Value Of Position Error Research Articles

Comparison of head posture and neck proprioceptive sense of individuals with chronic neck pain and healthy controls: A cross-sectional study.

Chronic pain can affect body perception at the central level by causing the somatosensory cortex to rearrange. Additionally, cervical afferent abnormalities in individuals with neck pain can impair proprioceptive sensitivity, potentially leading to alterations in body alignment and biomechanics. Nevertheless, there are insufficient studies exploring these notions. The main objective of this study was to compare the head posture and neck proprioceptive sense of individuals with chronic neck pain and healthy controls. Utilizing a cross-sectional study, a total of 76 volunteers comprising 38 individuals with neck pain and 38 matched healthy controls participated in the study. Head posture and cervical joint position sense were measured using a Cervical Range of Motion Deluxe (CROM) device. Firstly, the deviation angles of the head in three planes were evaluated, then the Head Repositioning Accuracy (HRA) test was performed to determine the joint position error. Visual Analogue Scale (VAS) was used to determine the severity of pain in individuals with neck pain. The deviation angles of the head in all three planes were significantly lower in the healthy control group (p< 0.05). Joint position error values were significantly higher in all directions (flexion-extension, right-left lateral flexion, and rotation) in the neck pain group (p< 0.001). The findings show that the proprioceptive sensation of the cervical region in individuals with neck pain was adversely affected, with changes were observed in the head posture. The abstract of this study was presented as a verbal declaration at the International Congress of Health Sciences-ICHES-IDU 2020 that was held in İzmir on 20-21 June 2020.

Depth-based vessel position fixing by means of a neural network

A depth-based vessel position fixing method on the basis of a neural network is proposed. The network takes as an input a sequence of depth values measured by an echo-sounder and predicts vessel latitude and longitude for the moment of the latest depth measurement. The neural network has a fully-connected feedforward architecture with several layers which satisfies conditions of the universal approximation in compliance with the Stone-Weierstrass theorem. The Adamax algorithm for the neural network training with controlling a maximum value of position error at each epoch is implemented. Modeling is conducted with the Python programming language and the Tensorflow library. The model surface of seabed is performed as a second-order polynomial. Training samples on the basis of virtual soundings at the coordinate net knots with the space resolution not worse than one cable are obtained. After samples obtaining the training of the neural network is conducted. A validation set is not used. Several neural networks are trained. They have different number of hidden layers and different number of neurons per each hidden layer. After training the test procedure is performed. Test samples are generated in the assumption that a vessel is moving along meridians which are not used at the stage of the preliminary soundings survey. The cases of mean and random test meridians are considered. The random meridians are obtained with a uniform random number generator. As the result, all the tested neural networks have shown approximately identical navigational accuracy which is close to the accuracy for the training set.

Clamp-shear coupling compensation of a walking piezo actuator combining ILC and hysteresis compensation

This paper presents an analysis and experimental study on clamp-shear coupling of a walking piezo actuators (WPA) during foot-switching. It is observed that the foot-switching introduces disturbances to the translator which causes undesired dynamic responses and this is indeed the primary factor that deteriorates motion precision. To address this issue, iterative learning control (ILC) carried out in stationary condition is applied to pre-compensate the driving waveform of WPA. An inverse PI hysteresis model is applied to mitigate the influence of hysteresis on control effectiveness at different actuator speeds. The proposed method offers simplified implementation and easier convergence compared to ILC carried out in walking condition. It also achieves consistent compensation effects across various operating frequencies. Experimental results show that the proposed method reduces peak to peak value of position error by 97 % comparing with the no compensation scenario, and 51 % with an operating frequency of 100 Hz comparing with ILC carried out in walking condition proposed in literature.

Research on the Dynamic Control Method of CFETR Multi-Purpose Overload Robot

The CFETR multi-purpose overload robot (CMOR) is a key subsystem of the remote handling system of the China fusion engineering test reactor (CFETR). This paper first establishes the kinematic and dynamic models of CMOR and analyzes the working process in the vacuum chamber. Based on the uncertainty of rigid-flexible coupling, a CMOR adaptive robust sliding mode controller (ARSMC) is designed based on the Hamilton-Jacobi equation to enhance the robustness of the control system. In addition, to compensate the influence of non-geometric factors on position accuracy, an error compensation method is designed. Based on the matrix differentiation method, the CMOR coupling parameter errors are decoupled, and then the gridded workspace principle is used to identify the parameter errors and improve the motion control accuracy. Finally, the CMOR rigid-flexible coupling simulation system is established by ADAMS-MATLAB/Simulink to analyze the dynamic control effect of ARSMC. The simulation results show that the CMOR end position error exceeds 0.1 m for single joint motion. The average value of CMOR end position error is less than 0.025 m after compensation, and the absolute error value is reduced by 4 times, improves the dynamic control accuracy of CMOR.

