Passive Compensation Research Articles

Passive Resistor Temperature Compensation for a High-Temperature Piezoresistive Pressure Sensor.

The main limitation of high-temperature piezoresistive pressure sensors is the variation of output voltage with operating temperature, which seriously reduces their measurement accuracy. This paper presents a passive resistor temperature compensation technique whose parameters are calculated using differential equations. Unlike traditional experiential arithmetic, the differential equations are independent of the parameter deviation among the piezoresistors of the microelectromechanical pressure sensor and the residual stress caused by the fabrication process or a mismatch in the thermal expansion coefficients. The differential equations are solved using calibration data from uncompensated high-temperature piezoresistive pressure sensors. Tests conducted on the calibrated equipment at various temperatures and pressures show that the passive resistor temperature compensation produces a remarkable effect. Additionally, a high-temperature signal-conditioning circuit is used to improve the output sensitivity of the sensor, which can be reduced by the temperature compensation. Compared to traditional experiential arithmetic, the proposed passive resistor temperature compensation technique exhibits less temperature drift and is expected to be highly applicable for pressure measurements in harsh environments with large temperature variations.

Semi-active reaction force compensation for a linear motor motion stage

Acceleration and deceleration of a mover excite unwanted vibration to the system base, causing a significant reduction of life and productivity to manufacturing equipment. The system base vibration of a linear motor motion stage can be reduced with a passive reaction force compensation (RFC) mechanism. However, the passive RFC mechanism cannot provide the capability to adjust its stiffness and damping coefficient in real-time. Therefore, resonance may occur if the frequency of the passive RFC mechanism accidentally matches with the frequency components of applied motion profile. This paper presents a semi-active RFC method for a linear motor motion stage using an additional fixed coil. The semi-active RFC mechanism can adjust damping coefficient by changing the resistor load or switching the period of the additional fixed coil. The semi-active RFC mechanism also does not require an additional amplifier or control axis. Mathematical analysis of the semi-active RFC is presented to demonstrate the adjustable damping capability by changing the load resistor. Finally, the effectiveness of the proposed semi-active RFC mechanism is verified via simulations and experiments.

Eddy current damper for passive reaction force compensation of a linear motor motion stage

This article presents an eddy current damper of a passive reaction force compensation mechanism for a linear motor motion stage. The reaction force compensation mechanism with a movable magnet track and eddy current damper resolves problems with the existing spring-based reaction force compensation mechanism such as resonance, design freedom, and difficulty of assembly and manufacturing. A simplified mathematical model of the eddy current damper is derived considering the sinusoidal magnetic flux density distribution and effective width of the eddy current damper, which shows important design factors of the eddy current damper–based reaction force compensation mechanism. Then, force of the eddy current damper according to the constant speed motion of the magnet track is investigated using multi-physical finite element analysis and is verified by experiments. Finally, the passive reaction force compensation with movable magnet track and eddy current damper is identified by experiments, and the finite element analysis of the eddy current damper is verified with free and forced vibration responses.

Passive and active gravity compensation of horizontally-mounted 3-RPS parallel kinematic machine

Taking a horizontally-mounted 3-RPS parallel kinematic machine (PKM) as an example, this paper investigates passive and active gravity compensation strategies for improving PKM precision. Herein, R, P and S denote revolute, actuated prismatic and spherical joint, respectively. Based on inverse position kinematic and force analysis, passive gravity compensation is firstly implemented by three extension springs. Geometric parameters of these springs are optimized by minimizing potential energy fluctuation within a prescribed workspace. Then deformation caused by gravity is adopted to evaluate compensation strategies. The deviations of an end reference point demonstrate that passive gravity compensation is capable of substantially balancing gravity. In order to further eliminate the effect of gravity, active gravity compensation is proposed to adjust spring displacements by several one degree-of-freedom (DoF) translational mechanisms. Deformation of the 3-RPS PKM is directly regarded as the objective function for determining the active translations. Overall, both passive and active gravity compensations are able to improve mechanism precision due to the partial and complete gravity balancing capability, respectively, which makes the 3-RPS PKM suitable for the application of rough and fine machining.

Improved fault ride through strategy for doubly fed induction generator based wind turbines under both symmetrical and asymmetrical grid faults

Due to the latest grid codes, wind turbines (WTs) are required to remain connected to grid under grid faults and supply reactive power into the grid. So, this paper proposes an improved fault ride through (FRT) strategy for doubly fed induction generators (DFIGs) under both symmetrical and asymmetrical grid faults. The proposed strategy is realized through active and passive FRT compensators. The active compensator is performed through control of the rotor- and grid-side converters of DFIGs to limit the stator and rotor over currents and inject reactive power into the grid to support the grid voltage recovery, respectively. The passive compensator is based on a three-phase rotor current limiter (RCL) resistor located in series with the rotor windings. It considerably reduces the rotor and stator overcurrent at the instants of grid faults occurrence and clearance. The proposed strategy decreases the stator and rotor over currents, electromagnetic torque oscillations and DC-link over voltage and also support grid voltage by supplying reactive power into the grid. In this way, the DFIG can fulfill the FRT requirements of the latest grid codes. Simulation studies using MATLAB/SIMULINK are conducted on a 1.5 MW DFIG-based WT to validate the effectiveness of the proposed FRT strategy.

