Three-stage polarization mode dispersion compensator capable of compensating second-order polarization mode dispersion

The impacts of polarization-dependent dispersion on systems are investigated briefly, based on which a three-stage polarization mode dispersion compensator has been proposed to compensate polarization-dependent chromatic dispersion and the principal states of polarization rotation rate at the same time. The two possible operating points of this compensator are also proposed. Numerical results show that the maximum tolerable polarization mode dispersion value after three-stage compensation has been improved by 17% per bit slot compared with using a two-stage compensator.     

Implementation of THD-reduction stereo audio amplifier using compensators and sigma–delta modulators

This paper presents an integrated stereo audio amplifier that employs sigma?Cdelta (????) modulation techniques with compensators. Traditional closed-loop audio amplifiers adopt pulse-width modulation or ???? modulation techniques. The design method proposed in this study uses a negative feedback closed-loop system with compensator and ???? modulator. This combination of compensator and ???? modulator significantly reduces the noise and total harmonic distortion (THD) compared with a traditional closed-loop system. The proposed negative feedback loop can automatically compensate for external perturbations, improving the precision of the eventual output. The compensator increases the audio-frequency loop gain, and leads to better rejection of audio-frequency disturbances. At a sample rate of 10?MHz, the proposed audio amplifier achieves 0.04% THD and a signal to noise ratio of 87?dB with efficiency above 92%. The proposed audio amplifier was implemented in a TSMC 3.3?V 0.35???m 2P4M CMOS process.     

一种标定Soleil-Babinet补偿器的新方法

提出了一种高精度标定索累-巴比涅(Soleil-Babinet)补偿器的新方法.在光谱扫描法测量系统中,将多级半波片置于被测补偿器后,以半波片的延迟量为基准,高精度地标定出补偿器的延迟量所对应的测微丝杆位移.该方法利用光强透过率和波长的关系得到延迟量,避免了光强值直接测量法误差源多、精度不高的缺点;同时解决了光谱扫描法不易测量零级相位器件的问题.实验中以工作波长为633 nm的多级半波片为基准,对Soleil-Babinet补偿器进行标定.分析表明,该方法在确定延迟量为0和λ的位置时,精度可达0.45 nm;0～λ范围之间的延迟量最大测量误差仅为3.2 nm.     

Stability improvement of V/f-controlled induction motor drive systems by a dynamic current compensator

Stability improvement of V/f-controlled induction motor drive systems by a dynamic current compensator is proposed. The proposed method uses a dynamic current compensator to improve the stability of the V/f-controlled induction motor drive systems. This method is easy to implement and helps eliminate the oscillations causing the instability of V/f-controlled induction motor drive systems.     

A compensator for the effects of high-order polarization modedispersion in optical fibers

We present a polarization mode dispersion compensator for the rotation of the principal states with frequency. This compensator requires only two control elements more than existing first-order compensators. These are the position of one polarization controller and the setting of a single delay. With the proposed scheme, compensation for first order can be decoupled from the compensation for higher orders and controlled independently. The effect of the compensator on signal transmission is evaluated with extensive numerical simulations     

双向二维快速伺服刀架的前馈控制研究

以压电陶瓷驱动器作为动力输入的快速伺服刀架具有输出力大和高频率响应的优点。压电陶瓷驱动器固有的迟滞现象严重影响了快速伺服刀架的输出定位精度。为解决此问题,通过引入归一化Bouc-Wen模型建立前馈控制补偿器,归一化Bouc-Wen模型解决了经典Bouc-Wen模型中存在的参数冗余问题。获得模型参数后,基于其逆模型搭建了前馈补偿器,并在搭建的实验平台上进行了单/双自由度轨迹跟踪性能测试。实验结果表明,对于等幅正弦波信号,经前馈控制环节补偿下快速伺服刀架的最大轨迹跟踪误差为1.18%,最大轨迹跟踪偏差为2.61%,证明该文所提出的前馈控制补偿器能提高快速伺服刀架的定位精度。     

A novel high-power low-distortion synchronous link converter-basedload compensator without the requirement of VAr calculator

