Error Compensation Technology Research Articles

A ball screw all-round error compensation technology based on novel hybrid deep learning for CNC machine tool

A ball screw all-round error compensation technology based on novel hybrid deep learning for CNC machine tool

Research on High-speed Electric Spindle Cooling Devices and Thermal Error Compensation Technology

Background: When computerized numerical control (CNC) machine tools are working, the electric spindle generates serious heat, which can easily cause the thermal elongation of the spindle and generate thermal errors. Designing cooling devices to control the generation of thermal errors in the spindle and utilizing thermal error compensation techniques for error compensation are essential for improving machining quality and productivity. Objective: By summarizing the current status of research on cooling devices and compensation technology of electric spindles in recent years, some conclusions have been drawn in this work to propose the future research direction. Methods: By reviewing patents on cooling devices and thermal error compensation technology of high-speed electric spindles published in recent years, we have explored the ideas for the improvement of existing cooling devices and compensation technology. Results: Some problems of the patents on current cooling devices and thermal error compensation technology are analyzed, and future research directions are proposed, respectively. Conclusion: As spindle power and speed continue to increase, the existing spindle cooling device and compensation technology also need to be continuously improved. Designers use intelligent technology to monitor the temperature changes during the work of the spindle and fast and accurate control of the cooling system so that the high-speed spindle cooling device tends to be intelligent. Aiming at the thermal error generated in the spindle working process, the designer enhances the error compensation effect by continuously improving and upgrading the key steps in the thermal error compensation technology, which in turn improves the spindle machining accuracy.

A Double Differential Torsional Accelerometer With Higher Than 10-kHz Measurement Bandwidth for Vibration Monitoring

This paper reports the design, fabrication, ASIC, package, and characterization of a z-axis accelerometer with double differential torsional configuration. Compared with typical comb structures, diagonally large depth non-penetrating quad-mass has a simple structure with a large feature size. Compared with traditional unbalanced proof mass structures, the fully differential sensitive configuration theoretically eliminates the influence of common mode errors such as interference force and temperature variations. Thus a high performance structure with high sensitivity and good stability was obtained. Meanwhile, the anchor was arranged internally to make the structure more compact and less stress sensitive. The sensitive structure has a size of 2.4mm×1.8mm. An optimization of kinetic properties was done to get large bandwidth and small mechanical thermal noise. The ASIC of the double differential torsional structure was implemented, which adopted single-cycle clock double-edge multiplexing to improve C/V conversion efficiency and reduce circuit noise. At the same time, the error compensation technology used on the ASIC makes the accelerometer sensitivity error less than 1% and zero bias error less than ±0.02V. The resonance frequency is about 16kHz, the ±5% bandwidth is larger than 10kHz, the cross-axis sensitivities of the x-axis and y-axis are less than 1.5% and 1%, respectively, the bias instability is less than 700μg, the noise spectral density is better than 30μg/√ Hz above 10Hz, the normalized drift over the full temperature range (-40 °C to 60 °C ) is less than 1.78g under uncompensated conditions.

Error Similarity Analysis and Error Compensation of Industrial Robots with Uncertainties of TCP Calibration

The machining system based on an industrial robot is a new type of equipment to meet the requirements of high quality, high efficiency and high flexibility for large and complex components of aircraft and spacecraft. The error compensation technology is widely used in robotic machining to improve the positioning accuracy of an industrial robot with the intention of meeting the precision requirements of aerospace manufacturing. However, the robot’s positioning accuracy decreases significantly when the orientation of the tool changes dramatically. This stems from the fact that the existing robot compensation methods ignore the uncertainties of Tool Center Point (TCP) calibration. This paper presents a novel regionalized compensation method for improving the positioning accuracy of the robot with calibration uncertainties and large orientation variation of the TCP. The method is experimentally validated through the drilling of curved surface parts of plexiglass using a KUKA KR2830MT robot. Compared with a published error compensation method, the proposed approach improves the positioning accuracy of the robot under the large orientation variation to 0.235 mm. This research can broaden the field of robot calibration technology and further improve the adaptability of robotic machining.

