Feedforward Control Algorithm Research Articles

Investigation of the maximum load alleviation potential using trailing edge flaps controlled by inflow data

The maximum fatigue load reduction potential when using trailing edge flaps on mega-watt wind turbines was explored. For this purpose an ideal feed forward control algorithm using the relative velocity and angle of attack at the blade to control the loads was implemented. The algorithm was applied to time series from computations with the aeroelastic code HAWC2 and to measured time series. The fatigue loads could be reduced by 36% in the computations if the inflow sensor was at the same position as the blade load. The decrease of the load reduction potential when the sensor was at a distance from the blade load location was investigated. When the algorithm was applied to measured time series a load reduction of 23% was achieved which is still promissing, but significantly lower than the value achieved in computations.

Feedforward Control Design Based on Laguerre Network Modelling

In this paper feedforward control algorithm is proposed to enhance the performances of the model reference control. The control design is based on discrete Laguerre networks which represent a simple and useful tool for the approximation of signals or systems. In this approach both the system model and the controller are expressed in the form of Laguerre network. The model reference control is an open-loop control strategy which aims at obtaining an optimal reference signal tracking. To ensure unmeasured disturbance rejection the control loop is closed using an additional integrating effect. A feedforward path is added to reject the effect of measurable disturbance with known dynamics.

Periodic spring–mass running over uneven terrain through feedforward control of landing conditions

This work pursues a feedforward control algorithm for high-speed legged locomotion over uneven terrain. Being able to rapidly negotiate uneven terrain without visual or a priori information about the terrain will allow legged systems to be used in time-critical applications and alongside fast-moving humans or vehicles. The algorithm is shown here implemented on a spring-loaded inverted pendulum model in simulation, and can be configured to approach fixed running height over uneven terrain or self-stable terrain following. Offline search identifies unique landing conditions that achieve a desired apex height with a constant stride period over varying ground levels. Because the time between the apex and touchdown events is directly related to ground height, the landing conditions can be computed in real time as continuous functions of this falling time. Enforcing a constant stride period reduces the need for inertial sensing of the apex event, which is nontrivial for physical systems, and allows for clocked feedfoward control of the swing leg.

Application of Artificial Neural Networks for Shunt Active Power Filter Control

Artificial neural network (ANN) is becoming an attractive estimation and regression technique in many control applications due to its parallel computing nature and high learning capability. There has been a lot of effort in employing the ANN in shunt active power filter (APF) control applications. Adaptive Linear Neuron (ADALINE) and feed-forward multilayer neural network (MNN) are the most commonly used ANN techniques to extract fundamental and/or harmonic components present in the nonlinear currents. This paper aims to provide an in-depth understanding on realizing ADALINE and feed-forward MNN-based control algorithms for shunt APF. A step-by-step procedure to implement these ANN-based techniques in MATLAB/Simulink environment is provided. Furthermore, a detailed analysis on the performance, limitation, and advantages of both methods is presented in the paper. The study is supported by conducting both simulation and experimental validations.

Towards active tracking of beating heart motion in the presence of arrhythmia for robotic assisted beating heart surgery.

In robotic assisted beating heart surgery, the control architecture for heart motion tracking has stringent requirements in terms of bandwidth of the motion that needs to be tracked. In order to achieve sufficient tracking accuracy, feed-forward control algorithms, which rely on estimations of upcoming heart motion, have been proposed in the literature. However, performance of these feed-forward motion control algorithms under heart rhythm variations is an important concern. In their past work, the authors have demonstrated the effectiveness of a receding horizon model predictive control-based algorithm, which used generalized adaptive predictors, under constant and slowly varying heart rate conditions. This paper extends these studies to the case when the heart motion statistics change abruptly and significantly, such as during arrhythmias. A feasibility study is carried out to assess the motion tracking capabilities of the adaptive algorithms in the occurrence of arrhythmia during beating heart surgery. Specifically, the tracking performance of the algorithms is evaluated on prerecorded motion data, which is collected in vivo and includes heart rhythm irregularities. The algorithms are tested using both simulations and bench experiments on a three degree-of-freedom robotic test bed. They are also compared with a position-plus-derivative controller as well as a receding horizon model predictive controller that employs an extended Kalman filter algorithm for predicting future heart motion.

