Desired Control Force Research Articles

Detached Eddy Simulations of a Reaction Control Jet from an Axi-Symmetric Body in a Supersonic Crossflow

The introduction of a control jet into a supersonic cross flow yields a substantial region of separated flow, manifesting in the vicinity of the injection site. This, in turn, alters the distribution of pressure on the primary body, thereby influencing the effectiveness of the injected jet’s capacity to produce the desired control forces and moments. In the context of an axi-symmetric parent body, this disruption typically leads to a reduction in effectiveness, owing to the overflow of the shock structures encompassing the parent body. The present study investigates the injection of a reaction control jet into a supersonic crossflow using different Detached Eddy Simulation (DES) techniques. The side jet is injected from an orifice on an axi-symmetric parent body, which is aligned with the crossflow direction. The effects of the side jet on the flow field are analysed in terms of general flow features and spectral behaviour of pressure and turbulent kinetic energy. The DES results are compared with those obtained from RANS using various turbulence models. The overall effect of a transient interaction pulse is characterized using URANS and two different DES models.

Deep reinforcement learning‐based active mass driver decoupled control framework considering control–structure interaction effects

AbstractControl–structure interaction (CSI) plays a significant role in active control systems. Popular methods incorporate actuator dynamics into an integrated control system to account for CSI, leading to a situation where existing structural control algorithms that ignore CSI cannot be applied directly. To address this issue, this study proposes a deep reinforcement learning (DRL) based active mass driver (AMD) decoupled control framework, in which a structural control algorithm is employed to generate the control force command without consideration of CSI, while a DRL agent is utilized to attenuate the CSI effects of AMD systems and achieve a desired control force. The DRL‐based AMD control framework is verified through a series of numerical experiments. Furthermore, the applicability of the control framework is confirmed in a wind‐excited 76‐story benchmark building. Comprehensive analysis indicates that the proposed control framework can effectively eliminate the CSI effects and apply accurate control force to the structure in various scenarios, which allows for an ideal structural response control.

Vibrations control of railway vehicles using decentralized proportional integral derivative controller with flow direction optimization algorithm

The reduction of vibration-induced discomfort in vehicles is an important goal in the field of transportation engineering. Several mathematical models with various controlling techniques, from classical to modern, have been employed to achieve better ride comfort. Still, no comprehensive solution has yet been found. Therefore, this paper proposes a 17-degree-of-freedom (minimum number of coordinates) dynamic model of a full-scale railway vehicle integrated with wheel-rail contact forces and an active suspension system. Two controllers, termed system and force tracking controllers, suppress the vehicle body's vibrations. Based on a multi-loop control structure, three optimally tuned Proportional Integral Derivative controllers evaluate the desired control forces and performs the system controller’s action. While the force-tracking controller generates the command voltage to track that forces. The parameters of controllers are tuned with a novel metaheuristic optimization algorithm known as the flow direction algorithm (FDA), and the results are compared with two other optimization techniques, i.e., particle swarm optimization and ant colony optimization. The simulated results show that the ride comfort of the vehicle is improved with FDA, as the root mean square values of the lateral, roll, and yaw accelerations are reduced by 42.01%, 33.12%, and 48.24%, respectively. Moreover, the simulated results of the proposed model are validated with the experimental results of accelerations. The simulated results show that the proposed system tuned with the metaheuristic algorithm outperforms with a significant reduction in vehicle vibrations.

