Passive Adaptive Control Research Articles

An adaptive backstepping control strategy based on radial basis function neural networks for the magnetorheological semi-active suspension

Owing to nonlinear issues such as external disturbances and uncertain parameters within the semi-active suspension system (SASS), the vibration amplitude of the suspension system tends to increase, and the time required for the suspension system to reach a steady-state response is prolonged. Hence, this paper proposes an adaptive backstepping control strategy based on radial basis function neural networks (RBF-NNs). Firstly, the damping force characteristics of the magnetorheological (MR) damper are tested, and the experimental data are utilized for parameters identification and fitting of the Bouc-Wen model. To establish a connection between the controller and the forward model of the MR damper, the forward model of the MR damper, the inverse model of the MR damper, and the model of the MR-SASS are constructed. Secondly, the backstepping controller and the adaptive backstepping controller based on RBF-NNs are designed. The stability and reliability of the closed-loop suspension system are verified through stability analysis using Lyapunov function. Finally, the dynamic characteristics of the passive control, backstepping control, and adaptive backstepping control strategies based on RBF-NNs applied to MR-SASS are analyzed under B-Class road excitation and speed bump road excitation. The acceleration, suspension dynamic deflection, and tire dynamic load are selected as the evaluation indices. The results demonstrate that the adaptive backstepping controller based on RBF-NNs significantly enhances the ride comfort of the SASS.

Self-Powered Passive Adaptive Control of Pitch Angle and Betz-Shaped Wind Tunnel

Owing to both the high cost and the complexity, for small turbines, the control of pitch angle is usually not a option though it could keep turbine working in high efficiency zone while wind speed changes. In order to solve this problem, a self-powered passive adaptive control system (SPACS) for pitch angle adjustment has been developed. Together with this SPACS idea, a Betz-shaped wind tunnel has also been developed which can reduce the size and running cost significantly if compared with conventional wind tunnels. In this paper the main technical principles will be presented together with some conceptual sketches and initial results.

Adaptive passive admittance control of a compliant collaborative robot

Compliance of the collaborative robots plays an important role in human-robot interaction. Due to the complex nonlinearities caused by the compliance, and parameter uncertainties, good performance control method for the compliant collaborative robot is always a challenging task. Therefore, to overcome the challenge of the compliance, and uncertain dynamics, this paper develops an adaptive passive admittance control (APAC) approach for a novel compliant collaborative robot, whose compliant mechanism is constituted of the inerters, springs, and dampers. First, through force-current analogy between mechanical network and electrical network, the compliance of the proposed collaborative robot with the inerters, springs, and dampers, is represented by a novel and simplified admittance matrix to facilitate dynamics model of the proposed collaborative robot. Then, for the proposed compliant collaborative robot, an APAC strategy is presented to dispose of the uncertain parameters of the dynamics. The inertial matrix, Coriolis matrix, admittance matrix, and gravity vector of the compliant collaborative robot are expressed as linear representation of orthogonal basis functions by using function approximation technique (FAT). The boundedness of the robot dynamics is proved by detailed stability analysis which uses Lyapunov function. Finally, simulation results indicate that the proposed APAC of the compliant collaborative robot is effective.

Fuzzy Adaptive Passive Control Strategy Design for Upper-Limb End-Effector Rehabilitation Robot.

Robot-assisted rehabilitation therapy has been proven to effectively improve upper-limb motor function in stroke patients. However, most current rehabilitation robotic controllers will provide too much assistance force and focus only on the patient's position tracking performance while ignoring the patient's interactive force situation, resulting in the inability to accurately assess the patient's true motor intention and difficulty stimulating the patient's initiative, thus negatively affecting the patient's rehabilitation outcome. Therefore, this paper proposes a fuzzy adaptive passive (FAP) control strategy based on subjects' task performance and impulse. To ensure the safety of subjects, a passive controller based on the potential field is designed to guide and assist patients in their movements, and the stability of the controller is demonstrated in a passive formalism. Then, using the subject's task performance and impulse as evaluation indicators, fuzzy logic rules were designed and used as an evaluation algorithm to quantitively assess the subject's motor ability and to adaptively modify the stiffness coefficient of the potential field and thus change the magnitude of the assistance force to stimulate the subject's initiative. Through experiments, this control strategy has been shown to not only improve the subject's initiative during the training process and ensure their safety during training but also enhance the subject's motor learning ability.

Experimental Studies on Adaptive-Passive Symmetrical Granular Damper Operation.

