Position Error Compensation Research Articles

A Study on the Application of WSN Positioning Technology to Unattended Areas

Wireless sensor network (WSN) is a kind of self-organized network that plays a critical role in the rescue and relief work of some unattended areas in recent years. With the application background of unattended areas, a positioning algorithm with high accuracy and coverage in the WSN is presented in this paper. First, in view of the complicated environment in unattended areas and demand for accurate positioning, this paper focuses on the ranging-based positioning technology, introduces double-hop ranging in the Euclidean algorithm into the 3D ranging process at the node, and proposes 3DL positioning algorithm on this basis. This proposed algorithm is able to achieve 3D positioning of network nodes and effectively enlarge the network positioning coverage by upgrading the positioned node with adequate accuracy to proxy anchor. Second, since unattended areas are mostly non-line-of-sight (NLOS) environments and node positioning accuracy is affected by NOLS factors, a 3DL-N positioning algorithm is proposed by introducing the way of making up for node positioning error based on the 3DL algorithm. The algorithm makes use of the relative positioning function of anchors to figure out the ranging correction parameter and node positioning error compensation value and adds it to the positioning process of the common to further improve its positioning accuracy. Finally, the simulation results indicate that the positioning algorithm proposed in this paper enjoys significant strengths in terms of positioning accuracy and coverage on the premise of consuming no higher node energy.

Compensation of Vertical Position Error Using a Force–Deflection Model in Friction Stir Spot Welding

Despite increasing need for friction stir spot welding (FSSW) for high-temperature softening materials, system deflection due to relatively high plunging force remains an obstacle. System deflection results in the vertical position error of a welding tool and insufficient plunge depth. In this study, we used adaptive control to maintain plunge depth, the plunging force was coaxially measured, and the position error was estimated using a force–deflection model. A linear relationship was confirmed between the force and deflection; this relationship is dependent on the stiffness of the welding system while independent of process parameters and base materials. The proposed model was evaluated during the FSSW of an Al 6061-T6 alloy sheet and a dissimilar metal combination of Al 6061-T6 alloy/dual phase (DP) 590 steel. Under varying process parameters, the adaptive control maintained a plunge depth with an error of less than 50 μm. Conventional position control has a maximum error of nearly 300 μm.

High Precision Position Measurement Method for Laguerre-Gaussian Beams Using a Quadrant Detector.

In this paper, we propose a new method to improve the position measurement accuracy for Laguerre-Gaussian beams on a quadrant detector (QD). First, the error effects of the detector diameter and the gap size are taken into account, and the position error compensation factor is introduced into the conventional formula. Then, in order to reduce the number of parameters, the concept of effective radius is proposed. Thus, a new analytical expression is obtained with a best fit using the least square method. It is verified by simulation that this approach can reduce the maximum error by 97.4% when the beam radius is 0.95 mm; meanwhile, the root mean square errors under different radii are all less than 0.004 mm. The results of simulation show that the new method could effectively improve the accuracy of the QD measurement for different radii. Therefore, the new method would have a good prospect in the engineering practice of beam position measurements.

An Efficient Calibration Algorithm for Large Aperture Array Position Errors in a GEO SAR

Geosynchronous orbit synthetic aperture radar (GEO SAR) plays an important role in wide-area surveillance and the continuous coverage of areas containing targets of interest. However, the relative position errors of large aperture arrays will distort the antenna pattern, which significantly degrades the target detection performance in a GEO SAR system. To address this issue, most of the conventional calibration methods are focused on the independent errors, without consideration of the parametric error model, which may increase the position estimation errors. To solve this problem, an efficient calibration algorithm for position errors in a GEO SAR is proposed in this letter. For the large antenna arrays, the parametric error model is first established. Then, the calibration method is performed to estimate the parameters of the position error model. Based on this, the accurate position errors can be obtained by the least-squares algorithm. Compared with the conventional methods, the target detection performance of a GEO SAR system can be significantly improved after the precise array position error compensation by the proposed algorithm. Moreover, the proposed algorithm transforms the estimation from 3-D positions to the finite parameters of the error model, which can considerably decrease the computational complexity and obtain a more accurate estimation of the position errors simultaneously. Several simulated results are presented to validate the proposed algorithm for the position error correction in a GEO SAR system.