Real-time hybrid simulation for seismic control performance evaluation of an active inerter damper system

Active structural control has been recognized as an intelligent method to mitigate seismic vibrations of structures by generating superior supplemental damping in structural engineering studies. Recently, active inerter damper (AID) that consists of an inerter and an actuation system has been evolved from active mass damper. AID has advantages of small volume and light weight because of the mechanical properties of inerter that amplify the inertial force by numerous times the mass of the inerter; therefore, installation of an AID system becomes simple in real engineering applications. However, it is difficult to validate seismic control performance of a multi-story specimen with an AID system in structural laboratories limited by capacity of testing facilities. In this study, real-time hybrid simulation (RTHS), which combines experimental testing with numerical simulation is applied to evaluate the control performance of the AID system. A 10-story shear building is numerically simulated as a benchmark building controlled by the AID, which is physically driven in the structural laboratory. A modal linear-quadratic regulator (LQR) with optimized weighting matrices is designed for generating the desired control force for the AID. Meanwhile, a surrogate model of the modal LQR is trained and implemented for comparison purpose. In addition, two force tracking controllers are implemented to reproduce the desired control force through the AID. Furthermore, three approaches for acquiring the achieved force of AID are proposed and employed to feedback the control force to the numerical model for completing the RTHS loop. Finally, mitigation of seismic response is compared and discussed methodically based on the RTHS results. This study suggests the most appropriate RTHS technique for evaluating the control performance of buildings with the AID system.

Enhancement of Control Jet Performance in Supersonic Crossflows Through Pilot Injection

Injection of a control jet into a supersonic crossflow creates a large region of separated flow in the vicinity of injection, altering the pressure distribution on the parent body, and consequently the effectiveness of the injected jet in producing the desired control forces and moments. In the case of an axisymmetric parent body, this disruption typically results in a loss of effectiveness due to the spillover of the shock structures around the parent body. In this study, a novel technique for enhancing this jet effectiveness on bodies of revolution by means of employing a pilot injection upstream of the main control jet is proposed and evaluated at different external flow conditions. We show that diverting a small fraction () of the primary control jet mass flow rate through an orifice situated five to 10 jet diameters upstream causes an earlier disruption of the external flow, leading to a weaker shock system around the primary injector. This reduces the extent of adverse interaction region and results in a lower spillover of the shock and vortical structures to the bottom side, leading to a significant improvement of the control effectiveness.

Prescribed Performance Control-Based Semi-Active Vibration Controller for Seat Suspension Equipped with an Electromagnetic Damper

Seat suspension plays a vital role in improving riding comfort and protecting drivers’ health. This paper develops semi-active seat suspension that equips a controllable electromagnetic damper (EMD) and proposes a prescribed performance control-based semi-active vibration controller with experimental validation. The semi-active EMD mainly consists of a permanent magnet synchronous motor, a ball screw, a three-phase rectifier, and a controllable external resistor, which can vary its damping from 90 to 800 N·s/m by tuning the controllable external resistor in real-time. The EMD is applied to seat suspension, and a semi-active controller is proposed for the EMD seat suspension. In order to control the seat suspension vibration, a prescribed performance method is applied to obtain a desired control force and then a force-tracking strategy is designed to make the EMD track the desired control force. Finally, the semi-active seat suspension with the proposed controller is tested in experiments with different vibration conditions. The semi-active seat suspension performs excellently for the bump, sine wave and random vibration. The root mean square (RMS) acceleration, the frequency-weighted RMS acceleration and the acceleration’s fourth power vibration dose value were reduced by 17.5%, 39.9%, and 25.4%, respectively, in the random vibration, compared with a passive system.

Semi-Active Vibration Control of Seat Suspension Equipped with a Variable Equivalent Inertance-Variable Damping Device

The seat suspension has a significant influence on riding comfort in many practical applications, such as heavy duty vehicles, military vehicles, and high-speed crafts. This paper proposes a seat suspension equipped with a variable equivalent inertance-variable damping (VEI–VD) device and a novel semi-active vibration control strategy. The VEI–VD device can control its equivalent inertance and damping by controlling two external resistors in its electric circuit. Especially, the VEI part of the device can store and release vibration energy via the inside flywheel, which enables the seat suspension to have a four-quadrant controllable capability in the available force–velocity diagram, similar to an active system. First, the dynamic model of the VEI–VD device is built, and a prototype is developed and tested to identify the model parameters and verify its characteristics. Then, a semi-active vibration control method is proposed for the VEI–VD seat suspension. The control method uses a sliding mode controller to acquire the desired control force for reducing vibration; then, according to the desired force and system states, the VEI–VD device is tuned by a force-tracking scheme to generate a real force. In the numerical validation, the vibration transmissibility of VEI–VD seat suspension around its natural frequency is tested with different states. The effectiveness of force-tracking control strategies for different types of suspensions is verified. In the random excitation test, the root means square acceleration of the VEI–VD seat is reduced by 30.72% compared with a passive seat. The VEI–VD seat suspension shows great potential in applications.

