钢丝绳传动的三轴转台伺服控制的设计

针对某机载平台中钢丝绳传动带来的非线性误差及外部扰动等因素直接影响平台相机成像质量的问题,提出一种模糊自适应前馈补偿的控制策略.首先对钢丝绳传动机构和高精度直流伺服电机进行了建模,并建立了摩擦模型,为转台速度环控制回路引入模糊自适应PID控制器.设计出前馈补偿和模糊自适应控制器的复合控制策略.Matlab仿真结果以及实...     

Robust design of independent joint controllers with experimentationon a high-speed parallel robot

A linear independent joint control scheme is proposed. The design is made robust by closing another feedback loop that uses acceleration information besides the typical position and velocity loops. Reconstruction of acceleration measurements is performed via a suitable state-variable filter. Linear feedforward compensation is used to improve tracking performance of the closed-loop scheme. The control algorithm is tested first in a discrete-time simulation on a single-joint drive system with imposed disturbance torques. Then, real-time implementation on a high-speed parallel robot is presented. The experimental results demonstrate the effectiveness of the proposed technique     

Robust motion controller design for high-accuracy positioningsystems

This paper presents a controller structure for robust high speed and accuracy motion control systems. The overall control system consists of four elements: a friction compensator; a disturbance observer for the velocity loop; a position loop feedback controller; and a feedforward controller acting on the desired output. A parameter estimation technique coupled with friction compensation is used as the first step in the design process. The friction compensator is based on the experimental friction model and it compensates for unmodeled nonlinear friction. Stability of the closed-loop is provided by the feedback controller. The robust feedback controller based on the disturbance observer compensates for external disturbances and plant uncertainties. Precise tracking is achieved by the zero phase error tracking controller. Experimental results are presented to demonstrate performance improvement obtained by each element in the proposed robust control structure     

噪声有源反馈自校正控制

提出了一种前馈补偿和误差反馈相结合的噪声有源自校正控制方法,给出了两种未知参数的在线自适应学习算法,在控制系统中引入两个反馈闭环以改善系统的性能。仿真结果表明,前馈补偿和误差反馈相结合的噪声有源自校正控制比传统的Ｆｉｌｔｅｒ－Ｘ控制更为有效。     

A voltage control strategy for current-regulated PWM inverters

Alternative voltage control strategies for current-regulated PWM inverters are analyzed, including previously established feedforward and feedforward/feedback controllers and a newly proposed decoupling feedback control strategy. The steady-state and dynamic characteristics of each of these control methods are illustrated and compared for a selected inverter design. It is shown that the feedforward controller exhibits steady-state error and an undesirable overshoot of the output voltages during startup. The addition of a feedback loop eliminates the steady-state error and reduces the overshoot; however, the natural response is underdamped regardless of the choice of feedback gains. A decoupling feedback control strategy that eliminates the disadvantages of the feedforward and feedforward/feedback controllers is described. Using the decoupling feedback controller, it is possible to eliminate the steady-state error and place the closed-loop poles wherever desired. Moreover, if the closed-loop poles are selected appropriately, it is possible to eliminate the overshoot of the output voltages during startup transients     

Control design of a novel compliant actuator for rehabilitation robots

Rehabilitation robots have direct physical interaction with human body. Ideally, actuators for rehabilitation robots should be compliant, force controllable, and back drivable due to safety and control considerations. Series Elastic Actuators (SEA) offers many advantages for these applications and various designs have been developed. However, current SEA designs face a common performance limitation due to the compromise on the spring stiffness selection. This paper presents a novel compact compliant force control actuator design for portable rehabilitation robots to overcome the performance limitations of current SEAs. Our design consists of a servomotor, a ball screw, a torsional spring between the motor and the ball screw, and a set of translational springs between the ball screw nut and the external load. The soft translational springs are used to handle the low force operation, while the torsional spring with high effective stiffness is used to deal with the large force operation. It is a challenging task to design the controller for such a novel design as the control system needs to handle both the force ranges. In this paper, we develop the force control strategy for this actuator. First, two dynamical models of the actuator are established based on different force ranges. Second, we propose an optimal control with friction compensation and disturbance rejection which is enhanced by a feedforward control for the low force range. The proposed optimal control with feedforward term is also extended to the high force range. Third, a switching control strategy is proposed to handle a transition between low force and high force control. The mathematical proof is given to ensure the stability of the closed-loop system under the proposed switching control. Finally, the proposed method is validated with experimental results on a prototype of the actuator system and is also verified with an ankle robot in walking experiments.     

