Papers by Keyword: Compensation

Abstract: Aiming to the disadvantages of traditional gap adjustment between rollers of printing machine, a method for gaps analysis and Compensation automatically was proposed. In this research, firstly the relationship between gap of rollers and the printing density is analyzed, established a theoretical model on the influence of the printing of the printing press, and a quantitative experimental. Secondly, constructs the analysis and compensation of process printing machine roller gap, and the actual cases are described. Finally, the method of automatic adjustment for gap can simplify the operations and has practical significance.

Abstract: Handling, welding or painting are currently the main fields of application for industrial robots. Due to their high flexibility and low investment costs industrial robots are increasingly used for machining processes in production environments. Robotic milling is one example of these processes, which nowadays can only be applied for tasks with low accuracy requirements and minor cutting forces. The main reason for this is the low stiffness of the robot structure and hence the huge deflection of the tool caused by the cutting forces. Robotic milling tests of aluminum show deviations of the programmed track in the millimeter range even with moderate depth of cut. To harness high possible savings of milling robots, a new method to increase the machining accuracy was developed at the Institute of Machine Tools and Industrial Management (iwb). The core of the method is a model-based controller for the compensation of deviations that are caused by the cutting forces. The input variables of the controller are the axis angles of the robot (provided by the robot controller) and the cutting forces (measured by a three-component force plate). Based on the cutting forces and the axis angles, the deflection of the Tool Center Point (TCP) is calculated by means of a simulation model. The calculated offset is transmitted to the robot controller so that the tool path is corrected. To implement the compensation strategy, a real-time model of the robot which includes all major compliances of the structure needs to be developed. Besides the real-time requirement, the model needs to be valid for the main working area of the robot. A major challenge in this regard is the determination of the relevant compliance parameters of the robot. In addition to the stiffness values of the gears and bearings the elasticities of the robot links need to be identified. The paper presents a novel method to determine the relevant stiffness parameters of a robot by measurements with a 3D-Scanning-Laser-Doppler-Vibrometer (LDV). In these measurements the robot is loaded with a defined force induced by an actuator at its TCP. During this process, the deflection of the robot is detected by the LDV at a multitude of measuring points. From the relative movements of the measuring points, the tilting-angles of the gears, bearings, and the structural components are calculated. Using the known torques caused by the defined load the stiffness parameters are calculated. In order to minimize the experimental effort it is aspired to identify all necessary parameters by one single measurement. To achieve this goal, the best measurement setup consisting of the position and the orientation of the TCP as well as the direction of the actuator force, is identified by a multibody system (MBS) to ensure sufficient torques in every axis of the robot and all directions (transmission direction and perpendicular to it). The simulation shows that such a measuring setup exists, so that the required parameters, which were validated in additional experiments, could be determined with a single measurement. The determined parameters are used in a controller model to calculate the displacement of the TCP due to the cutting forces during the machining process. Since this model needs to be very efficient regarding the computation time, a MBS cannot be used so that an analytical model must be developed. The analytical model is based on conventional forward kinematics, which is used for determining the position and orientation of the TCP of the robot. In conventional forward kinematics, the rotation of an axis is described by a transformation matrix, which also takes the (constant) dimensions of the robot arms into account. This description only includes a single degree of freedom to the joint angle of the axis and is extended to provide additional degrees of freedom to represent the elasticity of the gear and the bearing. To be able to consider the elasticity of the robot arms, additional transformation matrices are introduced in the center of the arm and the link arm. The computing time of this analytical model is in the range of 1 to 2 ms, so that the model is suitable for the control. In initial machining experiments with a robot of type KR 240 R2500 prime the proposed approach was validated. Milling tests with aluminium showed a significant reduction of the process-related path deviations using the presented control strategy.

Abstract: The major problem in the PV system is the poor PV consumption under viable irradiation condition. So in order to improve the power consumption of PV along with grid connected inverter, this system has been implemented with controller analysis and model. This system is mainly used for non linear load compensation under unbalanced condition. In the existing method, Peak current of the inverter is reduced during the unbalanced grid-voltage sags with the help of current harmonics injection which increases the total harmonic distortion. Double synchronous reference frame technique with PLL is used to synchronize PV with grid. As well as the maximum power point of PV is tracked using Incremental Conductance technique to reduce the error and improves the system efficiency. Selected simulation results using MATLAB/Simulink are reported in order to show the proposed system efficient.