Shoulder Proprioception and Its Correlation with Pain Intensity and Functional Disability in Individuals with Subacromial Impingement Syndrome-A Cross-Sectional Study.

Subacromial Impingement Syndrome (SAIS) is a common shoulder condition characterized by pain and functional impairment. Proprioception, the sense of joint position and movement, is crucial in maintaining joint stability and coordinating movements. The relationship between shoulder proprioception, pain intensity, and functional disability in individuals with SAIS remains unclear, with conflicting findings in the literature. This cross-sectional study aimed to evaluate shoulder proprioception, examine its correlation with pain intensity and functional disability, and contribute to our understanding of the clinical implications of proprioceptive deficits in individuals with SAIS. Forty-two individuals were diagnosed with SAIS, and an equal number of asymptomatic controls were recruited. Shoulder proprioception was assessed using a digital inclinometer, measuring joint position sense at various angles of flexion and rotation. Pain intensity was measured using the Visual Analog Scale (VAS), and functional disability was assessed using the Shoulder Pain and Disability Index (SPADI). Results: Individuals with SAIS exhibited significantly higher joint position error (JPE) values compared to asymptomatic controls in all measured angles of flexion and rotation (p < 0.001). Strong positive correlations were observed between JPE and pain intensity (r = 0.61 to 0.71, p < 0.01) and disability (r = 0.56 to 0.68, p < 0.01). These findings suggest impaired shoulder proprioception is associated with higher pain intensity and functional disability in SAIS. This study provides evidence of impaired shoulder proprioception in individuals with SAIS and its correlation with pain intensity and functional disability. The results highlight the clinical relevance of proprioceptive deficits in SAIS and emphasize the importance of incorporating proprioceptive assessment and targeted rehabilitation interventions into managing this condition. Future research should focus on longitudinal studies with larger and more diverse samples to further understand the underlying mechanisms and evaluate the effectiveness of proprioceptive interventions in improving outcomes for individuals with SAIS.

Accuracy Examination of the SDCM Augmentation System in Aerial Navigation

The paper presents a modified algorithm for determining the accuracy parameter of the system for differential corrections and monitoring (SDCM) navigation solution in air navigation. For this purpose, a solution to determine the resultant accuracy parameter was proposed by using two on-board global navigation satellite system (GNSS) receivers. The mathematical algorithm takes into account the calculation of a single point positioning accuracy for a given GNSS receiver and a weighting factor combining the position error values. The weighting factor was determined as a function of the number of tracked GNSS satellites used in the SDCM single point positioning solution. The resultant accuracy parameter was expressed in ellipsoidal coordinates BLh (B—latitude, L—longitude, h—ellipsoidal height). The study used GNSS kinematic data recorded by two on-board receivers: Trimble Alloy and Septentrio AsterRx2i, located in a Diamond DA 20-C1 aircraft. The test flight was performed near the city of Olsztyn in north-eastern Poland. Calculations and analyses were performed using RTKLIB software and the Scilab environment. On the basis of the performed tests, it was found that the proposed algorithm for SDCM system allows for improvement in the determination of the resultant accuracy value by 56–80% in relation to the results of position errors from a single GNSS receiver. Additionally, the proposed algorithm was tested for the European Geostationary Navigation Overlay Service (EGNOS) system, and in this case, the improvement in the accuracy parameter was even better and was in the range of 69–89%. The resulting SDCM and EGNOS positioning accuracy met the International Civil Aviation Organization (ICAO) certification requirements for SBAS systems in air navigation. The mathematical algorithm developed in this work was tested positively and can be implemented within the SBAS augmentation system in air navigation.

A Study of AGV Collaboration with IoT Concept to Avoid a Collision at Warehouse Intersection

Technology nowadays is always changing very fast. Automated tools are used to face the advanced technology in the warehouse industry, such as automated guided vehicles (AGV). It becomes a common daily vehicle when working in the warehouse, especially on the shop floor. It means collaboration between AGVs is needed and has become important. This paper suggests how to avoid collisions between AGVs and how to avoid obstacles is a practical problem if two or more AGVs interact with each other. This is a common need that should be addressed. As a result, a more effective system design should be created and implemented. This paper used a three-tier internet of things (IoT) structure to avoid collisions and reduce path deviation to design an AGV collaboration system. The IoT was used to authorize AGVs to communicate with each other by transmitting position messages. In this situation, AGV would be aware of other AGV positions and would decide what to do next. According to the findings, two AGVs can avoid colliding by knowing each other's positions in any path scenario by recognizing obstacles through Light Detection and Ranging (LIDAR) detection. This paper designed an AGV collaboration system using the Robot Operating System (ROS) and conducted an experiment to test its practicality. The experiment simulated a warehouse intersection in the real world. This study used the statistical ANOVA method to identify motion planning parameters concerning final AGV position error values.