A high-power low-distortion static VAr compensator based on a synchronous link converter has been proposed, where the harmonics are eliminated by incorporating a low-power insulated-gate-bipolar-transistor-based controlled current auxiliary converter in conjunction with a high-power gate-turn-off-thyristor-based converter. In this paper, a new load compensator based on this topology is proposed which does not require the information of the voltampere required by the load. As the requirement of the reactive voltampere calculator is eliminated, the scheme becomes insensitive to system frequency variations, temperature, and component aging. The control scheme required for the compensator is developed. The operation of the scheme is validated through extensive simulation studies. Experimental results obtained from a laboratory prototype are provided to demonstrate the viability of the scheme     

PMD补偿技术中影响射频功率反馈信号的因素

推导出了用射频功率作为反馈信息进行偏振模色散(PMD)补偿时,射频功率与光纤线路的差分群延迟(DGD)、偏振模已散补偿器的延迟时间、光功率在光纤中两个偏振主态之间功率分配比,以及补偿器的光快慢轴与光纤线路(或补偿器)快慢轴之间相对角度变化的关系。分析计算了在考虑到补偿器的光快慢轴与光纤线路有相对关系时的输出功率随其他参数变化的关系。     

An instantaneous reactive volt-ampere compensator and harmonicsuppressor system

A novel control method for a reactive volt-ampere compensator and harmonic suppressor system is proposed. It operates without sensing the reactive volt-ampere demand and nonlinearities present in the load. The compensation process is instantaneous, which is achieved without employing any complicated and involved control logic. The compensator is operated in cycle-by-cycle reference-current-controlled mode to achieve the instantaneous compensating feature. A mathematical model of the scheme is developed. Detailed analysis and simulation results are presented. A laboratory prototype of the compensator is developed to validate the results     

Multidimensional feedforward compensator for industrial systems through pole assignment regulator and observer

A feedforward-compensator-design technique is presented for industrial control systems. The proposed feedforward compensator can improve dynamic characteristics of multidimensional systems by modifying the input signals. The multidimensional feedforward-compensator design is based on the pole assignment regulator, the minimal-order observer, and the conversion from a closed-loop system to an open-loop system. The effectiveness of the proposed feedforward compensator is demonstrated by a simulation study of temperature control of a thermal power plant and by experiments of the contour control of an articulated robot arm.     

A three-phase parallel active power filter operating with PCC voltage compensation with consideration for an unbalanced load

The performance and dynamic characteristics of a three-phase parallel active power filter (APF) with point of the common coupling (PCC) voltage compensation with consideration for an unbalanced load is presented and analyzed in this paper. The proposed scheme employs a pulse-width modulation (PWM) voltage-source inverter and has two operation modes. First, it operates as a conventional active filter with reactive power compensation when PCC voltage is within the 15% voltage drop range. Second, it operates as a voltage compensator when PCC voltage is not within the 15% voltage drop range. Both the APF and the voltage compensator compensate asymmetries caused by nonlinear loads. Finally, the validity of this scheme is investigated through the analysis of simulation and experimental results for a prototype APF system rated at 10 kVA.     

State-dependent friction force compensation using periodic adaptive learning control

This paper uses the periodic adaptive learning control (PALC) for the compensation of a state-dependent non-Lipschitz external disturbance of electromechanical systems. Theoretically, we are interested in designing a non-Lipschitz friction force compensator, where the friction force is considered position-dependent external disturbance. The key idea of the proposed scheme is to make use of state-periodicity of an external disturbance on the iterative state domain. The state-periodical adaptive compensator designed based on Lyapunov stability analysis guarantees an asymptotical stability of the system after the first iterative trajectory and onwards. The designed-adaptive compensator is verified through an actual DC motor control test.     

Fuzzy logic torque ripple reduction by turn-off angle compensationfor switched reluctance motors

A fuzzy-logic-based turn-off angle compensator for torque ripple reduction in a switched reluctance motor is proposed. The turn-off angle, as a complex function of motor speed and current, is automatically changed for a wide motor speed range to reduce torque ripple. Experimental results are presented that show ripple reduction when the turn-off angle compensator is used     

A neural-network-based controller for the cost-effective operation of a hybrid compensator for nonactive power

The need to eliminate distortion from power networks has led to the development of various compensator topologies. The increasing cost of electrical energy requires the choice of the most cost-effective compensator operation. An investigation of a neural-network-based controller that chooses the most cost-effective compensator mode of operation on the basis of a continuous analysis of load conditions and the operational losses of the elements in the compensator structure are reported. The modeling of operational losses of each subtopology and the required control strategy are discussed. The results show that the operational loss savings due to the neural-network-controlled hybrid compensator were 30%-70% as compared to the conventionally controlled hybrid compensator, while also conforming to other control strategy requirements.     

