Research on Anti-Fluctuation Control of Winding Tension System Based on Feedforward Compensation

In the fiber winding process,strong disturbance,uncertainty,strong coupling,and fiber friction complicate the winding constant tension control.In order to effectively reduce the influence of these problems on the tension output,this paper proposed a tension fluctuation rejection strategy based on feedforward compensation.In addition to the bias harmonic curve of the unknown state,the tension fluctuation also contains the influence of bounded noise.A tension fluctuation observer(TFO)is designed to cancel the uncertain periodic signal,in which the frequency generator is used to estimate the critical parameter information.Then,the fluctuation signal is reconstructed by a third-order auxiliary filter.The estimated signal feedforward compensates for the actual tension fluctuation.Furthermore,a time-varying parameters fractional-order PID controller(TPFOPID)is realized to attenuate the bounded noise in the fluctuation.Finally,TPFOPID is enhanced by TFO and applied to control a tension control system considering multi-source disturbances.The stability of the method is analyzed by using the Lyapunov theorem.Finally,numerical simulations verify that the proposed scheme improves the tracking ability and robustness of the system in response to tension fluctuations.

STUDY ON THE FEEDFORWARD COMPENSATION OF THE MOTIONERRORS OF NC MACHINE TOOLS

A feedforward compensation naethod of the motion errors of NC machine tools imple- mented with software is proposed , with which the motion errors can be compensated whithout changing the original computer control systems of the NC machine tools. The experimental results show that the circular interpolation profile machining errors decrease by a factor of 2/3 after com- pensated.

Parallel Distributed Compensation/H∞Control of Lane‑keeping System Based on the Takagi‑Sugeno Fuzzy Model

Current research on lane-keeping systems ignores the effect of the driver and external resistance on the accuracy of tracking the lane centerline.To reduce the lateral deviation of the vehicle,a lane-keeping control method based on the fuzzy Takagi-Sugeno(T-S)model is proposed.The method adopts a driver model based on near and far visual angles,and a driver-road-vehicle closed-loop model based on longitudinal nonlinear velocity variation,obtaining the expected assist torque with a robust H∞controller which is designed based on parallel distributed compensation and linear matrix inequality.Considering the external influences of tire adhesion and aligning torque when the vehicle is steering,a feedforward compensation control is designed.The electric power steering system is adopted as the actuator for lane-keeping,and active steering redressing is realized by a control motor.Simulation results based on Carsim/Simulink and real vehicle test results demonstrate that the method helps to maintain the vehicle in the lane centerline and ensures driving safety.

New Method to Improve Dynamic Stiffness of Electro-hydraulic Servo Systems

Most current researches working on improving stiffness focus on the application of control theories.But controller in closed-loop hydraulic control system takes effect only after the controlled position is deviated,so the control action is lagged.Thus dynamic performance against force disturbance and dynamic load stiffness can’t be improved evidently by advanced control algorithms.In this paper,the elementary principle of maintaining piston position unchanged under sudden external force load change by charging additional oil is analyzed.On this basis,the conception of raising dynamic stiffness of electro hydraulic position servo system by flow feedforward compensation is put forward.And a scheme using double servo valves to realize flow feedforward compensation is presented,in which another fast response servo valve is added to the regular electro hydraulic servo system and specially utilized to compensate the compressed oil volume caused by load impact in time.The two valves are arranged in parallel to control the cylinder jointly.Furthermore,the model of flow compensation is derived,by which the product of the amplitude and width of the valve’s pulse command signal can be calculated.And determination rules of the amplitude and width of pulse signal are concluded by analysis and simulations.Using the proposed scheme,simulations and experiments at different positions with different force changes are conducted.The simulation and experimental results show that the system dynamic performance against load force impact is largely improved with decreased maximal dynamic position deviation and shortened settling time.That is,system dynamic load stiffness is evidently raised.This paper proposes a new method which can effectively improve the dynamic stiffness of electro-hydraulic servo systems.

Composite Feedforward Compensation for Force Ripple in Permanent Magnet Linear Synchronous Motors

This paper presents a method for compensating the force ripple in permanent magnet linear synchronous motors(PMLSMs)by adopting a composite feedforward compensation scheme.Firstly,the vector control system of PMLSMs is described,and various force disturbances influencing the electromagnetic thrust are analyzed.As a result,the mathematical model of the whole system considering the force ripple is established.Then,a novel composite feedforward compensation scheme is proposed,which consists of a recursive least squares(RLS)parameter identification component and two feedforward compensation loops corresponding to the reference position trajectory and the force ripple,respectively.Finally,the effectiveness and advantages of the proposed composite feedforward compensation are demonstrated by simulation.The main incentive of this paper is the combination with the composite feedforward compensation loop corresponding to the reference position trajectory to improve the compensation effect of force ripple in PMLSMs.

A feedforward compensation design in critical conduction mode boost power factor correction for low-power low total harmonic distortion

For low-power low total harmonic distortion（THD）,based on the CSMC 0.5μm BCD process,a novel boost power factor correction（PFC） converter in critical conduction mode is discussed and analyzed.Feedforward compensation design is introduced in order to increase the PWM duty cycle and supply more conversion energy near the input voltage zero-crossing points,thus regulating the inductor current of the PFC converter and compensating the system loop gain change with ac line voltage.Both theoretical and practical results reveal that the proposed PFC converter with feedforward compensation cell has better power factor and THD performance,and is suitable for low-power low THD design applications.The experimental THD of the boost PFC converter is 4.5%,the start-up current is 54μA,the stable operating current is 3.85 mA,the power factor is 0.998 and the efficiency is 95.2%.

An Application of Optimal Preview Control in Terrain Following System

An optimal preview method is applied to the design of terrain following controller for cruise missile. In this method, tracking errors and control increments are both considered in the quadratic cost function. Integrating the general optimal servo system with a preview feedforward compensation that feeds forward future command and future disturbance produces an optimal preview servo system. In the terrain following system, the flight altitude of the cruise missile is a command signal, and its future information can be known apriori. Hence, we have designed a terrain following controller with a basic state feedback and a feedforward compensation for future altitude information. Simulation results show that the performance of the terrain following system with such an optimal preview controller has been improved dramatically.

A High-Performance Operational Amplifier for High-Speed High-Accuracy Switch-Capacitor Cells

A high-speed high-accuracy fully differenttial operational amplifier （op-amp） is realized based on no-Miller-capacitor feedforward （NMCF） compensation scheme. In order to achieve a good phase margin, the NMCF compensation scheme uses the positive phase shift of left-half-plane （LHP） zero caused by the feedforvvard path to counteract the negative phase shift of the non-dominant pole. Compared to traditional Miller compensation method, the op-amp obtains high gain and wide band synchronously without the pole-splitting effect while saves significant chip area due to the absence of the Miller capacitor. Simulated by the 0.35 μm CMOS RF technology, the result shows that the open-loop gain of the op-amp is 118 dB with the unity gain-bandwidth （UGBW） of 1 GHz, and the phase margin is 61°while the settling time is 5.8 ns when achieving 0.01% accuracy. The op-amp is especially suitable for the front-end sample/hold （S/H） cell and the multiplying D/A converter （MDAC） module of the high-speed high-resolution pipelined A/D converters （AVCs）.