A mathematical algorithm of the facial symmetry plane: Application to mandibular deformity 3D facial data.

The three-dimensional (3D) symmetry reference plane (SRP) is the premise and basis of 3D facial symmetry analysis. Currently, most methods for extracting the SRP are based on anatomical landmarks measured manually using a digital 3D facial model. However, as different clinicians have varying definitions of landmarks, establishing common methods suitable for different types of facial asymmetry remains challenging. The present study aimed to investigate and evaluate a novel mathematical algorithm based on power function weighted Procrustes analysis (PWPA) to determine 3D facial SRPs for patients with mandibular deviation. From 30 patients with mandibular deviation, 3D facial SRPs were determined using both our PWPA algorithms (two functions) and the traditional PA algorithm (experimental groups). A reference plane, defined by experts, was considered the 'truth plane'. The 'position error' index of mirrored landmarks was created to quantitatively evaluate the difference among the PWPA SRPs and the truth plane, including overall differences and regional differences of the face (upper, middle and lower). The 'angle error' values between the SRPs and the truth plane in the experimental groups were also evaluated in this study. Statistics and measurement analyses were used to comprehensively evaluate the clinical suitability of the PWPA algorithms to construct the SRP. The average angle error values between the PWPA SRPs of the two functions and the truth plane were 1.21±0.65° and 1.18±0.62°, which were smaller than those between the PA SRP and the truth plane. The position error values of mirrored landmarks constructed using the PWPA algorithms for the whole face and for each facial partition were lower than those constructed using the PA algorithm. In conclusion, for patients with mandibular deviation, this novel mathematical algorithm provided a more suitable SRP for their 3D facial model, which achieved a result approaching the true effect of experts.

A hybrid VLP and VLC system using m-CAP modulation and fingerprinting algorithm

A global positioning system (GPS) with high positioning accuracy (PA) is not feasible for challenging environments such as tunnels, underground, complex buildings, etc. For such environments, the alternative technology of visible light positioning (VLP) system has emerged as a viable solution. In this paper, we propose for the first time, a hybrid multi-band carrier-less amplitude and phase (m-CAP) based VLP and visible light communications (VLC) system using the fingerprinting algorithm for determining the position of the receiver, i.e., VLP, and employing the unused sub-bands of m-CAP for VLC. We compare the results for different transmitter configurations and a range of step sizes in terms of the position error (PE) and the bit error rate (BER) performances. Results show that, PE increases with the step size, which is the most critical parameter in fingerprinting-based positioning systems, for a fixed bit energy to noise ratio (Eb∕N0). For a fixed Eb∕N0 of 10 dB the PE values are 4.5 and 10.7 cm for the step sizes of 1 and 20 cm, respectively. For a fixed step size, in contrast, PE decreases with increasing Eb∕N0. Numerical results for a fixed step size of 5 cm show that the PE is reduced from 13.8 to 3.3 cm by 10 dB increase in Eb∕N0. In addition, by increasing the step size, the quantization error overcomes the noise-induced error. We also show that, configurations I and II outperform configuration III in terms of the PE by about 8 to 6 cm at Eb∕N0 of 5 dB and BER (i.e., 1.56×10−4, 2.52×10−4 and 2.54×10−3 for configurations I, II and III, respectively at Eb∕N0 of 20 dB), since configuration III is approximately linear with a symmetrical fingerprint map and a lower illumination level.

Real-time PID control of a novel RCM mechanism designed and manufactured for use in laparoscopic surgery

