Locating Error when Clamping Workpiece between Centers

The total machining error includes some distinct errors summed up by following certain rules. One of these errors is the workpiece locating error, which occurs when the workpiece reference base does not match the workpiece locating surface. The paper analyses different definitions of positioning error, as they were proposed by different researchers or groups of researchers and presents an application valid in the case of turning a cylindrical workpiece with locating between the centers. A definition of locating error that takes into account the total differential of the size of the vector that joins the orientation surface with an element of the fixture was preferred. A fixture version was considered to ensure the locating and clamping of the workpiece on the lathes, with workpiece locating between the centers. This fixture uses a mandrel with a sliding center and an elastic collet.

Accommodating Casting and Fixturing Errors by Adjusting the Machining Coordinate Frame

In order to save valuable machining time expended on machining bad casting, a point-cloud based analysis is proposed to perform a pre-process check on raw casting material conditions. This analysis virtually compares the point cloud data of the raw casting with the nominal CAD model of the final casting and analyzes if the dimensional tolerances on the finished casting can be satisfied by adjusting the coordinate frame in which the casting is machined. The proposed analysis includes the segmentation of the raw point cloud-data followed by extracting the functional features. The material conditions of all planar surfaces are expressed using linear algebraic inequalities. A linear programming-based methodology is developed that helps in aligning the raw casting to the nominal CAD frame so that the conformity is guaranteed. The proposed methodology with the help of slack variables can deal with the casting with unsatisfiable material conditions. An example problem dealing with machining of raw casting clamped on a 4-axis machine-tool is presented to check the validity of proposed method. The virtual gage analysis accurately suggests a solution to compensate part variation caused by fixturing and locating error.

Analyzing of Cooperative Locating Error and Formation Configuration of AUV Based on Geometric Interpretation

Because the evaluation of the location performance of AUVs with the lower bound of the Cramer-Rao inequality is not intuitive, the geometric interpretation method is proposed based on geometric ellipse. The Fisher information matrix is used to replace the Cramer-Rao inequality. The priori information matrix and the measurement information matrix are synthesized into the posterior information matrix through singular value decomposition. The geometric ellipse is used to geometrically represent the posterior information matrix. The posterior information ellipse area is used to establish the location performance evaluation function. By analyzing the performance evaluation function, the optimal formation configurations of single-master, dual-master and three-master AUVs are designed. The implementation of the special formation configuration for the three-master AUV formation proposed in the paper is easier, while the location performance of the optimal formation configuration is not much inferior. The simulation results verify that the optimal formation configuration has a higher location accuracy and that the special formation configuration is effective.

Analysis and Correction of the Magnetometer’s Position Error in a Cross-Shaped Magnetic Tensor Gradiometer

When using the technique of magnetic gradient tensor measurements to obtain the position of magnetic objects, calibration of the magnetic tensor gradiometer plays a pivotal role in precisely locating the target, and extensive research has been carried out on this up to now. However, previous studies have always lacked sufficient discussion on the position error of magnetometers in magnetic tensor gradiometers caused by inaccurate installment of magnetometers. In this paper, we analyze and correct this position error based on a magnetic dipole source. The result of the simulation exemplifies that the magnetometer’s position error will affect the locating accuracy and, therefore, it is worth correcting this error. The relationship between position error and magnetic gradient tensor components is established, followed by an error correction method based on this relationship. Simulations illustrate that this method can effectively decrease the effect caused by the position error of magnetometers and improve the locating performance with locating error and magnetic moment errors dropping from 2 to 0.2 m and 6 × 10 5 A ⋅ m 2 to 5 × 10 4 A ⋅ m 2 , respectively.

Methodology to Develop Geometric Modeling of Accurate Drilled Cooling Holes on Turbine Blades

Film cooling is one of most developed technologies which enhance the gas turbine blades operation in today’s high-thrust-to-weight-ratio gas engines. The determination of the accurate cooling holes of turbine blades is of vital importance to improving the cooling performance. However, in all current methods for manufacturing drilled cooling holes on turbine blades, the complexity of the production processes will ineluctably cause unexpected consequences such as the deformation of the turbomachinery parts, the locating error caused by fixture layouts. These issues will cause deviations in the geometry and position of the drilled holes. In this paper, a methodology is proposed to analyze the deviation and to establish an improved geometric model of drilled cooling holes with accurate positional and geometrical parameters on turbine blades. The discontinuous deformation, including the non-uniform wall thickness and shrinkage distribution, was established by deformation characteristics decoupling analysis; the surface error generated by locating error was obtained using locating error analysis. An accurate model for film cooling holes can be established by considering the process-induced deviations in geometry and positioning. The relevance of the proposed method is verified using numerical and experimental results.

SmartFix: Indoor Locating Optimization Algorithm for Energy-Constrained Wearable Devices

Indoor localization technology based on Wi-Fi has long been a hot research topic in the past decade. Despite numerous solutions, new challenges have arisen along with the trend of smart home and wearable computing. For example, power efficiency needs to be significantly improved for resource-constrained wearable devices, such as smart watch and wristband. For a Wi-Fi-based locating system, most of the energy consumption can be attributed to real-time radio scan; however, simply reducing radio data collection will cause a serious loss of locating accuracy because of unstable Wi-Fi signals. In this paper, we present SmartFix, an optimization algorithm for indoor locating based on Wi-Fi RSS. SmartFix utilizes user motion features, extracts characteristic value from history trajectory, and corrects deviation caused by unstable Wi-Fi signals. We implemented a prototype of SmartFix both on Moto 360 2nd-generation Smartwatch and on HTC One Smartphone. We conducted experiments both in a large open area and in an office hall. Experiment results demonstrate that average locating error is less than 2 meters for more than 80% cases, and energy consumption is only 30% of Wi-Fi fingerprinting method under the same experiment circumstances.