Research on the Pose Error Compensation Technology for the Mass and Centroid Measurement of Large-Sized Aircraft Based on Kinematics

The accurate measurement of mass and centroid is indispensable for accurate control of aircraft. In order to eliminate the influence of assembly error and product pose error on the measurement results, a multi-station measurement idea that can self-compensate for the geometric parameter error is proposed in this paper based on. At the same time, the kinematic model of the mechanical structure of the measurement equipment is established to prove the effectiveness of the structure in error compensation theoretically, and the experimental verification of the standard part and aircraft is carried out. The test results show that the measurement results using the idea of the multi-station compensation measurement are significantly better than those of the more common methods, with the mass measurement accuracy of 0.03% and the centroid error within ±0.15 mm, meeting the requirement of high precision measurement for the mass properties.

Dynamic 3D measurement error compensation technology based on phase-shifting and fringe projection

Dynamic 3D measurement error compensation technology based on phase-shifting and fringe projection

Research Progress on Positioning Error Compensation Technology of Industrial Robot

Research Progress on Positioning Error Compensation Technology of Industrial Robot

Feedforward Model-Based Intelligent Compensation System for Spindle Dynamic Thermal Error

Among spindle dynamic errors, thermal error is an important factor affecting machining precision, the most convenient and economical solution for which is dynamic compensation of thermal error. In view of defects of complicated system, complex debugging, poor stability, high cost, etc., in the existing compensation approaches, thermal error compensation technology is investigated with compensation model established to complete the system design. The system is tested on the spindle of precise horizontal machining center. In the experiment, multiple linear regression, BP neural network, etc. are taken for technical analysis with dynamic feedforward model established. The experimental results indicate that the compensation system under study has dynamic compensation rate of over 90%, while the spindle has greatly shorter warm-up time, which can operate normally before entering the thermal steady state. The finally completed feedforward model-based intelligent compensation control system has good steady-state and dynamic compensation performance. In particular, its self-correction function greatly improves system adaptability and simplifies operation in use.

Research Review of Coordinate Measuring Machines

The fourth industrial revolution driven by digitalization, networking and intelligence has put forward new requirements for Coordinate Measuring Machines (CMMs). Two important development directions of Coordinate Measuring Machines are reviewed and analyzed in this paper. The first is the study of error compensation of Coordinate Measuring Machines, which includes the study of dynamic and static error and the study of dynamic error compensation technology. Dynamic error compensation is particularly important in high-speed measurement. And how to ensure measurement accuracy in high-speed measurement is an important direction for the development of Coordinate Measuring Machines. The second is about the intelligence of Coordinate Measuring Machines which includes CAD/CMM integration, independent decision-making, inspection planning, collision prevention and position recognition of the measured workpiece.

A Review of Key Technologies for High-Speed Motorized Spindles of CNC Machine Tools

The high-speed and high-precision motorized spindle is the future development trend of the CNC machine tool field, and has become the focus of research in the world. High-speed motorized spindles tend to develop in the direction of high precision, high speed, low energy consumption, high efficiency, and high reliability. We undertake a through, systematic review of the development history perspective of the research on precision bearing technology, dynamic balancing technology, thermal error measurement and compensation technology with regard to the key technologies of high-speed motorized spindles. On this basis, the current level of development of key technologies for high-speed motorized spindles is analyzed, and the objective advantages and disadvantages of existing technologies are summarized. Finally, the development tendency of high-speed motorized spindle technology is predicted and foreseen.