Design and experimental evaluation of a tactile display featuring magnetorheological fluids

This paper proposes a novel type of tactile display utilizing magnetorheological (Mr) fluid which can be applied to a robotic system in minimally invasive surgery to provide a surgeon with tactile information on remote biological tissues or organs. As a first step, an actuation mechanism for tactile function is devised utilizing the Mr fluid with a pin array mechanism. Based on the force responses of a human body, the tactile display is appropriately designed and a magnetic analysis is carried out to determine the design parameters using the finite element method. After evaluating the field-dependent force characteristics of the manufactured tactile display, a feed-forward control algorithm based on fuzzy logic is formulated to obtain the desired palpation force. Control performance is demonstrated via palpation force evaluation and psychophysical evaluation. In the results, the actual repulsive forces agreed well with the desired forces and the averaged relative error was less than 1.3%. In addition, the volunteers successfully recognized tactility with a favorable rating value of 3.36 on a five-point scale.

Comparison of Preshaping Profilers for Reducing Residual Vibrations After Rest-to-Rest Maneuvers

Generally, spacecraft with large flexible structures have multiple flexible modes with large effective masses and various mode shapes; therefore, the presence of uncertain high-order flexible modes should be considered in high-accuracy controller design. However, most researchers have proposed input preshaping algorithms that are valid only for a few flexible modes. Consequently, when these algorithms are applied to a flexible spacecraft having uncertain high-order flexible modes, residual vibrations might not be reduced sufficiently. This paper presents a smooth feedforward control algorithm for rest-to-rest maneuvers that significantly reduces residual vibrations at the endpoint of a maneuver. The new preshaping profiler is based on a filtering technique that combines a pair of sinc functions. The new profiler is compared to several conventional preshaping profilers. In addition, residual vibrations at the endpoint of maneuvers in the presence of unknown higher modes are found to be much smaller than those in other techniques. Only a hybrid-type profiler shows similar level of small residual vibrations comparable with the new profiler. The new profiler is suitable for rest-to-rest rotational maneuvers of a flexible spacecraft, especially when fine pointing accuracy is required at the endpoint of maneuvers; such accuracy is sometimes required for missions involving scientific observations.

High-Sampling Rate Dynamic Inversion—Filter Realization and Applications in Digital Control

This paper presents a stable inversion of nonminimum phase systems with highly efficient computation for high-sampling rate applications. The stable filter that inverts the dynamics of a nonminimum system is based on cascading a stable pole-zero cancellation infinite impulse response (IIR) filter with a high-order finite impulse response (FIR) filter which inverts the unstable zero dynamics. The high-order FIR filter is realized based on efficient IIR filter implementation first introduced by Powell and Chau then later modified by Kurosu. As a demonstrative example, the inversion filters are applied to feedforward tracking and repetitive control algorithms and realized by a field programmable gate array. The controllers are implemented at 100-kHz sampling rate to control the motion of a 4 degrees-of-freedom magnetically levitated shaft in experiment.

차량모델을 고려한 햅틱 큐 기어변속보조 시스템의 성능평가

This paper proposes a driver supportive device with haptic cue function which can transmit optimal gear shifting timing to a driver without requiring the driver's visual attention. Its performance is evaluated under vehicle model considering automotive engine, transmission and vehicle body. In order to achieve this goal, a torque feedback device is devised and manufactured by adopting the MR (magnetorheological) fluid and clutch mechanism. The manufactured MR clutch is then integrated with the accelerator pedal to construct the proposed haptic cue device. A virtual vehicle emulating a four-cylinder four-stroke engine, manual transmission system of a passenger vehicle and vehicle body is constructed and communicated with the manufactured haptic cue device. Control performances including torque tracking and fuel efficiency are experimentally evaluated via a simple feed-forward control algorithm.

Adaptive Resonant Vibration Control of a Piezoelectric Flexible Plate Implementing Filtered-X LMS Algorithm

Vibration in aerospace structures can lead to structural damage. To solve this problem, the implementation of active vibration control must be considered. This paper investigates active vibration control under the persistent resonant excitation of a clamped-clamped piezoelectric plate system. The finite element method (FEM) and ANSYS modal analysis methods are utilized to obtain the dynamics model and mode shapes of the plate. A two-norm criterion is used for optimal placement of piezoelectric sensors and actuators, taking into account the non-controlled modes to reduce spillover problems. A genetic algorithm (GA) is used to search the optimal locations of actuators/sensors. Then, a proportional derivative (PD) control algorithm and a filtered-X least mean square (filtered-X LMS) feed-forward control algorithm are designed for the system. Subsequently, numerical simulations with optimal placement of actuators and sensors are carried out to compare the performance of the controllers Finally, experiments are conducted. The experimental results demonstrate that the designed filtered-X LMS control algorithms can suppress the resonant vibration better than that of the PD control.

