Model-following Control Research Articles

Cooperative-transportation dynamics of two helicopters transporting a rocket booster undergoing planar motions

Helicopters are widely used in the field of material transportation as flying cranes. There have been attempts to utilize helicopters to capture a rocket booster that has been slowed down in the air by a parachute. However, when the rocket booster exceeds the load limit of single helicopter, the cooperative use of two or more helicopters must be considered. The cooperative system becomes coupled, and complicated, as a result of the dynamic effects added by multiple helicopters and cables, as well as the remaining liquid fuel in the rocket booster. This paper establishes a fully-coupled dynamic model of two helicopters transporting a rocket booster, which can describe the coupled effects among the helicopter attitudes, load pendulum, and liquid sloshing. In order to improve the ability to resist external disturbances, and induce minimal attitude oscillations and load pendulum swing during flight, a cooperative controller consisting of a modified model-following controller and a hybrid piecewise smoother is proposed. To quantitatively prove the control performance and robustness, computational simulations were performed comparing the proposed controller with a previous combined controller.

A Model-Following Control Approach to Peaking Attenuation in High-Gain Partial State Feedback for Nonlinear Systems

We consider the model-following control (MFC) scheme for a class of nonlinear minimumphase systems in Byrnes-Isidori form using the nonlinear model in the model control loop (MCL). For the control design we apply partial state feedback in the process control loop (PCL). In particular we consider a high-gain feedback of the external state in the PCL to stabilise the system globally. For the proposed MFC design the typical peaking phenomenon of the high-gain feedback can be overcome if a sufficiently accurate estimate of the initial process state is available. We further establish that the control effort of the proposed MFC design is guaranteed less than that of a comparable stabilising high-gain design using a single-loop feedback only. We demonstrate the design capability of peaking attenuation by a numerical example.

Evaluation of Helicopter Ship Deck Landing Control Laws in Piloted Simulations

This paper describes the implementation and the evaluation of newly designed helicopter ship deck landing control modes in a piloted simulation study. The ship deck landing modes are embedded in a model-following controller architecture. The employed control design is a complete model-following control system, which imposes the desired command model dynamics on the controlled helicopter. Different command types combined with various hold functions are implemented to make the task easier for the pilots. Three basic command modes and three advanced command modes, one without ship communication and two with ship communication, are implemented. A piloted simulation study was performed in a simulator to evaluate and compare the implemented control modes within a complete maritime scenario design. The evaluation of control modes is based on the success of helicopter ship deck landings which is assessed by a quantitative as well as a qualitative assessment. Simulation results demonstrate that the advanced command modes improved the task performance as well as reduced the pilot workload extensively in comparison to the basic command modes.

An Online Model-Following Projection Mechanism Using Reinforcement Learning

In this paper, we propose a model-free adaptive learning solution for a model-following control problem. This approach employs policy iteration, to find an optimal adaptive control solution. It utilizes a moving finite-horizon of model-following error measurements. In addition, the control strategy is designed by using a projection mechanism that employs Lagrange dynamics. It allows for real-time tuning of derived actor-critic structures to find the optimal model-following strategy and sustain optimized adaptation performance. Finally, the efficacy of the proposed framework is emphasized through a comparison with sliding mode and high-order model-free adaptive control approaches.

Towards the Testing and Validation of Autonomous Ships: Design of a Variable Stability Ship Control System

Maritime autonomous surface ships (MASSs) have received increased attention in both academic research and industrial applications in the global shipping and shipbuilding industry in recent years. According to its definition, a MASS can independently operate without human interaction. This brings the problem of how to test and evaluate the capabilities of the autonomous navigation control system developed for MASS. This paper proposes the novel concept of a variable stability ship and the design of its control system. A variable stability ship consists of a model-scaled ship, a model-following controller, and a hardware and software platform to implement its functions. The variable stability ship can replicate the dynamic responses of different reference ships despite their dissimilarities in physical parameters and hydrodynamic characteristics with the design of the model-following controller. Therefore, it can be used to test the performance of different control strategies on various ship types such that the R&D costs of physical model-based tests can be reduced, as well as shortening the time spent in developing physical ship models. Preliminary simulations are carried out to show its effectiveness and applicability.

