Vegetation Change in Great Lakes Coastal Wetlands: Deviation from the Historical Cycle

Water-level change is integral to the structure and function of Great Lakes coastal wetlands, and many studies document predictable relationships between vegetation and water level. However, anthropogenic stressors, such as invasive species, land-use change, and water-level stabilization, interact to shift the historical cycle (of native vegetation migration up- and down-slope) toward dominance by invasive Typha species. Knowing from earlier studies that water-level stabilization alters the historical vegetation cycle, we asked if similar shifts can occur where water levels are not stabilized. Using historical aerial photographs of three coastal wetlands (in Lake Michigan's Green Bay, Wisconsin), we determined that habitat dominated by Typha species has expanded to eliminate wet meadow habitat. Between 1974 and 1992, linear regressions showed strong, significant relationships of both meadow area (R² ≥ 0.894; p < 0.02) and marsh area (R² ≥ 0.784; p < 0.05) to water level in all three wetlands. In 2000, meadow area was below that predicted by the historical pattern due to the landward advance of marsh habitat during a year of decreasing water levels. In the same period, land use in the wetland watersheds converted from agriculture to urban. Urbanization and the replacement of native Typha latifolia by the invasive hybrid Typha xglauca may have overwhelmed the beneficial impact of water-level fluctuation. The documentation of vegetation shifts, as herein, is an essential step in the process of preserving and restoring ecological integrity.     

Robust Stable Fuzzy Control via Fuzzy Modeling and Feedback Linearization with Its Applications to Controlling Uncertain Single-link Flexible Joint Manipulators

In this paper, a robust stable fuzzy control design based on feedback linearization is presented. Takagi–Sugeno fuzzy model is used as representing the nonlinear plant model and uncertainty is assumed to be included in the model structure with known bounds. For this structured uncertainty, the closed system can be analyzed by applying the perturbation system stability analysis to the fuzzy feedback linearization systems and a sufficient condition is derived to guarantee the stability of the closed-loop system with bounded parameter uncertainties. Based on the developed analysis method, we can design a robust fuzzy controller by choosing the control parameters satisfying the robust stability condition.     

Kinematic calibration for a hybrid 5DOF manipulator based on 3-RPS in-actuated parallel manipulator

The measurement method is a decisive step for any calibration method. This paper studies the practical performance of a 5DOF manipulator based on a 3-RPS parallel mechanism. By comparing the controlling data that resides in parallel part and serial part at different orientations, a calibration method has been put forward and proved to be applicable. The precision of the calibrated model mainly depends on the number of measurements carried out. The distribution of measurement points also affects the precision and the measurement number could be significantly reduced if uniform distribution were ensured.     

微机控制水轮机活动导叶打磨设备控制器的研制

针对水轮机活动导叶的修复问题,设计了微机直接控制的水轮机活动导叶打磨用机械手控制器,它可控制五个自由度,方便地修复各种形状复杂的活动导叶.打磨机械手由磨削器及x、y、z方向运动部件组成,它以恒压力位置/力混合控制算法为基础,可实现水轮机活动导叶3D图形显示以及用数据库管理.     

On rotations and translations with application to robot manipulators

Robot motion is described by a set of positions and orientations of the robot's end-effector relative to some base coordinate system. Different methods to describe this motion are available and most of them are presented in this paper. Methods for position vector, free vector, and line vector transformation are presented and compared, and the advantages and disadvantages, the simplicity, and the number of arithmetic operations required of the different methods are addressed. An example of the application of these methods to a six degree-of-freedom robot is given.     

柔性臂动力学建模及比较研究

根据广义坐标的不同定义应用Lagrange方程建立了两种表达形式的水平面内转动的两自由度柔性机械臂动力学模型；分析了两类方程的不同特点和适用领域；将模型的仿真结果和实验结果进行对比分析，验证了模型的准确性；为柔性臂动力学分析和下一步研究提供了理论指导及重要的前提条件。     

无人机光电载荷及其应用

简要介绍了无人机优势及应用范围,对目前世界上主要固定翼无人机及无人直升机的光电载荷进行了研究分析,在此基础上,对新型无人飞行器概念平台进行介绍。最后总结了无人机光电载荷发展趋势,即随着无人机平台技术及光电载荷技术的迅速发展,长航时、良好隐身性、多用途、具备主动光电干扰能力、高智能将是无人机光电载荷的发展趋势。     

光学透镜模具组衬圈剥离系统

用不研磨精密浇注法加工生产超薄光学透镜是具有世界先进水平的新工艺．介绍了使用该工艺生产光学透镜过程中模具组橡塑衬圈的剥离加工系统———气动式双向自动剥离机的组成、工作原理及其电气控制系统     

无人机多假目标欺骗式干扰效能研究

无人机多假目标干扰是一种重要的欺骗干扰样式。分析了无人机多假目标干扰效果的评估指标,建立了多假目标数量计算和标准化模型,最后利用单目标突防被击中模型和突防成功目标数模型对无人机多假目标在不同干扰距离下的干扰效果进行了定量分析,并用仿真计算加以验证。     

Causal end-effector inversion of a flexible link manipulator

A new method to obtain the required base torque for the rest-to-rest manoeuvre of a single flexible link manipulator as its end-effector moves along a desired trajectory is introduced. Contrary to available causal and non-causal end-effector inversion techniques, this new approach does not require pre- and/or post-actuation and works even in the presence of the purely imaginary zeros for the transfer function. In this approach, the desired end-effector trajectory is divided into a finite number of segments. In each segment, but the last one, the desired trajectory is redefined so that a bounded continuous torque can be obtained using causal dynamic inversion. For the last segment the desired trajectory is redefined so that not only the causal inversion is achieved but also the final conditions are satisfied; that is, the end-effector reaches its desired position and the manipulator comes to rest at a given time. The redefinition of the desired trajectory at each segment employs summation of the stable exponential functions, which leads to a family of possible answers for the redefined trajectory. To obtain the best member of this family which minimizes the difference between the desired trajectory and redefined trajectory, an efficient search algorithm is proposed and used. Simulation results show the effectiveness of this new method.