This paper presents experimental studies on a controllable granular damper, whose dissipative properties are provided by the friction phenomenon occuring between loose granular material. In addition, in order to adjust to the current trends in vibration suppression, we built a semi-active device, controlled by a single parameter—underpressure. Such granular structures subjected to underpressure are called Vacuum-Packed Particles. The first section presents the state of the art. A brief description of the most often used intelligent and smart materials for the manufacture of dampers is presented. The main advantages of the proposed device are a simple structure, low construction cost, symmetrical principle of operation, and the ability to change the characteristics of the damper by quickly and suddenly changing the negative pressure inside the granular core. The second section provides a detailed description of the construction and operation principles of the original symmetrical granular damper. A description of its application in the laboratory research test stand is also provided. The third section presents the results of the experimental studies including the recorded damping characteristics of the investigated damper. The effectiveness of the ethylene–propylene–diene grains’ application is presented. The two parameters of underpressure and frequency of excitation were considered during the empirical tests. The influence of the system parameters on its global dissipative behavior is discussed in detail. The damper operation characteristics are close to linear, which is positive information from the point of view of the potential adaptive-passive control process. Brief conclusions and the prospective application of vacuum-packed particle dampers are presented in the final section.

Passive control of 3D adaptive shock control bumps using a sealed cavity

This paper presents a Fluid–Structure-Interaction study of a novel passive adaptive shock control bump concept. A flexible plate, clamped on all sides and placed above a sealed cavity, was tested beneath a Mach 1.4 normal shock in the Imperial College London supersonic wind tunnel. The plate was actuated into the shape of a 3D shock control bump by passively controlling the cavity pressure through an array of breather holes. Preliminary experiments were performed with active control of cavity pressure (via a vacuum tank) at Mach 1.4 and 2 to illustrate the potential of this concept. Full-field surface measurement techniques, namely photogrammetry and pressure sensitive paint, were employed in addition to static pressure tappings and schlieren photography. Results confirmed that cavity pressure plays a key role in determining the aerostructural behaviour of the flexible plate. In addition, it was found that carefully placed breather holes allowed the plate to deform into a 3D shock control bump when a shock was on the flexible region and remain flat otherwise. This shows significant potential for improving the off-design behaviour of adaptive shock control bumps.

Design of tunable hierarchical waveguides based on Fibonacci-like microstructure

A novel class of Fibonacci-based high performance tunable hierarchical waveguides is here proposed and special focus is devoted to the design of adaptive-passive control systems for the Bloch wave propagation. By exploiting the features of periodic approximants, the metamaterial is conceived by the proper repetition of an elementary cell along a fixed direction. This elementary cell is made up of two building blocks repeated according to the Fibonacci sequence, to form a quasi-periodic finite microstructured system The former building block is made of a homogeneous elastic material, while the latter is a microstructured two-phase laminate. One of these phases is piezoelectric shunted by a suitably conceived electrical circuit, such that the constitutive properties of the piezoelectric phase are tuned by adjusting its equivalent impedance/admittance. Moreover, the overall constitutive properties of the microstructured layer are determined, exploiting the scale separation, via an asymptotic homogenization scheme. Then, it is possible to determine the frequency band structure of the tunable waveguide by exploiting the transfer matrix approach. With the aim of providing broad design directions, attention is paid to characterizing the dispersion waves properties of the tunable Fibonacci-like superlattices described by several generations of the Fibonacci sequence and for different values of the orientation angle of the two-phase laminate.

The Design and Analysis of Double Cutter Device for Hinge and Suction Dredger Based on Feedback Control Method

The hinge and suction dredger is widely used in the construction field such as in river and lake management, water dredging, and port infrastructure projects, etc. With the continuous development of modern dredging technology, the traditional hinge and suction dredger cannot adapt to the complex environment during the construction process and there are problems such as large energy consumption and over-excavation and leakage excavation. In this paper, a double cutter dredger was designed that has a wider adaptability to water than a single cutter dredger. At the same time, based on the principle of passive adaptive control, the working parameters of the control system were calculated and determined, and an adaptive control algorithm was proposed to determine the water environment by using the current difference between the two cutters. Finally, the feasibility of the structure and algorithm was verified by experiments. The efficiency of cutter suction dredger was improved, and the energy consumption was reduced by 9–25% in the ideal state.

