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•An extended kinematic model considering the quasi-static crosstalk influence is established.•The optimized calculation model generates specialized calibration point sets using a ...space uniformity index.•A classified-description based method for volumetric error prediction is proposed.•Monte Carlo simulations and experiments are conducted to verify the effectiveness of proposed methods.
For large-scale machine tools, the impact of non-rigid body behavior on volumetric error accuracy cannot be ignored, which hasn't been considered in general volumetric error model. This paper presents a comprehensive error evaluation method for large-scale gantry machine tools considering non-rigid body effect, aiming to provide guidance for volumetric error calibration process. An extended kinematic model is established based on the analysis of crosstalk influence on geometric error motions. An optimized multilateration measurement with improved accuracy and robustness is carried out for volumetric error identification, verified by Monte Carlo simulations. The main novelty of the optimization is to introduce a space uniformity index to generate specialized calibration point sets for any measurement points. A new volumetric error prediction method based on classified descriptions of geometric error motions is proposed, according to their relationship with crosstalk. Experimental results show that the proposed method achieves higher prediction accuracy in crosstalk-sensitive directions.
•Propose a novel inverse multilateration based on tracking interferometer measurement for a five-axis machine tool.•Established a new error model to investigate the error propagation between rotary ...axes and the tracking interferometer.•Identify and calibrate the major error sources in advance to improve the accuracy and efficiency of measurement.•Propose an optimization for the number and distribution of measured points.•Both simulation and experiment show the proposed method could highly improve measurement accuracy and efficiency.
This paper proposes a novel inverse multilateration that improves the accuracy by sensitivity analysis and calibration of rotary axes’ position-independent geometric errors. In recent years, the tracking interferometer measurement with inverse multilateration has been widely adopted in the assessment and compensation of the five-axis machine tool. It uses the bi-rotary head as the steering mechanism to reduce cost, which also introduces errors from rotary axes. In this paper, a sensitivity analysis for position-independent geometric errors of rotary axes is proposed to reveal the error propagation mechanism and identify the main error sources. An optimization for the number and distribution of measured points is investigated based on the result of sensitivity analysis. Monte Carlo simulations and experiments are carried out on a bi-rotary head five-axis machine tool to verify the proposed method. The results show that the accuracy and efficiency of inverse multilateration measurement have been significantly improved.
•Explosive sound source localization through experimental and simulation studies.•Significance of reference microphone selection on positioning accuracy.•Optimization of the number of microphones and ...microphone spacing for sound source localization.•For distant source positioning, microphone spacing should be at least 0.34 times the source range.•Performance study of microphone array geometries using modified Levenberg-Marquardt algorithm.
The use of microphone array for sound source localization has been a trending area of research in speech source recognition, battlefield acoustics, etc. For such applications, the localization accuracy is significantly influenced by the number of microphones and their arrangement on the ground surface. Thus, this paper proposes optimized microphone array geometries with the optimized number of microphones for positioning near and distant sound sources. Moreover, this paper also discusses the significance of the reference microphone selection on positioning accuracy. Here, the time-delay-based multilateration approach is used to formulate the governing nonlinear hyperbolic equations for sound source localization. The resulting equations are solved using the least square optimizer, the modified Levenberg Marquardt algorithm. The source results for several customized array structures are validated through simulation and experimental studies. Based on the results, this paper proposes that at least six microphones are required to identify a source position (<1800 m) with 97 % accuracy at lower noise thresholds (SNR: (6 to 20) dB) and 95 % accuracy at higher noise thresholds (SNR: -6 to 0 dB). Moreover, the paper suggests that microphone spacing should be a minimum of 0.34 times the source range for localization of distant sound sources to improve accuracy at higher and lower noise levels.
•We characterize the effects of obstructions on footstep-induced floor vibrations.•This characterization enables obstruction-invariant indoor occupant localization while reducing the sensing ...requirements.•We first detect and estimate the obstruction mass by characterizing the attenuation.•Then, we find the propagation velocities by modeling the velocity-mass relationship.•Results shows 1.6X improvement compared to the baseline approach.
