Cross-coupling Problems Research Articles

The Cross-coupling Problem of Helicopter Rotors - A Review

Until recently it was beyond the capability of helicopter rotor models to predict correctly the cross-coupling response. During the mid-nineties it became clear that wake distortion effects are the main contributors to the cross-coupling response. Wake distortion effects can be modeled by using detailed free or prescribed wake models. However, these models require large computer resources and long computing times, thus they are not suitable for various applications. In such cases dynamic-inflow models can be corrected to account for the missing effect, by using the wake distortion coefficient or an aerodynamic phase lag. Recently, a new actuator disk model was developed where the wake distortion effect is obtained as an integral part of the derivation. In the paper all the methods of considering the wake distortion effects are reviewed and compared. The results of the various models are also compared to flight test results. Conclusions are drawn and further necessary research is identified.

Maximum Power Tracking for Magnetic Field Editing-Based Omnidirectional Wireless Power Transfer

This paper proposes and implements an optimized omnidirectional wireless power transfer (WPT) system using distributed transmitter coils is proposed. Under the consideration of practical WPT applications which involve human safety concerns, such as daily home apparatus or wireless rechargeable medical implants, the proposed system can achieve the shortest charging time within the safe limits of human exposure to radiofrequency electromagnetic energy. Based on the calculation of the magnetic intensity generated by multi-coupling WPT systems, a more processable magnetic threshold model is presented and analyzed based on the common standard. A newly developed optimization model of the transmitter currents and accordant control strategy is designed and presented to realize both maximum power tracking and flux suppression at target positions. The double-resonant circuit topology with LCC compensation is adopted to reach the stable and synchronized transmitter currents. The cross-coupling problem in multi-input WPT systems will be solved as well. Full-range magnitude control is realized with a single controller and direct current power source. The hybrid frequency pacing technique is adopted for lower switching frequency and higher system efficiency under weak coupling operations. Taking practical wireless rechargeable medical implant as the research object, both simulation and experimental results validate the feasibility and the prospect of the proposed system.

Research on associated motion simulation method and platform of control rod driving mechanism

The motion simulation analysis of the control rod drive mechanism is a typical multi-disciplinary cross-coupling problem covering electromagnetic field, flow field, and dynamic field. Ensuring effective simulation accuracy is an important advance for accurately predicting the reliability of nuclear reactors. In this paper, a multi-disciplinary co-simulation method is proposed based on time unit differentiation, which solves the coupling problem of parameters by micro-element thought. It can avoid affecting the accuracy of simulation results due to the inequality of multi-disciplinary parameters in the co-simulation process. This paper takes the nuclear reactor control rod drive mechanism as the verification object. The multi-disciplinary co-simulation platform in Isight is built based on the co-simulation method. By differentiating the overall process of multidisciplinary co-simulation according to time unit and using the same simulation time interval for each discipline, the Newmark method is used to determine the minimum simulation time integration step of each discipline. The multi-field co-simulation is carried out including electromagnetic field, flow field, gravitational field, and motion field of the driving mechanism in the working process. Through comparison with the actual measurement results, the simulation results have an error within 5%, which is better than existing motion simulation results of driving mechanism.

Dynamic analysis and coupling control of underactuated flight vehicles with single moving mass

Three-channel attitude motion of an underactuated flight vehicle with laterally configured single moving mass is investigated. Of particular interest are three interrelated issues, first, the discussion of longitudinal static stability and trim angle-of-attack considering the lack of active control input in the pitch channel, second, the problem of channel cross coupling and moving mass inertial coupling, third, the coupling control using the single moving mass offset to achieve command roll angle tracking and side slip angle stabilization for the underactuated system. Nonlinear dynamic analysis indicates that the longitudinal static stability and the trim angle-of-attack are determined by the installation position and the mass ratio of the moving mass, interestingly, installing the moving mass at the center-of-mass of the vehicle body not only makes the trim angle-of-attack insensitive to flight conditions and the mass ratio, but also can ensure the longitudinal static stability over a large range of the mass ratios. Moreover, analysis of three-channel coupling dynamics reveals that the entire system may experience oscillation even divergence when initial disturbance of side slip angle and frequent offset of the moving mass exist. Therefore, an improved underactuated active disturbance rejection controller is proposed to deal with the roll-yaw coupling control problem, and the stability of which is analyzed, additionally, the multiple controller parameters are optimized based on the particle swarm optimization algorithm. Closed-loop simulation results in different cases prove the effectiveness and robustness of the designed controller. The proposed control scheme sufficiently utilizes the control capability of the single moving mass to enhance the anti-disturbance ability of the flight vehicle system, which permits the economic benefits and application prospects.

