Dynamic Feedforward Control Research Articles

Adapting to Flexibility: Model Reference Adaptive Control of Soft Bending Actuators

Soft pneumatic actuators enable robots to interact safely with complex environments, but often suffer from imprecise control and unpredictable dynamics. This letter addresses these challenges through the use of model reference adaptive control, which modulates the input to the plant to ensure that it behaves similarly to a reference dynamic model. We use adaptive control to standardize the performance of soft actuators and eliminate their nonlinear behavior. We implement an adaptive controller chosen for its simplicity and efficiency, and study the ability of this controller to force different soft pneumatic actuators to behave uniformly under a variety of conditions. Next, we formulate an inverse dynamic feedforward controller, allowing soft actuators to quickly follow reference trajectories. We test the performance of the proposed feedforward controller with and without the adaptive controller, to study its open-loop effectiveness and highlight the improvements the adaptive controller offers. Our experimental results indicate that soft actuators can follow unstructured continuous signals through the use of the proposed adaptive control approach.

バドミントンのための高加速・高速な手首を有する人型ロボットアームの開発

Badminton needs dynamic and high speed motion, so previous humanoid robots were difficult to perform like human. For entertaining or training humanoid badminton robot in the future, we propose new robot arm which consists of structure integrated pneumatic cable cylinder and noninterfering many DoFs joints. We made a real robot arm with high acceleration and high speed wrist and conducted some performance evaluation test. Pronation joint achieved 32.4rad/s in 90 deg, which surpasses human wrist speed in badminton smash. It has also good reproducibility for dynamic feed-forward control or learning control. We also make it hit actual shuttle, and shuttle's initial velocity achieved 28m/s by full swing. And it succeeded skillful shot, spin hairpin, by utilizing the humanlike wrist. This research is the first step toward humanoid badminton robot.

Automated generation of feedforward control using feedback linearization of local model networks

An effective but yet simple approach is introduced to automatically attain a dynamic feedforward control law for non-linear dynamic systems represented by discrete-time local model networks (LMN). In this context, feedback linearization is applied to the generic model structure of LMN and the resulting input transformation is used as model inverse. This general and automated approach for model inversion is applicable even when the overall model complexity may be high. Thus, by representing a non-linear dynamic system by an LMN and applying the proposed feedforward control law generation, a dynamic feedforward control for such a non-linear system can be found automatically with the knowledge of measured input–output data only. However, when feedback linearization is considered, the stability of the internal dynamics plays a key role. This paper analyses the occurring internal dynamics for LMN, which directly result from the chosen model structure in identification, and discusses the effects on the transformed system. Finally, the effectiveness of the proposed data-driven feedforward control is demonstrated by a simulation example as well as by an actual application to the pre-distortion of a microelectromechanical systems (MEMS) loudspeaker with electrostatic actuation.

Linearizing an electrostatically driven MEMS speaker by applying pre-distortion

The market for tablets, laptops and mobile devices is increasing rapidly. Product designs trend to thinner housings at concurrently higher energy consumption, which plays a major role for battery-powered devices. Microelectromechanical (MEMS) speakers, fabricated in complementary metal oxide semiconductor (CMOS) compatible technology, merge energy efficient driving technology with cost economical fabrication processes. A recently developed finite element (FE) model for the precise computation of the non-linear MEMS speaker is presented. In addition, dynamic linearization is achieved by applying feedback linearization to the local model network (LMN) as a data-driven dynamic model of the MEMS speaker to obtain a dynamic feedforward control (FFC) for pre-distortion. In the FE model, we fully take into account geometric non-linearity, contact in the snap-in mode, non-linear electrostatic coupling forces as well as the moving of charged thin membrane-plate structures (electrodes) in an electric field. Furthermore, since we concentrate on MEMS loudspeaker applications, quality of sound plays a major role, where an undistorted and linear system defines the challenge. In the process of MEMS speaker design, both, the FE model and the FFC using LMN, can be used to optimize the MEMS speaker towards sound pressure level (SPL) and total harmonic distortion (THD).