Novel Compensation Method of Volumetric Errors for Micro-Coordinate Measuring Machines Using Abbe and Bryan Principles

To improve the accuracy of micro-coordinate measuring machines (CMMs) to nanometer scale, numerous hardware improvements have been studied and carried out in recent years, albeit with high costs and application limitations. Error compensation technology through software has also been applied because of its high precision, high efficiency and low cost. A global volumetric error compensation model on the basis of the Abbe and Bryan principles for micro-CMMs is proposed in this study. The volumetric errors of the general CMMs were also analyzed, and the transmission relationship between the volumetric and geometric errors was established in the proposed model. The parameters in the model, including 21 geometric errors and Abbe/Bryan offsets were measured and used to compensate for the volumetric errors. A zero-class gauge block was tested using a micro-CMM based on ISO 10360-2. With the volumetric error compensation, the standard deviations of the length measurements in the different diagonal directions were reduced by more than 65 %. Thus, the effectiveness of the proposed method was established. This study provides a general modeling method and compensation techniques of volumetric errors for people involved in accuracy improvement for CMMs and machine tools.

Research on aeromagnetic three-component error compensation technology for multi-rotor UAV

Aeromagnetic three-component data contain a large amount of geomagnetic information, which can help to obtain a quantitative interpretation of a magnetic anomaly and to improve the identification accuracy of an abnormal body. However, aeromagnetic three-component data of an unmanned aerial vehicle (UAV) include the carrier fixed interference error, inductive interference error, eddy current interference error, and attitude error. Therefore, carrier interference compensation and attitude compensation are necessary to obtain three-component data in a geographical coordinate system. This paper analyzes the difference of six types of attitude conversion matrices for the mutual conversion between the geographic and carrier coordinate systems. Based on the analysis results, the yaw-pitch-roll sequence has the smallest error when calculating the attitude conversion, so the compensation sequence of the roll-pitch-yaw is selected for attitude compensation. The characteristics of the UAV carrier interference error are also analyzed. A low-pass filter is set up for data preprocessing according to the high-frequency characteristics of the carrier eddy current interference, and carrier fixed interference and induction interference compensation models are constructed based on the Tolles-Lawson model. The aeromagnetic three-component comprehensive compensation error objective function is established by integrating attitude compensation and carrier interference compensation. In addition, an adaptive step-size cuckoo algorithm is proposed to obtain the minimum value of the objective function to solve 12 compensation parameters so that the accurate three-component data can be obtained quickly, efficiently, and accurately. Finally, a comprehensive compensation experiment is performed on the three-component aeromagnetic data, and the mean error of the three-component data after compensation is reduced to less than 0.72 nT.

Research on machining error prediction and compensation technology for a stone-carving robotic manipulator

Stone-carving robotic manipulators (SCRMs) have a broad range of applications due to their high efficiency, diverse processing capabilities, and strong flexibility. However, due to its weak rigidity, the milling accuracy of an SCRM is lower than that of a computer numerical control (CNC) machine for working stone into special shapes, making it difficult to meet the requirements of stone milling processing. To improve the milling accuracy of SCRMs, multi-iteration error compensation technology considering the coupling relationship between compensation and deformation is proposed in this paper. First, a global stiffness model of an SCRM in which the robot arm bars are regarded as flexible links is established, and the relationship between the milling force and milling depth is fitted based on a milling force prediction model. Then, the machining error and milling depth when processing a marble workpiece are predicted. Finally, a multi-iteration method is applied for calculation using an interval correction strategy to construct a discrete control system for error compensation in the SCRM. The feasibility and effectiveness of the proposed compensation technology are verified by an experiment using the KUKA-240-2900 SCRM system.