Electronic frequency compensation of AlN-on-Si MEMS reference oscillators

In this paper we report on the design of a frequency compensation system for AlN-on-Si MEMS reference oscillator to replace temperature compensated crystal oscillators (TCXOs) in cellular handsets. A 76.8MHz, 105ppm Temperature Stable, AlN-on-Si MEMS Oscillator is designed to demonstrate the frequency compensation scheme. Double layers of SiO2 are used for passive temperature compensation. The oscillator consumes 850μA, with phase noise of −127dBc/Hz at 1kHz frequency offset. Temperature drift errors and initial frequency offset of ±8000ppm are combined and further tackled electronically. A simple digital compensation circuitry generates a compensation word to a 21-bit MASH 1-1-1 ΔΣ modulator included in LTE fractional N-PLL for frequency compensation. Temperature is sensed using 4.6μA, 11.5 bit temperature to digital converter TDC with resolution of 0.1°C in 100ms conversion time. The paper presents the first AlN-on-Si oscillator platform with ±0.5ppm frequency stability over temperature ranges from −40°C to 85°C. The system runs on 1.8V supply in 32nm CMOS.

Active and passive compensation of APPLE II-introduced multipole errors through beam-based measurement

The effect of an APPLE II-type elliptically polarized undulator (EPU) on the beam dynamics were investigated using active and passive methods. To reduce the tune shift and improve the injection efficiency, dynamic multipole errors were compensated using L-shaped iron shims, which resulted in stable top-up operation for a minimum gap. The skew quadrupole error was compensated using a multipole corrector, which was located downstream of the EPU for minimizing betatron coupling, and it ensured the enhancement of the synchrotron radiation brightness. The investigation methods, a numerical simulation algorithm, a multipole error correction method, and the beam-based measurement results are discussed.

Phase error compensation methods for high-accuracy profile measurement

In a phase-shifting algorithm-based fringe projection profilometry, the nonlinear intensity response, called the gamma effect, of the projector-camera setup is a major source of error in phase retrieval. This paper proposes two novel, accurate approaches to realize both active and passive phase error compensation based on a universal phase error model which is suitable for a arbitrary phase-shifting step. The experimental results on phase error compensation and profile measurement of standard components verified the validity and accuracy of the two proposed approaches which are robust when faced with changeable measurement conditions.

A low-voltage ride-through capability enhancement scheme of doubly fed induction generator based wind plant considering grid faults

This paper presents an improved low-voltage ride-through (LVRT) capability scheme of a grid connected doubly fed induction generator (DFIG) during any type of grid fault. In this context, an effective switching strategy based on computation of rotor current components has been suggested for the proposed passive protection circuits of a rotor side converter (RSC). Simultaneously, the RSC will control the fundamental rotor current within its available capacity for providing reactive power to the faulty grid. The proposed passive protection circuits comprise both stator and rotor side series resistor based passive compensators. The stator passive compensator will only be operated at starting and ending instant of fault to restrict rotor inrush current regardless of the type of fault. On the other hand, the rotor passive compensator is conditionally activated at the time of unbalanced fault to keep the overall rotor current under control. During both types of fault, RSC performs dual functions as partially scaled active compensator cum fractional reactive power generation controlling element. Thus, coordinated operation of passive compensator(s) and RSC will improve the LVRT ability of DFIG based wind power plants under any fault scenario. Various simulations are performed on 1.5 MW DFIG to show the advantage of this proposed control strategy.

SIX BASIC STATES OF POLARIZATION EXPERIMENTAL ANALYSIS FOR MULTIPLE STAGE PASSIVE COMPENSATION ON SINGLE MODE OPTICAL FIBER

We report a statistical approach of analyzing experimental data on three stages of passive compensations of light State of Polarization (SOP) in standard single mode optical fiber. Fidelity of every basic six SOPs which consist of two pairs of linear state of polarization and a pair of circular state of polarization were also analyzed by performing an experiment to measure the Stoke parameter of every state. Experimental results have shown that all six basic SOPs were maintained according to the state of the source at every stage of respective paths. These observations were regardless of different optical fiber length at the second stage of passive compensation. We achieved to ensure that the final destination of SOP will have similar state with its source at fidelity of above 96%.

