Real-time Compensation Method Research Articles

Compensation of temperature effects in force-balanced microelectromechanical system accelerometers

The reduction of temperature effect is crucial for high-precision MEMS accelerometers. This study presents an automatic real-time compensation method for reducing the temperature effect on the scale factor of force-balanced MEMS accelerometers. Thermistors with negative temperature coefficient are connected in series to the circuit for counteracting the thermal responses of the accelerometers. The compensation system is theoretically analysed, predicting an optimal working temperature with zero-temperature coefficient that agrees with the experimental results with a confidence level of 99.73 %. The temperature effect on the scale factor is reduced from 419 ppm/°C to ±8 ppm/°C at the working temperature with a variation of ±0.5 °C. Compared with other works, the proposed method has advantages on simplified procedures, high efficiency and improved resource utilization, which is promising to large-scale applications in industrial sensors.

An Enhanced Real-time Iterative Compensation Method for Fast Tool Servos with Resonance Suppression

An Enhanced Real-time Iterative Compensation Method for Fast Tool Servos with Resonance Suppression

Stochastic characteristics analysis on GNSS observations and real-time ROTI-based stochastic model compensation method in the ionospheric scintillation environment

Stochastic characteristics analysis on GNSS observations and real-time ROTI-based stochastic model compensation method in the ionospheric scintillation environment

Real-time polarization compensation method in quantum communication based on channel Muller parameters detection

Polarization drift in fiber and free-space optical links is a major factor in the dynamic increase of bit error rate in polarization-coded quantum key distribution (QKD) systems. A dynamic polarization compensation method applicable to both links is a challenge. Here we propose a universally applicable real-time polarization compensation method, that the Muller parameters of the optical links are first detected using a polarization detector, and then the optimal parameters of the controller are obtained by gradient descent algorithm. Simulation results indicate advantages over current methods, with fewer waveplates, faster speed, and wider applicability for various optical links. In equivalent experiments of both satellite and fiber optical links, the average polarization extinction ratio of 27.9 dB and 32.2 dB are respectively achieved. The successful implementation of our method will contribute to the real-time polarization design of fiber and free-space QKD systems, while also contributing to the design of laser-based polarization systems.

Implementing Real-Time DOV Compensation: A Practical Approach Using a MLP on an NPU Embedded in an INS

This paper explores the impact of gravity disturbances on INS accuracy and presents a method for real-time compensation during the navigation process. By utilizing data from the precise gravity model, EGM2008, a novel approach to compensate for the DOV in real time on the INS’s built-in NPU was introduced. This method predicts gravity disturbances while traveling for platforms on both land and water, utilizing the MLP technique. To predict these gravity disturbances, four distinct MLP models, MLP1~MLP4, were designed and their supervised learning results were compared using HMSE and RMSE. This comparative analysis allowed us to identify that the MLP4 model exhibited the best performance. In order to validate the proposed method, MLP4 was implemented inside the NPU and the measured execution time was 1.041 ms. The field test was conducted with real-time execution of the MLP4 model on the NPU of the INS. The results of this field test clearly demonstrated the effectiveness of the proposed approach in enhancing position accuracy. Over the course of a 2 h field test, it was evident that employing the proposed method improved position accuracy by a notable 27%.

Real-time measurement and compensation based on iGPS for industrial robotic pose accuracy

In order to satisfy the requirements of industrial robotic pose accuracy in the operation process, measurement and compensation methods based on iGPS (indoor Global Positioning System) are proposed. An iGPS measuring network is established by solving transformation relations between robotic coordinates and iGPS coordinate, setting up measuring field and calibrating external parameters of transmitters. According to the measured values of iGPS, pose accuracies are calculated, and robotic poses are compensated by modifying command pose and secondary motion fine-tuning respectively. Experiments are designed to verify the measurement and compensation methods. The robotic poses of pre and post compensation are depicted based on 30 successive motion cycles. The pose accuracies are calculated and the effects of the two compensation methods are compared. Experimental results show that the robotic pose accuracies are greatly improved by using the proposed methods, and the real-time compensation method of secondary motion fine-tuning has better compensation effect, which proves the feasibility and effectiveness of the real-time measurement and compensation method based on iGPS.

