Decoupling Performance Research Articles

Design and Analysis of a Novel Piezo-Actuated XYθz Micropositioning Mechanism with Large Travel and Kinematic Decoupling

A novel hybrid-type XYθz micropositioning mechanism driven by piezoelectric actuators is proposed in this paper. With the purpose of realizing a large motion range and 3-DoF independent motion within a compact size, the mechanism is designed using a symmetric translational part and a rotational part that are linked serially. The translational part is based on a double-amplification mechanism incorporating a guidance mechanism for decoupling; the rotational part uses a nonuniform beam with an amplification mechanism to translate the linear output displacement of piezoelectric actuators into a large rotational angle around the Z axis. To precisely predict the output displacements and implement dimensional design, electromechanical models of the translational mechanism and rotational mechanism are established. According to the theoretical model, dimensional optimization is carried out to achieve large motion ranges within a compact size. A prototype of the proposed mechanism is fabricated according to the optimized results, and the performance of the mechanism is validated by experiment. The experimental results show that translational travel in X and Y directions of 204.2 μm and 212.8 μm, respectively, and travel of 8.7 mrad in the θz direction can be realized in a small size of 106 mm × 106 mm × 23 mm. And, the output coupling was evaluated to be below 3%, indicating an excellent decoupling performance.

Simulation of the influence of imperfections on dynamical decoupling of a superconducting qubit**Project supported by the National Basic Research Program of China (Grant No. 2011CBA00304), the National Natural Science Foundation of China (Grant No. 60836001), and the Research Fund from Beijing Innovation Center for Future Chip.

Dynamical decoupling is widely used in many quantum computing systems to combat decoherence. In a practical superconducting quantum system, imperfections can plague decoupling performance. In this work, imperfections in a superconducting qubit and its control system are modeled via modified Hamiltonian and collapse operator. A master equation simulation is carried out on the qubit under 1/f environment noise spectrum. The average dephasing rate of qubit is extracted to characterize the impact of different imperfections on the decoupling from dephasing. We find that the precision of pulse position, on–off ratio, and filtering effect are most critical. Bounded pulses have weaker impact, while variation in pulse width and qubit relaxation are insignificant. Consequently, alternative decoupling protocols, jitter mitigation, cascaded mixers, and pulse shaping can be conducive to the performance of decoupling. This work may assist the analysis and optimization of dynamical decoupling on noisy superconducting quantum systems.

Double-layer Dynamic Decoupling Control System for the Yaw Stability of Four Wheel Steering Vehicle

The four-wheel steering (4WS) is an efficient method to improve the manoeuvrability of electric vehicle with the tendency of understeer, by providing the sufficient steering angles. Because of the various kinds of driving environments, the inner coupling between the active front and rear wheels of the 4WS vehicle is a challenging problem, which usually results in unstable yaw stability of the vehicle. In order to solve this coupling problem, this paper presents a double-layer dynamic decoupling control system (DDDCS), which consists of an upper part-dynamic decoupling unit (DDU) and a lower part-steering control unit (SCU). The DDU is presented to solve the dynamic coupling problem between the active front and rear wheels, and separately establishes two decoupled models by the diagonal decoupling method. The SCU is designed to obtain the decoupled control signals by the model predictive controller, then, the yaw stability of 4WS vehicle can be guaranteed. The results of the simulation show that the proposed DDDCS has good decoupling performance and stable yaw performance for 4WS vehicle.

A Compact LTCC Decoupling-Network Based on Coupled-Resonator for Antenna Interference Suppression of Adjacent Frequency Bands

A low-temperature co-fired ceramic (LTCC) coupled resonator decoupling network (CRDN) with asymmetric input/output (I/O) couplings for suppressing interference between two adjacent frequency bands is proposed in this paper. Based on LTCC multilayer technology, a second-order CRDN module is realized by strongly coupled semi-lumped LC resonators in a very small volume of 3.2 mm $\times2.5$ mm $\times1.2$ mm. A wide range of mutual admittance and different self-admittances of the CRDN can be realized by adjusting the asymmetric I/O couplings. Thus, a satisfactory decoupling performance covering two contiguous bands, as well as good matching in each band, can be realized without additional matching networks. To prove the concept, two planar inverted-F antennas working in TD-LTE and Wi-Fi frequency bands, along with the corresponding decoupling network, are designed, fabricated, and tested. The measured results have demonstrated that more than 15-dB isolation improvement can be achieved within the two operating bands, showing the feasibility of this ”one-fit-all” integrated solution. More importantly, the design methodology and circuit topology presented in this paper are general and can be applied to practical multi-input multi-output system applications.