Dynamics and control of dual-quadrotors slung a slender beam with attitude-pendulum coupling effects

The dual-quadrotors slung system may be utilized in the handling service of heavy and bulky loads. However, the coupled oscillations between the quadrotor attitudes and suspended load exhibit complicated dynamic behaviors, which degrade the safety and efficiency of the transport system. Although many works have been focused on the multiple quadrotors suspending a load, those prior studies did not consider the coupling effects between the quadrotor attitudes and the cable pendulum. This paper established a nonlinear dynamic model of dual-quadrotors carrying a slender beam undergoing planar motions, which described the coupled attitude-pendulum oscillations. Then a frequency estimator was resulted from the system parameters for investigating the dynamics. In addition, a novel combined modified model-following control and discontinuous piecewise smoother was proposed to suppress oscillations. The technical results in the simulations not only describe the dynamic behavior of the analytical model but also validate the effectiveness of the control method.

Artificial Intelligence-Enhanced UUV Actuator Control

This manuscript compares deterministic artificial intelligence to a model-following control applied to DC motor control, including an evaluation of the threshold computation rate to let unmanned underwater vehicles correctly follow the challenging discontinuous square wave command signal. The approaches presented in the main text are validated by simulations in MATLAB®, where the motor process is discretized at multiple step sizes, which is inversely proportional to the computation rate. Performance is compared to canonical benchmarks that are evaluated by the error mean and standard deviation. With a large step size, discrete deterministic artificial intelligence shows a larger error mean than the model-following self-turning regulator approach (the selected benchmark). However, the performance improves with a decreasing step size. The error mean is close to the continuous deterministic artificial intelligence when the step size is reduced to 0.2 s, which means that the computation rate and the sampling period restrict discrete deterministic artificial intelligence. In that case, continuous deterministic artificial intelligence is the most feasible and reliable selection for future applications on unmanned underwater vehicles, since it is superior to all the approaches investigated at multiple computation rates.

The Use of a Model-Based Controller for Dynamics Improvement of the Hydraulic Drive with Proportional Valve and Synchronous Motor

Electrohydraulic drives consist of several nonlinear elements, and the use and design of their control system is difficult. One of the most important parameters of the industrial drive is its settling time, which characterizes their dynamics. An interesting control method, which can be used for the improvement of electrohydraulic drive properties, is the model-following control (MFC). This technique enables to ensure the good control parameters of nonlinear systems in quite an easy way. In this paper, a modification consisting of changing the oil flow factor in the reference model is proposed. This improves both the dynamics of the electrohydraulic servo drive and the adaptation to the load forces, and thus energy consumption. The article describes the application of the MFC method to control an electrohydraulic servo drive in which a special proportional valve, with an permanent magnet synchronous motor (PMSM), is used. To verify the effectiveness of this method, a theoretical description of the drive is proposed. The applied MFC control system is then modeled and investigated in simulations. Lastly, laboratory investigations are made and chosen results are presented and described in the paper. The results obtained in simulation are compared with results obtained in laboratory tests. The investigations show that the usage of MFC shortens the drive settling time and, in this way, improves its dynamics.

Combining Input Shaping and Adaptive Model-Following Control for Vibration Suppression

Vibration suppression in servo systems is significant in high-precision motion control. This paper describes a vibration-suppression method based on input shaping and adaptive model-following control. First, a zero vibration input shaper is used to suppress the vibration caused by an elastic load to obtain an ideal position output. Then, a configuration that combines input shaping with model-following control is developed to suppress the vibration caused by changes of system parameters. Finally, analyzing the percentage residual vibration reveals that it is effective to employ the sum of squared position error as a criterion. Additionally, a golden-section search is used to adjust the parameters of a compensator in an online fashion to adapt to the changes in the vibration frequency. A comparison with other input shaper methods shows the effectiveness and superiority of the developed method.