Improving Accuracy of Real-Time Positioning and Path Tracking by Using an Error Compensation Algorithm against Walking Modes.

Wide-range application scenarios, such as industrial, medical, rescue, etc., are in various demand for human spatial positioning technology. However, the existing MEMS-based sensor positioning methods have many problems, such as large accuracy errors, poor real-time performance and a single scene. We focused on improving the accuracy of IMU-based both feet localization and path tracing, and analyzed three traditional methods. In this paper, a planar spatial human positioning method based on high-resolution pressure insoles and IMU sensors was improved, and a real-time position compensation method for walking modes was proposed. To validate the improved method, we added two high-resolution pressure insoles to our self-developed motion capture system with a wireless sensor network (WSN) system consisting of 12 IMUs. By multi-sensor data fusion, we implemented dynamic recognition and automatic matching of compensation values for five walking modes, with real-time spatial-position calculation of the touchdown foot, enhancing the 3D accuracy of its practical positioning. Finally, we compared the proposed algorithm with three old methods by statistical analysis of multiple sets of experimental data. The experimental results show that this method has higher positioning accuracy in real-time indoor positioning and path-tracking tasks. The methodology can have more extensive and effective applications in the future.

The Conjunctive Compensation Method Based on Inertial Navigation System and Fluxgate Magnetometer

Eliminating the magnetic interference of the carrier platform is an important technical link and plays a vital role in aeromagnetic survey. The traditional compensation method is based on the Tolles–Lawson (T-L) model and establishes the linear relationship between the aircraft interference magnetic field and the aircraft attitude. The compensation coefficients are solved by designing the calibration flight. At present, almost all aeromagnetic systems use the fluxgate magnetometer fixed to the aircraft to realize the attitude measurement of the flight platform. However, the fluxgate magnetometer has problems, such as non-orthogonal error, zero drift error, and linearity error limited by the production process, and the fluxgate magnetometer is also very susceptible to external magnetic interference as a magnetic sensor. These lead to the aircraft attitude calculated by the fluxgate magnetometer being inaccurate, thus reducing the compensation effect. In this article, we analyze the influence of the fluxgate magnetometer noise on compensation and propose a new conjunctive compensation method based on inertial navigation systems (INS) and fluxgate magnetometer information to improve the compensation effect. The flight experiment data show that the proposed method can significantly improve the quality of aeromagnetic data. Compared with the traditional compensation method only based on fluxgate magnetometer information, the improved ratio is increased by 30–60%, and it is a real-time compensation method. It shows that the proposed method has a remarkable compensation effect for aeromagnetic interference.

A Novel Dual-Differential Edge Sensor Based on the Eddy Current Effect

In this article, a kind of edge sensor based on the eddy current effect is proposed to realize accurate detection of the nano-level resolution in a large temperature span. Compared with edge sensors with different principles used in optical telescope projects, eddy current edge sensor has the advantages of being insensitive to nontarget direction and immune to nonferromagnetic medium. The proposed dual-differential edge sensor (DDES) greatly simplifies its installation and reduces the number of support components for sensors to half by replacing the complementary symmetrical installation method. By analyzing the detection principle, a kind of precise demodulation circuit and real-time temperature compensation method is also designed to guarantee the sensor’s ultrahigh stability. The prototype of the sensor is manufactured and verified that the resolution can reach within 2 nm in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$300 ~\mu \text{m}$ </tex-math></inline-formula> , and the temperature drift (TD) performance is less than 6 nm/°C under the large temperature span from −25 °C to +25 °C. The installation error measurement convinced that the current structure has an excellent installation error tolerance, which has the potential to apply in the engineering application of astronomical telescope mirror splicing.