Stable Inverse Dynamics for Feedforward Control of Nonminimum-Phase Underactuated Systems

Abstract An enhanced inverse dynamics approach is here presented for feedforward control of underactuated multibody systems, such as mechanisms or robots where the number of independent actuators is smaller than the number of degrees of freedom. The method exploits the concept of partitioning the independent coordinates into actuated and unactuated ones (through a QR-decomposition) and of linearly combined output, to obtain the internal dynamics of the nonminimum-phase system and then to stabilize it through proper output redefinition. Then, the exact algebraic model of the actuated sub-system is inverted, leading to the desired control forces with just minor approximations and no need for pre-actuation. The effectiveness of the proposed approach is assessed by three numerical test cases, by comparing it with some meaningful benchmarks taken from the literature. Finally, experimental verification through an underactuated robotic arm with two degrees of freedom is performed.

Trajectory Control for Vibrating Screen with Magnetorheological Dampers.

The article presents a method of vibrating screen trajectory control based on MR (magnetorheological) dampers applied in a screen suspension. A mathematical description of the dynamic screen model was derived, and parameters of this model were estimated based on experimental data from a semi-industrial vibrating screen. The investigated screen included a single mechanical exciter with unbalanced masses, generating a circular vibration trajectory and operating with over-resonant frequency close to 19 Hz. It was experimentally tested in several phases of operation: start-up, nominal operation at a target vibration frequency and shutdown. The implemented screen model was further extended and included several MR dampers oriented horizontally and vertically in the form of Bouc–Wen models. The Bouc–Wen model was identified based on experiments carried out for an MR damper subjected to harmonic excitations generated by the MTS (material testing system). Dominant frequencies of excitation varied by up to 20 Hz during experiments. The main novelty of the reported solution is that according to the proposed control algorithm, the desired forces generated by MR dampers emulate an additional virtual mechanical exciter of the vibrating screen. In turn, it interacts with the available exciter, resulting in conversion of the trajectory from circular to linear, which was validated in the presented study. For the purpose of simulation accuracy, the desired control force was additionally limited within the simulator by MR damper dissipative domain, which maps the constraints of a semi-active damper. The presented approach allows one to obtain a close to linear trajectory with only one exciter and with semi-active control of suspension stiffness. The results were successfully repeated with different configurations of desired trajectory, indicating that the effectiveness of the desired linear trajectory generation depends on its orientation. The reported findings may lead to the design of new vibrating screen constructions, taking advantage of the semi-active control of a suspension in the attenuation of disturbance resulting from varying processed material parameters.

Generalized Chebyshev problem in nonholonomic mechanics and control theory

The paper is based on the talk with the same name given at the International scientific conference on mechanics “The Ninth Polyakhov’s Reading” dedicated to the 200th anniversary of the birth of the prominent Russian scientist Pafnuty Lvovich Chebyshev. The generalized Chebyshev problem is formulated, in which the motion of a system in the presence of given generalized forces should satisfy an additional system of linear differential equations in which the order of each equation exceeds three. These problems constitute a new class of control problems in which the motion program is given in the form of the above additional system of differential equations. These equations can be considered as linear nonholonomic constraints of high order, whose reactions are the desired control forces. To solve such problems, two theories were developed at the Department of Theoretical and Applied Mechanics of St. Petersburg University. In the first theory, we construct a consistent system of differential equations for the generalized coordinates and the Lagrange multipliers, which are considered as equitable unknown functions of time. The second theory is based on the generalized Gauss principle. The application of the theory is illustrated by the solution of a real space mechanics problem about the motion of an Earth satellite after fixing the value of its acceleration at some point in time. Especially efficient is the application of the second theory to the determination of the optimal control force for transferring a mechanical system with a finite number of degrees of freedom from an existing phase state to a new specified state within a specified period of time. The new method is used to solve the model problem of controlled horizontal motion of a cart bearing the axes of several mathematical pendulums. It is shown that the use of the generalized Gauss principle for solving this problem is undoubtedly superior to that of the classical Pontryagin maximum principle.