Design and testing of a novel 2-DOF compound constant-force parallel gripper

This paper presents the design and testing of a novel flexure-based compliant parallel gripper with compound constant-force mechanism. One uniqueness of the microgripper lies in that it achieves two-degree-of-freedom (2-DOF) independent constant-force parallel grasping operations. In each direction, the grasping is executed along with active and passive constant-force properties. The passive constant-force property eliminates the use of force control while the active constant-force enlarges the grasping range by reducing the required driving force. Besides, the passive constant-force property can protect the grasped object from overloading. The parallel-kinematic flexure mechanism design enables nearly decoupled operations in 2-DOF manipulation. Analytical modeling of the microgripper mechanism is carried out based on pseudo-rigid-body method and elliptic integral approach, which is verified by conducting simulation study with nonlinear finite-element analysis (FEA). Parametric study is conducted to investigate the influence of dominant design variable on the microgripper performance. To demonstrate the performance of the gripper, a prototype is fabricated by 3D printer. Experimental results reveal that the devised microgripper owns a good decoupling performance and constant-force property in parallel grasping operation.

Optimal design of a piezo-actuated 2-DOF millimeter-range monolithic flexure mechanism with a pseudo-static model

Abstract Flexure-based displacement amplifiers are frequently used to magnify the small stroke of piezoelectric actuators. In this paper, a hybrid rhombus-lever multistage displacement amplifier with an improved boundary constraint is proposed to develop a parallel millimeter-range XY monolithic mechanism while retaining a relatively high dynamic frequency. A concise pseudo-static model developed by the authors is utilized to analyze the kinetostatic and dynamic performances of the designed flexure mechanism and then the geometric parameters are optimized in terms of both kinetostatics and dynamics. Different from the previous Lagrange-based dynamic methods for compliant mechanisms, cumbersome calculations of the kinetic and elastic energies as well as adopting Lagrange’s equation are all avoided. With the proposed pseudo-static model, the kinetostatics and dynamics of the flexure mechanism can be analyzed concurrently in a programmed statics-similar way, suggesting its superiority for fast performance prediction and parameter optimization during the early stage of design. Finally, a prototype of the XY monolithic mechanism is manufactured and experimentally tested for evaluating its performances. Experimental results show that the designed flexure mechanism has a motion range in excess of 1.2 mm × 1.2 mm with a resonance frequency of 128 Hz. The cross-coupling error is measured to be less than 2%, indicating an acceptable decoupling performance.

Static Decoupling Performance Analysis and Design of Bionic Elbow Joint

The static decoupling performance is closely related to the efficiency of the bionic elbow joint mechanism. The bionic elbow joint has good static decoupling and has high efficiency and carrying capacity. First, the movement structure and characteristics of the elbow joint are analyzed, a kind of bionic elbow joint is proposed, the position inverse solution is deduced, and force Jacobin matrix of the bionic elbow joint is obtained. Second, the static coupling performance evaluation index and the global static coupling performance index are established, the performance atlas are drawn. Thirdly, by use of the Monte Carlo method the structural parameters of the bionic elbow joint are optimized and selected based on the spatial model theory, and a novel the bionic elbow joint is designed based on parameters optimization, and the static decoupling is verified by the simulation experiment of the bionic elbow joint. The analysis results shows the static decoupling performance of the bionic elbow joint is symmetrical, and with the working space of the attitude output angle increases, the static decoupling decreases gradually. Structural parameters and have great influence on the global static decoupling performance. The structural parameters of is 90mm, is 70mm,and is 30mm, the bionic elbow joint has good static decoupling. This paper lays a foundation for further analysis and research of the bionic elbow joint.