An adaptive control algorithm for smart base isolation systems based on seismic early warning system

The common control strategy of smart base isolation composed of a low-damping rubber bearing and a magneto-rheological (MR) damper is to use MR damper in semi-active form. One drawback of this strategy is increasing the acceleration of isolated structure due to adding MR damper, especially under low-intensity earthquakes. This paper proposes a new adaptive-passive control approach for smart base isolation system. In this approach, MR damper performs in passive form while its behaviour is adjusted proportionally to intensity of the incoming earthquake which can be provided by a seismic early warning system (SEWS). For comparison purposes, hybrid control system has been also designed using the common control strategy in semi-active form. Because of the lack of high accuracy of SEWS in predicting the earthquake intensity, the performance of proposed control approach has been evaluated for an error of 20% in the estimated earthquake intensity. Evaluation of the performance of these control strategies under testing earthquake records shows that adaptive-passive control algorithm works better than semi-active control algorithm in controlling the seismic response of structure and the proposed control algorithm has effective performance under a wide range of earthquake intensities.

Direct power control for VSC-HVDC systems: An application of the global tracking passivity-based PI approach

This paper proposes a direct power control (DPC) for a high-voltage direct-current system using voltage source converters (VSC-HVDC) by applying passivity-based control theory. This system allows doing an efficient and reliable integration of electrical network from renewable energy sources. The DPC model permits instantaneous control of the active and reactive power without employing the conventional inner-loop current regulator and the phase-locked loop, thus diminishing investment costs and increasing the reliability of the system. The proportional-integral passivity-based control (PI-PBC) is chosen to control the direct power model of the VSC-HVDC system since this system exhibits a port-Hamiltonian formulation in open-loop and as PI-PBC can exploit this formulation to design a PI controller, which guarantees asymptotically stable in closed-loop based on Lyapunov’s theory. Passivity-based control is an active research subject in the control community which has gained a reputation of being a very theoretical subject. Nevertheless, it can have advantages from a practical point of view including an implementation similar to the conventional controls for power systems applications. The paper is oriented to the power & energy systems community, taking into account this practical approach. The proposed controller is assessed by simulations in a two-terminal VSC-HVDC system and compared with a PI direct power controller. Four simulation conditions using MATLAB/SIMULINK were conducted to verify the effectiveness of PI-PBC against a PI controller and a perturbation observer-based adaptive passive control under various operating conditions.

Adaptive-passive control of flow over a sphere for drag reduction

A new adaptive-passive control device is introduced to optimally reduce the drag on a sphere over a wide range of Reynolds numbers, Re = 0.4 × 105–4.4 × 105. The device, called an adaptive moving ring (AMR), is designed to change its size (i.e., protrusion height) adaptively depending on the wind speed (i.e., the Reynolds number) without energy input. An empirical model is formulated to accurately predict the drag coefficient as a function of the size of AMR and the Reynolds number. Based on the model, we estimate how the optimal size of AMR should vary with the Reynolds number to maximize the drag reduction. Following the estimation of the optimal size, the optimally tuned AMR reduces its protrusion height with increasing Reynolds number, and the drag decreases monotonically by up to 74% compared to that of a smooth sphere. The drag reduction by AMR is attributed to different mechanisms depending on the Reynolds number. For low Reynolds numbers, the locally separated flow at large AMR is energized by the disturbance induced by AMR and reattaches to the sphere surface, forming a large recirculation region. Then, the main separation is delayed downstream due to the increased near-wall momentum. On the other hand, at high Reynolds numbers, no recirculation zone is formed at AMR due to its low protrusion height, but a secondary separation bubble is generated on the rear sphere surface. Therefore, the boundary-layer flow becomes turbulent, and the main separation is significantly delayed, resulting in more drag reduction than for low Reynolds numbers.

EcoVibe: On-Demand Sensing for Railway Bridge Structural Health Monitoring

Energy efficient sensing is one of the main objectives in the design of networked embedded monitoring systems. However, existing approaches such as duty cycling and ambient energy harvesting face challenges in railway bridge health monitoring applications due to the unpredictability of train passages and insufficient ambient energy around bridges. This paper presents eco-friendly vibration (ECO VIBE), an on-demand sensing system that automatically turns on itself when a train passes on the bridge and adaptively powers itself off after finishing all tasks. After that, it goes into an inactive state with near-zero power dissipation. ECO VIBE achieves these by: first, a novel, fully passive event detection circuit to continuously detect passing trains without consuming any energy. Second, combining train-induced vibration energy harvesting with a transistor-based load switch, a tiny amount of energy is sufficient to keep ECO VIBE active for a long time. Third, a passive adaptive off control circuit is introduced to quickly switch off ECO VIBE. Also this circuit does not consume any energy during inactivity periods. We present the prototype implementation of the proposed system using commercially available components and evaluate its performance in real-world scenarios. Our results show that ECO VIBE is effective in railway bridge health monitoring applications.