Inverse dynamic analysis and position error evaluation of the heavy-duty industrial robot with elastic joints: an efficient approach based on Lie group

Heavy-duty industrial robots have great advantages in the manufacturing industry. Considering the heavy process load and low stiffness of the robot, an accurate and efficient dynamic model plays an important role in the behavior analysis and performance improvement in the robot. This paper presents a novel methodology for the inverse dynamic analysis of the heavy-duty industrial robot with elastic joints. In particular, high-order kinematics and dynamics are concisely deduced using Lie group to deal with elastic joints for the robot inverse dynamic analysis. Meanwhile, position errors of the end-effector due to elastic joints are evaluated through the inverse dynamic analysis when the robot is in heavy-duty applications. Compared with previous approaches, the advantage of proposed method is that new formulas for inverse dynamic analysis are shown to be more concise and computationally efficient using Lie group. Moreover, the position error evaluation method considering dynamic forces is proved to be more accurate than the traditional method when the robot is in the high-speed application. Because of the high computational efficiency and accurate evaluation results, the proposed approach is applicable to trajectory optimization and position error compensation, especially for the robot in heavy-load and high-speed applications.

A polar-region-adaptable systematic bias collaborative measurement method for shipboard redundant rotational inertial navigation systems

The shipboard redundant rotational inertial navigation system (RINS) configuration, including a dual-axis RINS and a single-axis RINS, can satisfy the demand of marine INSs of especially high reliability as well as achieving trade-off between position accuracy and cost. Generally, the dual-axis RINS is the master INS, and the single-axis RINS is the hot backup INS for high reliability purposes. An integrity monitoring system performs a fault detection function to ensure sailing safety. However, improving the accuracy of the backup INS in case of master INS failure has not been given enough attention. Without the aid of any external information, a systematic bias collaborative measurement method based on an augmented Kalman filter is proposed for the redundant RINSs. Estimates of inertial sensor biases can be used by the built-in integrity monitoring system to monitor the RINS running condition. On the other hand, a position error prediction model is designed for the single-axis RINS to estimate the systematic error caused by its azimuth gyro bias. After position error compensation, the position information provided by the single-axis RINS still remains highly accurate, even if the integrity monitoring system detects a dual-axis RINS fault. Moreover, use of a grid frame as a navigation frame makes the proposed method applicable in any area, including the polar regions. Semi-physical simulation and experiments including sea trials verify the validity of the method.

Sensorless Speed Control of PMSM for Driving Air Compressor with Position Error Compensator

Sensorless Speed Control of PMSM for Driving Air Compressor with Position Error Compensator

An adaptive self-learning compensation approach for thermal errors on 5-axis machine tools handling an arbitrary set of sample rates

Prediction and compensation of thermal position and orientation errors of a 5-axis machine tool by supervised online machine learning based on information from process-intermittent probing, used to identify and update a thermal autoregressive with exogenous input (ARX) model, is presented. The method of Weighted Least Squares (WLSQ) is introduced for adaptive parameter updates, to handle the diverse sample rates of the measured errors by on-machine probing. The down time for modelling is almost eliminated, by a continuous adaption of the model parameters. The compensation reduces more than 95% of the occurring errors during an experimental investigation of 88h.

Online Advanced Angle Adjustment Method for Sinusoidal BLDC Motors with Misaligned Hall Sensors

This letter presents an improved approach for high performance operation of brushless dc (BLDC) motors with hall sensors. The hall sensors in BLDC motors are ideally placed 120 electrical degrees apart. However, hall sensor placement may be significantly incorrect, particularly in high-pole and small-sized motors. These misaligned hall sensors can cause serious torque ripple, and it can be difficult to apply advanced angle control. Therefore, a position error compensator is needed before an advanced angle control method is applied. In this letter, on the basis of the position error compensator, an online advanced angle adjustment method using input voltage and input current is proposed. Using the proposed method, balanced hall sensor signals can be obtained and the high-performance operation can be achieved. The effectiveness of the proposed approach is verified through experimental results.