Hybrid Fuzzy Decoupling Control for a Precision Maglev Motion System

This paper presents a hybrid fuzzy decoupling control strategy, and its implementation for leveling and positioning a maglev wafer carrier in an integrated circuit (IC) packaging application. The maglev platform possesses micron scale positioning and can carry the wafers with precision motion between workstations. Because the maglev system is open-loop unstable, there are strong nonlinear interactions between electromagnets and the exact nonlinear system model is unknown, it is hard to achieve a good decoupling control performance by using conventional control strategy. Therefore, in this paper, a hybrid fuzzy decoupling control with good decoupling performance is proposed. The decoupling control uses a master–slave structure, which consists of a linear master decoupling control term and a nonlinear slave intelligent compensation term. The master decoupling term decouples the main interactions of the coupled maglev system. Using the decoupled main system as reference, the slave intelligent term compensates the nonlinear interactions. Furthermore, for this control strategy, establishing the exact linear or nonlinear model is not necessary, only an approximated linear model is needed. The experimental results show that the proposed control strategy decouples most of the interactions between the electromagnetic actuators. Experimental comparisons also highlight that the master–slave decoupling control has shorter settling time and smaller steady-state error than a conventional adaptive fuzzy controller and proportional-integral-differential controller.

An optimized BP neural network based on genetic algorithm for static decoupling of a six-axis force/torque sensor

In order to improve the measurement precision of 6-axis force/torque sensor for robot, BP decoupling algorithm optimized by GA (GA-BP algorithm) is proposed in this paper. The weights and thresholds of a BP neural network with 6-10-6 topology are optimized by GA to develop decouple a six-axis force/torque sensor. By comparison with other traditional decoupling algorithm, calculating the pseudo-inverse matrix of calibration and classical BP algorithm, the decoupling results validate the good decoupling performance of GA-BP algorithm and the coupling errors are reduced.

Kinematic Decoupling Analysis and Design of a Biomimetic Robotic Elbow Joint.

The research of a biomimetic robotic manipulator is based on the flexible characteristics of the human upper limb joint, and a biomimetic robotic elbow joint plays a very significant role in the kinematic control of the biomimetic robotic manipulator. Most robotic elbow joints encountered today have a common disadvantage of bad neutrality, low rotational capability, and poor biomimetics. To overcome some difficulties, this paper presents a novel biomimetic robotic elbow joint. The structural model of the elbow joint is described, and the position equation is solved. Secondly, the kinematic equation of the elbow joint is established, the kinematic decoupling performance evaluation index of the elbow joint is defined, the kinematic decoupling characteristics of the elbow joint are analyzed, and the kinematic decoupling performance map in the workspace is drawn. Thirdly, using the spatial model theory, the structural parameters of the elbow joint are optimized, the structural parameters are selected by the Monte Carlo method, and the novel biomimetic robotic elbow joint is designed. The analysis results showing the kinematic decoupling performance of the elbow joint are symmetrical and the kinematic decoupling performance decreases with the increase of the angle, and there is a good kinematic decoupling in the workspace of about 35% in the vicinity of the initial position. When the structural parameters of the elbow joint are Re1 = 90 mm, Re2 = 70 mm, and Re3 = 30 mm, the elbow joint has a very good kinematic decoupling. This paper can lay a foundation for further analysis and research of the biomimetic robotic elbow joint.

DQ Current Control of Voltage Source Converters With a Decoupling Method Based on Preprocessed Reference Current Feed-forward

Axes cross-coupling in dq-frame will deteriorate the current control performance, especially for applications with low switching/sampling frequency. Decoupling methods based on inductor current state feedback and complex vector proportional-integrator controllers are usually performed to solve this problem. In this paper, an alternative decoupling method based on preprocessed reference current feed-forward is proposed, which can provide excellent decoupling performance even with considerable control delay. The current control of grid-connected voltage source converters is analyzed with complex-coefficient transfer functions. It is revealed that the decoupling performance of current control schemes is closely related to the symmetry of current closed-loop transfer function bode diagrams. The current closed-loop transfer function should show a standard symmetrical bode diagram with respect to 0 Hz, if axes cross-coupling is well decoupled. A quantitative index named cross-coupling function is then proposed to analyze and comprehensively compare the decoupling performance of the proposed method and existing ones in terms of the influence of the control delay, inductance estimation error, grid frequency deviation, and voltage disturbance. Experimental tests are implemented to validate the performance of the proposed method and comparison results.

Active Disturbance Rejection Control of Bearingless Induction Motor

To improve the dynamic control performance of bearingless induction motor (BLIM), the active disturbance rejection control strategy is presented. Based on the rotor flux orientation inverse decoupling strategy, an active disturbances rejection control (ADRC) system is designed to replace the PID control system. The cross coupling items, motor parameter change and load are all regarded as disturbance. The total disturbance is estimated by an extended state observer (ESO), and compensated by a nonlinear state error feedback (NLSEF) controller. Simulation results show that the system has better dynamic decoupling performance and strong robustness.