An Electromagnetic Variable Inertance and Damping Seat Suspension With Controllable Circuits

This article proposes a novel semiactive electromagnetic device with the capability of variable inertance and damping (VIVD) and an energy storage priority control (ESPC) strategy for vibration reduction of vehicle seat suspensions. The VIVD device can control its inertance and damping by adjusting resistances in a variable admittance (VA) circuit different from the traditional mechanical damper. The circuit and mechanical dynamics model of the VIVD seat suspension is analyzed and verified with tests, and the energy storage characteristic and controllability of the VIVD device are explored. Also, the frequency response characteristics of the VIVD device are derived from the admittance characteristics of the VA circuit. For the semiactive VIVD seat suspension, an H∞ controller is designed to obtain the desired control force. An ESPC strategy is proposed to make the electromagnetic force of the VIVD device track the desired control force. The test results show that the VIVD seat suspension can successfully suppress the seat's vibration, which is better than the traditional variable damping seat suspension performance. Under the random excitation, the root means square acceleration of the VIVD seat is reduced by 32.99% compared with a passive seat. This new semiactive VIVD device shows great potential in engineering applications.

Semi‐active control of air suspension with auxiliary chamber subject to parameter uncertainties and time‐delay

AbstractSuspension systems are critical to the ride comfort and handling stability of vehicles, but traditional passive suspensions fail to achieve optimal performance in the two aspects. Semi‐active suspension controller changes the suspension stiffness or damping to improve the ride comfort and handling stability, which has the potential advantages of low energy consumption and high reliability. In this paper, the model of an air spring with an auxiliary chamber and a variable throttle orifice is proposed and the semi‐active control strategy of air suspension is carried out. The parameters of the air spring with auxiliary chamber are optimized to improve the performance when the control system fails and to increase the basic performance for semi‐active control. Based on the linear matrix inequality approach to robust H∞ control, the semi‐active control strategy of the air suspension is studied, in which parameter uncertainties and time delay are considered to improve control robustness. An inverse model of the air spring is then established to calculate the area of the variable throttle orifice, by which the desired control force is tracked accurately. Finally, the effectiveness of the semi‐active control system of the air suspension is verified by numerical simulation. Comparing with the passive suspension, not only under nominal parameters, but also with parameter uncertainties, time delay, and both parameter uncertainties and time delay, the semi‐active control system proposed in this paper has good control performance as well as is strong robustness to parameter uncertainties and time delay.

Smart dampers-based vibration control – Part 2: Fractional-order sliding control for vehicle suspension system

Semi-active suspension systems of vehicles using smart dampers (SmDs) such as magnetorheological dampers (MRDs) are actively developing as an attractive methodology to improve both ride comfort and road holding of many different vehicles including sedans. Because of the complex dynamic response of the SmDs and the whole system, an exact estimation of the time-varying control signal is difficult. Especially, the reality has shown that i) the error of the inverse SmDs (I-SmDs) due to noise in the measurement database used to build them may fade the control efficiency, and ii) for many high nonlinear systems, fractional-order derivative (FD)-based mathematical description could reflect their characteristics, attributes, and dynamic behaviors better than that using the integer-order-derivative-based traditional way. From the above aspects, we present an FD-based new control system for the half-car semi-active suspension system with MRDs. The proposed control system named FD-SMC consists of I-SmDs which are relied on measured data processed by the new filter CoFilter presented in Part 1 and FD-based sliding mode control (SMC) technique. The FD-SMC determines the control force, and subsequently, I-SmDs estimates current intensity applied to MRDs to generate the desired control forces. Surveys including a real application using an experimental apparatus are carried out to verify the control effectiveness of the proposed method as well as the possibility of development of this orientation.