Application of Multisensor Information Fusion Technology in the Measurement of Dynamic Machining Errors of Computer Numerical Control (CNC) Machine Tools

A CNC machine tool is process control equipment integrating machine, electricity, and liquid, which makes its fault diagnosis complex and special due to its own advanced, complex, and intelligent characteristics. Traditional diagnostic methods rely on the engineering experience of technical personnel, which incorporates human subjective factors, and can only perform qualitative analysis, resulting in low diagnostic efficiency. And through a single sensor to detect and diagnose the machine tool, the accuracy and credibility of the decision are low, and the system is also weak against interference. In this paper, we first summarize the composition and working principle of CNC machine tools and analyze the working condition signals generated by CNC machine tools and the sensors that collect the signals and decide to use a multisensor multisignal fusion‐based approach to monitor the machine tool status. It is possible to obtain more effective and valuable information from the observed information through multiple sensors so that the goal of fusion can be achieved. In this paper, a multisensor fusion technique based on wavelet transform and neural network fusion is applied to a machine tool condition monitoring system. The theoretical basis of wavelet analysis and neural network is introduced, and the composition of the condition monitoring system and the process of applying multisensor fusion technology based on wavelet analysis and neural network in the condition monitoring system are given. A complete software and hardware system for online monitoring of CNC machine tools is established. In order to improve the accuracy of the mathematical model, the use of a neural network to fit the nonlinear data and the use of coarse set theory to simplify the relevant data can effectively solve the accurate establishment of the mathematical model in the error compensation method. The thermal error compensation method for CNC machine tools is proposed based on rough set theory, ant colony algorithm, and neural network. This paper first investigates the current development of error compensation technology for CNC machining centers, analyzes the various error sources of CNC machine tools, and finds out the influencing factors affecting the errors of CNC machine tools.

Research Progress of Error Compensation Technology for Pulsed Laser Time-of-Flight Ranging

Research Progress of Error Compensation Technology for Pulsed Laser Time-of-Flight Ranging

Research on Application of Key Technologies of Error Compensation for CNC Machine Tools Based on Computer

The CNC Machine Tools with high efficiency, high precision and high stability is the inevitable trend of the modern manufacturing industry development.This development trend puts forward the extremely high request to the CNC machine tool error compensation technology. However, the error of CNC machine tools have a variety of reasons, these errors affect each other, which leads to the inevitable error. At the high efficiency processing, we must ensure the high stability and high precision of the machine tool. Which requires the error compensation function to maintain high stability and high compensation accuracy, when the CNC machine tool is under the action of high speed and dynamic load. The rapid development of computer technology provides us with more possibilities to solve error compensation. CNC machine tool error compensation technology based on computer is an important means to improve the machining accuracy in the manufacturing industry, which reduce the error in the production process and increase the production efficiency. This paper firstly analysis the error classification and error source percentage of CNC machine tools. And then it analysis the movement error when the CNC machine tools is working. Finally, it puts forward the key technique and application of error compensation based on computer.

Adaptive fuzzy control for permanent magnet synchronous motors considering input saturation in electric vehicle stochastic drive systems

In this paper, an adaptive fuzzy control method based on command filtering is proposed for permanent magnet synchronous motors (PMSMs) stochastic nonlinear systems (SNSs) with input saturation in electric vehicle. The unknown stochastic nonlinear functions are approached by the fuzzy logic system (FLS). Then, the command filtering error compensation technology is used to solve “explosion of complexity” problem and compensation signals are utilized to abate the influence of filtering errors. And stochastic Lyapunov functions are selected to analyze the stability of the system. In addition, the iron losses and input saturation for PMSMs in EV stochastic drive systems are considered, which makes the designed controller more practical. Finally, the effectiveness of the approach is intuitively illustrated by simulation results.