Nonlinearity Compensation and High-Frequency Flexibility Suppression Based RIC Method for Precision Motion Control Systems

For precision motion systems widely applied in industrial manufacturing equipments, it is critical to achieve both high trajectory tracking accuracy and superior disturbance rejection ability. In this article, a novel nonlinearity compensation and high-frequency flexibility suppression based real-time iterative compensation (RIC) method is proposed to achieve excellent tracking performance in practice. The unexpected nonlinearity and high-frequency flexible mode of the plant, which limits the achievable control performance, is first compensated and suppressed. Subsequently, a RIC method based on accurate linear prediction model is proposed to further reduce the tracking error by adding a compensation term to the initial reference trajectory. The trajectory compensation idea of RIC is comparative to remarkable iterative learning control (ILC), but the proposed RIC can online generate and adjust the compensation term during real-time motion without abundant offline iteration trials in ILC. This mechanism significantly enhances the robustness to trajectory variations and external disturbances. Comparative experiments carried out on a ball-screw-driven precision motion stage with full-closed loop position feedback validate the effectiveness and superiority of the proposed method for various trajectory tracking tasks. The proposed method outperforms ILC on tracking performance, and possesses the robustness to various disturbances and reference variations, which leads to industrial application significance.

Real-time trajectory position error compensation technology of industrial robot

In order to meet the requirements of high positioning accuracy and trajectory accuracy of industrial robots in the field of high-precision operation, this paper studied the real-time compensation method of the robot trajectory error used laser tracker to measure the end position of robot in real time. This real-time error calculation method of robot trajectory based on continuous dynamic time warping (CDTW), which was studied to determine the position error of robot trajectory at each moment. Moreover, this paper researched the PID parameter tuning technology of response surface model method based on gray analysis and got a real-time compensation method. The compensation value was fed back to the robot for motion compensation in real time through KUKA RSI. The last, the influence of compensation parameters and period was analyzed and the error compensation experiment of positioning, linear trajectory and arc trajectory were carried out. After compensation, the absolute positioning error of the robot was less than 0.06 mm and the trajectory position error was less than 0.15 mm, which greatly improved the position accuracy of the robot.

Real-Time Iterative Compensation Based Contouring Control Method for Polar Coordinate Motion Systems

For precision planar contouring control systems widely applied in industrial scenarios, additional contouring control action is usually added to two axes respectively to enhance contouring motion performance. In this article, planar motion is innovatively described in the polar coordinate system but not Cartesian one, and a novel definition of polar-radius error (PE) is proposed to evaluate contouring performance. Compared to traditional contouring error defined in Cartesian coordinate system, PE is more suitable for describing the deviation between the actual contour and the reference one, especially at contour vertexes where the traditional definition is defective. Based on the definition of PE, a real-time iterative compensation method is subsequently designed for radial motion axis to improve its trajectory tracking performance and to suppress the contouring error indirectly. The compensation mechanism is merely implemented on only one axis rather than both axes of planar motion, which makes it simpler for practical applications than other existing contouring control algorithms. Comparative experiments with different error definitions and control modes are carried out on machine tool systems to illustrate the effectiveness of the proposed contouring control framework.

Equivalent Measurement and Real-Time Compensation of Error Caused by Intensity Change in Deep Sub-Nanometer Displacement Measuring Interferometry

Heterodyne interferometry is playing an increasingly important role in the field of high-end equipment manufacturing. In photolithography, the precision requirement of displacement metrology is increasing to a deep sub-nanometer scale with the decrease in the critical dimension of chips. The error caused by light intensity changes was investigated, and its principle was found to be related to the time difference in photoelectric conversion. On the basis of the analysis of dynamic characteristics of interference light intensity changes in a heterodyne Michaelson interferometer, the influencing factors, and the features of the measurement error, equivalent measurement and real-time compensation methods were investigated and proposed. Experiments revealed that the error was 220 pm using the method of best-gain detection, while it was 4.8 nm using the method of auto-gain detection over a wide dynamic range when the light intensity was reduced by 30%. However, the proposed compensation method successfully reduced the error to less than 40 pm. Therefore, the real-time compensation method based on equivalent measurement can maintain the signal-to-noise ratio while improving the precision of photoelectric conversion, removing the error caused by intensity changes, and helping heterodyne interferometry achieve deep sub-nanometer precision.