Simultaneous vortex- and wake-induced vibration suppression of tandem-arranged circular cylinders using active feedback control system

This paper deals with the active flow-induced vibration (FIV) suppression of two identical tandem-arranged circular cylinders at a low Reynolds number of Re=100. The adopted control system employs fuzzy PID controller in which the desired control force is computed based on the cylinder displacement amplitude, and applied transversely for effective attenuation of flow-induced instabilities in both transverse and streamwise directions. Moreover, the effect of FIV suppression of each cylinder on the response amplitude of other one, and the simultaneous vibration reduction of both cylinders are investigated based on fully-coupled fluid-structure interaction (FSI) simulations. The rigid body motion equations in streamwise and transverse directions are incorporated into the computational fluid dynamics solver to treat the coupling which exists between the fluid flow and cylinders movement. Next, in the utilized co-simulations, the active fuzzy PID controller implemented in Matlab/Simulink is coupled with the FSI oscillator model constructed in computational fluid dynamics solver package. It was shown that, the sudden suppression of the upstream cylinder vibration causes quick distortion in the flow field around the rear cylinder, and consequently, its steady-state response amplitude is destabilized and experiences transient fluctuations once again. On the contrary, the decrease in the transverse oscillation of the downstream cylinder leaves no sensible effect on the vibration of upstream cylinder. In particular, the active control system effectively reduces the transverse displacement amplitudes of upstream and downstream cylinders by as much as 99.9% and 98.7%, respectively, for Vr=5.5, while the corresponding values are 99.8% and 99.7% for Vr=7.5. This superb performance of active FIV control systems is mainly due to de-synchronization-type action in which the vortex shedding frequency is deviated from the oscillator natural frequency. Lastly, it is demonstrated that the vortex shedding patterns for uncontrolled cylinders, which primarily depend on reduced velocity, are turned very similar to that of the stationary cylinders after adopting the fully active control systems.

Robust adaptive controller for semi-active control of uncertain structures using a magnetorheological elastomer-based isolator

The isolator based on magnetorheological elastomers (MREs) that is used with semi-active controllers has emerged as a kind of smart devices that could potentially improve vibration control in traditional systems. The nonlinear damping characteristics of the isolator make the controller design more difficult. Generally, the command current/voltage is determined according to the relative responses in conventional semi-active controllers. However, these controllers may exhibit unsatisfactory isolation performance and even cause instability owing to significant excitations or nonlinear effects. In this study, the design of the new semi-active controller for an MRE-based isolator was investigated to overcome the drawbacks of traditional controllers from two perspectives. Firstly, an inverse model is designed for the isolator so that it can be used to predict an appropriate electric current supplied to the electromagnet based on the desired control force. Secondly, a robust adaptive controller for semi-active control is proposed for a nonlinear system with unknown dynamic parameters. The control scheme consists of three parts: a standard adaptive linearizing controller, an adaptive sliding mode controller, and a single robust controller. The proposed method guarantees zero convergence of the displacement response and provides robust stability. In addition, the singularity problem that usually appears in standard adaptive control is eliminated. Simulations demonstrate that the proposed controller exceeds the performance of the passive system as assessed in the protection of a two-story shear building during seismic events.