Quantitative robustness analysis of model following control for nonlinear systems subject to model uncertainties

Abstract We investigate a model following control (MFC) design for nonlinear minimumphase systems subject to model uncertainties. The model following control architecture is a two degrees-of-freedom structure consisting of two control loops. The model control loop (MCL) includes a nominal model of the process. The design of the process control loop (PCL) is based on the error system resulting from the nominal design and the actual process. Both control loops are designed using (partial) feedback linearisation. We analyse the robustness in view of the norm of the uncertainty and the region of attraction compared to a single-loop (partial) feedback linearisation control. It turns out that the proposed approach is able to stabilize significantly larger uncertainties, shows better tracking performance, and exhibits a larger region of attraction (based on a quadratic Lyapunov function).

Motion and vibration control of a stacker crane by 2-degree-of-freedom model-following control using an internal characteristic of the model

Motion and vibration control of a stacker crane by 2-degree-of-freedom model-following control using an internal characteristic of the model

Handling-Qualities Perspective on Rotorcraft Load Alleviation Control

The objective of this research effort is to assess the impact of load alleviation control on the quantitative handling-qualities specifications (also known as predicted handling qualities) of both conventional helicopters and compound rotorcraft in forward flight. First, an overview on how the harmonic decomposition methodology is used toward load alleviation control is presented. Next, flight control laws are developed based on an explicit model-following architecture. Parametric studies are performed to provide insights on how both the feedforward and feedback paths of the model-following control laws can be used to alleviate the rotor loads. The impact of load alleviation on predicted handling qualities is studied. It is shown that, for the standard helicopter configuration considered, load alleviation comes at the cost of a degradation in handling qualities. However, for the compound rotorcraft considered, allocation of the control signal to the redundant control surfaces provides load alleviation without degradation in predicted handling qualities. The flight control laws are subsequently optimized using the Control Designer’s Unified Interface to meet a comprehensive set of stability, handling-qualities, and performance specifications for specific mission task elements while minimizing the unsteady rotor loads.

Model Following Control of a Higher Order Plant by a Lower Order Model

In this paper, based on Model Following Control (MFC) approach, a robust controller is used to control a flexible robot manipulator along a pre-defined trajectory. Here two degree of freedom plant is considered that has two different inertias. The plant is run by the single degree of freedom ideal model. Primarily, an ideal model is formulated from the mathematical expression and by selecting a suitable feedback amplifier gain a well-defined response is established. A reference input voltage is given to the model and the plant is driven by the errors, generated from the differences of the states between the plant and model. Here special attention is given to the fact that how precisely the states of the plant can follow the ideal states of the model. The proposed model following control (MFC) system may be used successfully in industrial robots.

Control of a Robot Manipulator using Model Following Control

In this work the simulation results of a 2 degree of freedom plant driven by model are shown. Here Model following control (MFC) system is applied to operate the plant in a better way. Initially a model is constructed, whose states are ideal with respect to the control parameters. The plant and the model essentially have same physical parameters. An input is given to the model and the plant is run by the errors, computed by comparing the states of the plant and model. In this way the plant is forced to follow the ideal states of the model. The results show that the plant is able to follow the model very accurately. The robust control observed in the scheme can be easily implemented for better performance of industrial robots.

A traction controller of a two-wheel mobile robot with feedforward compensator

A simple traction controller was derived from a model following control (MFC) using bilinear transformation. The controller was simplified by adjusting some dynamic parameters. The experiments were conducted to evaluate the validity of the controller by comparing with the classical PD controller. In the experiments, while the traction controller can prevent slippage, tracking control performance needed to be improved. The feedforward compensation was added to reduce the traction error. The experimentation using the simple controller with feedforward shows that the position error has been reduced while maintaining the traction force between floor and wheels.

The H∞ Model Following Control: An LMI Approach

The aim of this paper is to develop a new approach for a solution of the model following control (MFC) problem with a dynamic compensator by using linear matrix inequalities (LMIs). TheH1 model following control problem is derived following LMI formulation. First, the H1 optimal control problem is revisited by referring to Lemmas assuring all admissible controllers minimizing the H1 norm of the transfer function between the exogenous inputs and the outputs. Then, the solvability condition and a design procedure for a two degrees of freedom (2 DOF) dynamic feedback control law is introduced. The existence of a 2 DOF dynamic output feedback controller for the model following control is proven and the stability of the closed-loop system is satisfied by assuring the Hurwitz condition. The benchmark thermal process (PT-326) as the first order process with timedelay is regulated by the presented 2 DOF dynamic output feedback controller. The simulation results illustrate that the presented controller regulates a system with dead-time as a large set of generic industrial systems and the H1 norm of the closed-loop system is assured less than the H1 norm of the desired model system.