Improved Load Tracking Performance for Combined Cycle Gas Turbine Plants through Flatness Based Feedforward Control

The increasing competition on the energy market along with the highly variable feed-in from renewable energy sources have a far-reaching impact on the operation of conventional power plants. In order to stay competitive, utility companies need to adopt an operation regime that is characterized by fast cycling. At the same time, the operation has to remain as efficient as possible. In combined cycle gas turbine (CCGT) plants, the total power output is the combination of gas turbine (GT) power output and steam turbine (ST) power output. These are coupled through the dynamic behavior of the heat recovery steam generator (HRSG). A model based feedforward control concept can be used to improve the performance during load changes. Thereby, the process dynamics of the HRSG and the turbines are taken into account in the feedforward control algorithm. Thus, GT and ST power output are coordinated in an optimal way which in turn improves the load tracking capabilities as compared to standard control concepts. This is demonstrated in this contribution by simulations studies.

승용디젤엔진의 EGR, VGT 시스템을 위한 비선형 정적 모델 기반 피드포워드 제어 알고리즘 설계

This paper presents a feedforward control algorithm for the EGR and VGT systems of passenger car diesel engines. The air-to-fuel ratio and boost pressure are selected as control indicators and the positions of EGR valve and VGT vane are used as control inputs of the EGR and VGT controller. In order to compensate the non-linearity and coupled dynamics of the EGR and VGT systems, we have proposed a non-linear model-based feedforward control algorithm which is obtained from static model inversion approach. It is observed that the average modeling errors of the feedforward algorithm is about 2% using stationary engine experiment data of 225 operating conditions. Using a feedback controller including proportional-integral, the modeling error is compensated. Furthermore, it is validated that the proposed feedforward algorithm generates physically acceptable trajectories of the actuator and successfully tracks the desired values through engine experiments.

Optimal Control for Three-Axle Vehicle's All-Wheel Steering

In order to develop fieldwork car’s dynamic stability, a new control system for three-axle vehicle’s all-wheel steering is put forward. A nonlinear three degree of freedom (3-DOF) all-wheel steering model is built. The tire’s magic formula and the tire vertical load’s solving method based on displacement are applied to the model and the ideal yaw rate is given. Using feedforward and feedback control algorithm, a zero sideslip angle proportional feedforward and optimal feedback control system is designed. The system is simulated on MATLAB/Simulink platform and results show the vehicle’s dynamic stability is obviously developed.

Control of transient vibrations due to stage movements in 6-dof active pneumatic table by inertial force compensation

Passive pneumatic tables are popularly used in precision measurements or processes for isolation of ground vibrations over frequency ranges higher than resonance frequencies of a few Hz typically. Recently, active pneumatic tables are also used often because the passive systems are liable to table excitations in the low resonance frequency ranges, causing long settling times.In studies on the active tables, disturbances onto the tables were often regarded to be unknown and, hence, feedback control algorithms were implemented. However, the disturbances are mostly due to inertial forces due to movement of equipment on the table, e.g., x–y stages. Such a movement is given relative to the table as command inputs. Since absolute motion of the table is normally measured in an active isolation table, absolute motion of the equipment can be easily estimated for calculation of the inertial force exerted onto the table by the moving equipment. Consequently, by compensating dynamic pressure inside the pneumatic chamber to counteract with the inertia force due to the equipment motion, resultant forces acting onto the table can be made zero.In this paper, how to apply the proposed feed-forward control algorithm to a 6-degree of freedom active pneumatic table with time-delay pneumatic control is presented. Performance of the inertial force compensation control evaluated through experiments is also discussed.

