基于DSP定时器在伺服位置控制中的应用

对DSP定时器功能及相关寄存器进行一般性的介绍。鉴于相位检测器与定时器共享引脚,将相位检测器作为定时器的输入引脚,用编码器反馈值作为计数值,利用定时器的比较寄存器产生的中断,将位置反馈和实时控制结合起来,由电机不同的旋转速度来设定定时器计数比较值,从而实现对伺服的实时位置控制。通过实验数据表明,定时器能够应用于对实时性和精度要求较高的伺服实时位置控制。     

Thermodynamic modeling of the V–Si system supported by key experiments

The V–Si system is reassessed based on a critical literature review involving recently reported data and the present experimental data. These new data include the thermodynamic stability of V ₆Si₅ and the enthalpies of formation for the compounds calculated by first-principles method. Two alloys were prepared in the region of (Si)+V Si₂ and annealed at 1273 K for 14 days. After X-ray diffraction (XRD) and chemical analysis of these alloys were performed, the eutectic reaction (L⇔(Si)+V Si₂) temperature was determined by differential thermal analysis (DTA). Self-consistent thermodynamic parameters for the V–Si system were obtained by optimization of the selected experimental values. The calculated phase diagram and thermodynamic properties agree well with the experimental ones. Noticeable improvements have been made, compared with the previous assessments.     

Diffusional mobility for fcc phase of Al–Mg–Zn system and its applications

Diffusional mobility for fcc phase of the Al–Mg and Al–Mg–Zn systems was critically assessed by using the DICTRA software (Diffusion Controlled Transformation). Good agreement was obtained from comprehensive comparisons between the calculated and experimental diffusion coefficients. The developed mobility database enables reasonable prediction of diffusion and solidification behaviours resulting from interdiffusion, such as concentration profile of diffusion couples and solidification curve of the Al–Mg alloys.     

Hopping on Even Ground and Up Stairs with a Single Articulated Leg

This paper presents a method for generating gaits for a one-legged articulated hopping robot. A static optimization procedure produces the initial joint velocities for the flight phase, using the principle of conservation of angular momentum and assuming (nearly) passive flight. Two novel objective functions for this static optimization enable one to choose different gaits by simply changing a few parameters. A dynamic optimization procedure yields a solution for the flight trajectory that minimizes control effort. The stance phase (when the foot is touching the ground) becomes a standard two point boundary value problem, also solved with a dynamic optimization procedure. During the stance phase, the physical joint limitations, ground reaction forces, and the trajectory of the zero-moment point all constrain the solution. After these single-phase optimizations, a complete-cycle optimization procedure, incorporating both flight and stance phases, further reduces the control effort and balances the motion phases. In simulation, the leg hops on even ground and up stairs, exhibiting energy-efficient and intuitively satisfying gaits.     

基于相位编码的音频信息隐藏方法

针对听觉感知无差异时的局部相位失真条件,在宽带音频信号实验的基础上,提出一种利用局部相位分区实现信息隐藏的新算法。相对于经典的相位调制算法,利用局部相位信息,在保证听觉相似性的同时,能提高信息的嵌入量、改善误码率。理论分析和实验结果表明了该算法的有效性。     

低杂散低相噪频率合成器的设计

DDS＋PLL是目前频率合成技术的常用组合方式之一。首先就DDS＋PLL的几种常用合成方式的特点进行了简单介绍．然后着重利用DDS激励PLL的混频合成方式,实现了一种低杂散低相噪的频率合成器的设计。设计中首先在理论分析的基础上选出了合理的设计方案,然后对各项指标进行了可行性分析,尤其对输出相位噪声和组合杂散进行了详尽的阐述。最终通过理论分析,合理的选取时钟频率巧妙地避开了近端的杂散,用试验结果证明了该方案的可行性。     

Multivariable direct adaptive decoupling controller using multiple models and a case study

In this paper, a multivariable direct adaptive controller using multiple models without minimum phase assumption is presented to improve the transient response when the parameters of the system jump abruptly. The controller is composed of multiple fixed controller models, a free-running adaptive controller model and a re-initialized adaptive controller model. The fixed controller models are derived from the corresponding fixed system models directly. The adaptive controller models adopt the direct adaptive algorithm to reduce the design calculation. At every instant, the optimal controller is chosen out according to the switching index. The interaction of the system is viewed as the measured disturbance which is eliminated by the choice of the weighing polynomial matrix. The global convergence is obtained. Finally, several simulation examples in a wind tunnel experiment are given to show both effectiveness and practicality of the proposed method. The significance of the proposed method is that it is applicable to a non-minimum phase system, adopting direct adaptive algorithm to overcome the singularity problem during the matrix calculation and realizing decoupling control for a multivariable system. Supported by the National Natural Science Foundation of China (Grant Nos. 60504010, 60864004), the National High-Tech Research and Development Program of China (Grant No. 2008AA04Z129), the Key Project of Chinese Ministry of Education (Grant No. 208071), and the Natural Science Foundation of Jiangxi Province (Grant No. 0611006)     

利用相位的自旋1/2量子系统的相干控制

针对两个自旋1/2粒子组成的封闭量子系统, 建立了具有Ising相互作用的量子系统模型. 在此基础上通过具有特定幅值及相对相位的半反直觉脉冲, 制备了相应的量子相干态. 并通过系统数值仿真实验, 归纳出系统终态与相对相位之间的近似关系式, 分析了控制脉冲的幅值和时间延迟对制备过程的影响. 利用部分绝热通道技术实现了相位相干控制.