Automated generation of a dynamic feedforward control law using local model networks with disturbance inputs

AbstractAn effective approach is presented, which automatically generates a dynamic feedforward control law for nonlinear dynamic systems represented by a discrete‐time local model network (LMN) as one class of data‐driven models. In this context, feedback linearization is applied to the generic model structure of LMN and the resulting input transformation is used as model inverse. Thus, by representing a nonlinear dynamic system by an LMN and applying the proposed feedforward control law generation, a dynamic feedforward control for such a nonlinear system can be found automatically with the knowledge of measured input/output data only. In addition, several disturbance inputs are considered in the feedforward control law without restrictions on their relative degree. However, only multiple input LMN where no internal dynamics are involved, i.e. the LMN has full relative degree with respect to the control signal input, are considered in this manuscript. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sensorless Control of PMSM for the Whole Speed Range Using Two-Degree-of-Freedom Current Control and HF Test Current Injection for Low-Speed Range

In this paper, an innovative sensorless two-degree-of-freedom current control scheme for the whole speed range is proposed. It consists of a model-based dynamic feedforward control to set the reference response and model reference tracking controllers providing disturbance rejection and the position error signals needed for sensorless control. For low- and zero-speed operation, alternating test current injection is used to gain a position error signal. A flatness-based test signal precontrol provides compensation for secondary saliencies like cross-saturation and higher harmonics. For mid- and high-speed operation, it is shown how the model-based dynamic feedforward control can be modified to obtain a high-quality position error signal from the tracking controller. No additional model-based estimator evaluating back-EMF information is needed. The effectiveness of the proposed method is proven by experimental results.

HF Test Current Injection-Based Self-Sensing Control of PMSM for Low- and Zero-Speed Range Using Two-Degree-of-Freedom Current Control

This paper deals with an innovative self-sensing control scheme based on test current instead of voltage injection. Using two-degree-of-freedom current control, one can overcome the bandwidth limitations that made test current injection unattractive during the last 20 years. The two-degree-of-freedom control scheme consists of a model-based dynamic feedforward control to set the reference response and model reference tracking controllers providing disturbance rejection and position error signals for self-sensing control. Since two-degree-of-freedom control is a model-based control scheme, the compensation for secondary saliencies is inherently included in the precontrol. It is analytically shown that, in the case of alternating test current instead of voltage injection, just the precise knowledge, in general, of the current- and position-dependent secondary diagonal element of the inductance matrix is needed in the case of inductance saliency-based self-sensing control. The effectiveness of the proposed method is proven by experimental results.

Reduction of the dynamic coupling in an underwater vehicle-manipulator system using an inverse dynamic model approach

This paper proposes a control strategy for station keeping of an underwater vehicle- manipulator system when the manipulator is asked to perform a certain task. The control structure consists of an inverse dynamic feedforward controller, the interaction forces between subsystems and a PILIM feedback controller for pitch control of the vehicle. The UVMS includes a 6-DOF vehicle and a 3-link manipulator, where the manipulator has a significant mass compared to the vehicle. The equations of motion are based on a tree representation of the UVMS and are described with the Newton-Euler algorithm. Hydrodynamic effects and friction considerations are taken into account in the forward dynamic model, while in the inverse dynamic model they are ignored. Simulation results show the validity of the inverse dynamic model approach without perfect knowledge of the system for station keeping of the vehicle. A key contribution of the study is that it is based on a lightweight underwater system. The main problem addressed in this paper is the station keeping of an underwater vehicle when the attached manipulator is moving. It is demonstrated that an inverse dynamic model used as a feedforward controller is a viable solution in the presence of system uncertainties.