Power maximization of variable-speed variable-pitch wind turbines using passive adaptive neural fault tolerant control

Power maximization has always been a practical consideration in wind turbines. The question of how to address optimal power capture, especially when the system dynamics are nonlinear and the actuators are subject to unknown faults, is significant. This paper studies the control methodology for variable-speed variable-pitch wind turbines including the effects of uncertain nonlinear dynamics, system fault uncertainties, and unknown external disturbances. The nonlinear model of the wind turbine is presented, and the problem of maximizing extracted energy is formulated by designing the optimal desired states. With the known system, a model-based nonlinear controller is designed; then, to handle uncertainties, the unknown nonlinearities of the wind turbine are estimated by utilizing radial basis function neural networks. The adaptive neural fault tolerant control is designed passively to be robust on model uncertainties, disturbances including wind speed and model noises, and completely unknown actuator faults including generator torque and pitch actuator torque. The Lyapunov direct method is employed to prove that the closed-loop system is uniformly bounded. Simulation studies are performed to verify the effectiveness of the proposed method.

Perturbation observer-based adaptive passive control for nonlinear systems with uncertainties and disturbances

In this paper, a perturbation observer-based adaptive passive control scheme is developed to provide great robustness of nonlinear systems against the unpredictable uncertainties and disturbances therein. The proposed scheme includes a high-gain perturbation observer and a robust passive controller. The high-gain perturbation observer is designed to estimate online the perturbation aggregated from the combinatorial effect of system nonlinearity, parameter uncertainty, unmodelled dynamics and fast time-varying external disturbances. Then the robust passive controller, using the estimated perturbation, can produce the minimal control effort needed to compensate for the magnitude of the actual current perturbation. Furthermore, the convergence of estimation error of the high-gain perturbation observer and the closed-loop system stability are analyzed theoretically. Finally, two practical examples are given to show the effectiveness and advantages of the proposed approach over the accurate model-based passive control scheme and the linearly parametric estimation-based adaptive passive control scheme.

Perturbation observer based adaptive passive control for damping improvement of multi-terminal voltage source converter-based high voltage direct current systems

This paper proposes a Perturbation Observer-based adaptive passive control (POAPC) for damping improvement of multi-terminal voltage source converter-based high voltage direct current (VSC-MTDC) systems. The POAPC is designed for an N-terminal VSC-MTDC system, and the perturbation is defined as a lumped term including interactions between terminals, unmodelled dynamics and unknown external disturbances, which are estimated online via a perturbation observer. Then an extra system damping is injected for each terminal to improve the transient dynamics via passivation. The POAPC does not require an accurate system model and measurements of full states; only the DC voltage and active and reactive power need to be measured. Case studies are carried out on a four-terminal VSC-MTDC system under four scenarios such as active and reactive power reversal, faults at AC bus, offshore wind farm connection, and fast time-varying parameter uncertainties. Simulation results verify its effectiveness under various operating conditions, compared with that of conventional proportional-integral (PI) control and classical passive control (PC).

Adaptive-passive control of structure-borne noise of rotating machinery using a pair of shunted inertial actuators

In this article, two piezo-based rotating inertial actuators are considered for the suppression of the structure-borne noise radiated from rotating machinery. Each inertial actuator comprises a piezoelectric stack element shunted with the Antoniou’s gyrator circuit. This type of electrical circuit can be used to emulate a variable inductance. By varying the shunt inductance it is possible to realise two tuneable vibration neutralisers to suppress tonal frequency vibrations of a slowly rotating machine. Also, reductions in the noise radiated from the machine housing can be achieved. First, a theoretical study is performed using a simplified lumped parameter model of the system at hand. The simplified model consists of a rotating shaft and two perpendicularly mounted shunted piezo-based rotating inertial actuators. Second, the shunted piezo-based rotating inertial actuators are tested on an experimental test bed comprising a rotating shaft mounted in a frame. The noise is radiated by a plate that is attached to the frame. The experimental results show that a reduction of 11 dB on the disturbance force transmitted from the rotating shaft through the bearing to the housing can be achieved. This also generates a reduction of 9 dB for the plate vibration and the radiated noise.