An Overview of Analog Feedback Part II: Amplifier Configurations in Generic Device Technologies

In this second installment of a two part paper that overviews analog feedback circuits, computationally efficient and general feedback analysis techniques applicable to virtually all three and four terminal device technologies are formulated. As developed in Part I, these techniques coalesce signal flow and two port network theories in a way that clearly illuminates the loop gain, driving point I/O impedances, and other characteristics of any type of feedback configuration. More than simply developing the signal flow-two port methodology, this paper demonstrates its design-oriented utility by applying the new technique to the problem of assessing the performance attributes and limitations of four single loop and two dual loop feedback architectures.Three advantages are gleaned by the signal flow-two port method of feedback network analysis. The first advantage is its amenability to a straightforward application of the stability theories and compensation strategies discussed in Part I. The second is its ability to underscore the magnitude of potentially troublesome feedforward factors associated with the feedback network. Once the extent of this parasitic feedforward is highlighted, the topological nature of appropriate feedforward compensation is relatively easy to innovate. The third advantage of signal flow-two port analytical methods is its ability to simplify the analysis of dual loop feedback architectures. This last advantage is noteworthy in view of the fact that dual feedback loops offer the only practical analog mechanism for desensitizing the gain and I/O impedances with respect to uncertainties in open loop parameters.     

Dynamic Performance of an APWM Resonant Inverter for High Frequency AC Power Distribution System

In this paper, the feedforward and feedback control loops are designed for the asymmetrical pulsewidth-modulated (APWM) resonant inverter to achieve fast transient response for the application in high frequency ac power distribution systems. In the proposed control scheme, the modulated integral control acts as a feedforward loop and provides pre-regulation for the feedback loop. As a result, the APWM resonant inverter has fast transient response against the line and load variation. Simulation and experimental results are presented to prove the dynamic performance of the APWM resonant inverter     

A novel ball handling mechanism for the RoboCup middle size league

This paper presents the hardware design and control design of a novel ball handling mechanism in the RoboCup Middle Size League used by team Tech United Eindhoven. The ball handling mechanism consist of two levers with two actively driven wheels attached to it, to exert forces on the ball in order to control its position relative to the robot. The proposed design is fully compliant to the rules and regulations imposed by the RoboCup Middle Size League community. The control design consists of a cascaded velocity and position feedback loop in combination with a feedforward controller which compensates for the robots ego motion. The proposed design is validated on a robot used by the Tech United Eindhoven team.     

舰载测量雷达船摇稳定回路设计

速率陀螺敏感于天线空间运动角速率,故可将陀螺感受的角速率信息作为反馈信息构成负反馈回路,通过加入船摇扰动前馈补偿环节,实现稳定回路的复合控制。再通过误差校正后将船摇补偿输出到功放,驱动天线方位及俯仰运动,达到隔离船摇扰动对天线指向影响的目的。设计已成功应用于舰载测量雷达的研制中,经对雷达性能测试,船摇隔离度达到50 dB。     

Amplifier linearization using RF feedback and feedforwardtechniques

The performance of feedback as a distortion reduction technique is highly dependent on the integrity of the feedback path. Any error or noise generated in this path is directly reflected into the output of the amplifier. Linearized RF power amplifiers (PAs) using Cartesian feedback require a demodulator in the feedback loop, and this is a potential source of linear errors, nonlinear errors, and noise. RF feedback with Cartesian compensation is proposed as a technique for overcoming some of these problems. The scheme is most suited to systems requiring an RF input. In addition, the RF nature of the input, feedback, and error signals enables the addition of a feedforward loop to further improve the linearization capability while still maintaining good efficiency. Design equations and simulation results are given for such a system. Disadvantages include the limited bandwidth (estimated at 1 MHz) and the need for additional circuits to generate the RF input signal when included in an integrated transmitter     

Force control of a very lightweight single-link flexible arm based on coupling torque feedback

In this paper, a feedback control law is proposed for regulating the contact force exerted by a very lightweight single-link flexible manipulator when it comes into contact with a motionless object. This control law is based on a lumped-parameter model. The tracking of the desired contact force is obtained by using a feedback loop control of the coupling torque between the motor and the flexible arm. To achieve a good performance on the force control it is only necessary to measure the coupling torque at the root of the arm. Neither the contact force sensor nor the angular position sensor of the motor are used in the control method. A modified PID controller is proposed for this control law. In this work the force control problem is studied for both free and constrained motions of the flexible manipulator, and a collision detection algorithm is also described.     

A DSP-based adaptive controller for a smooth positioning system

The implementation of a self-tuning regulator for the positioning of a direct-drive servomotor is described. The servo motor is a permanent magnet DC motor in which no speed reducer is used. The auto-tuning regulator consists of two major loops. The inner loop contains a feedback (PD or PID) regulator with additional feedforward terms. The parameters of the feedforward compensation are adjusted by the outer loop, which contains an online parameter estimator. The estimator is based on a recursive least-squares equation, and the estimated parameters are the load inertia and viscous friction. This self-tuning regulator has been simulated with PC.MATLAB, and the results demonstrate the high performance of the scheme. Experimental results obtained with a small DC motor (Electrocraft E-576) are presented, and these results show good agreement with the digital simulation results. There are two innovative aspects to this work. First, parameter estimation is used to adapt the feedforward compensation terms instead of the gains of the feedback controller, as usually is the case in conventional indirect self-tuning regulators. Secondly, the complete adaptive controller has been implemented using a single-chip digital signal processor (DSP), which results in the reduction of system hardware and cost     