Application of the GoRoSo Feedforward Algorithm to Compute the Gate Trajectories for a Quick Canal Closing in the Case of an Emergency

AbstractThe canal delivery system in the Left Hemidelta area of the Ebro River in Spain consists of a tree-shaped net of open canals. The overall system can be quickly isolated in the case of an emergency by closing the upstream pool. Transients, in which the initial state is hydraulically far from the final state, are difficult to handle and cannot be made in only one gate movement in order to protect the canal lining. Therefore, they have to be as smooth as possible. GoRoSo is a feedforward control algorithm for irrigation canals based on sequential quadratic programming. With this tool, it is possible to calculate the gate trajectories that smoothly carry the canal from the initial state to the final state by keeping the water depth constant at checkpoints. The paper shows the efficient implementation of GoRoSo in both the closure and opening operations of the canal delivery system.

MR 햅틱 큐를 이용한 차량 기어변속 보조장치의 성능평가

This paper proposes a driver supportive device with haptic cue function which can be applicable for vehicles adopting manual transmission system to transmit gear-shifting information to a driver by kinesthetic forces. This haptic cue function is implemented on accelerator pedal by utilizing magnetorheological(MR) fluid and clutch mechanism. In order to achieve this goal, an MR clutch mechanism is devised to be capable of rotary motion of accelerator pedal. The proposed MR clutch is then optimally designed and manufactured under consideration of spatial limitation of vehicles. After transmission torque is experimentally evaluated according to field intensity. The manufactured MR clutch is integrated with accelerator pedal and electric motor to establish the haptic cue device. Control performances are experimentally evaluated via a simple feed-forward control algorithm.

Robust common rail pressure control algorithm for light-duty diesel engines

This paper proposed a robust common rail pressure control algorithm for light-duty diesel engines. In this study, rail pressure and the driving current of pressure control valve are selected as a performance variable and a control input, respectively. The proposed algorithm is composed of feedforward and feedback controllers. In order to achieve fast tracking performance, the feedforward control algorithm is derived from the empirical model which represents physical relation between the driving current of the pressure control valve and the common rail pressure. The feedback algorithm is designed using integral control method to compensate the modeling error of the feedforward algorithm. According to the quantitative feedback theory, the feedback algorithm is robustly designed with consideration of the plant model uncertainty which is originated from the metering unit's operating conditions. The proposed common rail pressure control algorithm was validated through various conditions of engine experiments. From the experimental results, it is observed that the algorithm shows a good degree of tracking performance and robustness.

Improved discrete-time model for a digital controlled single-phase full-bridge voltage inverter

An improved discrete-time model for a digital controlled single-phase full-bridge voltage inverter is proposed in this paper. Based on state-space averaging in every switching cycle, the improved discrete-time model combines the advantages of the average model and the traditional discrete-time model, which can accurately analyze the digital control delay and sample-and-hold process inherently in digital controlled system. Consequently, under the accuracy premise, the improved discrete-time model can effectively simplify the traditional discrete-time modeling. As an example, an LC filter capacitor-voltage and inductor-current feed-back plus voltage-reference feed-forward control algorithm is analyzed based on the improved discrete-time model. The stability boundary and oscillation frequency are accurately predicted. Finally, theoretical results are verified by simulations and experiments.

Nonlinear active noise control for headrest using virtual microphone control

In this paper, a feed-forward nonlinear active noise control algorithm is developed using the Filtered-S LMS (FSLMS) algorithm and virtual microphone control for an active headrest application. Virtual microphone control is implemented to attenuate noise at the ears of the headrest occupant using the physical microphones placed at remote locations. The proposed nonlinear virtual microphone control algorithm is verified in real-time in a headrest. Different nonlinear noise processes are studied and it is shown that in all cases, the FSLMS algorithm outperforms the FXLMS algorithm in controlling nonlinear primary noise at a virtual location.

A Multi-Input FFFB Control Algorithm for Railway Rapid Transit Vehicle Speed Regulation

The purpose of this research is to develop a multi-input control algorithm for the speed regulation of railway transit vehicle. The Taipei railway transit vehicle is chosen as the simulation object in this research. This transit vehicle has three carts and is push-pull type; only the first and the last carts are empowered. The control algorithm is to calculate the appropriate driving forces for the power units such that vehicle can follow a specified speed pattern. A feed-forward and feed-back control algorithm is designed to achieve this purpose. In the system, a dynamics variable observer is also developed to reduce required sensors for the controller. The results show that the developed controller is suitable for this purpose and the observer achieves acceptable observation quality for the controller application.