非最小相位系统输出跟踪的最优预测控制方法

讨论了一类非最小相位系统的输出跟踪问题。非最小相位系统广泛存在于机器人柔性结构控制、飞机的飞行控制和航天器发射等实际问题中。由于非最小相位系统内部动态的不稳定性 ,传统的一些输出跟踪方法将导致系统的某些变量发散。文中通过讨论系统的有界理想状态轨迹 ,将期望跟踪的输出进行了扩充 ,利用预测控制方法研究了一类非最小相位系统的输出跟踪问题 ,从理论上证明了利用预测控制可以使非最小相位系统稳定地渐近跟踪期望输出。最后给出了仿真结果。

双曲极小相位系统的必要条件及一类非线性对称大系统的反馈镇定

给出仿射非线性系统为双曲极小相位的一个必要条件，并讨论了一类非线性对称大系统的镇定问题，将该大系统的镇定归结为两个低阶系统的镇定。

非最小相位系统的最小方差自适应控制

目标函数修正法可设计含有不稳定零点的非最小相位最小方差系统控制器,设定被控对象某时刻输入、输出、零均值、方差、平移算子,可建立其输入输出模型。定义目标函数、输出误差,若控制输入是不稳定和非收敛的,通过修正目标函数,解误差方程得出极小控制律。仿真表明修正目标函数后的最小方差控制具有较好的跟随性。

可控震源零相位转换问题探讨

当前对于可控震源零相位资料小相位转换存在较大争议,是否为必需流程?何时进行转换?转换后对地震子波的影响如何?本文通过对可控震源的扫描信号自相关子波、模拟大地吸收后可控震源的子波和实际可控震源采集数据做小相位转换处理分析,发现相位转换过程中的相位漂移现象不可避免,并明确给出修改方法,一定程度上解决了相位漂移的问题;文章肯定了相位转换的必要性,同时给出处理次序。

探究可控震源地震资料处理中需要注意的问题

在使用可控震源地震勘探作业的过程中,尽管其施工效率相对较高,但是在地震资料处理的过程中仍然存在众多的问题,只有对地震资料进行合理的处理,才能推动可控震源地震勘探作业的进一步发展。本文主要根据可控震源地震勘探作业的基本特点,结合目前常见技术的发展情况,提出地震资料处理过程中需要注意的问题,为提高地震资料处理质量奠定基础。

可控震源地震资料处理中需要关注的问题探讨

可控震源高效采集技术广泛应用于宽方位、高密度地震勘探,该技术在提高野外施工效率获得TB级地震数据的同时,给室内数据处理带来了相位和初至不清晰、特有噪声严重、数据量大的挑战。在分析可控震源采集数据的相位和初至波变化特点、不同类型的噪声及其特征等的基础上,讨论了可控震源地震资料处理中需要关注的问题。针对可控震源子波零相位特点,采用可控震源地震资料小相位处理技术,以满足反褶积等处理技术对相位假设的需求;针对可控震源采集的地震资料初至不清楚的不足,采用初至波优化处理及人工智能初至拾取技术,以满足处理中基于初至波的静校正技术的应用条件;针对可控震源地震资料存在的谐波干扰、“黑三角”强能量干扰、邻炮干扰等特殊噪声,采用针对性技术予以识别与压制,以提高地震资料信噪比;针对可控震源采集的地震数据量大的特点,采用数据特征统计方法与数据压缩技术对地震资料进行质量分析与监控。某沙漠区可控震源采集地震资料处理实例证明,上述处理技术应用效果良好。

基于有理正交系对有理解析信号的分解算法研究

对LPSD算法进行改进,引入有理正交基来替换原来的三角函数基。与三角函数基相比,有理正交基的优势是能自适应地选取基函数的系数。采用能量下降最快的思想和最小均方误差思想逐步求得基函数的系数,然后分解出极小相位信号与全相位信号。与LPSD算法相比,改进后算法比之前在耗时与算法迭代步数上有很大改进,信号拟合效果更好。

A New High Performance FM Transmitter

A new FM transmitter is reported. It adopts a fractional-N PLL synthesizer to realize the FM modulator. An extra offset current has also been applied to eliminate the effects of the mismatch in CP. The chip is fabricated with CSMC 0.5μm DPTM CMOS technology. Experiments show that it achieves THD≤0.08% and SNR≤ 82dB,and the maximum outband emission energy ≤ 90dBc/Hz. Furthermore,it also uses an auto frequency adjusting method to avoid tuning up the external inductances. All these merits are very suitable for FM transmission.

A Novel Digital Transceiver for CT0 Standard

This paper introduces a novel digital transceiver for the cordless telephone zero （CT0） standard,which uses a digital modulation and demodulation technique to handle the signal instead of the traditional analog meth-od. In the transmitter,a fractional-N phase locked loop （PLL） is utilized to realize the continuous phase frequency shift key （CPFSK） modulation,and a 2 Ts raised cosine （2RC） shaping technique is used to reduce the occupied bandwidth. In the receiver,a novel digital method is proposed to demodulate the 2RC CPFSK signal. This chip is fabricated using an SMIC 0.35μm mixed signal CMOS process with a die size of 2mm × 2mm. With an external low noise amplifier （LNA）,the sensitivity of the chip is better than -103dBm.