Abstract: Numerical simulation by finite element method has become a powerful tool in predicting and preventing the unwanted effects of sheet metals technological processing. One of the most important problems in sheet metal forming is the compensation of springback. To improve the accuracy of the formed parts, the die surfaces are required to be optimized so that after springback the geometry falls at the expected shape. This paper presents and discusses numerical simulation procedure of die compensation by using the methods of Simplified Displacement Adjustment (SDA). This analysis use Benchmark 3 models of Numisheet 2011. Sensitively analysis was done by using finite element method (FEM) show that the springback values are influenced by element size, integration points and material properties.

Abstract: For high bit-rate optical communications system, the changes in temperature or power fluctuations are due to the dispersion of the dispersion tolerance than the system. Therefore, the dispersion compensation unit must have the functionality to adapt to the dynamic generation of tunable optical communication network development. This article describes several dynamic tunable compensation techniques and the basic principles of the performance characteristics of the situation at home and abroad, including the chirped fiber grating method, the virtual image phased array method, GT interferometer method, the array method and the planar waveguide grating method, and a brief discussion of tunable dispersion compensation technology in the future direction of development.

Abstract: This paper mainly introduces an optimal design of PI control based on compensation to eliminating the interference and improving the performance of the system. With the mathematic model of shunt APF in d-p rotating coordinate, simulation indicates that there is a period disturbing signal in the current closed loop of shunt APF based on the conventional PI control, which obviously impacts on the current tracking performance of the system. So a new PI control based on compensation is put forward. Through the simulation in the platform of Matlab/Simulink, it turns out that this method can improve the current tracking performance of APF and stable performance of the system.

Abstract: An on-line offset current compensation method is proposed to improve ultra-high resistance (UHR) measurement more accurately and reliably. Iterative compensation algorithm is firstly adopted to generate compensation current by adjusting the compensation DAC to decrease the offset current to approximate zero, and then on-line offset current measurement algorithm is employed to ensure the time-varying offset current is always in an appropriate range. This algorithm can maintain a continuous unsaturated measurement process. Experiment results show that the uncertainty (k=2) is 1.4% for 10¹⁴Ω and 5.5% for 10¹⁵Ω under ±1000V based on the offset current compensation method proposed, which has been successfully implemented in a commercial UHR meter.

Abstract: The improvement of the machining accuracy of boring and milling machines is imposed by the more and more demanding conditions on the accuracy of the work pieces to be machined. The specificity of this family, of boring and milling machines, consists of the horizontal motion of the milling spindle (quill) with implications on the application point of the gravity center. Thus, the variation of the application point of the sum of the component elements weights of the column saddle subassembly leads to modifications of the oil film thickness in the hydrostatic guideways, affecting the geometrical accuracy of the machine. This work is presenting a system of compensation and hydrostatic guiding of the column saddle subassembly. This new compensation system allows the pressure in the pockets to be modified by taking in consideration the position of the application point of the weight of the entire column saddle subassembly. The implementation of this compensation and guiding system on the boring and milling machine model AFP 220 has led to an increasing of two times the geometrical accuracy of the horizontality of the column saddle`s motion, compared to the variant without compensation.

Abstract: Measurement and calculation of angle is an important link in borehole inclinometer work. Although the tilt sensor adopted from volume, dropping resistance , vibration resistance and other performance indicators are good embodiment currently, Measured using instrument performance, environmental factors and technical level of operator has certain influence on the angle measurement., According to the measured data to obtain regression model of angle value through on-the-spot test to calibrate measuring angle in this paper. The value has certain measurement error, measurement error is reduced by application of actual error compensation algorithm. Theory analysis and simulation calculation shows that obtaining mean maximum is 0.13452 after compensation by this method, the results of mean maximum is 4.72104 without compensation, it shows that this method is effective.

Abstract: In this paper, a thermal error analysis and compensation method for a high precision aspheric measuring platform driven by a linear motor system is presented. After analyzing the heat source of thermal deformation, the thermal deformation of guide is selected to be object, and the thermal analysis method of guide in heat balance state is proposed. According to the motor temperature at different positions, the thermal error curve of guide is obtained through simulation. Modeling the global positioning error of measuring platform and the compensation model of thermal error using polynomial fitting, the thermal error compensation experiments is implemented by applying compensation system of measuring platform's controller. The experimental results show that the maximum positioning error in heat balance state is reduced from 1.5μm to 0.7μm, which verify the validity of thermal error compensation model.