Systematic Design Method and Experimental Validation of a 2-DOF Compliant Parallel Mechanism with Excellent Input and Output Decoupling Performances

The output and input coupling characteristics of the compliant parallel mechanism (CPM) bring difficulty in the motion control and challenge its high performance and operational safety. This paper presents a systematic design method for a 2-degrees-of-freedom (DOFs) CPM with excellent decoupling performance. A symmetric kinematic structure can guarantee a CPM with a complete output decoupling characteristic; input coupling is reduced by resorting to a flexure-based decoupler. This work discusses the stiffness design requirement of the decoupler and proposes a compound flexure hinge as its basic structure. Analytical methods have been derived to assess the mechanical performances of the CPM in terms of input and output stiffness, motion stroke, input coupling degree, and natural frequency. The CPM’s geometric parameters were optimized to minimize the input coupling while ensuring key performance indicators at the same time. The optimized CPM’s performances were then evaluated by using a finite element analysis. Finally, a prototype was constructed and experimental validations were carried out to test the performance of the CPM and verify the effectiveness of the design method. The design procedure proposed in this paper is systematic and can be extended to design the CPMs with other types of motion.

Electron Decoupling with Dynamic Nuclear Polarization in Rotating Solids.

Dynamic nuclear polarization (DNP) can enhance NMR sensitivity by orders of magnitude by transferring spin polarization from electron paramagnetic resonance (EPR) to NMR. However, paramagnetic DNP polarizing agents can have deleterious effects on NMR signals. Electron spin decoupling can mitigate these paramagnetic relaxation effects. We demonstrate electron decoupling experiments in conjunction with DNP and magic-angle-spinning NMR spectroscopy. Following a DNP and spin diffusion period, the microwave irradiation frequency is quickly tuned on-resonance with electrons on the DNP polarizing agent. The electron decoupling performance shows a strong dependence on the microwave frequency and DNP polarization time. Microwave frequency sweeps through the EPR line shape are shown as a time domain strategy to significantly improve electron decoupling. For 13C spins on biomolecules frozen in a glassy matrix, electron decoupling reduces the line widths by 11% (47 Hz) and increases the intensity by 14%.

Design and Development of a Three-Component Force Sensor for Milling Process Monitoring.

A strain-type three-component table dynamometer is presented in this paper, which reduces output errors produced by cutting forces imposed on the different milling positions of a workpiece. A sensor structure with eight parallel elastic beams is proposed, and sensitive regions and Wheastone measuring circuits are also designed in consideration of eliminating the influences of the eccentric forces. To evaluate the sensor decoupling performance, both of the static calibration and dynamic milling test were implemented in different positions of the workpiece. Static experiment results indicate that the maximal deviation between the measured forces and the standard inputs is 4.58%. Milling tests demonstrate that with same machining parameters, the differences of the measured forces between different milling positions derived by the developed sensor are no larger than 6.29%. In addition, the natural frequencies of the dynamometer are kept higher than 2585.5 Hz. All the measuring results show that as a strain-type dynamometer, the developed force sensor has an improved eccentric decoupling accuracy with natural frequencies not much decreased, which owns application potential in milling process monitoring.

Design, Development, and Application of a Compact Flexure-Based Decoupler With High Motion Transmission Efficiency and Excellent Input Decoupling Performance

Here, we present the design, development, and application of a compact flexure-based decoupler, which is commonly utilized in compliant parallel mechanisms (CPMs) to transmit the motion of an actuator and protect the actuator from suffering transverse loads. The kinematic structure selection of the decoupler is first introduced. Then, several specific design requirements are proposed to guarantee its key performances. On this basis, the detailed structures of each part of the decoupler are discussed and the geometric parameters are optimized to obtain an ideal decoupler. The performances of the optimized decoupler are verified with finite element analysis (FEA). According to the optimized results, a prototype is fabricated and experimental tests on the input axial stiffness and natural frequency are presented. Both FEA and the experimental results demonstrate the excellent performance of the decoupler. Finally, the proposed decoupler is applied in the development of a 2-DOF CPM. The definition and calculation expression for the input coupling degree (ICD) of the CPM are given, and its geometric parameters are optimized to reduce the ICD. A prototype of the CPM is fabricated for the performance evaluation. A new method is proposed to test the ICD of the CPM by detecting the variations of axial forces along the two axes. Contouring properties of 2-D trajectories are also provided. The experimental results not only demonstrate the excellent decoupling performance of the CPM but also verify the effectiveness of the adoption of the decoupler.