Event-Driven-Based Water Level Control for Nuclear Steam Generators

Safety is a critical issue in nuclear power exploitation and utilization. With respect to a pressurized water reactor in a nuclear power unit, a steam generator is a crucial device, whose water level control performance directly affects the safety and stability of the pressurized water reactor. In this paper, based on an event-driven control methodology, a novel steam-generator water level control strategy is proposed to lower the computing load of the control system and extend the service life of actuators. The theoretic stability analysis for a closed-loop system with an event detector is adequately expressed. The two-degree-of-freedom internal-model-control feedback controller and the dynamic feedforward controller, both of which are triggered by the same event detection logic, are designed to guarantee local performance. In addition, a gain-scheduling measure is adopted to combine local controllers to ensure the overall performance under all power levels. Comparing case studies shows that the proposed control strategy exhibits good capability to manage the utilization of a process control unit and the control action, with no deterioration in the control performance.

Linear parameter varying feedforward control synthesis using parameter-dependent Lyapunov function

This paper presents the dynamic feedforward control synthesis for linear parameter varying (LPV) systems. It is assumed that all system matrices are dependent on varying parameters, which are measurable with sensor or observable. The parameters have bounded variation rates. Parameter-dependent Lyapunov function is used for the feedforward control synthesis such that the robust stability is assured for all varying parameters at the time of the operation. The method is formulated in terms of linear matrix inequalities for LPV feedforward controller that guarantees the stability of the transfer matrix having \(L_{2}\)-gain. This compensator is designed by adding on the feedback controller in two degrees of freedom control configuration. This controller can be used for the disturbance attenuation or decreasing the tracking error. The numerical examples and simulations are given to provide the applicability of the proposed solution.

Automatic Generation of Feedforward Controllers using Dynamic Local Model Networks

A new approach for the automatic generation of a dynamic feedforward control law for nonlinear dynamic systems represented by discrete-time local model networks (LMN) is proposed. The generic model structure of LMNs offers the opportunity to apply such a general and automated approach for model inversion, even when the overall model complexity may be high. LMNs can represent nonlinear dynamic systems of almost arbitrary complexity. Their generic structure allows the generation of a feedback linearizing input transformation in a highly automated way. This paper proposes and discusses such an approach for the important class of LMNs with minimum-phase property. As a subclass of the class of minimum-phase LMNs, only those without numerator dynamics are considered in this manuscript. By using the input transformation, which results from feedback linearization, the feedforward control law is obtained. It can then be applied online for any reference trajectory without pre-planning. Thus, by representing a nonlinear dynamic system by the generic structure of an LMN and applying the proposed feedforward control law generation, a dynamic feedforward control for such a nonlinear system can be found automatically. Finally, the effectiveness of the method is shown on results for a Wiener model.

Dynamic analysis and model-based feedforward control of a 2-DoF translational parallel manipulator driven by linear motors

Purpose – Based on the inverse kinematics and task space dynamic model, this paper aims to design a high-precision trajectory tracking controller for a 2-DoF translational parallel manipulator (TPM) driven by linear motors. Design/methodology/approach – The task space dynamic model of a 2-DoF TPM is derived using Lagrangian equation of the first type. A task space dynamic model-based feedforward controller (MFC) is designed, which is combined with a cascade PID/PI controller and velocity feedforward controller (VFC) to construct a hybrid PID/PI+VFC/MFC controller. The hybrid controller is implemented in MATLAB/dSPACE real-time control platform. Experiment results are given to validate the effectiveness and industrial applicability of the hybrid controller. Findings – The MFC can compensate for the nonlinear dynamic characteristics of a 2-DoF TPM and achieve better tracking performance than the conventional acceleration feedforward controller (AFC). Originality/value – The task space dynamic model-based hybrid PID/PI+VFC/MFC controller is proposed for a 2-DoF linear-motor-driven TPM, which reduces the tracking error by at least 15 percent compared with conventional hybrid PID/PI+VFC/AFC controller. This control scheme can be extended to high-speed and high-precision trajectory tracking control of other parallel manipulators by reprogramming the feedforward signals of traditional cascade PID/PI controller.

