A high performance adaptive on-time controlled valley-current-mode DC–DC buck converter

This paper presents an AOT-controlled(adaptive-on-time,AOT)valley-current-mode buck converter for portable application.The buck converter with synchronous rectifier not only uses valley-current-mode control but also possesses hybridmode control functions at the same time.Due to the presence of the zero-current detection circuit,the converter can switch freely between the two operating modes without the need for an external mode selection circuit,which further reduces the design difficulty and chip area.The converter for the application of high power efficiency and wide current range is used to generate the voltage of 0.6–3.0 V with a battery source of 3.3–5.0 V,while the load current range is 0.05–2 A.The circuit can work in continuous conduction mode with constant frequency in high load current range.In addition,a stable output voltage can be obtained with small voltage ripple.In pace with the load current decreases to a critical value,the converter transforms into the discontinuous conduction mode smoothly.As the switching period increases,the switching loss decreases,which can significantly improve the conversion efficiency.The proposed AOT controlled valley current mode buck converter is integrated with standard 0.18μm process and the simulation results show that the converter provides well-loaded regulations with power efficiency over 95%.When the circuit switches between the two conduction modes drastically,the response time can be controlled within 30μs.The undershoot voltage is controlled within 25 mV under a large current hopping range.

Adaptive detection of range-spread targets in homogeneous and partially homogeneous clutter plus subspace interference

Adaptive detection of range-spread targets is considered in the presence of subspace interference plus Gaussian clutter with unknown covariance matrix.The target signal and interference are supposed to lie in two linearly independent subspaces with deterministic but unknown coordinates.Relying on the two-step criteria,two adaptive detectors based on Gradient tests are proposed,in homogeneous and partially homogeneous clutter plus subspace interference,respectively.Both of the proposed detectors exhibit theoretically constant false alarm rate property against unknown clutter covariance matrix as well as the power level.Numerical results show that,the proposed detectors have better performance than their existing counterparts,especially for mismatches in the signal steering vectors.

A Decorrelation Constant Modulus Algorithm for Multitarget Separation Using Adaptive Arrays

In this paper, an adaptive digital filter algorithm is presented to optimize the signal-to-noise ratio of an antenna array with multiuser signal inputs. These synchronous communication signals have constant envelope property and are transmitted through a Multiple-Input/Multiple-Output （MIMO） linear channel. This Multiuser Constant Modulus Algorithm （MU-CMA） using an antenna array can compensate for both Interuser Interference （IUI） and Intersymbol Interference （ISI）. The method is derived by minimizing the cost function of the constant modulus signals as well as cross-correlations between them. The simulation result in this paper shows the performance of this algorithm.

Stability Analysis of q-axis Rotor Flux Based Model Reference Adaptive System Updating Rotor Time Constant in Induction Motor Drives

q-axis rotor flux can be chosen to form a model reference adaptive system(MRAS)updating rotor time constant online in induction motor drives.This paper presents a stability analysis of such a system with Popov’s hyperstability concept and small-signal linearization technique.At first,the stability of q-axis rotor flux based MRAS is proven with Popov’s Hyperstability theory.Then,to find out the guidelines for optimally designing the coefficients in the PI controller,acting as the adaption mechanism in the MRAS,small-signal model of the estimation system is developed.The obtained linearization model not only allows the stability to be verified further through Routh criterion,but also reveals the distribution of the characteristic roots,which leads to the clue to optimal PI gains.The theoretical analysis and the resultant design guidelines of the adaptation PI gains are verified through simulation and experiments.

Robust adaptive beamforming for constant modulus signal of interest

It is required in the diagonally loaded robust adaptive beamforming the automatic determination of the loading level which is practically a challenging problem.A constant modulus restoral method is herein presented to choose the diagonal loading level adaptively for the extraction of a desired signal with constant modulus(a common feature of the phase modulation signals).By introducing the temporal smoothing technique,the proposed constant modulus restoral diagonally loaded robust adaptive beamformer provides increased capability compared with some existing robust adaptive beamformers in rejecting interferences and noise while protecting the signal-of-interest.Simulation results are included to illustrate the performance of the proposed beamformer.

Adaptive broadband beamformer for nonuniform linear array based on second order cone programming

Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of minimizing the beamformer＇s output power while keeping the distortionless response （DR） in the direction of desired signal and keeping the constant beamwidth （CB） with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming （SOCP）. The computer simulations are presented which illustrate the effectiveness of our beamformer.

