile, the nodal coordinates of the local impact region are kept unchanged, therefore the total degrees of freedom （DOFs） are greatly cut down and the computational cost of the simulation is significantly reduced. By using additional constraint method, the impact constraint equations and kinematic constraint equations are derived, and the Lagrange equations of the first kind of flexible multi-body system are obtained. The impact of an elastic beam with a fixed half disk is simulated to verify the efficiency and accuracy of this method.     

Flapping dynamics of a flexible propulsor near ground

The flapping motion of a flexible propulsor near the ground was simulated using the immersed boundary method. The hydrodynamic benefits of the propulsor near the ground were explored by varying the heaving frequency (St) of the leading edge of the flexible propulsor. Propul-sion near the ground had some advantages in generating thrust and propelling faster than propulsion away from the ground. The mode analysis and flapping amplitude along the Lagrangian coordinate were examined to analyze the kine-matics as a function of the ground proximity (d)and St. The trailing edge amplitude (atail)and the net thrust (Fx)were influenced by St of the flexible propulsor. The vortical structures in the wake were analyzed for different flapping conditions.     

Experimental assessment of performance characteristics for pitching flexible propulsors

Using a flexible hydrodynamic foil that pitches to produce thrust, the most pertinent aspects of a fish-like propulsion system are replicated in a controlled environment. The pitching and flexing combination creates a hydroelastic coupling in which the fluid and flexible foil simultaneously affect each other's behavior. The project investigated relationships for the propulsors’ thrust and efficiency performance to gain a better understanding of the dynamic interaction with the surrounding fluid. The analysis was conducted through reduction of the measured force and torque data. The experiments took place in a large recirculating water channel, using full span flexible propulsor models and a higher Reynolds number than previous flexible propulsor experiments. The propulsor pitched about a fixed axis at its quarter chord, with a six-axis load cell measuring the forces and torques on the shaft. The efficiency of the propulsor and the Coefficients of Thrust and Lift are presented as functions of both Strouhal Number and Stiffness Coefficient. The ensemble data will facilitate the engineering of fish-like propulsion systems for future application of this technology.     

Energy harvesting of a heaving and forward pitching wing with a passively actuated trailing edge

This study experimentally investigates the energy harvesting capabilities of an oscillating wing with a passively actuated trailing edge. The oscillation kinematics are composed of a combined heaving and forward pitching motions, where the pitching axis is well behind the wing center of mass. Passive actuation is attained by connecting the trailing edge with the wing body using a torsion rod. The degree of flexibility of the trailing edge is represented by the Strouhal number based on the trailing edge natural frequency. The trailing edge passive response is studied for oscillation Strouhal numbers of 0.017, 0.025 and 0.033. Instantaneous aerodynamic forces are measured in a closed loop wind tunnel at a Reynolds number of 40 000, based on the free stream velocity and the wing chord length. Measured results include the effective angle of attack induced by the trailing edge actuation as well as the lift and moment during the oscillation cycle. For the imposed kinematics in this study, the pitching motion has a positive contribution to the mean power output whereas the heaving motion has a relatively small but negative contribution. Additionally, by decreasing the natural frequency of the trailing edge closer to that of the imposed oscillation frequency, the magnitude of the lift and moment forces and hence the mean power output, increases. It is found that there exists a strong correlation between mean power output and the effective angle of attack, shown through the passive trailing edge response, resulting in an increase in energy harvesting potential.     

Excavation model of soil sampling device based on particle image velocimetry

This work aims to establish an energy-efficient strategy for sampling Martian subsurface soil for future extraterrestrial-life exploration missions. To this end, requirements for a robotic arm are carefully examined and an end-effector shape suitable for subsurface soil sampling is determined. A soil–tool interaction model is formulated based soil-flow measured by particle image velocimetry (PIV). The proposed model calculates the resistance forces and torque generated during the sampling procedure and is validated through a comparison of experimental data obtained from the force sensor and numerical data calculated from the proposed model. Results indicate that the proposed model provides an accurate estimation of the force generated during soil sampling. Furthermore, the interaction model is capable of estimating the robotic arm's energy consumption and calculating the most efficient tool size to use.     

Flexible Triboelectric Nanogenerator from Micro-nano Structured Polydimethylsiloxane

Triboelectric nanogenerator (TENG) can convert mechanical energy to electrical energy through contact electrification and electrostatic induction. Single-friction-surface triboelectric nanogenerator (STENG) extends potential application because a finger can be used as one friction surface in the contact electrification. In this work, a fully flexible STENG has been made, consisting of polydimethylsiloxane(PDMS) with micro-nano structures on its observe side and a flexible electrode on its reverse side. The femtosecond laser ablation was introduced to make micro-nano structures on PDMS and Ag nanowires (Ag NWs) were embedded in PDMS to serve as flexible induction electrode. It has been demonstrated that the energy conversion efficiency increases greatly because of the existing micro-nano structures on PDMS. Further, the mechanism of STENG was proved. Owing to the fully flexible characteristics in both the electrode and PDMS, STENG works well when it is adhered on any subject, for example, on clothes by tape.     

基于柔性铰链支撑的动镜扫描系统

为了改进傅里叶变换红外光谱仪的动镜驱动装置,设计了一种基于柔性铰链支撑的动镜扫描系统。采用柔性铰链的支撑方式和音圈电机的驱动方式,利用具有高精度高稳定性的直角型柔性铰链支撑机构支撑动镜,利用音圈电机驱动动镜前后往复运动,采用DSP控制系统对动镜的匀速进行控制。实验结果表明所设计的动镜扫描系统具有方向稳定性、速度稳定性、抗震性能优越等优点。     

Thicknesses of 70 southern spiral galaxies

Using the method proposed by Peng (1988) and analyzing the spiral patterns, the thicknesses of 70 southern spiral galaxies whose images were taken from the Digitized Sky Survey at Xinglong Observational Station of Beijing Observatory were measured. The spiral arms of all these galaxies have been fitted on their images with some logarithmic spiral curves to get their optimum inclinations. Project supported by the Yational Natural Science Foundation of China, the National Climbing Project of China and the Doctoral Program Foundation of State Education Cummission.