High-accuracy ultrasonic method for in-situ monitoring of oil film thickness in a thrust bearing

The ultrasonic method has been widely applied to measure the oil film thickness – a critical variable that reflects lubrication conditions. However, due to the thermal dependence of ultrasonic signals, significant deviations in film thickness measurements are introduced, hindering the in-situ application of the ultrasonic technique. To address this issue, a real-time temperature compensation method that can accurately obtain the frequency domain information of the reference signal is proposed. Specifically, the reflection from the substrate-coating interface compensates for the thermal effect on the phase increment and amplitude attenuation – this is noted as “self-calibration”. An extra experimental test with a substrate-coating-air structure is performed to calibrate the thermal effect on the coating-induced phase shift – this part is denoted as “pre-calibration”. The combination of “self-calibration” and “pre-calibration” enables the overall temperature compensation strategy. After the effectiveness validation with a temperature-controlled experiment, the proposed method is implemented in a thrust bearing in a heavy-duty hydropower generator with full running conditions, including loading and unloading, normal speed and shut-down. The largely ranged oil film thickness (3–330 μm) is ultrasonically measured and compared with the theoretical value, showing a higher measurement accuracy than the eddy current method.

Shortening the delivery time of proton therapy by real-time compensation method with raster scanning

Among the various scanning techniques, spot and raster scanning are the most frequently adopted. Raster scanning turns off the beam only when each isoenergy slice irradiation is completed. This feature intrinsically solves the leakage dose and frequent beam-switching problems encountered during spot scanning. However, to shorten the delivery time of raster scanning, a sophisticated dose control strategy is required to guarantee dose distribution. In this study, a real-time compensation method with raster scanning for synchrotron systems was designed. It is characterized by a small spot-spacing planning strategy and real-time subtraction of the transient number of particles delivered between two planning-spot positions from the planned number of particles of the subsequent raster point. The efficacy of the compensation method was demonstrated by performing accurate raster scanning simulations with an in-house simulation code and accurate final dose evaluations with a commercial treatment planning system. Given the similar dose evaluation criteria under a practical high scanning speed, compared with the spot scanning method, the total delivery time of the compensated raster scanning method was significantly shortened by 53.3% in the case of irradiating a cubical target and by 28.8% in a pelvic case. Therefore, it can be concluded that real-time compensated raster scanning with a fast scanning configuration can significantly shorten the delivery time compared to that of spot scanning. It is important to reduce the pressure on patients caused by prolonged immobilization and to improve patient throughput capacity at particle therapy centers.

A two-stage method for real-time baseline drift compensation in gas sensors

Baseline drift caused by slowly changing environment and other instability factors affects significantly the performance of gas sensors, resulting in reduced accuracy of gas classification and quantification of the electronic nose. In this work, a two-stage method is proposed for real-time sensor baseline drift compensation based on estimation theory and piecewise linear approximation. In the first stage, the linear information from the baseline before exposure is extracted for prediction. The second stage continuously predicts changing linear parameters during exposure by combining temperature change information and time series information, and then the baseline drift is compensated by subtracting the predicted baseline from the real sensor response. The proposed method is compared to three efficient algorithms and the experiments are conducted towards two simulated datasets and two surface acoustic wave sensor datasets. The experimental results prove the effectiveness of the proposed algorithm. Moreover, the proposed method can recover the true response signal under different ambient temperatures in real-time, which can guide the future design of low-power and low-cost rapid detection systems.