Decoupled Average Current Control of Coupled Inductor Single-Input Dual-Output Buck Converter

Multiple-output dc–dc converters are compact and cost effective as compared to multiple parallel dc–dc converters. This article focuses on a coupled-inductor single-input dual-output (CI-SIDO) buck converter. For the CI-SIDO converter, achieving independent regulation of output voltages and maintaining good dynamic performance are difficult due to cross-regulation and cross-coupling problems. In addition, tuning of controller parameters is challenging. Thus, this article proposes a decoupled average current control (ACC) to suppress cross-coupling and cross-regulation in CI-SIDO buck. It also demonstrates the method of decoupling of inductor currents and the stability issue that exists in ACC of CI-SIDO buck. The analysis shows that decoupling of inductor currents makes the design of controllers independent and simplifies the closed-loop transfer functions. Based on the conditions of decoupling and stability, a systematic design procedure for a Type-II compensator is developed. The proposed control method is compared with the voltage-mode control by using MATLAB/Simulink results. The comparison shows that the proposed ACC exhibits better dynamic performance. Finally, the proposed method is validated using experimental results.

An Accurate Discrete Current Controller for High-Speed PMSMs/Gs in Flywheel Applications

High-speed Permanent-Magnet Synchronous Motors/Generators (PMSMs/Gs) in a Flywheel Energy Storage System (FESS) are faced with high cross-coupling voltages and low switching-to-fundamental frequency ratios. High cross-coupling voltages between d-q axis current loops lead to transient current errors, which is more serious at lower switching-to-fundamental-frequency ratios. If the delays are not properly considered during the current controller design in a digital control system, the low switching-to-fundamental-frequency ratios may result in oscillatory or unstable responses. In this study, an accurate discrete current controller for high-speed PMSMs/Gs is proposed based on an accurate discrete model that takes the phase and magnitude errors generated during the sampling period into consideration, and an Extended State Observer (ESO) is applied to estimate and compensate the back EMF error. The cross-coupling problem is well settled, and the current loop dynamic at lower switching-to-fundamental frequency ratios is improved. Finally, the proposed discrete controller is validated on a 12,000 rpm PMSM/G prototype.

The cross-coupling problem caused by the structure of a combined radial-axial magnetic bearing for DC motors

Different from separated magnetic bearing units, combined radial-axial magnetic bearing (CRAMB) has cross coupling problem caused by structure itself. This paper focuses on the study of cross coupling problem for a CRAMB caused by structure itself. A

Fault-tolerant measurement mechanism research on pre-tightened four-point supported piezoelectric six-dimensional force/torque sensor