Adaptive coherence estimator based on the Krylov subspace technique for airborne radar

A novel adaptive detector for airborne radar space-time adaptive detection （STAD） in partially homogeneous environments is proposed. The novel detector combines the numerically stable Krylov subspace technique and diagonal loading technique, and it uses the framework of the adaptive coherence estimator （ACE）. It can effectively detect a target with low sample support. Compared with its natural competitors, the novel detector has higher proba- bility of detection （PD）, especially when the number of the training data is low. Moreover, it is shown to be practically constant false alarm rate （CFAR）.

Semi-blind Adaptive Beamforming for High-throughput Quadrature Amplitude Modulation Systems

A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna arrayts elements, are first utilised to provide a rough initial least squares estimate of the beamformer＇s weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.

A New Two-Stage Tunable Space-Time Adaptive Detector

In order to improve the rejection capability of mismatched interferer signals,a new two-stage detector is proposed under homogeneous scenarios with unknown covariance matrix,which is obtained by cascading the adaptive matched filter(AMF)detector and the enhanced RAO(EnRAO)detector.The new detector has constant false alarm performance,and the closed-form expression of probability of false alarm and probability of detection is derived.The performance of the new detector is assessed,and analyzed in comparison with other detectors.The results show that,the proposed detector can provide enhanced rejection capability in the case of mismatch,but the performance of the detector is slightly lost under the condition of matching.

Continuous on-line adaptation of the rotor time constant in FOC induction machine system

Rotor time constant is an important parameter for the indirect lleld oraentateO control of mauc- tion motor. Incorrect rotor tittle constant value will cause the flux observer generating a wrong angu- lar orientation of the rotor field. A new approach serves for rotor time constant on-line adaptation by setting the stator current to be zero for a short period. A smooth eorrector is designed to prevent ab- normal detection result from making adaptation. Impact of zero current duration on detection error and rotor speed is analyzed by experiments.

New multitarget constant modulus array for CDMA systems

A new mulfitarget constant modulus array is proposed for CDMA systems based on least squares constant modulus algorithm. The new algorithm is called pre-despreading decision directed least squares constant modulus algorithm （D-DDLSCMA）. In the new algorithm, the pre-despreading is first applied for multitarget arrays to remove some multiple access signals, then the despreaded signal is processed by the algorithm which united the constant modulus algorithm and decision directed method. Simulation results illustrate the good performance for the proposed algorithm.

A current-mode buck DC–DC controller with adaptive on-time control

A current-mode buck DC-DC controller based on adaptive on-time （AOT） control is presented. The on-time is obtained by the techniques of input feedforward and output feedback, and the adaptive control is achieved by a sample-hold and time-ahead circuit. The AOT current-mode control scheme not only obtains excellent transient response speed, but also achieves the independence of loop stability on output capacitor ESR. In addition, the AOT current-mode control does not have subharmonic oscillation phenomenon seen in fixed frequency peak current-mode control, so there is no need of the slope compensation circuit. The auto-skip pulse frequency modulation （PFM） mode improves the conversion efficiency of light load effectively. The controller has been fabricated with UMC 0.6-μm BCD process successfully and the detailed experimental results are shown.

L0 Regularization for the Estimation of Piecewise Constant Hazard Rates in Survival Analysis

In a survival analysis context, we suggest a new method to estimate the piecewise constant hazard rate model. The method provides an automatic procedure to find the number and location of cut points and to estimate the hazard on each cut interval. Estimation is performed through a penalized likelihood using an adaptive ridge procedure. A bootstrap procedure is proposed in order to derive valid statistical inference taking both into account the variability of the estimate and the variability in the choice of the cut points. The new method is applied both to simulated data and to the Mayo Clinic trial on primary biliary cirrhosis. The algorithm implementation is seen to work well and to be of practical relevance.

A novel constant modulus array for multiuser detection

This paper proposes a new multitarget constant modulus array structure for code division multiple access (CDMA) systems. The new algorithm for the structure is called pre-despreading and wavelet denoising constant modulus algorithm (D-WD-CMA). In the new algorithm, the pre-despreading is applied to multitarget arrays to remove some multiple access inter- ferences. After that the received signal is subjected to wavelet de-noising to reduce some noise, and used in CMA adaptive iteration for signal separation. Simulation results showed that the proposed algorithm performed better than the traditional CMA algorithm.