An ANN-Based Precision Compensation Method for Industrial Manipulators via Optimization of Point Selection

Industrial manipulators are widely used in the manufacture of products due to their high flexibility and low costs. High absolute positioning accuracy is the key to guarantee the product quality, which is commonly improved through the error compensation technology. Due to the variety, complexity, and unpredictability of the error sources, the influence of the nongeometric errors on the absolute positioning accuracy of manipulators is uncertain. In result, the existing error compensation methods are difficult to obtain satisfying results, especially for manipulators with large joint flexibility that need to work in different task scenarios. In this paper, an artificial neural network- (ANN-) based precision compensation method via optimization of point selection is proposed, which deals with the kinematic errors and joint stiffness errors in different task scenarios. Firstly, the quasi-random sequence (QRS) method and the product of exponentials (POE) model are combined to identify and compensate the geometric parameters. The QRS method can select points evenly in the workspace. And the POE model can avoid the singularity problem of Denavit–Hartenberg (DH) model. Secondly, a continuous joint stiffness compensation model in the whole workspace is established through ANN. In order to get better compensation results for the current task scenario, the point selection method based on trajectory similarity is adopted to determine the training data of ANN. Finally, the experiments are conducted on a 6-DOF industrial manipulator to demonstrate the validity of the proposed method. The results show that the ANN-based method via optimization of point selection could be an effective solution for the precision compensation.

Thermal error detection and compensation technology for spindle of horizontal CNC machine tool with large torque

Titanium alloys and other difficult-to-machine materials are machined using large-torque CNC machine tools, and asymmetric mechanical spindle is employed in its spindle system. The mechanical spindle demonstrates high power and large torque. The asymmetric design makes the spindle structure more compact while reducing assembly requirements. Nevertheless, when processed, the asymmetric spindle shows complex thermal characteristics and makes it difficult to ensure real-time control, which easily results in significant errors for parts. To eliminate the uncontrollable thermal error, the efforts are made as follows. Firstly, the cold state and hot state attributes in thermal error analysis of mechanical spindle are defined, and the method to distribute the measuring position of asymmetric mechanical spindle temperature is proposed. Secondly, a three-dimensional space detection and analysis method for thermal error of six-vector eight-test based on rotation error vector and deviation error vector is suggested. Thirdly, according to the experimental results, the six-vector thermal error of the three-dimensional space is determined, and then a thermal error compensation technology based on Siemens space coordinate transformation parameters is proposed. Finally, the S specimen recommended by ISO 10791-1-annex A was used for machining verification before and after thermal error compensation. By comparing the 0.129 mm deviation before compensation and the 0.085 mm deviation after compensation, the machining accuracy of parts is discovered to improve by 34.1%. Therefore, the above research lays a theoretical foundation for the follow-up thermal error detection and compensation for the asymmetric spindle of large torque CNC machine tools of the same type.

Thermal Error Modeling for Machine Tools: Mechanistic Analysis and Solution for the Pseudocorrelation of Temperature-Sensitive Points

The temperature-sensitive point is the input variable of the thermal error compensation model of computer numerical control (CNC) machine tools. At present, the most commonly used selection method is to measure the multipoint temperature and thermal error of the machine tool synchronously and select several temperature measurement points with the highest thermal error correlation as temperature-sensitive points according to the measurement data. This study reveals that this method sometimes has obvious mis-selection and causes the model to fail. The reason is that the weak correlation temperature measurement point away from the machine tool heat source amplifies the volatility of the correlation evaluation result, owing to the small overall change. If the calculated result exceeds the true strong correlation temperature measurement point, it will be incorrectly selected as the temperature-sensitive point. This scenario has been termed herein as the pseudocorrelation problem. With the gradual popularization of thermal error compensation technology for CNC machine tools, pseudocorrelation will seriously affect the mass production pass rate. Therefore, the study analyzes and rigorously proves the mathematical mechanism of this problem, and the temperature measurement point preselection algorithm based on the correlation coefficient volatility determination factor (CCVDF) is proposed to eliminate potential pseudocorrelation temperature points before selecting temperature-sensitive points. After 1000 random simulation experiments, the failure rate of Z-direction thermal error modeling after preselection decreased from 5.1% to 0.5%, and the Y-direction error decreased from 33.7% to 1.5%. This algorithm can greatly improve the qualification rate of large-scale equipment of thermal error compensation technology.