Real-time Bad Pixel Detection and Compensation Method for Short-wave Infrared Camera

Real-time Bad Pixel Detection and Compensation Method for Short-wave Infrared Camera

Real-time optimization compensation method based on a novel two-level multi-block hybrid model for the hydrometallurgy process

Considering the mismatch of complex process models under the influence of external environment changes and uncertain disturbance, the optimization results are not the real optimal values, and the process operating performance deviates from the optimal operation, a real-time optimization compensation method based on a two-level multi-block is proposed. Firstly, the interval plant-wide hierarchical optimization (IPHO) method is used to perform the uncertain optimization for the hydrometallurgical plant-wide process. The hierarchical optimization method is adopted, which simplifies the optimization model and realizes the hierarchical compensation operation when the process is running at the non-optimal grade. Furthermore, the interval number-based uncertain optimization method is utilized to solve the uncertain optimization problem in the presence of uncertain disturbance variables under the upper procedure-layer. Secondly, the data compensation method based on just-in-time learning (JITL) is constructed, which realizes the real-time compensation operation of the production index set-points obtained by the optimization of the procedure-layer. Thirdly, to realize the optimization compensation of the lower process layer, the real-time optimization compensation method based on self-optimization control (SOC) is proposed to compensate the manipulated variables set-points of each sub-block. Therefore, within a certain disturbance range, the operation compensation of the non-optimal operation process can be realized by performing the above-mentioned hierarchical compensation decision in real-time. Finally, an industrial simulation experiment of the hydrometallurgical production process is carried out. Compared with the traditional operation optimization and compensation methods, the proposed method can realize the self-optimization adjustment of the non-optimal operation process faster and more effectively, which can minimize the economic loss of the plant-wide production process.

Research on a real-time polarization compensation method for dynamic quantum communication terminals

In the experiment of quantum key distribution in free space, the polarization degradation and the propagation directions of the four polarization-encoded quantum light beams vary relative to each other and reduce the service life of the terminals, which severely limits their practical application. In order to solve the above problems, we report research on real-time polarization compensation methods for dynamic quantum communication terminals. The difference from Micius is that our proposed system emits quantum lights through the same optical fiber to ensure high-precision coaxiality, and uses a set of wave plates to compensate for both the polarization degradation caused by single-mode fiber and the polarization change caused by optical elements. We introduce our polarization compensation methods in detail and present a design for a dynamic polarization compensation scheme and experimental device. The final experimental polarization extinction ratio of our dynamic optical system is greater than 30 dB after real-time polarization compensation, which meets quantum communication requirements. The successful implementation of this method can effectively improve terminal service life and provide a foundation for the practical applications of quantum communication.

A novel real-time optimization compensation method based on POPOA for the gold hydrometallurgy process

The gold hydrometallurgy process has been prevalent in the hydrometallurgical industry. With a further understanding of the process, the process mechanistic model has been constructed for performing control and optimization. However, due to random disturbances and changing operating conditions, the operating performance of the nominal model-based process has changed. To further perform real-time optimization of the gold hydrometallurgy process, a novel real-time optimization (RTO) compensation method based on the process operating performance optimality assessment (POPOA) is proposed in this paper. Firstly, the operating performance of the online process is judged by the process operating performance optimality assessment algorithm. For the case that the process operating performance is the optimal grade, in which the process operating state is close to the optimal state, but it is not in the optimal state due to some small disturbances in the process, the self-optimizing control (SOC) method is realized by taking the combinations of measurements as the controlled variables (CVs), which are tracked at the optimally insensitive set-points. Furthermore, under the condition of the operating performance is non-optimal grade due to the influence of serious disturbances or obvious change of operating conditions, a similarity detection procedure is complemented based on a SOC model base for searching the CVs set-points relative to similar models. When there is no usable set-point, it is necessary to perform the SOC offline modeling to update the model, or to find similar cases in the historical optimal operational case base to realize the compensation operation strategy based on just-in-time (JIT). Specifically, when similar samples cannot be found in the historical SOC base and the optimal operational case base, the plant-wide optimization model must be rebuilt to meet the requirements of the actual industrial production process. Finally, an industrial simulation experiment of the hydrometallurgical production process is carried out. The simulation results verify the effectiveness and practicability of the proposed new RTO compensation scheme.