High-precision and fault-tolerant six-dimensional force/torque sensor is one of the core components of intelligent robots for force feedback perception. This paper is aiming at the fault-tolerant measurement mechanism research on piezoelectric six-dimensional force/torque sensors with four-point support structure. Based on principle of leverage and deformation consistent, the fault-tolerant measurement mechanism of the pre-tightened four-point supported piezoelectric six-dimensional force/torque sensor is revealed. The mapping mathematical models of spatial six-dimensional force and four-fulcrum quartz crystal group detection signal for the sensor without signal fault and with signal fault are constructed respectively. The static calibration system of the sensor is built to realize the fault-tolerant static calibration experiment of the four-point supported piezoelectric six-dimensional force/torque sensor prototype under unidirectional loading without signal fault and with signal fault. In order to improve the measurement precision of six-dimensional force/torque sensor for robot, a decoupling method based on Genetic Algorithm to optimize Back Propagation algorithm (GABP) for piezoelectric six-dimensional force/torque sensor is adopted to solve the nonlinear cross coupling problem of multiple-input and multiple-output. Through Maltlab software, the test data are analyzed and calculated, and the percentage coupling error matrix of the sensor is calculated. The percentage coupling error is different when the sensor is fault-free and the fault-free measurement model is different. When the sensor is fault-free, the linearity of the sensor is the best and the maximum coupling error is less than 1.5%. When the sensor has any branch fault, the overall performance of the sensor is relatively weakened and the maximum coupling error increases. When the sensor has two branch faults, the linearity of the sensor is the worst. It cannot satisfy the requirement of accurate measurement. The research content is of great significance to the development and practicality of fault-tolerant multi-point supported piezoelectric six-dimensional force/torque sensor.

Research on the optimal dispatch of wind power consumption based on combined heat and power with thermal energy storage

In this paper, a hierarchical scheduling framework is proposed to dispatch electricity and thermal in CHP system with thermal energy storage for the consumption of wind power. An optimization mathematical model is proposed to demonstrate the characteristics of the whole system. The modified PSO algorithm is used to solve the coordinated dispatching problem. The traditional way of working between electricity and thermal is independent while the proposed mathematical model combined electricity and thermal, it’s more accurate to take the relationship between electricity and thermal into consideration. This model has good performance in solving the cross coupling problem. The simulation results indicate that the proposed optimization mathematical model has good dispatching performance on reducing coal consumption. The most important contribution of this paper are accelerating the consumption of wind power in Northern China and saving coal consumption, which can save plenty of money and prevent air pollution. Further work will be reflected in the demonstration project.

Two-axis gimbal platform controller design in finite time application occasions: LMI approach

In this paper, a controller design approach based on LMI optimization method is proposed for the two-axis gimbal platform in finite time application. This method is based on the linear parameter varying (LPV) model of the two-axis gimbal platform, considering the cross-coupling problem between the pitch and yaw channel. Firstly, the dynamic equation of the two-axis gimbal platform is analyzed and its LPV model is obtained. Then, the sufficient conditions which can ensure the LPV system is finite time bounded(FTB) are introduced, and the controller is designed accordingly. Finally, the performance of the platform with finite time controller and PI controller is analyzed qualitatively. The results show that the proposed controller can guarantee the tracking accuracy in finite time and effectively suppress the coupling interference between the pitch and yaw channel.

Modeling and Analysis of Coupling Performance of Dynamic Stiffness Models for a Novel Combined Radial-Axial Hybrid Magnetic Bearing

The combined radial-axial magnetic bearing (CRAMB) with permanent magnet creating bias flux can reduce the size, cost, and mass and save energy of the magnetic bearing. The CRAMB have three-degree-of-freedom control ability, so its structure and magnetic circuits are more complicated compared to those of the axial magnetic bearing (AMB) or radial magnetic bearing (RMB). And the eddy currents have a fundamental impact on the dynamic performance of the CRAMB. The dynamic stiffness model and its cross coupling problems between different degrees of freedom affected for the CRAMB are proposed in this paper. The dynamic current stiffness and the dynamic displacement stiffness models of the CRAMB are deduced by using the method of equivalent magnetic circuit including eddy current effect, but the dynamic current stiffness of the RMB unit is approximately equal to its static current stiffness. The analytical results of an example show that the bandwidth of the dynamic current stiffness of the AMB unit and the dynamic displacement stiffness of the CRAMB is affected by the time-varying control currents or air gap, respectively. And the dynamic current stiffness and the dynamic displacement stiffness between the AMB unit and the RMB unit are decoupled due to few coupling coefficients.

