Semi-analytical assessment of the relative accuracy of the GNSS/INS in railway track irregularity measurements

An aided Inertial Navigation System (INS) is increasingly exploited in precise engineering surveying, such as railway track irregularity measurement, where a high relative measurement accuracy rather than absolute accuracy is emphasized. However, how to evaluate the relative measurement accuracy of the aided INS has rarely been studied. We address this problem with a semi-analytical method to analyze the relative measurement error propagation of the Global Navigation Satellite System (GNSS) and INS integrated system, specifically for the railway track irregularity measurement application. The GNSS/INS integration in this application is simplified as a linear time-invariant stochastic system driven only by white Gaussian noise, and an analytical solution for the navigation errors in the Laplace domain is obtained by analyzing the resulting steady-state Kalman filter. Then, a time series of the error is obtained through a subsequent Monte Carlo simulation based on the derived error propagation model. The proposed analysis method is then validated through data simulation and field tests. The results indicate that a 1 mm accuracy in measuring the track irregularity is achievable for the GNSS/INS integrated system. Meanwhile, the influences of the dominant inertial sensor errors on the final measurement accuracy are analyzed quantitatively and discussed comprehensively.

Automated Analysis of the Two-Minute Walk Test in Clinical Practice Using Accelerometer Data

One of the core problems for people with multiple sclerosis (pwMS) is the impairment of their ability to walk, which can be severely restrictive in everyday life. Therefore, monitoring of ambulatory function is of great importance to be able to effectively counteract disease progression. An extensive gait analysis, such as the Dresden protocol for multidimensional walking assessment, covers several facets of walking impairment including a 2-min walk test, in which the distance taken by the patient in two minutes is measured by an odometer. Using this approach, it is questionable how precise the measuring methods are at recording the distance traveled. In this project, we investigate whether the current measurement can be replaced by a digital measurement method based on accelerometers (six Opal sensors from the Mobility Lab system) that are attached to the patient’s body. We developed two algorithms using these data and compared the validity of these approaches using the results from 2-min walk tests from 562 pwMS that were collected with a gold-standard odometer. In 48.4% of pwMS, we detected an average relative measurement error of less than 5%, while results from 25.8% of the pwMS showed a relative measurement error of up to 10%. The algorithm had difficulties correctly calculating the walking distances in another 25.8% of pwMS; these results showed a measurement error of more than 20%. A main reason for this moderate performance was the variety of pathologically altered gait patterns in pwMS that may complicate the step detection. Overall, both algorithms achieved favorable levels of agreement (r = 0.884 and r = 0.980) with the odometer. Finally, we present suggestions for improvement of the measurement system to be implemented in the future.

High-Precision Surface Scattering Measurement System and Uncertainty Analysis Applied in Laser Protective Materials Diagnostics

The current measurement system of surface scattering rate applied in laser protective materials has the defects of low accuracy, discontinuous diagnosis region and narrow infrared measuring waveband. In order to make up for these shortcomings, a high-precision material-surface-scattering-rate measurement system based on a three-hole integrating sphere is proposed, which can realize the high-precision quantitative measurement on any region of coating surface from near-infrared to far-infrared band. Firstly, a new quantitative relationship between the luminous flux received by detector and the surface scattering rate of coating is obtained by modifying the existing integrating sphere scattering model. Secondly, a high-precision scattering characteristic measurement system based on a three-hole integrating sphere is designed and achieved. The influence of the main design parameters of the integrating sphere on the expected measuring accuracy of the system is investigated by using a TracePro simulation. Accordingly, the optimal design parameters of the system are given. Then, the main sources of the relative measurement uncertainty for the scattering rate are investigated experimentally, and four main relative uncertainty factors are evaluated quantitatively. Finally, according to the error propagation theory, the total experimental relative measurement uncertainty of the system is obtained, which is ± 2.22% and 26–56% higher than the current measuring accuracy. The new coating-scattering-rate measurement system proposed in this paper can provide an effective experimental detection means for high-precision quantitative measurement and a performance evaluation for laser-protective-coating surface-scattering rate.

Analysis of Tungsten Halogen Lamps Characteristics

The authors briefly review distinctions of tungsten halogen lamps (THL) and analyse the results of their own measurements of characteristics of three types of THL manufactured by Saransk lighting equipment plant LISMA. Rated power, luminous flux, and correlated colour temperature of lamps were measured. Relative measurement errors with consideration of possible technological errors for these products do not exceed 0.84 % for values of rated power and 0.29 % for values of correlated colour temperature in batches of 13 pcs. The analysis conducted shows that the technical level of development and production technology of Saransk lighting equipment plant LISMA provides high quality of THL.