Fuzzy sliding mode controller design for semi-active seat suspension with neuro-inverse dynamics approximation for MR damper

To improve the ride comfort of car, this paper proposed a semi-active seat suspension with magneto-rheological (MR) damper and designed a new fuzzy sliding mode controller with expansion factor (FSMCEF) based on the neuro-inverse dynamics approximation of the MR damper. This FSMCEF combines the advantages of both sliding mode controller (SMC) and fuzzy controller (FC) with expansion factor (EF), and it takes an ideal skyhook model as the reference, and creates a sliding mode control law based on the errors dynamics between the seat suspension and its reference model. Further fuzzy rules are used to suppress the chattering occurred in the above sliding mode control by fuzzifying the sliding mode surface and its derivative. Moreover, in order to compute the required control current for MR damper after solving the desired control force using FSMCEF, this paper presented a BP algorithm based neural network inverse model, located between the FSMCEF and the MR damper, taking the displacement, velocity of the MR damper and the desired control force output by FSMCEF as its input, and predicting the control current required to input MR damper. The predicting error and stability of the neural network inverse model for MR is investigated by sample testing. In addition, the stability analysis of FSMCEF is also completed by under nominal system and non-nominal system with parameter uncertainty and external disturbance. The results of numerical simulations show that the vibration reduction effect of the semi-active seat is obviously improved using FSMCEF compared with using PID controller and SMC.

Semi-active control of magnetorheological elastomer base isolation system utilising learning-based inverse model

Magnetorheological elastomer (MRE) base isolations have attracted considerable attention over the last two decades thanks to its self-adaptability and high-authority controllability in semi-active control realm. Due to the inherent nonlinearity and hysteresis of the devices, it is challenging to obtain a reasonably complicated mathematical model to describe the inverse dynamics of MRE base isolators and hence to realise control synthesis of the MRE base isolation system. Two aims have been achieved in this paper: i) development of an inverse model for MRE base isolator based on optimal general regression neural network (GRNN); ii) numerical and experimental validation of a real-time semi-active controlled MRE base isolation system utilising LQR controller and GRNN inverse model. The superiority of GRNN inverse model lays in fewer input variables requirement, faster training process and prompt calculation response, which makes it suitable for online training and real-time control. The control system is integrated with a three-storey shear building model and control performance of the MRE base isolation system is compared with bare building, passive-on isolation system and passive-off isolation system. Testing results show that the proposed GRNN inverse model is able to reproduce desired control force accurately and the MRE base isolation system can effectively suppress the structural responses when compared to the passive isolation system.

SEISMIC DESIGN OF MAGNETORHEOLOGICAL DAMPERS BETWEEN DIFFERENT SIZES BUILDINGS UNDER OPTIMUM PARAMETERS

The effectiveness of optimal semi-active dampers for reaching the optimum gains of the response of the adjacent buildings connected by magnetorheological (MR) dampers subjected to seismic motion is examined in this study. One of the challenges is to improve an effective optimal control strategy, utilizing the capabilities of the MR dampers. Hence, a SIMULINK block in MATLAB program was developed to compute the desired control forces at each floor level and to the obtain number of dampers. Linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) controllers are used for achieving the desired control forces, whilst the desired voltage is synthesized based on clipped voltage law (CVL). The control objective is to diminish both the displacement and acceleration responses. As a result, MR dampers can deliver noteworthy displacement response control that is possible with less voltage for the shorter building.

Novel fuzzy sliding controller for MRD suspensions subjected to uncertainty and disturbance

In this paper, the design of an adaptive optimal fuzzy sliding controller (AOFSC) for semi-active magnetorheological damper (MRD) vehicle suspension system subjected to uncertainty and disturbance (UAD) whose time-varying rate may be high but bounded is presented. This is a combination of an adaptive optimal fuzzy sliding mode controller (FSMCop), a nonlinear disturbance observer (NDO) and an inverse MRD model to create the desired control force, including the compensation part for UAD. An adaptive control law is proposed to establish a fuzzy-gain update law for the AOFSC and a parameter tie for the NDO such that the convergence of system's dynamic response is a Lyapunov asymptotically stable process. Surveys via simulations along with via an experimental apparatus showed that the high capability to exterminate vibration, robust stability, and the economic efficiency are the main advantages of the proposed AOFSC.

MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations

This paper describes a semi-active vibration absorber (SVA) concept based on a real-time controlled magnetorheological damper (MR-SVA) for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD). Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.