PurposeThe purpose of this study is to design and manufacture a new remote center of motion (RCM) mechanism for use in laparoscopic surgical operations. In addition, obtaining the forward and inverse kinematic equations of the RCM mechanism and performing real-time position control with the Proportional–Integral–Derivative (PID) control method.Design/methodology/approachAt the design stage, it is benefited from similar triangle rule. To obtain the kinematic equations in a simple way and facilitate control, two-fold displacement ratio is provided between the limbs where linear motion occurs. The rotation and displacement amounts required to move at the RCM point have been calculated by using the kinematic equations of the mechanism. Limb dimensions and motion limits are determined in the manner to avoid singularities and collisions. The x, y and z coordinates of the end effector have been defined as the reference point. Control of the mechanism was provided by PID control. To generate the user interface and control algorithm, MATLAB/Simulink real-time toolbox has been used. Four reference points were determined, control was performed and position error values were examined. MF634 Humusoft data acquisition card has been preferred to collect data from encoders.FindingsA novel RCM mechanism has been designed and manufactured. Kinematic equations of this mechanism have been obtained. Position control of the cannula tip has been performed using PID control method for four different reference points. After settlement, maximum position error has been observed as 0.45 mm.Practical implicationsStructure of the designed mechanism is quite simple. Thus, costs are quite low. The operation area of the operator is widened by hanging the mechanism from the ceiling, so operational capability of health personnel is increasing. It helps to decrease the operation time and increase the success of the operation.Originality/valueWith this study, it is aimed to contribute to the literature by designing a new RCM mechanism. The rotation of the mechanism around the RCM point is provided by only one rotary motor, and the displacement of the RCM point in the vertical axis is provided by only one linear motor. The mechanism is also a surgical robot. The designed system is suitable for use in robot-assisted laparoscopic surgery in terms of maneuverability.

Kinematic calibration of bracket type parallel posture alignment mechanism considering the gravity effect

Purpose The purpose of this study is to improve the position and posture accuracy of posture alignment mechanism. The automatic drilling and riveting machine is an important equipment for aircraft assembly. The alignment accuracy of position and posture of the bracket type posture alignment mechanism has a great influence on the operation effect of the machine. Therefore, it is necessary to carry out the kinematic calibration. Design/methodology/approach Based on analysis of elastic deformation of the bracket and geometric errors of the posture alignment mechanism, an improved method of kinematic calibration was proposed. The position and posture errors of bracket caused by geometric errors were separated from those caused by gravity. The method of reduction of dimensions was applied to deal with the error coefficient matrix in error identification, and it did not change the coefficient of the error terms. The target position and its posture were corrected to improve the error compensation accuracy. Furthermore, numerical simulation and experimental verification were carried out. Findings The simulation and experimental results show that considering the influence of the elastic deformation of the bracket on the calibration effect, the error identification accuracy and compensation accuracy can be improved. The maximum value of position error is reduced from 5.33 mm to 1.60 × 10−1 mm and the maximum value of posture error is reduced from 1.07 × 10−3 rad to 6.02 × 10−4 rad, which is superior to the accuracy without considering the gravity factor. Originality/value This paper presents a calibration method considering the effects of geometric errors and gravity. By separating position and posture errors caused by different factors and correcting the target position and its posture, the results of the calibration method are greatly improved. The proposed method might be applied to any parallel mechanism based on the positioner.

Internal Multimodel Control for Nonlinear Overactuated Systems

This paper deals with the synthesis of a novel internal multimodel control designed for nonlinear overactuated systems. The multimodel approach is proposed to deal with system nonlinearity. A base of linear models is considered to describe the nonlinear system in the whole operating domain and then squared by adding virtual outputs. An internal model controller, obtained by a specific inversion method, is proposed for each model of the base. Thus, the global system control parameters are deduced through fusion of the elementary controller parameters by means of two techniques: commutation or residual approach. The case of three inputs/two outputs system is studied to illustrate the ability of both techniques to satisfy a tolerance interval for position error values, overshoot, settling time specifications and robustness requirement.

Calibration of Positional Errors in Coordinate Measuring Machines and Machine Tools Using a Laser Interferometer System

Dimensional inspections in manufactured workpieces allow assess the quality of the manufacturing process, in this context the quality and development of measurement systems are issues addressed by many researchers. The coordinate measuring machines (CMMs) are versatile systems, can measure complex geometries quickly and accurately. Positional errors are parts of volumetric error and affect the correct positioning of probe in CMMs or of the tool in machine tools. Faced with this, the purpose this investigation is show a method to calibrate the positional errors in a bridge-type coordinate measuring machine, this method collects data in dynamic mode and reduces cyclic errors. The calibration of positional errors was performed using laser interferometry in the “on-the-fly” mode and a method to reduce cyclic errors was applied. The highest value of position error occurred in x axis with value positive of 10μm in the position of 220mm, while in the y and z axis the higher absolute values were 2μm and 6μm respectively. From calibration and compensating of positional errors it is possible to reduce the effects of the volumetric errors in machines with axis of linear displacements as the CMMs and machine tools.