Rationalising Heteronuclear Decoupling in Refocussing Applications of Solid‐State NMR Spectroscopy

Factors affecting the performance of 1H heteronuclear decoupling sequences for magic‐angle spinning (MAS) NMR spectroscopy of organic solids are explored, as observed by time constants for the decay of nuclear magnetisation under a spin‐echo (T2' ). By using a common protocol over a wide range of experimental conditions, including very high magnetic fields and very high radio‐frequency (RF) nutation rates, decoupling performance is observed to degrade consistently with increasing magnetic field. Inhomogeneity of the RF field is found to have a significant impact on T2' values, with differences of about 20 % observed between probes with different coil geometries. Increasing RF nutation rates dramatically improve robustness with respect to RF offset, but the performance of phase‐modulated sequences degrades at the very high nutation rates achievable in microcoils as a result of RF transients. The insights gained provide better understanding of the factors limiting decoupling performance under different conditions, and the high values of T2' observed (which generally exceed previous literature values) provide reference points for experiments involving spin magnetisation refocussing, such as 2D correlation spectra and measuring small spin couplings.

Fifty shades of green: Revisiting decoupling by economic sectors and air pollutants

Using a consistent dataset for eighteen EU countries, six economic sectors, and six pollution indicators, we analyze decoupling of production–based emissions from GDP growth from 1995 to 2008. Computing decoupling factors as defined by the OECD (2002), we find that in almost all sectors and by almost all pollutants the median EU country had at least some decoupling. However, considerable heterogeneity in its magnitude can be observed across countries, sectors, and pollutants. For most pollutants and sectors, median decoupling performance improved from 2001–2008 compared to 1995–2001, while between–country disparities increased simultaneously. In a second step, we investigate country–level changes in decoupling states between the two sub–periods based on Tapio (2005). We find high diversity across countries and over time. To explain these differences across countries and sectors, we assess the impact of environmental policy stringency, and find tentative evidence that stricter policy encourages decoupling, however the effects are small and imprecise, differ by economic sector and pollutant, and take several years to materialize.

Decoupling Principle Analysis and Development of a Parallel Three-Dimensional Force Sensor.

In the development of the multi-dimensional force sensor, dimension coupling is the ubiquitous factor restricting the improvement of the measurement accuracy. To effectively reduce the influence of dimension coupling on the parallel multi-dimensional force sensor, a novel parallel three-dimensional force sensor is proposed using a mechanical decoupling principle, and the influence of the friction on dimension coupling is effectively reduced by making the friction rolling instead of sliding friction. In this paper, the mathematical model is established by combining with the structure model of the parallel three-dimensional force sensor, and the modeling and analysis of mechanical decoupling are carried out. The coupling degree (ε) of the designed sensor is defined and calculated, and the calculation results show that the mechanical decoupling parallel structure of the sensor possesses good decoupling performance. A prototype of the parallel three-dimensional force sensor was developed, and FEM analysis was carried out. The load calibration and data acquisition experiment system are built, and then calibration experiments were done. According to the calibration experiments, the measurement accuracy is less than 2.86% and the coupling accuracy is less than 3.02%. The experimental results show that the sensor system possesses high measuring accuracy, which provides a basis for the applied research of the parallel multi-dimensional force sensor.

Radial position control of a magnetically suspended rotor system in a direct-driven spindle using inverse system scheme

Direct-driven spindles have no mechanical transmission trains and gears, and are the key actuators for computerized numerical control machine tools. These magnetically suspended rotor systems are required to provide fast response and high precision. However, these systems are non-linear and strongly coupled. The traditional proportional, integral, derivative (PID) control method has been widely used for such systems owing to its relative simple realization. However, the tracking, disturbance rejection and robustness properties of the controlled plant may not be satisfied. To solve these problems, this paper presents a decoupling control strategy based on an inverse system scheme and combines it with the internal model control method to guarantee system robustness to the parameter uncertainty and external disturbance. By introducing an inversion of the magnetically suspended rotor system into the original system, a new pseudolinear system is developed. It can be shown that this addition effectively eliminates the influence of the unmodelled dynamics, and improve the accuracy and robustness of the whole system. The simulation and experimental results show that when compared with the traditional control scheme, the proposed control scheme provides good decoupling and robustness performance for the magnetically suspended rotor system in different operating conditions.