两种逆变器双环反馈控制技术分析与比较

为了提高逆变器的稳定性和供电质量,文中介绍了一种基于极点配置的逆变器瞬时电压电流PI控制器的设计方法,建立了系统模型,比较分析了基于电感电流反馈控制和基于电容电流反馈控制技术。仿真结果表明,基于电感电流电压双环控制技术具有较好的输出特性。     

Manipulating rigid payloads with multiple robots using compliantgrippers

This paper describes an approach to nonmodel-based decentralized controls of multirobot systems utilizing structural flexibility in gripper design to avoid large unwanted internal forces acting on multirobot systems. It is proven in theory that a simple proportional and derivative (PD) position feedback plus gravity compensation controller can regulate the desired position/orientation of a payload manipulated by multiple robots with compliant grippers and simultaneously damp vibrations of compliant grippers. By adding a force feedforward control to the PD scheme, a hybrid position/force control scheme is further developed to control internal forces between robots and the payload in the particular directions, in the event that the compliance of grippers is low or negligible in these directions. Experiments conducted with two CRS A460 industrial robots manipulating a beam, using a rigid and a compliant gripper, confirm these theoretical predictions     

Feedforward current control of boost single-phase PFC converters

This paper presents the theory and application of feedforward current control for boost single-phase ac-dc converters with power factor correction. The proposed feedforward signal involves the instantaneous line voltage and the derivative of the reference current. The new control method is compared to existing feedback and feedforward control methods and is shown to significantly reduce input current harmonic distortion, particularly for applications where the current loop crossover frequency is relatively low compared to the line frequency. Implementation of the proposed control using analog devices and the associated issues, such as performance sensitivity to parameter variation and uncertainties, are presented. Analysis results are complemented by numerical simulation and experimental results from a prototype converter. Targeted applications of the proposed method are airborne systems where the line frequency is high, as well as low-cost digital control for terrestrial 50-60-Hz systems where the current loop crossover frequency is limited by the speed of the digital controller.     

Control strategies for enhanced power smoothing in wind energysystems using a flywheel driven by a vector-controlled induction machine

This paper presents a novel control strategy for power smoothing in wind energy applications, especially those feeding a stand-alone load. The system is based on a vector-controlled induction machine driving a flywheel and addresses the problem of regulating the DC-link system voltage against both input power surges/sags from a wind turbine or sudden changes in load demand. The control is based on a feedforward compensation scheme augmented by a nonlinear controller. Two feedforward compensation schemes are discussed and the limitations and performance of each scheme are analyzed. Experimental results are presented which verify the excellent performance of the feedforward compensation technique     

A technique for improving gain and noise figure of common-gate wideband LNAs

This paper presents a novel compensation design for regulators, i.e., modified NMCF (nested Miller compensation with feedforward Gm stage), resulting in a linear LDO (low dropout) regulator whose performance is independent of the off-chip capacitor and its ESR (equivalent series resistor). The proposed compensation method ensures the stability of the feedback loop and the sufficient phase margin of the LDO regulator. Besides, the transient response become faster. The analysis of the stability is derived to solidify the proposed design. The proposed design is implemented using TSMC 0.35 μm 2P4M CMOS process. The results verify the performance and the stability on silicon. The power supply rejection ratio is 25 dB @ [200 Hz, 3 MHz], [50 Ω, 500 Ω] provided that the input voltage varies from 4 to 5 V.     

A method for combustion phasing control using cylinder pressure measurement in a CRDI diesel engine

The start of combustion (SOC) in the combustion chamber has a considerable influence upon all performances of the engine. In this paper, cylinder pressure was investigated as a means for the closed-loop SOC control of a common-rail direct injection (CRDI) diesel engine. In order to detect the SOC, the crank angle position where the difference pressure became 10 bar was selected as the pressure variable. Using this pressure variable as a feedback variable, an adaptive feedforward control was proposed. The feedforward controller consisted of the radial basis function network (RBFN) and the feedback error learning method, which was used for the training of the network. The proposed SOC control strategy showed a far better regulation performance than that of the linear feedback controller. A further extension of the strategy based on the individual cylinder pressure feedback, the individual cylinder SOC control strategy, effectively reduced cylinder-by-cylinder SOC variation in steady and transient engine operations.     

Genetic algorithm tuning of Lyapunov-based controllers: anapplication to a single-link flexible robot system

In this paper, a systematic controller design approach is proposed to guarantee both closed-loop stability and desired performance of the overall system by effectively combining genetic algorithms (GAs) with Lyapunov's direct-controller design method. The effectiveness of the approach is shown by using a simple and efficient decimal GA optimization procedure to tune and optimize the performance of a Lyapunov-based robust controller for a single-link flexible robot. The feedback gains of the controller are tuned by the GA optimization process to achieve good results for tip motion control of the single-link flexible robot based on some suitable fitness functions. The paper includes results of simulation experiments demonstrating the effectiveness of the proposed genetic algorithm approach