Influence of inaccurate wavelet phase estimation on seismic inversion

On the assumption that the seismic wavelet amplitude spectrum is estimated accurately, a group of wavelets with different phase spectra, regarded as estimated wavelets, are used to implement linear least-squares inversion. During inversion, except for the wavelet phase, all other factors affecting inversion results are not taken into account. The inversion results of a sparse reflectivity model （or blocky impedance model） show that： （1） although the synthetic data using inversion results matches well with the original seismic data, the inverted reflectivity and acoustic impedance are different from that of the real model. （2） the inversion result reliability is dependent on the estimated wavelet Z transform root distribution. When the estimated wavelet Z transform roots only differ from that of the real wavelet near the unit circle, the inverted reflectivity and impedance are usually consistent with the real model; （3） although the synthetic data matches well with the original data and the Cauchy norm （or modified Cauchy norm） with a constant damping parameter has been optimized, the inverted results are still greatly different from the real model. Finally, we suggest using the L1 norm, Kurtosis, variation, Cauchy norm with adaptive damping parameter or/and modified Cauchy norm with adaptive damping parameter as evaluation criteria to reduce the bad influence of inaccurate wavelet phase estimation and obtain good results in theory.

Multi-spacecraft Intelligent Orbit Phasing Control Considering Collision Avoidance

This paper proposes an intelligent low-thrust orbit phasing control method for multiple spacecraft by simultaneously considering fuel optimization and collision avoidance. Firstly,the minimum-fuel orbit phasing control database is generated by the indirect method associated with the homotopy technique. Then,a deep network representing the minimum-fuel solution is trained. To avoid collision for multiple spacecraft,an artificial potential function is introduced in the collision-avoidance controller. Finally,an intelligent orbit phasing control method by combining the minimum-fuel neural network controller and the collision-avoidance controller is proposed. Numerical results show that the proposed intelligent orbit phasing control is valid for the multi-satellite constellation initialization without collision.

MINIMUM-PHASE FIR PRECODER DESIGN FOR MULTICASTING OVER MIMO FREQUENCY-SELECTIVE CHANNELS

To maximize the throughput of frequency-selective multicast channel, the minimum-phase Finite Impulse Response (FIR) precoder design is investigated in this paper. This problem can be solved in two steps. Firstly, we focus on designing a nonminimum-phase FIR precoder under the criterion of maximizing the throughput, and develop two efficient algorithms for the FIR precoder design from perspectives of frequency domain and time domain. In the second step, based on the theory of spectral factorization, the nonminimum-phase FIR precoder is transformed into the corresponding minimum-phase FIR precoder by a classic iterative algorithm without affecting the throughput. Numerical results indicate that the achievable rate of the proposed design has remarkable improvement over that of existing schemes, moreover, the group delay introduced by the FIR precoder is minimized.

A Method of Image Symmetry Detection Based on Phase Information

Traditional methods for detecting symmetry in image suffer greatly from the contrast of image and noise, and they all require some preprocessing. This paper presents a new method of image symmetry detection. This method detects symmetry with phase information utilizing IogGabor wavelets,because phase information is stable and significant, while symmetric points produce patterns easy to be recognised and confirmable in local phase. Phase method does not require any preprocessing, and its result is accurate or invariant to contrast, rotation and illumination conditions. This method can detect mirror symmetry, rotating symmetry and curve symmetry at one time. Results of experiment show that, compared with pivotal element algorithm based on intensity information, phase method is more accurate and robust.

A new phase comparison pilot protection based on wavelet transform

Current phase comparison based pilot protection had been generally utilized as primary protection of the transmission lines in China from the 1950＇s to the 1980＇ s, Comentional phase comparison pilot protection has a long phase comparison time, which results in a longer fault-clearing time. This paper proposes a new current phase comparison, pilot protection scheme that is based on non-power frequency fauh eun＇ent component. The phase of the fourth harmonic eun＇ent of each end of the protected line has heen abstracted hy utilizing complex wavelet transformation and then compared in order to determine whether the inner fauh occurs or not. This way can greatly deerease fauh-elearing time and improve performances of this pilot protection when fault occurs under the heavy-load current and asymmetrical operation eonditions, Many EMTP simulations have verified the proposed scheme＇s correctness and effectiveness.

Amplitude phase control for electro-hydraulic servo system based on normalized least-mean-square adaptive filtering algorithm

The electro-hydraulic servo system was studied to cancel the amplitude attenuation and phase delay of its sinusoidal response,by developing a network using normalized least-mean-square (LMS) adaptive filtering algorithm.The command input was corrected by weights to generate the desired input for the algorithm,and the feedback was brought into the feedback correction,whose output was the weighted feedback.The weights of the normalized LMS adaptive filtering algorithm were updated on-line according to the estimation error between the desired input and the weighted feedback.Thus,the updated weights were copied to the input correction.The estimation error was forced to zero by the normalized LMS adaptive filtering algorithm such that the weighted feedback was equal to the desired input,making the feedback track the command.The above concept was used as a basis for the development of amplitude phase control.The method has good real-time performance without estimating the system model.The simulation and experiment results show that the proposed amplitude phase control can efficiently cancel the amplitude attenuation and phase delay with high precision.