Perturbation estimation based coordinated adaptive passive control for multimachine power systems

This paper proposes a perturbation estimation based coordinated adaptive passive control (PECAPC) of generators excitation system and thyristor-controlled series capacitor (TCSC) devices for complex, uncertain and interconnected multimachine power systems. Discussion begins with the PECAPC design, in which the combinatorial effect of system uncertainties, unmodelled dynamics and external disturbances is aggregated into a perturbation term, and estimated online by a perturbation observer (PO). PECAPC aims to achieve a coordinated adaptive control between the excitation controller (EC) and TCSC controller based on the nonlinearly functional estimate of the perturbation. In this control scheme an explicit control Lyapunov function (CLF) and the strict assumption of linearly parametric uncertainties made on system structures can be avoided. A decentralized stabilizing EC for each generator is firstly designed. Then a coordinated TCSC controller is developed to passivize the whole system, which improves system damping through reshaping the distributed energies in power systems. Case studies are carried out on a single machine infinite bus (SMIB) and a three-machine system, respectively. Simulation results show that the PECAPC-based EC and TCSC controller can coordinate each other to improve the power system stability, finally a hardware-in-the-loop (HIL) test is carried out to verify its implementation feasibility.

Physical performance and self-report outcomes associated with use of passive, adaptive, and active prosthetic knees in persons with unilateral, transfemoral amputation: Randomized crossover trial.

Prosthetic knees are a vital component in an artificial limb. Contemporary knees include passive, (mechanical), adaptive (computerized), or active (motorized) control systems and have the potential to mitigate amputation-related functional impairments and activity limitations. A 14 mo randomized crossover trial was conducted. Participants (n = 12, mean age = 58 yr) were tested under three conditions: passive control (existing knee), adaptive control (Ossur Rheo Knee II), and active control (Ossur Power Knee II). Training and acclimation time were provided to participants in the adaptive and active knees. Outcome measures included indoor tests (Timed Up and Go test [TUG], stairs, and ramp), outdoor tests (walking course and perceived exertion), step activity monitor, self-report surveys (mobility, balance confidence, physical function, fatigue, and general health), and fall incidence. Mixed-effects linear regression modeling was used to evaluate data. Compared with passive control, adaptive control significantly improved comfortable TUG time (difference = 0.91 s, p = 0.001) and reported physical function (difference = 1.26 [T-score], p = 0.03). Active control significantly increased comfortable TUG, fast TUG, and ramp times (difference = 3.02, 2.66, and 0.96 s, respectively, all p < 0.03) and increased balance confidence (difference = 3.77, p = 0.003) compared with passive control. Findings suggest that adaptive knee control may enhance function compared with passive control but that active control can restrict mobility in middle-age or older users with transfemoral amputation. ClinicalTrials.gov; "Use of Passive, Adaptive, and Active Prosthetic Knees in Persons With Unilateral, Transfemoral Amputation": NCT02219230; https://clinicaltrials.gov/ct2/show/NCT02219230.

Analysis of multi-physics interaction effects in a coupled dynamical electro-magneto-mechanical (2+2×1/2)DOF system

Abstract The operation of electro-magneto-mechanical systems involves the interaction of these three physical domains. In the paper, this interaction is analysed for a lumped parameter model, which consists of a two degrees of freedom (2DOF) linear mechanical system coupled via a nonlinear electro-magnetic field with two electrical circuits, contributing with 1/2DOF each. Dynamics of this multi-physical model is considered both in the nonlinear and in the linearised problem formulations. In the former case, the method of multiple scales is used to describe softening and modal interaction phenomena. The 2−1 (super-harmonic) internal resonance is investigated, where stability and jump phenomena are analysed. The regimes of uni- and bi-modal responses are identified and a parametric study performed. The mathematical description of nonlinearities, introduced by multi-physical coupling, is compared with the classical formulation of nonlinear stiffness of a spring. For the linearised problem, the equivalent stiffness and the damping, as functions of the parameters of electro-magnetic elements, are assessed. The ranges of these parameters, when the nonlinear multi-physics interaction effects are suppressed by the dissipation effects of the same origin, are identified. The analytical predictions are verified by the numerical simulations. The relevance of the reported results to the operation of electro-magnetic adaptive passive control systems, capable to alter a natural frequency and add damping, is discussed.

Neural Network-based Adaptive Passive Output Feedback Control for MIMO Uncertain System

A neural network--based adaptive passive output feedback control problem is studied for a class of multi-input multi-output nonlinear systems with unknown nonlinearities and unknown parameters. Neural networks are used to identify unknown nonlinearities, and the update laws of weight parameters and constant parameters are proposed. The design methods of the adaptive passive controllers for this class of systems are discussed in the paper. The corresponding adaptive passive controllers and parametric adaptive laws are designed and presented respectively. It is proved that the closed-loop system composed of the original system and the designed controller is stable by the Lyapunov method, and the controller designed can render the closed system adaptive passive. Finally, a simulation example is given to prove the effectiveness and feasibility of the proposed method. DOI: http://dx.doi.org/10.11591/telkomnika.v10i6.1600 Full Text: PDF