Verification of PEMS measurement accuracy based on light vehicle emission test system

For the requirements of the portable emission measurement system (PEMS) measurement accuracy for limits and measurement methods for emissions from light-duty vehicles(CHINA 6), based on the light-duty vehicle emission test system in steady-state conditions and WLTC conditions for PEMS gaseous pollutants, mass flow rate , particle number (PN) verify accuracy of measurement. The results showed that the relative measurement errors of CO, CO2, NOx, fuel consumption and mass flow rate were −5.49%, 2.53%, 10.55%, 2.09% and −2.79%. The relative measurement errors of CO, CO2, NOx, fuel consumption and PN under WLTC condition were 6.67%, 2.54%, 12.96%, 2.37% and −16.08%, which meeting the requirements of the regulations.

Study on short-term creep effect and hysteresis for the HBM Z4A force transducer under compressive and tensile forces

The results of creep tests (for compressive and tensile forces) for the HBM Z4A force transducer made in a Force Standard Machine (FSM) working in the range from 1 kN to 55 kN in the Central Office of Measures are described. Studies have shown that the largest indications of the force transducer (given in electrical units, mV/V) in the first seconds of testing are most likely due to the mechanical properties of the materials from which the transducer is built. Higher values of relative hysteresis error and relative measurement uncertainty were observed for the compressive forces.

Evaluation of hull vibration reduction using multi-layer transom cover for outboard motor

The article discusses the results of experiments on measuring vibration of the hull of a small vessel using various methods of vibroinsulation of outboard motors SEA PRO (nominal capacity 5 h.p.) and SEA PRO (nominal capacity 2.5 h.p.). There have been recorded the harmful effects of prolonged exposure to vibration on the human body, as well as on the boat hull and outboard motor. The peak vibration level was measured and the effectiveness of different types of vibroinsulation was evaluated. The experiments were carried out using a vibrometer Ekofizika-110A made in Russia (relative measurement error ± 0.5 dB) and a vibrometer AR63A made in China (relative measurement error ± 5%). The illustrations of the vibrometers used are presented. It was determined that a multi-layer transom cover is a fairly effective way to reduce the vibration of the motor boat hull. The highest efficiency was achieved for the outboard motor SEA PRO 5.0 when it was running at full speed; a 17.3% reduction in vibration was recorded when using the relative value of vibration acceleration (dB). For the outboard motor SEA PRO 2.5 running at medium speed the decreased vibration (9.5%) was recorded when using the relative value of vibration acceleration (dB). The conclusion has been made about the prospects of reducing the vibration of outboard motors and the need for scientific and experimental research, as well as for the development of standards for permissible vibration of the motor boat hull, which can limit the harmful effect on the crew, the boat structure and the outboard motor. The formula of the logarithmic levels of vibration acceleration in relative units is given in accordance with generally accepted sanitary rules and regulations.

Multirobot Collaborative Navigation Algorithms Based on Odometer/Vision Information Fusion

Collaborative navigation is the key technology for multimobile robot system. In order to improve the performance of collaborative navigation system, the collaborative navigation algorithms based on odometer/vision multisource information fusion are presented in this paper. Firstly, the multisource information fusion collaborative navigation system model is established, including mobile robot model, odometry measurement model, lidar relative measurement model, UWB relative measurement model, and the SLAM model based on lidar measurement. Secondly, the frameworks of centralized and decentralized collaborative navigation based on odometer/vision fusion are given, and the SLAM algorithms based on vision are presented. Then, the centralized and decentralized odometer/vision collaborative navigation algorithms are derived, including the time update, single node measurement update, relative measurement update between nodes, and covariance cross filtering algorithm. Finally, different simulation experiments are designed to verify the effectiveness of the algorithms. Two kinds of multirobot collaborative navigation experimental scenes, which are relative measurement aided odometer and odometer/SLAM fusion, are designed, respectively. The advantages and disadvantages of centralized versus decentralized collaborative navigation algorithms in different experimental scenes are analyzed.

Simultaneous Localization and Mapping Based on Kalman Filter and Extended Kalman Filter

For more than two decades, the issue of simultaneous localization and mapping (SLAM) has gained more attention from researchers and remains an influential topic in robotics. Currently, various algorithms of the mobile robot SLAM have been investigated. However, the probability-based mobile robot SLAM algorithm is often used in the unknown environment. In this paper, the authors proposed two main algorithms of localization. First is the linear Kalman Filter (KF) SLAM, which consists of five phases, such as (a) motionless robot with absolute measurement, (b) moving vehicle with absolute measurement, (c) motionless robot with relative measurement, (d) moving vehicle with relative measurement, and (e) moving vehicle with relative measurement while the robot location is not detected. The second localization algorithm is the SLAM with the Extended Kalman Filter (EKF). Finally, the proposed SLAM algorithms are tested by simulations to be efficient and viable. The simulation results show that the presented SLAM approaches can accurately locate the landmark and mobile robot.