Improved Control Strategy of Grid Side Rectifier for the Double-Fed Wind Power System

In the double-fed wind power system, gird voltage sags would result in some serious problems such as a fluctuation of the DC-link voltage, an instantaneous energy feedback from turbine side to grid side, which affected the steady performance of the wind power system. According to these problems, a dynamic feed forward control strategy based on the traditional feed forward control was studied, with an inhibition of above disturbances. MATLAB simulation and DSP experiments verify the effectiveness of the improved control strategy.

Robust delay-dependent feedforward control of neutral time-delay systems via dynamic IQCs

This paper studies the design problem of delay-dependent based robust and optimal feedforward controller design for a class of time-delay control systems having state, control and neutral type delays which are subject to norm-bounded uncertainties and type measurable or observable disturbance signals. Two independent loops which include state-feedback and dynamic feedforward controller form the basis of the proposed control scheme in this study. State-feedback controller is generally used in stabilisation of the nominal delay-free system, whereas the feedforward controller is used for improving disturbance attenuation performance of the overall system. In order to obtain less conservative results, the delay and parametric uncertainty effects are treated in operator view point and represented by frequency-dependent (dynamic) integral quadratic constraints (IQCs). Moreover, sufficient delay-dependent criterion is developed in terms of linear matrix inequalities (LMIs) such that the time-delay system having parametric uncertainties is guaranteed to be asymptotically stable with minimum achievable disturbance attenuation level. Plenty of numerical examples are provided at the end, in order to illustrate the efficiency of the proposed technique. The achieved results on minimum achievable disturbance attenuation level and maximum allowable delay bounds are exhibited to be less conservative in comparison to those of controllers having only feedback loop.

Model-based Decoupling Control of VGT and EGR with Active Disturbance Rejection in Diesel Engines

Exhaust gas recirculation (EGR) system and variable geometry turbocharger (VGT) system are applied in diesel engine to reduce PM and NOX. Cooperative control of EGR and VGT has tremendous impact on the emission reduction. In order to gain more fine-grained control of intake mass flow rate and intake boost pressure, a new decoupling method based on active disturbance rejection control (ADRC) beyond the traditional feedback control is proposed in this paper. When EGR valve controls the intake mass flow rate, the fluctuation of air mass caused by VGT is regarded as disturbance, estimated and cancelled by ADRC, so does the boost pressure control. Meanwhile, a model based dynamic feed-forward controller is applied to further speed the system up. Simulation results show that the response speed and tracking accuracy of both boost pressure and intake mass flow rate are dramatically enhanced simultaneously in various transient conditions. Furthermore, the proposed method also has remarkable advantages over traditional solution in terms of disturbance rejection performance.

Delay-dependent feedforward control of time-delay systems with parametric uncertainties via dynamic IQCs

SUMMARY This paper studies the design problem of a robust delay-dependent H ∞ feedforward controller design for a class of linear uncertain time-delay system having state and control delays when the system is subject to L2-type disturbances. The proposed controller scheme involves two main controllers, which are static state-feedback and dynamic feedforward controllers. The state-feedback controller is used for stabilizing the delay and uncertainty-free system, whereas the feedforward controller performs disturbance attenuation. Dynamic type integral quadratic constraints (IQCs), which consist of frequency-dependent multipliers, have been introduced to represent the delays and parametric uncertainties in the system where the degree of the multiplier used in IQC representation is in an adjustable nature. This scheme allows the designer to obtain less conservative controllers with increasing precision. Sufficient delay-dependent criteria in terms of linear matrix inequalities are obtained such that the uncertain linear time-delay system is guaranteed to be globally, uniformly, asymptotically stable with a minimum disturbance attenuation level. Several numerical examples together with the simulation studies provided at the end illustrate the usefulness of the proposed design. Copyright © 2012 John Wiley & Sons, Ltd.