Study on the Handling Qualities Enhancement of Fixed-wing Aircraft Using Adaptive Neural Network

This paper intends to propose the integrated design framework of a model-following controller (MFC) combined with both an adaptive neural network (ANN) and a linear observer to enhance the handling qualities (HQ) of a fixed-wing aircraft. To achieve this objective, the HQ requirements (HQRs) applicable to a light sports aircraft and the controller structure have been defined. And, the controller design parameters are optimized to meet HQRs using the CONDUIT®. Thereby, the integrated design environment can determine the control gains and ANN’s tuning parameters in an optimum manner and the level of HQ achievable with the designed parameters can be automatically evaluated. The paper tries to clarify the effect of the ANN with the linear observer on the HQ enhancement. To achieve this, the control laws in the attitude command response types have been designed and their tracking performances are investigated with and without ANN elements to identify the improved HQ with the ANN. In addition, a series of comparative simulation studies on the effects of external disturbances on the attitude tracking performance are carried out to show the enhanced robustness with the proposed controller structure. The results show that the ANN control can dramatically improve the level of HQ and provide the favorable robustness to external disturbances. Therefore, the results of the present study can provide the efficient ways of the HQ enhancement by adopting the ANN in the conventional MFC structure and by designing the controller parameters with the integrated design processes of CONDUIT®.

Investigations of applications of smart materials and methods in fluid valves and drives

In the paper the investigations performed at the Division of Mechtronic Devices at Poznan University of Technology in the area of application of both: smart materials in electro-hydraulic and electro-pneumatic valves, and new methods to control of hydraulic servo drives, are presented. In a first part the piezo bender actuator is shortly described and its application in servo valve is proposed. This actuator replaced the torque motor in the available on the market servo valve. The new valve simulation model is proposed. The simulation and investigations results of the servo valve with the piezo bending actuator are included. In the next part of the paper the application of piezo tube actuator in flapper-nozzle pneumatic valve is described. The test stand and investigations results are presented. Later, in the article, the Model Following Control (MFC) and Fractional order Control (FoC) methods are described. Their application in control of electrohydraulic servo drive is proposed. Some investigations results are included in the paper, showing the advantages of those control methods.

Implementation of tactical maneuvers with maneuver libraries

This study creates and combines the general maneuver libraries for fixed-wing aircraft to implement tactical maneuvers. First, the generalized maneuver libraries are established by analyzing the characteristics of tactical maneuvers required in battlefields. The 7th order polynomial is applied to both the creation of the maneuver libraries and the generation of the trajectories or flight paths for modal inputs. To track the desired trajectory, we design the Attitude Command Attitude Hold (ACAH) system and the Rate Command Rate Hold (RCRH) system using Model Following Controller (MFC). Moreover, the Line-of-Sight (LOS) guidance law is designed. In particular, the CONDUIT® is employed to optimize the gains so that the control systems meet the aircraft Handling Qualities (HQ) criteria. Finally, flight simulations are performed for the longitudinal loop, immelmann-turn, and climb-slalom-descent maneuvers to verify that tactical aggressive maneuvers are realizable via the combination of maneuver libraries. This study can contribute to the development of flight techniques for aircraft tactical maneuvers and to the revision of air force operational manuals.

Study of the model-following control for electromechanical brake system

X-by wire is one of the key technologies to realize vehicle intelligence.Electromechanical brake (EMB) is a form of wire brake.A one-fourth vehicle model based on electromechanical brake system was established and model-following controller was designed with the wheel angular acceleration as the state parameter. The simulation of the braking process on different roads at some speeddemonstrates that the controller has a good feasibility and effectiveness.The brake actuator is built by the torque motor, deceleration mechanism and motion conversion mechanism.A bench experiment for the brake actuator was conducted. Clamping force of brake caliper can meet the braking requirements.