On stability and performance of disturbance observer-based-dynamic load torque compensator for assistive exoskeleton: A hybrid approach

A disturbance observer-based-dynamic load-torque compensator for current-controlled DC-drives, as joint actuator of assistive exoskeletons, has been recently proposed. It has been shown that this compensator can effectively linearize and decouple the coupled nonlinear dynamics of the human-exoskeleton system, by more effectively compensating the associated nonlinear load-torques of the exoskeleton at the joint level. In this paper, a detailed analysis of the current controlled DC drive-servo system using the said compensator, with respect to performance and stability is presented, highlighting the key factors and considerations affecting both the stability and performance of the compensated servo system. It is shown both theoretically and through simulation results that the stability of the compensated servo system is compromised as performance is increased and vice-versa. Based on the saturation state of the servo system, a new hybrid switching control strategy is then proposed to select stability or performance-based compensator and controller optimally. The strategy is then experimentally verified both at the joint and task space level by using the developed four active-degree of freedom exoskeleton test rig.     

Analysis and real-time implementation of a radial-basis-function neural-network compensator for high-performance robot manipulators

System performance of robot manipulators with nonadaptive controllers might degrade significantly in the presence of structured or unstructured uncertainties. In order to improve the system performance, a novel radial-basis-function (RBF) neural-network (NN) compensator is proposed. With the RBF NN compensator introduced, the system errors and the NN weights with large dispersion in the initial NN weights are guaranteed to be bounded in the Lyapunov sense. The NN weights of the RBF NN compensator are adaptively tuned. Several software-based controllers, including the computed-torque control (CTC) and a few RBF NN schemes, are implemented in an industrial manipulator in real time. Experimental results are obtained to demonstrate the relative effectiveness of the proposed controllers in improving the tracking performance of the robot manipulators associated with structured or unstructured uncertainties.     

Phase compensation second-order repetitive control for CVCF PWM inverters

Phase compensation for high-order repetitive control (HORC) can improve system transient and steady-state performances. The phase compensator is often designed as the inverse transfer function of a closed-loop system. No other phase compensation methods for HORC have been reported up to now. Hence, in this paper, a simple approximate phase cancellation second-order repetitive control (RC) is proposed. The compensator is a linear combination of two different linear phase lead compensators, which can better fit the inverse of a plant model phase curve compared with the conventional linear phase compensator. Optimisation is introduced to design the parameters of the approximate phase cancellation second-order RC. Analysis and design of the second-order repetitive controlled pulse width modulation inverter system are presented. Simulations and experiments are provided to demonstrate the effectiveness of the optimisation method and verify the advantage of the approximate phase cancellation compensator.     

Design and implementation of an adaptive neural-network compensatorfor control systems

Recently, many studies have been made for intelligent controls using the neural-network (NN). These NN approaches for control strategies are based on the concept of replacing the conventional controller with a new NN controller. However, it is usually difficult and unreliable to replace the factory-installed controller with another controller in the workplace. In this case, it is desirable to install an additional outer control loop around the conventional control system to compensate for the control error of the preinstalled conventional control system. This paper presents an adaptive NN compensator for the outer loop to compensate for the control errors of conventional control systems. The proposed adaptive NN compensator generates a new command signal to the conventional control system using the control error that is the difference between the desired reference input and the actual system response. The proposed NN-compensated control system is adaptable to the environment changes and is more robust than the conventional control systems. Experimental results for a SCARA-type manipulator show that the proposed adaptive NN compensator enables the conventional control system to have precise control performance     

Comments on “A neural network compensator for uncertaintiesof robotics manipulators”

It is shown in this letter that the function of the neural network compensator proposed in the original paper is redundant. Perfect rejection of both structured and unstructured uncertainties in the robot dynamic model can be achieved directly without the compensator