Improved single-miller passive compensation network for three-stage CMOS OTAs

A compensation technique for low-power three-stage operational transconductance amplifiers is presented in this paper. The compensation network is made up of passive components and entails only one Miller capacitor. Design equations describing the amplifier behavior for different capacitive load conditions are reported along with three design examples for different capacitive loads, namely, 1 nF, 100 and 10 pF. The amplifier exhibits a gain-bandwidth product equal to 2.48, 6.74 and 7.66 MHz in the three cases while dissipating only 150, 150 and 57.5 μW from 2.5 V, respectively. Simulation results are found in good agreement with theoretical analysis and show an improvement in both small-signal and large-signal amplifier performance over many previously reported solutions.

Fiber-optic radio frequency transfer based on passive phase noise compensation with frequency dividing and filtering.

In this Letter, a passive phase noise compensation-based fiber-optic frequency transfer scheme with frequency dividing and filtering is proposed. The probe signal is divided at the remote site and effectively discriminated from the backscattering noises by electrical bandpass filtering at the local site. By combining the bidirectional transmission with the same wavelength on a single fiber, the scheme can reach the maximum bidirectional propagation symmetry and effectively suppress the effect of backscattering at the same time. The proposed scheme is experimentally demonstrated and compared with the scheme with backscattering. The relative frequency stabilities of 3.9×10(-14)/s and 1.2×10(-16)/10(4) s are reached for 40 km transfer, which obviously outperform the scheme with backscattering, especially in terms of short-term stability, and are closed to the floor of the back-to-back experimental system.

Application of an extreme control system to operate the reactive power compensator of an electric locomotive

Efficient use of fuel and energy resources is a high-priority area in the energy development strategy of railway transport up to 2030 adopted by OAO Russian Railways. Currently, ac electric locomotives with power rectifier–inverter transformers make up the majority of the usable fleet, in the range of 0.65 to 0.85. This is a cause of not only significant energy losses in the network of traction energy supply, but also restrictions affecting the speed of the locomotive. The energy characteristics of ac electric locomotives can be imptoved via compensation of the reactive power component. The reactive power compensator consists of series-connected capacitor C and inductance L connected to the secondary winding of the transformer. The LC circuit parameters are calculated for reactive power compensation of an electric locomotive in the nominal operation mode. In this article, a reactive power compensation device for electric locomotive made based on a regulated passive compensator was considered. The management of reactive power compensator is carried out by means of extreme control method. It is shown that the extreme control method for a reactive power compensator does not provide for direct calculation of the reactive power of an electric locomotive and significantly simplifies the management structure of a reactive power compensator.

External mechanical disturbances compensation with a passive differential measurement principle in nanoforce sensing using diamagnetic levitation

Nanoforce sensors using passive magnetic springs associated to a macroscopic seismic mass are known to be a possible alternative to force sensors based on elastic microstructures like Atomic Force Microscopes if the nanoforces that have to be measured are characterized by a bandwidth limited to a few Hertz. The estimation of the unknown force applied to the seismic mass is based on the deconvolution of the noisy measurement of the mass displacement which has an under-damped dynamic. Despite their high performances in terms of linearity, resolution and measurement range, such force sensors are extremely sensitive to low frequency environmental mechanical disturbances, like the angular variations of the anti-vibration table supporting the device or the residual seismic vibrations that are not filtered by the table. They are also sensitive to the temperature evolution of the ambient air. The evaluation, modeling and compensation of such environmental disturbances have to be specifically studied in the context of magnetic springs associated to a macroscopic seismic mass because of their important negative effects in terms of low frequency drifts and oscillatory disturbances. This article presents an estimation and a passive compensation strategy of the low frequency and non-stationary mechanical disturbances that is based on a differential principle. This approach is applied to a nanoforce sensor based on diamagnetic levitation developed in the last decade. It does not necessitate to add new types of sensors in the measurement chain such as very high resolution and low frequency inclinometers or accelerometers in order to estimate the mechanical disturbances. In term of performances, the force estimation error remains in the nanonewton level over periods of time of several minutes when external temperature remains constant.

Investigation of the Transient Inductance for a Pulsed Alternator With Fully Passive Compensation

The passively compensated pulsed alternator (PCPA) is one of the most competitive pulsed power technologies for future electromagnetic launcher systems. The PCPA is mostly designed for the high pulse repetition frequency military applications, such as the railgun, coilgun, and electrothermal chemical gun. The PCPA is a high-energy and high-power (sub-GW) electrical synchronous generator operating in a fast-transient, short-pulse regime. Due to its low internal impedance during the discharge, the pulsed alternator is capable of extremely high output current, almost two orders of magnitude higher than similar rotating synchronous generators of the same size. This paper has investigated the transient inductance of the armature winding of a PCPA, including the internal inductance and the end leakage inductance. A novel method is proposed to decrease the end leakage inductance in which the end windings are surrounded by totally enclosed conductive shields settled at the stator ends. The analytic formulas of the internal inductance and the end leakage inductance are deduced using the magnetic vector potential method. The concept of end winding shielding can be generalized to other types of compensated pulsed alternators, such as the selective PCPAs and actively compensated pulsed alternators.