Evolutionary neural networks and DNA computing algorithms for dual-axis motion control

A new method is proposed to deal with the dual-axis control of a multi-variables system with two induction motors. Investigation of resolving the cross-coupling problem of dual-axis platform is addressed by a neural net-based decoupling compensator and a sufficient condition ensuring closed-loop stability is derived. An evolutionary algorithm processing the universal seeking capability is proposed for finding the optimal connecting weights of the neural decoupling compensator and the gains of PID controllers. Extensive numerical studies verify the performance and applicability of the proposed design under a variety of operating conditions.

A Solution to the 2-Pyridyl Organometallic Cross-Coupling Problem: Regioselective Catalytic Direct Arylation of Pyridine N-Oxides

Direct arylation reactions of pyridine N-oxides occur in excellent yield with complete selectivity for the 2-position with a wide range of aryl bromides. This reactivity permits the use of inexpensive, commercially available, and bench-stable pyridine N-oxides as replacements for problematic 2-metallapyridines in palladium-catalyzed cross-coupling reactions.

Analysis of Capacitive and Inductive Coupling inside Hybrid Integrated Power Electronic Module

Electromagnetic compatibility has to be given enough attention in the design of hybrid Integrated Power Electronic Module (IPEM) due to the sharply decreased distances between power devices and the control/driving circuits as compared to such distances for conventional power electronic equipment built with discrete devices. The high dν/dt, di/dt and high frequency parasitic ringing emanating from the switching circuit can cause serious EMI within the control/driving circuit due to cross-coupling. This paper analyzes the capacitive and inductive cross-coupling problems inside an IPEM. Finite Element Method (FEM) is used to extract the mutual capacitances between the metal bars in the model. Then the influence of dν/dt can be estimated. The high frequency circulating current in the bridge circuits is also investigated since it causes magnetic interference due to mutual inductance coupling. The mutual inductance is calculated with the simplified Partial Element Equivalent Circuit (PEEC) approach and image method. The experiment validates the effectiveness of this evaluation. In the end, the electromagnetic shielding is discussed.

Atomic force microscope with improved scan accuracy, scan speed, and optical vision

We have developed a new atomic force microscope (AFM), with a z scanner independent of the xy scanner. Unlike conventional AFM systems, our xy scanner moves only the sample in the xy plane, while the z scanner controls the AFM probe along the z axis. The xy scanner is a single module parallel-kinematics flexure stage that guarantees high orthogonality and minimum out-of-plane motion. The z scanner is a one-dimensional flexure stage with negligible out-of-axis motion. Separating the z scanner from the xy scanner practically eliminates the x–z cross coupling problem inherent in conventional AFMs. Furthermore, the z servo response is no longer limited by the xy scanner characteristics, allowing us to make full use of our high performance z scanner. Our system uses the laser beam bounce detection method, and only the cantilever and the photodetector are mounted on the z scanner to realize a lightweight probing unit. We have devised a unique design such that the photodetector signal measures only the cantilever deflection and not the z-scanner motion. Our new AFM provides fast z servo response and high scan accuracy.

Cross-coupling between open-ended coaxial radiators

A solution is given for the problem of cross-coupling between a pair of open-ended coaxial cables, excited in the TEM mode and terminating in a ground plane. New integral and series representations are derived for the mutual admittance of the TEM modes, and useful low frequency and far-field approximations are found. Computed results are given for several examples of cables radiating into lossless dielectric media. Measured data is given for a pair of cables radiating in air and computed results agree very well over a wide frequency range. These results show the coupling coefficient increasing initially with frequency, in contrast to waveguide radiators where the coupling coefficient mainly decreases with frequency; the levels attained are significant, particularly above the cut-off of the TE/sub 11/ mode. Cross-coupling is shown to be greatest when the inner-to-outer conductor ratio is about 0.53. The solution should be useful for analysing arrays of coaxial horns and obtaining the permittivity and permeability of materials.