Delay-Dependent Feedforward Control of Uncertain Neutral Time-Delay Systems via Dynamic IQCs

This paper deals with the design problem of a delay-dependent ℋ∞ based robust optimal feedforward controller for a class of time-delay control systems having state delays, control delays and neutral delays when the system is subject to norm bounded uncertainties. The proposed scheme in this study is formed by two independent loops which include state-feedback and dynamic feedforward controller. The delay and parametric uncertainty effects are represented by dynamic Integral Quadratic Constraints (IQCs). Furthermore, sufficient delay-dependent criteria is developed in terms of Linear Matrix Inequalities (LMIs) such that the time-delay system with parametric uncertainty is guaranteed to be asymptotically stable with a minimum disturbance attenuation level. The achieved results on the minimum allowable disturbance attenuation level in the provided numerical examples are exhibited to be less conservative in comparison to those of controllers having only feedback loop.

Research Based on Simulink of Hearth Negative Pressure Control System

Aiming at the furnace control system present situation of complex working conditions are not easy to be understood, this paper hearth negative pressure control system for detailed analysis; Combining the identification system known model and combining with matlab for stability analysis; Set in simulink negative pressure system control model. Choose PI and dynamic feed-forward control method to realize control and realize the dynamic interference effectively suppress, attain better control effect

Comparative Investigation of Feed-Forward Control Algorithms

The paper presents investigation results of four different structures of feed-forward control algorithms applied for controlling processes, in which the time delay in the disturbance path is less than that in process path. The control algorithms were investigated via computer simulation of feed-back / feed-forward control system performance at various type disturbances and dynamical parameters of controlled process. The performance index for comparison of the transient responses in the control systems was the integral of absolute error. The investigation results show statistically significant improvement of the control system performance by using the dynamic (lead-lag) algorithm connected in series with PD control algorithm in a feed-forward controller as compared to the steady-state, the ordinary dynamic and the modified dynamic feed-forward control algorithms. Ill. 3, bibl. 6, tabl. 3 (in English; abstracts in English and Lithuanian). http://dx.doi.org/10.5755/j01.eee.115.9.754

Dynamic Feedforward Control of a Novel 3-PSP 3-DOF Parallel Manipulator

Parallel manipulators with less than six degrees of freedom (DOF) have been increasingly used in high-speed hybrid machine tools. The structural features of parallel manipulators are dynamic, a characteristic that is particularly significant when these manipulators are used in high-speed machine tools. However, normal kinematic control method cannot satisfy the requirements of the control system. Many researchers use model-based dynamic control methods, such as the dynamic feedforward control method. However, these methods are rarely used in hybrid machine tools because of the complex dynamic model of the parallel manipulator. In order to study the dynamic control method of parallel manipulators, the dynamic feedforward control method is used in the dynamic control system of a 3-PSP (prismatic-spherical-prismatic) 3-DOF spatial parallel manipulator used as a spindle head in a high-speed hybrid machine tool. Using kinematic analysis as basis and the Newton-Euler method, we derive the dynamic model of the parallel manipulator. Furthermore, a model-based dynamic feedforward control system consisting of both kinematic control and dynamic control subsystems is established. The dynamic control subsystem consists of two modules. One is used to eliminate the influence of the dynamic characteristics of high-speed movement, and the other is used to eliminate the dynamic disturbances in the milling process. Finally, the simulation model of the dynamic feedforward control system of the 3-PSP parallel manipulator is constructed in Matlab/Simulink. The simulations of the control system eliminating the influence of the dynamic characteristics and dynamic disturbances are conducted. A comparative study between the simulations and the normal kinematic control method is also presented.The simulations prove that the dynamic feedforward control method effectively eliminates the influence of the dynamic disturbances and dynamic characteristics of the parallel manipulator on high-speed machine tools, and significantly improves the trajectory accuracy. This is the first attempt to introduce the dynamic feedfordward control method into the 3-PSP spatial parallel manipulator whose dynamic model is complex and provides a study basis for the real-time dynamic control of the high-speed hybrid machine tools.