A Method for Estimating and Compensating Quasistatic Errors of Machine Tools

1993 ◽  
Vol 115 (1) ◽  
pp. 149-159 ◽  
Author(s):  
P. M. Ferreira ◽  
C. Richard Liu
Keyword(s):  
Parameter Estimation ◽  
Error Compensation ◽  
Machine Tools ◽  
Experimental Results ◽  
Compensation Scheme ◽  
Order Of Magnitude ◽  
Magnitude Improvement

Quasistatic errors are the major contributors to positioning inaccuracies of machine tools. These errors, estimated to account for 70 percent of the errors of the machine, have been observed to be as high as 70 to 120 μm for production class machining centers. In this paper, a model for these errors is developed. Further, it is shown that the parameters for this model can be estimated by the observation of a few (nine) error vectors in the machine’s workspace. These two results form the basis for a viable error compensation scheme; the model for error compensation and the parameter estimation for updating the model. Experimental results verify the validity of the approach. An order-of-magnitude improvement in the accuracy of the machine, with respect to a calibration frame, was observed.

Enhanced Thermionic Emission Cooling in High Barrier Superlattice Heterostructures

1998 ◽  
Vol 545 ◽  
Author(s):  
Ali Shakouri ◽  
Chris LaBounty ◽  
Patrick Abraham ◽  
Joachim Piprek ◽  
John E. Bowers
Keyword(s):  
Barrier Height ◽  
Thermoelectric Properties ◽  
Barrier Layer ◽  
Thermionic Emission ◽  
Experimental Results ◽  
Hot Electrons ◽  
Cooling Efficiency ◽  
Bulk Materials ◽  
Order Of Magnitude ◽  
Magnitude Improvement

AbstractThermionic emission current in heterostructures can be used to enhance thermoelectric properties beyond what can be achieved with conventional bulk materials. The Bandgap discontinuity at the junction between two materials is used to selectively emit hot electrons over a barrier layer from cathode to anode. This evaporative cooling can be optimized at various temperatures by adjusting the barrier height and thickness. Theoretical and experimental results for nonisothermal thermionic emission in heterostructures are presented. Single stage InGaAsP-based heterostructure integrated thermionic (HIT) coolers are fabricated and characterized. Cooling on the order of a degree over one micron thick barriers has been observed. Nonisothermal transport in highly doped tall barrier superlattices is also investigated. An order of magnitude improvement in cooling efficiency is predicted for InAlAs/InP superlattices.

Robust Control of Piezo Actuator for Active Error Compensation in Diamond Turning

2000 ◽  
Author(s):  
Jianming Yu ◽  
C. James Li
Keyword(s):  
Control Strategy ◽  
Error Compensation ◽  
Diamond Turning ◽  
Piezo Actuator ◽  
Turning Process ◽  
Robust Controller ◽  
Error Sources ◽  
Hysteresis Nonlinearity ◽  
Order Of Magnitude ◽  
Magnitude Improvement

Abstract This paper describes a new control strategy for the micro positioning system used in a diamond turning process to improve workpiece geometry in spite of hysteresis nonlinearity and guideway/spindle errors. The control strategy consists of two nested loops. The inner loop is a model-based robust controller, which compensates for the hysteresis nonlinearity associated with piezo actuators, and the outer loop is a P-integrator learning controller which eliminates the unmodeled error sources such as guideway and spindle errors. This control strategy was applied to the error compensation in a diamond turning process. Cutting tests were conducted and showed an order of magnitude improvement in the workpiece form accuracy from 10 μm to 1μm on an aluminum alloy disk.

On-Line Roundness Error Compensation via P-Integrator Learning Control

1992 ◽  
Vol 114 (4) ◽  
pp. 476-480 ◽  
Author(s):  
C. J. Li ◽  
S. Y. Li
Keyword(s):  
Error Compensation ◽  
Learning Control ◽  
Experimental Results ◽  
Compensation Scheme ◽  
Research Project ◽  
Turning Operations ◽  
Roundness Error ◽  
Cnc Lathe ◽  
On Line ◽  
Metrology System

The work described is the result of a research project for developing a roundness error compensation scheme in turning processes based on the p-integrator learning controller and an on-line metrology system. The objective is to eliminate the repeatable error in turning operations. The scheme was realized on a CNC lathe. The effectiveness of the scheme is supported by the experimental results obtained through workpiece inspections.