Numerical Simulation for Focal Region Characterization in a New Solar Concentrator

Considering the sun light nonparallelism, Monte Carlo ray tracing method and specular reflection law are employed to simulate the effects of focal plane position error, pointing error to spot shape and energy distribution on focal plane of a new type of space solar concentrator. The results show that: with the absolute value of focal plane position error increasing, focal spot radius increases and peak energy flux value on focal plane decreases; when absolute value of focal plane position error is same, focal spot shape and energy distribution is almost the same; with pointing error increasing, the deviation of focal spot from the focal plane center increases and round focal spot becomes oval focal spot gradually. This will provide a reference for the new space solar concentrating and absorbing system design.

Application in prestiction friction compensation for angular velocity loop of inertially stabilized platforms

To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms (ISPs) with DC motor direct-drive, the methods of modeling and compensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed experimentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified LuGre model is proposed to describe the characteristic of the friction in the prestiction regime. Furthermore, the state switch condition of the three friction regimes including presliding, gross sliding and prestiction is presented. Finally, a composite compensation controller including a nonlinear friction observer and a feedforward compensator based on the novel LuGre model is designed to restrain the nonlinear friction and to improve the control precision. Experimental results indicate that compared with those of the conventional proportion–integration–differentiation (PID) control method and the PID plus LuGre model-based friction compensation method, the dwell-time has decreased from 0.2s to almost 0s, the position error decreased to 86.7% and the peak-to-peak value of position error decreased to 80% after the novel compensation controller is added. It concludes that the composite compensation controller can greatly improve the control precision of the dynamic sealed ISPs.

The effect of fatigued internal rotator and external rotator muscles of the shoulder on the shoulder position sense

The purpose of this study was to investigate which muscle group, the agonist or antagonist, contributes most to the shoulder position sense (SPS). The SPS was tested under 2 conditions: fatigued shoulder internal rotator (IR) muscles (pectoralis major and latissimus dorsi) and fatigued external rotator (ER) muscles (infraspinatus). In each condition, the SPS was measured before and after a fatiguing task involving the IR or ER muscles by repeating shoulder joint rotation. SPS was measured using a method in which subjects reproduced a memorized shoulder joint rotation angle. The position error values in all conditions (fatigued IR and ER muscles) and measurement periods (before- and after-fatigue task) were compared using 2-way analysis of variance with repeated measures (IR/ER×before/after). Position error increased significantly after both fatigue tasks (before- vs. after-fatigue: IR muscle, 2.68° vs. 4.19°; ER muscle, 2.32° vs. 4.05°). In other words, SPS accuracy decreased when either the agonist or antagonist muscle was fatigued. This finding indicated that SPS may be affected by an integrated information of the afferent signals in the agonist and antagonist muscles.

High resolution position estimation using partial pulses

The fundamental principles of radio frequency partial pulses for indoor position location are presented. It is shown experimentally that root-mean-squared x and y position error values of less than 0.1 m can be obtained. The advantages of partial pulses over spread spectrum are also noted.

リップ型工具による小口径ガラスロッド端面の球面加工精度

Following a proposal of the new convex spherical finishing method using lip type tool, this paper describes the relation between the position errors and the accuracy of the spherical shapes on end of small diameter glass rods. The position errors between the glass rod and the lip type tool axis bring two kinds of effects upon the shapes on them. The position error caused by parallel slide of the glass rod axis toward the lip type tool axis on the plane including the both axes changes only the value of spherical radius, and its rate depends on the top angle of the tool. On the other hand, the position error caused by normal slide of the glass rod axis to the plane deforms the spherical shapes to the aspherical shapes. The expressions of these aspherical shapes are formulated, and the correlative equations between the position error values and the counts of interference fringes of these shapes are also made out. The experiments are performed for optical small diameter glass rod works (φ2.0×L110mm) using lip type grinding tool filled up with 7μm diamonds. The experimental results are that when the position error value ΔZ is 2.5μm toward the normal direction, the spherical shape deforms to aspherical shape having an apical umbilical point at a center of the surface of revolution, and about four peaces of interference fringe appear. Both of them are almost in agreement with the calculated results on the experiments.

Path accuracy limitations of inertially based flight trajectory control system in a turbulent environment

Parameter optimization is a powerful technique for synthesizing optimal control systems for stochastic, reduced state feedback, fixed configuration control systems. This paper illustrates the application of parameter optimization to optimize inertial measurement based vertical and lateral control systems for a jet transport aircraft. The mean square gust induced path deviation is minimized subject to penalty on the mean square effector activity. The resulting solutions are presented as curves which display minimum RMS position error and parameter values as a function of RMS effector activity. The optimized solutions are compared to the performance achieved by a conventional trajectory control system using Instrument Landing System measurements.