Inherent Coupling Effect Research Articles

Load torque composite synchronous control of dual‐driven systems

AbstractFor enhancing the load torque synchronization performance of dual‐driven systems, the inherent coupling effect between the parallel axes is analyzed first and could be described as two distinct components of the synchronous error. Thus, the feedforward‐feedback composite synchronous control scheme is proposed in this paper to eliminate these desynchronization factors. Secondly, the selection of synchronization objectives such as speeds, positions or currents of parallel axes is analyzed, which may not accurately reflect the actual load desynchronization due to mismatch dynamics. To overcome this drawback, the synchronous feedback controller is modified by incorporating a load torque observer, which can provide good adaptation to modelling errors, disturbances and eliminate the load desynchronization effectively. Simulation and experimental results demonstrate significant improvement in load torque synchronization performance achieved by the proposed control scheme.

An Atraumatic Mock Loop for Realistic Hemocompatibility Assessment of Blood Pumps.

Conventional mock circulatory loops (MCLs) cannot replicate realistic hemodynamic conditions without inducing blood trauma. This constrains in-vitro hemocompatibility examinations of blood pumps to static test loops that do not mimic clinical scenarios. This study aimed at developing an atraumatic MCL based on a hardware-in-the-loop concept (H-MCL) for realistic hemocompatibility assessment. The H-MCL was designed for 450 ± 50 ml of blood with the polycarbonate reservoirs, the silicone/polyvinyl-chloride tubing, and the blood pump under investigation as the sole blood-contacting components. To account for inherent coupling effects a decoupling pressure control was derived by feedback linearization, whereas the level control was addressed by an optimization task to overcome periodic loss of controllability. The HeartMate 3 was showcased to evaluate the H-MCL's accuracy at typical hemodynamic conditions. To verify the atraumatic properties of the H-MCL, hemolysis (bovine blood, n = 6) was evaluated using the H-MCL in both inactive (static) and active (minor pulsatility) mode, and compared to results achieved in conventional loops. Typical hemodynamic scenarios were replicated with marginal coupling effects and root mean square error (RMSE) below 1.74 ± 1.37 mmHg while the fluid level remained within ±4% of its target value. The normalized indices of hemolysis (NIH) for the inactive H-MCL showed no significant differences to conventional loops ( ∆NIH = -1.6 mg/100 L). Further, no significant difference was evident between the active and inactive mode in the H-MCL ( ∆NIH = +0.3 mg/100 L). Collectively, these findings indicated the H-MCL's potential for in-vitro hemocompatibility assessment of blood pumps within realistic hemodynamic conditions, eliminating inherent setup-related risks for blood trauma.

Motion synchronization in a dual redundant HA/EHA system by using a hybrid integrated intelligent control design

This paper presents an integrated fuzzy controller design approach to synchronize a dissimilar redundant actuation system of a hydraulic actuator (HA) and an electro-hydrostatic actuator (EHA) with system uncertainties and disturbances. The motion synchronous control system consists of a trajectory generator, an individual position controller for each actuator, and a fuzzy force tracking controller (FFTC) for both actuators. The trajectory generator provides the desired motion dynamics and designing parameters of the trajectory which are taken according to the dynamic characteristics of the EHA. The position controller consists of a feed-forward controller and a fuzzy position tracking controller (FPTC) and acts as a decoupled controller, improving position tracking performance with the help of the feed-forward controller and the FPTC. The FFTC acts as a coupled controller and takes into account the inherent coupling effect. The simulation results show that the proposed controller not only eliminates initial force fighting by synchronizing the two actuators, but also improves disturbance rejection performance.

Simulation of non-Gaussian stochastic processes by amplitude modulation and phase reconstruction

Stochastic processes are used to represent phenomena in many diverse fields. Numerical simulation method is widely applied for the solution to stochastic problems of complex structures when alternative analytical methods are not applicable. In some practical applications the stochastic processes show non-Gaussian properties. When the stochastic processes deviate significantly from Gaussian, techniques for their accurate simulation must be available. The various existing simulation methods of non-Gaussian stochastic processes generally can only simulate super-Gaussian stochastic processes with the high-peak characteristics. And these methodologies are usually complicated and time consuming, not sufficiently intuitive. By revealing the inherent coupling effect of the phase and amplitude part of discrete Fourier representation of random time series on the non-Gaussian features (such as skewness and kurtosis) through theoretical analysis and simulation experiments, this paper presents a novel approach for the simulation of non-Gaussian stochastic processes with the prescribed amplitude probability density function (PDF) and power spectral density (PSD) by amplitude modulation and phase reconstruction. As compared to previous spectral representation method using phase modulation to obtain a non-Gaussian amplitude distribution, this non-Gaussian phase reconstruction strategy is more straightforward and efficient, capable of simulating both super-Gaussian and sub-Gaussian stochastic processes. Another attractive feature of the method is that the whole process can be implemented efficiently using the Fast Fourier Transform. Cases studies demonstrate the efficiency and accuracy of the proposed algorithm.

Fault-Tolerant Adaptive Control of High-Speed Trains Under Traction/Braking Failures: A Virtual Parameter-Based Approach

Advanced control is a key technology for enhancing safe and reliable operation of high-speed trains. This paper presents an automated train control scheme for high-speed trains with combined longitudinal aerodynamics and tracking/braking dynamics, with special emphasis on reliable position and velocity tracking in the face of traction/braking failures. The controller is synthesized using a so-called virtual-parameter-based backstepping adaptive control method, which exhibits several salient features: 1) The inherent coupling effects are taken into account as a result of combining both longitudinal and traction/braking dynamics; 2) fully parameter independent rather than partially parameter independent control algorithms are derived; and 3) closed-loop tracking stability of the overall system is ensured under unnoticeable time-varying traction/braking failures. The effectiveness of the developed control scheme is authenticated via a formative mathematical analysis based on Lyapunov stability theory and validated via numerical simulations.