High-Density Memristor-CMOS Ternary Logic Family

2020 ◽  
Author(s):  
Xiaoyuan Wang ◽  
Pengfei Zhou ◽  
Jason Eshraghian ◽  
Chih-Yang Lin ◽  
Herbert Ho-Ching Iu ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Practical Implementation ◽  
Switching Speed ◽  
High Data ◽  
Fast Switching ◽  
Data Density ◽  
Order Of Magnitude ◽  
High Transconductance ◽  
Logic Functions ◽  
Magnitude Improvement

<div>This paper presents the first experimental demonstration</div><div>of a ternary memristor-CMOS logic family. We systematically</div><div>design, simulate and experimentally verify the primitive</div><div>logic functions: the ternary AND, OR and NOT gates. These are then used to build combinational ternary NAND, NOR, XOR and XNOR gates, as well as data handling ternary MAX and MIN gates. Our simulations are performed using a 50-nm process which are verified with in-house fabricated indium-tin-oxide memristors, optimized for fast switching, high transconductance, and low current leakage. We obtain close to an order of magnitude improvement in data density over conventional CMOS logic, and a reduction of switching speed by a factor of 13 over prior state-of-the-art ternary memristor results. We anticipate extensions of this work can realize practical implementation where high data density is of critical importance.</div>

Study of the route correction system for the on-board navigation system of an unmanned aerial vehicle on the grounds of radar images of the terrain

2020 ◽  
pp. 129-134
Keyword(s):  
Predictive Model ◽  
Unmanned Aerial Vehicle ◽  
Predictive Models ◽  
Navigation System ◽  
Error Compensation ◽  
Compensation Scheme ◽  
Radar Images ◽  
Aerial Vehicle ◽  
System Errors ◽  
Correction System

The system of route correction of an unmanned aerial vehicle (UAV) is considered. For the route correction the on-board radar complex is used. In conditions of active interference, it is impossible to use radar images for the route correction so it is proposed to use the on-board navigation system with algorithmic correction. An error compensation scheme of the navigation system in the output signal using the algorithm for constructing a predictive model of the system errors is applied. The predictive model is building using the genetic algorithm and the method of group accounting of arguments. The quality comparison of the algorithms for constructing predictive models is carried out using mathematical modeling.

scholarly journals Incremental Construction of Generalized Voronoi Diagrams on Pointerless Quadtrees

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Quanjun Yin ◽  
Long Qin ◽  
Xiaocheng Liu ◽  
Yabing Zha
Keyword(s):  
Voronoi Diagrams ◽  
Surrounding Area ◽  
Repair Mechanism ◽  
Local Repair ◽  
Order Of Magnitude ◽  
Generalized Voronoi Diagrams ◽  
Incremental Construction ◽  
Coarse To Fine ◽  
Multiple Granularities ◽  
Magnitude Improvement

In robotics, Generalized Voronoi Diagrams (GVDs) are widely used by mobile robots to represent the spatial topologies of their surrounding area. In this paper we consider the problem of constructing GVDs on discrete environments. Several algorithms that solve this problem exist in the literature, notably the Brushfire algorithm and its improved versions which possess local repair mechanism. However, when the area to be processed is very large or is of high resolution, the size of the metric matrices used by these algorithms to compute GVDs can be prohibitive. To address this issue, we propose an improvement on the current algorithms, using pointerless quadtrees in place of metric matrices to compute and maintain GVDs. Beyond the construction and reconstruction of a GVD, our algorithm further provides a method to approximate roadmaps in multiple granularities from the quadtree based GVD. Simulation tests in representative scenarios demonstrate that, compared with the current algorithms, our algorithm generally makes an order of magnitude improvement regarding memory cost when the area is larger than210×210. We also demonstrate the usefulness of the approximated roadmaps for coarse-to-fine pathfinding tasks.

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