自动化视角下长纤磨浆机PLC控制系统设计研究

与加工木浆、草浆等短纤的磨浆机相比,以亚麻纤维、棉絮等为主要加工材料的长纤磨浆机天然具有较为苛刻的生产条件。为提升长纤磨浆机的设备适应性,基于自动化视角设计了一种针对长纤磨浆机的PLC控制系统。该系统在传统PLC控制系统的基础上增设了一个脉冲控制器,可以帮助磨浆机从启动状态快速进入磨浆状态,以及从短纤磨浆状态快速切换为长纤磨浆状态,与传统磨浆机相比在工作效率、设备适应性等方面具有更为显著的优势。

一种双控制模式的同步降压型DC/DC转换器

为突破转换器在输出电容选型上的局限性,保证转换器快速的负载瞬态响应,基于自适应恒定导通时间控制的两种控制模式,提出一种可根据输出电容类型选择控制模式的同步降压型DC/DC转换器。在D-CAP模式下,支持具有适当等效串联电阻的电容等作为输出电容;在电流模式下,支持等效串联电阻较低的陶瓷电容作为输出电容。基于0.35μm BCD工艺,使用Cadence软件对转换器进行瞬态仿真。结果表明,该设计在两种模式下都具有快速的瞬态响应。

改进GSA算法在机器人路径规划中的应用研究

针对万有引力搜索算法(GSA)收敛精度低和易陷入局部最优等问题,提出一种改进万有引力搜索算法(IGSA)。引入当前迭代次数t动态调整引力常数,以增强算法逃离局部最优能力;基于边界值改进粒子越界处理策略,以保留粒子多样性,提高算法收敛精度;同时,将中垂线算法用于游离粒子的位置更新,以加速游离粒子的收敛;为适应前述策略,提出自适应权重因子更新粒子位置策略,以提高算法的收敛速度。算法在10个基准测试函数上的结果表明,改进算法在稳定性、收敛速度和精度方面具有较大优势。最后将改进算法应用于机器人路径规划,并与其他智能仿生算法进行路径规划仿真对比实验,结果表明本文改进算法规划路径更短、拐点更少、搜索效率更高。

Communication Resource-Efficient Vehicle Platooning Control With Various Spacing Policies

Platooning represents one of the key features that connected automated vehicles may possess as it allows multiple automated vehicles to be maneuvered cooperatively with small headways on roads. However, a critical challenge in accomplishing automated vehicle platoons is to deal with the effects of intermittent and sporadic vehicle-to-vehicle data transmissions caused by limited wireless communication resources. This paper addresses the co-design problem of dynamic event-triggered communication scheduling and cooperative adaptive cruise control for a convoy of automated vehicles with diverse spacing policies. The central aim is to achieve automated vehicle platooning under various gap references with desired platoon stability and spacing performance requirements, while simultaneously improving communication efficiency. Toward this aim, a dynamic event-triggered scheduling mechanism is developed such that the intervehicle data transmissions are scheduled dynamically and efficiently over time. Then, a tractable co-design criterion on the existence of both the admissible event-driven cooperative adaptive cruise control law and the desired scheduling mechanism is derived. Finally, comparative simulation results are presented to substantiate the effectiveness and merits of the obtained results.

带恒功率负载多电平Buck变换器逆解耦自适应滑模控制

针对带恒功率负载(CPL)多电平Buck变换器的强耦合问题及负阻抗特性引起的不稳定问题,提出一种逆解耦自适应滑模控制策略。建立带CPL多电平Buck变换器的非线性数学模型,基于逆系统方法证明系统的可逆性,并推导逆系统表达式,将模型线性化解耦为多个伪线性子系统,抵消负阻抗特性的影响。通过选取线性滑模面和指数趋近律以减弱滑模抖振,并将自适应机制引入到滑模控制中,进而为线性子系统分别设计自适应滑模控制器,进一步提高系统控制性能。基于李雅普诺夫理论对控制系统的稳定性和鲁棒性进行验证。与现有控制方法进行比较,仿真结果表明,所提控制策略具有更强的鲁棒性和优越性。最后,搭建原理样机进行实验对比,实验结果验证了所提控制策略的正确性和有效性。

具有DCM环路校准的ACOOT控制全集成Buck

为解决高频下过零检测不精确所导致DCM模式下转换器存在较大反向电感电流损耗的问题,提出了一种基于自适应固定导通与关断时间控制的全集成Buck转换器。该控制方式属于脉冲频率调制(PFM),可根据输入输出电压和负载大小自动地调整导通时间和关断时间,改善轻载时输出电压纹波和效率。此外,设计了DCM校准环路,实现了精确的DCM工作。采用SMIC 65 nm CMOS工艺进行电路设计。仿真结果表明:在2.5 V输入电压,1.2 V输出电压,负载范围为0~150 mA条件下,最大输出电压纹波为69 mV,峰值效率提高系数为34.2%,峰值效率为73%;当负载为10 mA时,峰值效率为51.1%。