A comprehensive analysis and implementation of vector control of permanent magnet synchronous motor

Permanent magnet synchronous motor (PMSM) is gaining much attention in the area of high performance drives with the recent development in solid state electronics, processors, and intelligent computing. The development of ASIC and advanced VLSI technologies compact size and high efficiency of PMSM made it a suitable candidate for servo drives. This paper describes a brief analysis of permanent PMSM. The advantages over widely used DC motors and induction motors are also discussed in detail. To overcome the inherent coupling effect and the sluggish response of scalar control the vector control is employed. By using the vector control, the performance of AC machines can be made similar to that of a DC machine. To implement the vector control two-axis mathematical model in d-q reference frame is obtained. The performance of proposed controller is investigated for different speed and torque values. The effectiveness of proposed controller is verified through simulations.

Non-linear decoupling control of vehicle plane motion

This article studies the decoupling control strategies for a quasi-linearised vehicle model consisting of three degrees of freedom. The key feature of the model is that it preserves strong non-linearities and inherent coupling effects between longitudinal acceleration/braking force, steering angles and state variables of the vehicle, based on which two kinds of decoupling controllers are presented. Firstly, a control law for approximate decoupling of longitudinal, lateral and yaw motions is derived, which requires small control magnitude. Next, by selecting the virtual control inputs, a new input–output map is built, and the input–output decoupling controller is proposed. Furthermore, according to the characteristics of the vehicle model, an exponentially stable observer is designed. Several simulations are included to illustrate the proposed control scheme.

Nonlinear decoupling control of four-wheel-steering vehicles with an observer

This paper studies the input-output decoupling control for the nonlinear vehicle model consisting of three degrees of freedom. The technique of quasi-linearization is used to simplify the vehicle model, which preserves inherent coupling effects between longitudinal acceleration/braking force, steering angles and the vehicle states. By choosing the combined control inputs, the input-output map of the vehicle dynamical system is reconstructed. Based on the model, the input-output decoupling controller is proposed. Furthermore, an asymptotically stable observer is presented. A modified form of mean value theorem is used to design the observer for the nonlinear vehicle system with bounded Jacobian. The observer gain can be obtained by solving linear matrix inequalities (LMIs). Several simulations are carried out to show the improvements in vehicle handling and stability due to the inputoutput decoupling control.

Analysis of interface cracks in layered piezoelectric composites by a SGBEM

AbstractPiezoelectric materials offer many possibilities in advanced engineering structures due to their inherent coupling effects between mechanical and electrical fields and are widely applied in smart devices and structures like transducers, actuators and sensors [2]. An important application of piezoelectric materials is related to layered or laminated composites because they can be optimized to satisfy the high‐performance requirements according to different in‐service conditions. Beside cracks inside homogeneous domains, one of the most dominant failure mechanisms in layered or laminated composites is the interface failure. Interface cracks and interface debonding may be induced by the mismatch of the mechanical, electrical and thermal properties of the material constituents during the manufacturing process and the in‐service loading conditions. This paper presents a hypersingular symmetric Galerkin boundary element method (SGBEM) for crack analysis in two‐dimensional (2D), layered and linear piezoelectric solids. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Novel L-B Hybrid Langevin Transducer Type Linear Ultrasonic Motor With Modal Coupling Reducing Configuration

For most longitudinal and bending hybrid linear ultrasonic motor, there exists an inherent coupling effect between two modals due to the structure defect, which shows the phenomenon of one phase piezoceramic exciting the other phase vibration or vice versa. A new modal decoupling motor was proposed with the longitudinal piezoceramics positioned in the middle part of Langevin transducer and the bending piezoceramics at longitudinal antinodal plane. The prototype, designed with frequency tuning method, showed obvious modal coupling reduction in impedance characteristics and laser vibrometer measurement, and also surpass previous motor in output performance.

Neuroadaptive Output Tracking of Fully Autonomous Road Vehicles With an Observer

Automated vehicle control systems are a key technology for intelligent vehicle highway systems (IVHSs). This paper presents an automated vehicle control algorithm for combined longitudinal and lateral motion control of highway vehicles, with special emphasis on front-wheel-steered four-wheel road vehicles. The controller is synthesized using an online neural-estimator-based control law that works in combination with a lateral velocity observer. The online adaptive neural-estimator-based design approach enables the controller to counteract for inherent model discrepancies, strong nonlinearities, and coupling effects. The neurocontrol approach can guarantee the uniform ultimate bounds (UUBs) of the tracking and observer errors and the bounds of the neural weights. The key design features are (1) inherent coupling effects will be taken into account as a result of combining of the two control issues, viz., lateral and longitudinal control;(2) rather ad hoc numerical approximations of lateral velocity will be avoided via a combined controller-observer design; and (3) closed-loop stability issues of the overall system will be established. The algorithm is validated via a formative mathematical analysis based on a Lyapunov approach and numerical simulations in the presence of parametric uncertainties as well as severe and adverse driving conditions.

Performance of combined DDLL and AGC loop for direct-sequence spread-spectrum systems

The automatic gain control (AGC) loops are usually used in communication systems to stabilize the performance. In this paper, the combined performance of digital delay-locked loop (DDLL) and AGC loop for direct-sequence spread-spectrum systems is analyzed. Especially, the inherent coupling effects between DDLL and AGC loop are developed. The numerical results show that the DDLL with AGC loop can offer a reliable and satisfactory performance.