Carrier signal injection‐based sensorless control for permanent magnet synchronous machine drives with tolerance of signal processing delays

In the case of high precision A/D converters, carrier signal injection based position estimation methods can adopt a relatively higher injection frequency (>1/10 pulse width modulation (PWM) switching frequency), which can lead to enhanced system bandwidths. However, simultaneously, signal processing delay effects (e.g., PWM duty ratio updating delay, etc.) become prominent, resulting in large phase shifts of carrier currents. On the other hand, the high frequency (HF) resistance effects may also be enlarged. Consequently, large oscillating position estimation errors will arise for the pulsating injection method due to carrier signal distortions induced by the delay and HF resistance effects. In order to suppress the undesirable position errors, based on the theoretical analyses, a new compensation strategy of maximizing the useful inductive saliency part and minimising the resistive saliency components using a PI regulator is proposed. The proposed position error suppression method is very easy and simple to implement, and moreover can significantly improve the sensorless control performance. Furthermore, the similar compensation strategy can also be applied for the position error compensation for rotating injection method as will also be discussed in this paper. Finally, the theoretical analyses and compensation effectiveness are validated by experiments on a laboratory interior permanent magnet machine.

Measurement and analyses on positioning accuracy for optical processing robots

The high flexibility optical processing system based on the industrial robot can process large or complex workpieces. But the positioning error characteristics of the industrial robot will cause the decrease of positioning accuracy during grinding, which leads to a lower processing efficiency and processing precision. This paper studies the method of decreasing positioning error, which is verified by simulation and optical processing experiments: Firstly, the positioning error of the polishing tool that fixed at the end of robot in the working area is measured in real-time by using an API T3 laser tracker, and the errors of dwell points are compensated. The measurement experimental results show that the positioning accuracy of the polishing tool meets the high-precision optical processing requirements with the compensation. The dwell time error and the removal error caused by the positioning error before and after compensation are simulated, and the results show that after compensation, the removal error on 80% full aperture is reduced from 3.68% to 0.90%. At last, through the method of the position error compensation to replan the trajectory, the improvement of the processing efficiency and the accurate control on grinding are verified by polishing experiments.

Analysis of an Ultra-precision Positioning System and Parametrization of Its Structural Model for Error Compensation

Conventional compensation of position errors of machine tools relies only on measured values. Due to this principle it is not always possible to compensate the errors in time, especially dynamic ones. Moreover, the relevant control variables cannot always be measured directly. Thus, this approach proves to be insufficient for high precision applications. In this context, a model-based error prediction allows for minimal position errors. However, ultra-precision applications set high demands for the models’ accuracy. This paper presents the design of an accurate and real time-capable structural model of an ultra-precision positioning system. The modeling method for the developed ultra-precision demonstrator is shown and the initial parameter identification is presented.

Laser Interferometer Based Measurement for Positioning Error Compensation in Cartesian Multi-Axis Systems

Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely affected by various error sources, including geometric imperfections, thermal deformations, load effects, and dynamic disturbances. The increasing demand for higher dimensional accuracy in various industrial applications has created the need to develop cost-effective methods for enhancing the overall performance of these mechanisms. Improving the accuracy of a MAS by upgrading the physical structure would lead to an exponential increase in manufacturing costs without totally eliminating geometrical deviations and thermal deformations of MAS components. Hence, the idea of reducing MAS’s error by a software-based alternative approach to provide real-time prediction and correction of geometric and thermally induced errors is considered a strategic step toward achieving the full potential of the MAS. This paper presents a structured approach designed to improve the accuracy of Cartesian MAS’s through software error compensation. Four steps are required to develop and implement this approach: (i) measurement of error components using a multidimensional laser interferometer system, (ii) tridimensional volumetric error mapping using rigid body kinematics, (iii) volumetric error prediction via an artificial neural network model, and finally (iv) implementation of the on-line error compensation. An illustrative example using a bridge type coordinate measuring machine is presented.

Leap motion controller three dimensional verification and polynomial correction

Abstract We propose a leap motion controller (LMC) dimensional verification based on ISO 10360-2:2009 with a coordinated measuring machine (CMM) as the reference framework. A pointer device comprising a thin aluminum cylinder was used to simulate a human finger. This was mounted on the spindle of the CMM to mark known positions over the LMC workspace. Polynomial tendency line corrections were applied to reduce the error in the LMC and CMM framework alignment. One dimension verification results were less than 0.1 mm in the X and Z axes, whereas the Y axis produced unsuitable results. The mean error was 9.6 mm in three-dimensional (3D) verification. Our findings demonstrate the difference between manufacturer quoted accuracy (0.01 mm) to that practically obtainable when the pointer was placed in a known position. LMC needs to add tracking models and position error compensation in applications requiring high accuracy, such as industrial processes or surgical procedure simulations.