In this paper, we characterize the effects of obstructions on footstep-induced floor vibrations to enable obstruction-invariant indoor occupant localization. Occupant localization is important in smart building applications such as smart healthcare and energy management. Maintenance and installment requirements limit the application of current sensing approaches (e.g., mobile-based, RF-based, and pressure-based sensing) in real-life applications. To overcome these limitations, prior work has utilized footstep-induced structural vibrations for occupant localization. The main intuition behind these approaches is that the footstep-induced floor vibration waves take different amounts of time to arrive at different sensors. These Time-Differences-of-Arrival (TDoA) can then be leveraged to locate the footstep by assuming similar velocities between the footstep and various sensor locations. This assumption makes these approaches suitable for open areas; however, real buildings have various types of obstructions (e.g., walls, furniture, etc.) which affect wave propagation velocities and hence significantly reduce localization accuracy. Therefore, the prior work requires unobstructed paths between footsteps and sensors for accurate occupant localization, which increases the sensing density requirement and thus, instrumentation and maintenance costs. We have observed that the obstruction mass is one of the key factors in affecting the wave propagation velocity and reducing the localization accuracy. Therefore, to overcome the obstruction challenge, we localize footsteps by considering different velocities between the footsteps and sensors depending on the existence and mass of obstruction on the wave path. Specifically, we (1) detect and estimate the mass of the obstruction by characterizing the wave attenuation rate, (2) use this estimated mass to find the propagation velocities for localization by modeling the velocity-mass relationship through the lamb wave characteristics, and (3) introduce a non-isotropic multilateration approach which robustly leverages these propagation velocities to locate the footsteps (and the occupants). In field experiments, we achieved average localization error of 0.61 meters, which is (1) the same as the average localization error when there is no obstruction and (2) 1.6X improvement compared to the baseline approach.
•GNSS positioning precision derivation.•Use of Doppler information to improve positioning precision.•In harsh environments, Doppler measurements are all the more favourable.
The main objective of ...Global Navigation Satellite Systems (GNSS) is to precisely locate a receiver based on the reception of radio-frequency waveforms broadcasted by a set of satellites. Given delayed and Doppler shifted replicas of the known transmitted signals, the most widespread approach consists in a two-step algorithm. First, the delays and Doppler shifts from each satellite are estimated independently, and subsequently the user position and velocity are computed as the solution to a Weighted Least Squares (WLS) problem. This second step conventionally uses only delay measurements to determine the user position, although Doppler is also informative. The goal of this paper is to provide simple and meaningful expressions of the positioning precision. These expressions are analysed with respect to the standard WLS algorithms, exploiting the Doppler information or not. We can then evaluate the performance improvement brought by a joint frequency and delay positioning procedure. Numerical simulations assess that using Doppler information is indeed effective when considering long observation times, and particularly useful in challenging scenarios such as urban canyons (constrained satellite visibility) or near indoor situations (weak signal conditions which need long integration times), thus providing new insights for the design of robust and high-sensitivity receivers.
In this paper, we present an indoor positioning system were trichromatic white LEDs are used as transmitters and an optical processor based on a-SiC:H technology as mobile receiver. The optical ...processor is realized using a double p-i-n photodetector with two UV light biased gates. The relationship between the optical inputs (transmitted data) and the corresponding digital output levels (received data) is established and decoded.
The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The position of the device is estimated using the visible multilateration method through the strength of the signal received from several non-collinear transmitters. The location and motion information is found by mapping position and estimates the location areas. Since the indoor position and transmitted data of the different LED light sources is known from building floor plans and lighting plans, the corresponding transmitted data information, indoor position and travel direction of the mobile device can be determined.
In this study, the problem of multipath in radar sensor networks for human activity recognition (HAR) has been examined. Traditionally considered as a source of additional clutter, the multipath is ...being investigated for its potential to be exploited through the creation of virtual radar nodes. These virtual nodes are conceptualized to observe targets from aspect angles that differ from those of physically existing radars. To realize this idea, an innovative processing pipeline is proposed that extracts information from multipath signals to improve HAR. The pipeline isolates and tracks the line-of-sight (LOS) and multipath components of a moving human target performing continuous sequences of activities observed by a network of three radar sensors. Furthermore, the method has been verified with experimental data consisting of six activities and 14 volunteers by comparing classification metrics with the use of a single radar as well as only the LOS components of the three radars in the network. A 12-layer convolutional neural network (CNN) classifier has been designed to operate on range-Doppler (RD) images derived from the LOS and multipath components, extracted by the proposed method. A substantial performance improvement using the leave-one-person-out (L1Po) test set is demonstrated in the order of +11% by exploiting a multiradar network with its LOS and multipath components.
This paper outlines the evaluation methodology for a Telescopic Simultaneous Ballbar (TSB) developed for distance measurement using an interferometer as a reference equipment. The procedure is ...executed in a 3-axis machine tool, one of the final applications of the TSB that is machine tool volumetric verification. Two distinct evaluation techniques are devised, with the new virtual line approach enabling an assessment of the TSB's performance within an extended verification volume and requiring only a single alignment position for the interferometer. The measurement repeatability of the equipment is assessed and its measurement uncertainty is estimated in workshop conditions. The results reveal the flexibility of the TSB measurement process similar to that of a laser tracker and the degree of measurement accuracy, which shows values comparable to the interferometer. Consequently, the TSB could facilitate faster and more accurate machine tool verification and calibration compared to existing systems.
•Method for evaluating a Telescopic Simultaneous Ballbar using an interferometer is proposed.•Simultaneous operation of three interferometric lines for machine tool volumetric verification.•The virtual lines enable TSB verification in a wider MT volume using single alignment positions.•Standard deviation of the TSB distance measurement error is below 0.6 μm.•TSB measurement uncertainty in workshop conditions shows values below 1.3 μm.
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