Migration/inversion for transversely isotropic elastic media

SUMMARY Seismic migration and inversion are closely related processes for obtaining images of the subsurface. Both techniques attempt to infer petrophysical and structural parameters from seismic data, and both are driven by an underlying mathematical model for wave propagation in the earth. In this sense, migration can be regarded as the first step in’ a general linearized-inversion scheme; we adopt this viewpoint here in formulating a joint migration/inversion method for anisotropic elastic media. Our derivation is based on the distorted-wave Born approximation, where approximate Green’s functions for the background medium are determined using asymptotic ray theory. We also make use of a stationary-phase correction to account for out-of-plane scattering in a 2-D earth model. The inversion is cast as a discrete, generalized l2 optimization problem, which we regularize using a priori model variances. An approximate solution is obtained in one or more iterations using a quasi-Newton technique. Our implementation is tailored for weakly anisotropic elastic media possessing transversely isotropic (TI) symmetry, and so is well suited for investigations of earth models characterized by a singe set of parallel fractures or periodic thin layering. Several TI model parametrization schemes are evaluated for a vertical-incidence narrow-aperture recording configuration. By applying singular-value decomposition to the approximate Hessian operator used in the inversion, we find that when the symmetry axis of the medium is vertically oriented the condition number is minimized by choosing vertical impedance parameters, density and Thomsen’s (1986) anisotropy parameters. Elastic stiffnesses and density may be a better parametrization choice if the symmetry axis is either horizontal or unknown. The small effective rank (2-3) of the Hessian in our narrow-aperture tests implies that migration inversion (without a priori constraints) of surface-reflection data may be inadequate to fully characterize a TI medium, which would require six parameters. However, this result does not in itself justify the use of simpler isotropic inversion schemes, since the principal eigenvectors determined here represent a blend of ‘isotropic’ and ‘anisotropic’ information about the earth. A suite of point-diffractor tests shows that individual perturbation amplitudes recovered in the inversion are smaller, but cover a larger region of the image, than those used in the original model, consistent with the band-limited nature of the input signal. Parameter cross-coupling problems affect the inversion results for all parameters, but are more prominent in the inversion images for anisotropy parameters. In our tests, the linearized-inversion results converge to a local minimum after three iterations, and the scatterer distributions in the inversion images are essentially fixed after a single iteration.

Cross Coupling in High Speed Digital Systems

It is now well understood that the design of the signal distribution systems of high speed digital machines is as important as the design of the circuits themselves. The integrated circuit technology of today is pressing back the frontiers of speed and simultaneously providing more circuitry per unit area. A signal distribution system with suitable electrical characteristics for these high speed circuits and which is physically compatible with the circuit size is sorely needed. A candidate for such an application is the multilayer board. This paper considers the problem of cross coupling from line to line in multilayer when the excitation function is a fast rise time voltage pulse. Curves and equations are given which enable the design of a system with a given system characteristic impedance and a specified cross-coupling ratio. Experimentally obtained wave shapes from single ground plane transmission lines are given, and a practical numerical example is worked.

A rate gyroscope based on interaction of sonic waves

A new form of rate gyroscope based on interaction between standing sonic waves in solid media is described. One form of the device, using a solid, ring-shaped medium, is analyzed in order to establish the relationship between the modes of the two waves that must exist to produce sensitivity to angular rate. In addition, the analysis establishes estimates for the angular-rate sensitivity in terms of the basic instrument parameters. The theoretical feasibility of the proposed instrument has been confirmed by experiments conducted on a simple laboratory model. The results indicate that strain-induced and mass unbalance cross-coupling between the driving and sensing waves can produce uncertainty in the instrument output signal. These unwanted cross-coupling effects are the practical limitation on the instrument performance at the present time. Methods for their reduction and cancellation are discussed for the ring-shaped transducer. The problem of unwanted cross-coupling seems to be present in sonic gyroscopes, in general, and is not unique to solid media alone. In particular, some preliminary experiments with fluid devices show them to have similar cross-coupling problems. In conclusion, the major advantages over conventional rate gyroscopes of instruments based on interaction of sonic waves appear to be: low power consumption, long life, (potentially) high reliability, ruggedness, and low cost. These advantages must be weighed against the primary disadvantage of the lower precision that is available at the present state of the development.