Compensation Method of Position Signal Error with Misaligned Hall-Effect Sensors of BLDC Motor

This paper presents an improved approach for compensating rotor position signal displacement in brushless DC (BLDC) motors with misaligned hall-effect sensors. Typically, the halleffect sensors in BLDC motors are located in each phase and positioned exactly 120 electrical degrees apart. However, limitations in mechanical tolerances make it difficult to place hall-effect sensors at the correct location. In this paper, a position error compensator to counteract the hall-effect sensor positioning error is proposed. The proposed position error compensator uses least squares error analysis to adjust the relative position error and back-EMF information to reduce the absolute offset error. The effectiveness of the proposed approach is verified through several experiments.

A two-layered cross coupling control scheme for a three-dimensional motion control system

A two-layered modeling and compensation scheme is proposed to reduce the contouring error of a three-dimensional motion control system. In the proposed scheme, the contouring error model of the three-dimensional motion control system is divided into two layers: the top layer and the bottom layer. The proposed multi-layered structure of the contouring error model presents more flexibility in the control system design because the cross coupling controllers in different layers can be designed separately. In this paper, a nonlinear PI controller and a position error compensator are designed in the bottom layer in order to achieve high contouring accuracy in the XY plane, while a unilateral compensator is designed in the top layer to further reduce contouring error in the three dimensional space. Finally, experiments are performed to verify the performance of the proposed two-layered modeling and compensation scheme. Experiment results show that the designed two-layered cross coupling controller can obtain higher contouring accuracy than traditional cross coupling controller both in the XY plane and in the XYZ space.

Using a Dynamic Interval Type-2 Fuzzy Interpolation Method to Improve Modeless Robots Calibrations

This paper is an extended research for a novel technique for the position error compensations of the robot and manipulator calibration process based on an IT2FEI (interval type-2 fuzzy error interpolation) method. Traditional robots calibration implements either model or modeless method. The compensation of position error in modeless method is to move the robot's end-effector to a target position in the robot workspace, and to find the target position error based on the measured neighboring 4-point errors around the target position. A camera or other measurement device is attached on the robot's end-effector to find and measure the neighboring position errors, and compensate the target position with the error interpolation results. By using the IT2FEI technique provided in this paper, the accuracy of the position error compensation can be greatly improved, which has been confirmed by the simulation results given in this paper. Compared with some other popular traditional interpolation methods, this IT2FEI technique is a better choice. The simulation results show that more accurate compensation result can be achieved using this technique compared with the type-1 fuzzy interpolation method.

Position and orientation error analysis and its compensation for a wheeled train uncoupling robot with four degrees‐of‐freedom

A wheeled train uncoupling robot with four degrees-of-freedom has been developed to replace humans in the uncoupling task in a marshalling field for designating freight cars to different destinations. To successfully achieve the task in practical applications, the positioning accuracy of the robot is an important issue to be considered. Based on the kinematic model using Denavit–Hartenberg method, the matrix differential method is applied here to establish the static position and orientation error model. The impact of parameter errors upon the static pose error of the uncoupling manipulator is analysed. The flexibility of the robot's key components is taken into consideration to analyse its impact on the position and orientation error of the manipulator. The position and orientation error compensation is developed by using input motion planning method to improve the pose accuracy of the robot. Additional motions are added to each joint of the robot such that the uncoupling manipulator can generate a corresponding tiny perturbation, which is used to eliminate the positioning error, ensuring the uncoupling action is completed successfully.

全息光栅制作中基底定位误差分析及补偿方法

全息光栅制作中基底定位误差分析及补偿方法

The Laser Focus Position Control System Based on Motion Controller

Laser cutting focus position automatic tracking system of control precision directly affects the quality of laser cutting processing. There is a low anti-jamming capability, poor quality,poorer openness and poorer dynamic response short comings in the inductive sensor or the capacitive sensor and constitute of the single chip microcomputer control system. This paper introduces a laser focus automatic tracking system based on motion controller, using optical encoder as displacement sensor, use the motion controller of master-slave tracking (electronic gear) function implementation focus position error compensation quickly. Improve the quality of system control, openness, the stability and reliability.