Properties of an improved Gabor wavelet transform and its applications to seismic signal processing and interpretation

This paper presents an analytical study of the complete transform of improved Gabor wavelets （IGWs）, and discusses its application to the processing and interpretation of seismic signals. The complete Gabor wavelet transform has the following properties. First, unlike the conventional transform, the improved Gabor wavelet transform （IGWT） maps time domain signals to the time-frequency domain instead of the time-scale domain. Second, the IGW＇s dominant frequency is fixed, so the transform can perform signal frequency division, where the dominant frequency components of the extracted sub-band signal carry essentially the same information as the corresponding components of the original signal, and the sub- band signal bandwidth can be regulated effectively by the transform＇s resolution factor. Third, a time-frequency filter consisting of an IGWT and its inverse transform can accurately locate target areas in the time-frequency field and perform filtering in a given time-frequency range. The complete IGW transform＇s properties are investigated using simulation experiments and test cases, showing positive results for seismic signal processing and interpretation, such as enhancing seismic signal resolution, permitting signal frequency division, and allowing small faults to be identified.

Euler-Bernoulli梁的非同位控制

对一端固定,一端加剪切力反馈的Euler-Bernoulli梁,运用Legendre谱方法对一个非同位控制系统进行研究,得到了最优反馈增益系数和系统衰减率.结果表明这样的非同位控制系统可以有效的增大系统衰减率,使系统具有更好的稳定性.同时指出所研究的系统是极小相位的.

ADRC BASED INPUT DISTURBANCE REJECTION FOR MINIMUM-PHASE PLANTS WITH UNKNOWN ORDERS AND/OR UNCERTAIN RELATIVE DEGREES

The capability of ADRC is studied for linear time-invariant SISO minimum-phase systems with unknown orders, uncertain relative degrees, and unknown input disturbances. It is proved that ADRC can reject the unknown input disturbance and guarantee the close-loop stability for the plants with unknown but bounded relative degrees. Meanwhile, some close-loop performances can be achieved. The influence of the sensor noise is also discussed. And it is demonstrated by numerical examples that one ADRC with fixed parameters can be applied to a group of plants of different orders, relative degrees, and parameters.

Extracting outer function part from Hardy space function

Any analytic signal fa(e^(it)) can be written as a product of its minimum-phase signal part(the outer function part) and its all-phase signal part(the inner function part). Due to the importance of such decomposition, Kumarasan and Rao(1999), implementing the idea of the Szeg?o limit theorem(see below),proposed an algorithm to obtain approximations of the minimum-phase signal of a polynomial analytic signal fa(e^(it)) = e^(iN0t)M∑k=0a_k^(eikt),(0.1)where a_0≠ 0, a_M≠ 0. Their method involves minimizing the energy E(f_a, h_1, h_2,..., h_H) =1/(2π)∫_0^(2π)|1+H∑k=1h_k^(eikt)|~2|fa(e^(it))|~2dt(0.2) with the undetermined complex numbers hk's by the least mean square error method. In the limiting procedure H →∞, one obtains approximate solutions of the minimum-phase signal. What is achieved in the present paper is two-fold. On one hand, we rigorously prove that, if fa(e^(it)) is a polynomial analytic signal as given in(0.1),then for any integer H≥M, and with |fa(e^(it))|~2 in the integrand part of(0.2) being replaced with 1/|fa(e^(it))|~2,the exact solution of the minimum-phase signal of fa(e^(it)) can be extracted out. On the other hand, we show that the Fourier system e^(ikt) used in the above process may be replaced with the Takenaka-Malmquist(TM) system, r_k(e^(it)) :=((1-|α_k|~2e^(it))/(1-α_ke^(it))^(1/2)∏_(j=1)^(k-1)(e^(it)-α_j/(1-α_je^(it))^(1/2), k = 1, 2,..., r_0(e^(it)) = 1, i.e., the least mean square error method based on the TM system can also be used to extract out approximate solutions of minimum-phase signals for any functions f_a in the Hardy space. The advantage of the TM system method is that the parameters α_1,..., α_n,...determining the system can be adaptively selected in order to increase computational efficiency. In particular,adopting the n-best rational(Blaschke form) approximation selection for the n-tuple {α_1,..., α_n}, n≥N, where N is the degree of the given rational analytic signal, the minimum-phase part of a rational analytic signal can be accurately and efficiently extracted out.

Neural correlates of audio-visual modal interference inhibition investigated in children by ERP

In order to detect cross-sectional age characteristics of cognitive neural mechanisms in audio-visual modal interference inhibition,event-related potentials(ERP) of 14 10-year-old children were recorded while performing the words interference task.In incongruent conditions,the participants were required to inhibit the audio interference words of the same category.The present findings provided the preliminary evidence of brain mechanism for the children's inhibition development in the specific childhood stage.