Eddy current damper type reaction force compensation mechanism for linear motor motion stage

The base vibration of a linear motor motion stage has been reduced with a passive reaction force compensation (RFC) mechanism based on a movable magnet track and springs. This paper presents the design procedure of an eddy-current damper (ECD) type RFC mechanism for a linear motor motion stage. The RFC mechanism with a movable magnet track and an ECD can overcome the disadvantages of the spring based RFC mechanism such as resonance and difficulty of assembly due to springs. A lumped parameter model for the ECD type RFC mechanism is derived considering sinusoidal magnetic flux density and the effective width of the ECD according to magnet track motion. Then, an iterative design procedure for ECD type RFC mechanisms is proposed to meet system requirements such as the transmission ratio of the reaction force and the maximum magnet track motion. Finally, a design example illustrates the effectiveness of the proposed design procedure for an ECD type RFC mechanism.

Increase in the Power Factor of the Electric ac Loco-motive due to a New Structure of Compensator Operation

The paper presents a device developed on the basis of the adjustable passive reactive power compensator and intended for the increase in the power factor of the electric AC locomotive. Such configuration contributes to the increase in the power factor of a locomotive in its all working modes of operation due to approximation of its power factor value to the maximum possible values. The compensator is operated by the method of extreme voltage control of autonomous voltage inverter. Mathematical modeling of work of an electric locomotive equipped with such compensator was performed with MATLAB package and showed a possibility of increase in the power factor up to 0.98.

Four-Wire Delta Service Sinusoidal Operation and Compensation Simulator

An off-line simulator based on Excel used to evaluate the operation of four-wire delta (4WD) services as well as the effects of reactive and imbalance compensators in sinusoidal steady-state conditions is described in this paper. Voltages, currents and powers in the primary and secondary windings of the transformer as well as in the high voltage (HV) and low voltage (LV) lines and in the loads are calculated through that simulator. The apparent powers in the mains, transformer and loads are determined applying Buchholz’s and unified power measurement (UPM) formulations in both scalar and vector notations. The effects of the neutral current are especially examined, in order to minimize them, and the optimal wye load distribution is determined by the simulator. The simulator provides the necessary elements of passive reactive and unbalanced compensators that optimize the 4WD transformer operation too. Those compensators are determined for each load, and they can be separately selected and included in the simulation process or not. An application example is finally used to step by step explain how the simulator runs.

Design of Passive Weight Compensation for a Robotic Manipulator

A serial link manipulator consist of various unbalanced bars (links) attached by torsional joints that are subjected to torque loads due to the weight and configuration of the manipulator. This paper proposes a solution to passive weight compensation for serial link manipulators, using torsional springs. A set of characteristic points is selected and evaluated through sensibility analysis to define the required maneuvers. A nonlinear optimization methodology is used to find the springs parameters to minimize the energy consumption during the execution of the defined maneuvers. The energy saving is estimated through simulation as well as the effect of the maximum preload allowed for the spring.

Passive temperature compensation in hydraulic dashpot used for the shut-off rod drive mechanism of a nuclear reactor

Passive temperature compensating hydraulic dashpot has been studied numerically as well as experimentally in this paper. Study is focused on reducing the clearances of the hydraulic dashpot at elevated temperature which intern compensates for the reduction in viscosity of damping oil and the dashpot gives uniform performance for wide range of temperature variation. Temperature compensation effects are mainly due to difference in the thermal expansion of materials. Different combinations of materials are used to reduce the dashpot clearances at elevated temperature. Finite element commercial code COMSOL Multiphysics 5.1 has been used for numerical analysis. Fluid-structure analysis has been carried-out to study the thermal expansion and pressure generated in the hydraulic dashpot. Multiphysics study with solid mechanics, laminar flow and moving mesh interfaces has been carried-out. Thermal expansion results of study-1 (solid mechanics) are further extended in to study-2 (laminar flow and moving mesh) and dashpot pressure is estimated. These results show that bimetallic strip improves the dashpot performance at 55°C but do not fully compensate beyond that and less severe impacts occurs. Specific combinations of design and materials have been presented in this paper for obtaining maximum temperature compensation. A novel passive temperature compensating hydraulic dashpot design has been presented, which is suggested for use over wide range of temperature change without much variation in the damping performance.