This work proposes a new positioning method based on multiple ultrasonic sensors for the autonomous mobile robot. Unlike the conventional ultrasonic positioning methods, this new method can realize higher accuracy ultrasonic positioning without additional temperature information. Three ultrasonic sensors are used for positioning. A generalized measurement model is established for general sensor configuration. A simplified measurement model, which considers the computational complexity, is also established for linear/simplified sensor configuration. Three time-of-flight signals are obtained from the three ultrasonic sensors. The coordinates of the target are calculated by the ratios of time-of-flights. Positioning experiments were carried out to verify the feasibility and effectiveness of the proposed method. Experimental results show that the new ultrasonic positioning method is effective, both the two established models can implement positioning successfully, and the positioning accuracy is satisfactory. Compared with the conventional ultrasonic positioning method with the default ultrasonic velocity, the positioning accuracy is greatly improved by the proposed method. Compared with the ultrasonic positioning method with additional temperature compensation, the results obtained by the proposed method are comparable.

Based on linear back projection (LBP) algorithm, density-based spatial clustering of applications with noise (DBSCAN) algorithm and image fusion technique, a new image reconstruction method of capacitively coupled electrical impedance tomography (CCEIT) is proposed in this work. LBP is used to obtain the original image of the real part and the original image of the imaginary part. The gray level thresholds of the two original images are determined by DBSCAN clustering algorithm and the initial image of the real part and the initial image of the imaginary part are obtained by gray level threshold filtering, respectively. Finally, the two initial images are fused and the final image is obtained. Image reconstruction experiments are carried out with a 12-electrode CCEIT system prototype. The experimental results verify the effectiveness of the proposed image reconstruction method. Experimental results show that the quality of the final image is satisfactory. Compared with the conventional electrical tomography (ET) image reconstruction methods, the new proposed image reconstruction method needs less prior knowledge or manual intervention and realizes more effective usage of the impedance information. The research results also indicate that the DBSCAN clustering algorithm is an effective way to determine the gray level thresholds of the original images and the mean square error (MSE) is a reasonable criterion for image fusion. Meanwhile, LBP + DBSCAN is an effective algorithm for image reconstruction and image fusion technique is an effective way to utilize the whole impedance information of the conductive gas–liquid two-phase flow.

This article focuses on the improvement of density peaks clustering (DPC, also known as clustering by fast search and find of density peaks) by the introduction of the grid clustering. A grid division is used to divide the data space into grid cells. The global characteristic of grid cell replaces the characteristic of the data points. The local density of DPC is replaced by the density of the grid cell. The cut-off distance of DPC is no longer needed. Then, the cluster centers are determined adaptively based on the quantities. Finally, a two-stage allocation strategy (neighborhood searching and border grid cell assigning) is introduced to obtain the final clustering results. Six datasets are used to experimentally verify the effectiveness and performance of the proposed algorithm. Experimental results show that the improvement of DPC is successful. Compared with DPC, the proposed algorithm is more efficient with less manual intervention.

A new contactless bubble/slug velocity measurement method of the gas-liquid two-phase flow in small channels is proposed by extending the contactless conductivity detection technique to the contactless impedance detection (CID) technique. Two kinds of CID sensors with different constructions (tubular construction and radial construction) are developed to obtain the total impedance information (the real part, the imaginary part, and the amplitude) of the gas-liquid two-phase flow. Two bubble/slug velocity measurement systems with different constructions, the tubular three-electrode velocity measurement system and the radial four-electrode velocity measurement system, are developed. With the obtained total impedance information, three initial estimation values of the bubble/slug velocity are determined by the principle of the cross correlation velocity measurement. Then, with the real-time flow pattern identification result implemented by the fuzzy C-means, a corresponding velocity measurement model [which is the linear combination of the three initial estimation values of the bubble/slug velocity and is developed by the penalty function method and the Davidon-Fletcher-Powell algorithm] is applied to obtain the final bubble/slug velocity. Two groups of the bubble/slug velocity measurement system prototypes with three different inner diameters are developed. The bubble/slug velocity measurement experiments are carried out. The experimental results show that the proposed method is effective. For the two bubble/slug velocity measurement systems with different constructions, the maximum relative errors of the bubble/slug velocity measurement are all less than 4.5%. The research results also indicate that making full use of the total impedance information is an effective approach to improve the accuracy of the velocity measurement.

A new flow pattern identification method based on the optical flow algorithm for gas-liquid two-phase flow in small channels is presented. In this method, an improved optical flow algorithm, the optical flow algorithm based on curvature domain descriptor, is proposed to overcome the influence of uneven illumination. Then, the characteristic of the optical flow field is analyzed and two features of the optical flow field, the mean value and standard deviation of each column, are extracted. Further, principal component analysis (PCA) and K-means clustering algorithm are applied to implement flow pattern identification of the two-phase flow. The evaluation of the improved optical flow algorithm was performed on two optical flow datasets. The results indicate that the improved optical flow algorithm can increase the accuracy of optical flow estimation and improve the robustness of the algorithm to illumination changes. Flow pattern identification experiments of the gas-liquid two-phase flow were carried out in a small channel with the inner diameter of 4.23mm. The experimental results show that the proposed flow pattern identification method is effective. With the proposed method, the accuracies of flow pattern identification for typical flow patterns are all above 92.5%.

This work reports a new simulated inductor which is suitable for a Contactless Electrical Tomography (CET) system and can effectively overcome the unfavorable influence of coupling capacitance on the measurement results. By detailed analysis and comparison, it is found that the grounded simulated inductor has a simple circuit construction but its output current is not equal to its input current, while the floating simulated inductor can be used as an independent inductor module but its circuit structure is relatively complex. A new simulated inductor is designed by compensating the currents from the common node of an introduced independent power source to the main circuit. The new simulated inductor combines the advantages of the grounded simulated inductor and the floating simulated inductor. It has the simple construction similar to that of the grounded simulated inductor and its input current is equal to the output current, which means it can be used as an independent module. The impedance measurement and practical image reconstruction experiments were carried out to verify the effectiveness of the new simulated inductor. The experimental results show that the design of the new simulated inductor is successful, and the performance of the impedance measurement is satisfactory. The signal-to-noise ratio of the CET system is improved. Meanwhile, the research work also indicates that in the case when the independent power source is not available, the new simulated inductor is also an effective alternative method. But the phase difference between input signal and output signal is approximately 90° when the elimination principle is realized.