Comparison of Japanese and European NCs through Wing Profile Machining Test
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This study compares the motion characteristics of 5-axis machine tools with Japanese and European NCs under wing profile machining. Productivity is one of the most important factor in the industrial field. It is known that the cycle time of the machining process typically depends on the manufacturer, control mode, and setting of the NC controllers, even though the identical cutter path is applied. In order clarify the influence of the manufacture and control mode of the NC controllers onto the cycle time and velocity profile of the machining, wing profile machining tests are carried out by 5-axis machining centers with different type of NCs. Identical CL data is used for the tests. Effect of TCP control mode on to the cycle time and velocity profile is also investigated. As the results, it is clarified that the TCP control mode can significantly reduce the cycle time. In addition, it is clarified that the jerk is limited when the European NC is used although the acceleration is limited in case the Japanese NC is used.Keywords:
Jerk
Mode (computer interface)
Presented is a modified trapezoidal cam profile with adjustable forward and backward acceleration. The profile is suitable for single-dwell cam and follower applications. The main benefit of the profile is that it allows cam designers to choose easily a value for the maximum forward or maximum backward acceleration to achieve design objectives. An additional benefit of the profile is that it has a continuous jerk curve. Follower acceleration is one of the primary factors affecting cam wear and follower jump, two main concerns of cam designers. Large forward acceleration against a load creates cam-follower interface forces that can cause excessive wear. Backward acceleration tends to reduce the cam-follower interface force, and if the backward acceleration is sufficiently large, separation between the cam and follower (“follower jump”) can occur. The cam profile presented in this paper gives cam designers an easy way to adjust the maximum forward or backward acceleration to prevent these problems.
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Dwell time
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In general, gearshift is related to change of acceleration due to the changing gear ratio. Modern double-clutch transmissions allow for shaping the acceleration transition by controlling the torques transmitted by the clutches. Thus, the question arises about an optimal transition law for the acceleration. The paper demonstrates that jerk and change of jerk may be considered as major sources of discomfort. Thus, a bi-criterion optimization problem is formulated for finding an optimal acceleration transition and an associated shift control. The problem is solved by analytical and polynomial approaches, and a theoretically optimal solution is shown. The latter is applied to a simple simulation model of a double-clutch transmission to demonstrate its applicability.
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The linear and exponential acceleration/deceleration algorithms are adopted in traditional acceleration/deceleration control in CNC systems,but the machine vibration due to the mutation of acceleration also exists.S-curve acceleration and deceleration is adopted in some advanced CNC systems at present,but actually,S-curve is treated as Piecewise Polynomials,the value of jerk is piecewise constant,some discrete points may arose the mutation of jerk.An acceleration/deceleration control method based on Jerk control is presented,by restricting the value of jerk,and use of filters to complete smooth processing to reduce the machine vibration due to the jerk mutation,accordingly realize the high quality surface machining,and the machine tools can achieve a good acceleration and deceleration performance at the same time.
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Constant (computer programming)
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This paper proposes the new speed control method of electric vehicles by generating the longitudinal speed pattern for improving the ride comfort against the longitudinal acceleration/deceleration. Since the longitudinal acceleration/deceleration of EVs causes the discomfort of passengers, reducing such bad effect of acceleration/deceleration acting on passengers is very important for not only the ride comfort of passengers but also vehicle running safety. The proposed method is applying the general optimal control theory and it generates the speed pattern for improving the passenger ride quality based on evaluating the variations of acceleration and the jerk which is time derivative of the acceleration. The effectiveness of the present method is demonstrated through numerical experiments compared with some conventional methods.
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Ride quality
Acceleration time
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Acceleration is discontinuous in the traditional acceleration and deceleration algorithms such as the linear and the exponential,which cause flexible impact in NC machining.However,the jerk of S-curve acceleration and deceleration is step change,which confines the flexibility.So,a kind of polynomial acceleration and deceleration control method is proposed,which guarantees the acceleration and jerk are continuous and makes the CNC system more flexible.This algorithm is analyzed and discussed the feedrate profile planning in detail.Simulation is performed to verify the advantage of the proposed method.
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Experimental studies of objective and subjective passenger response to various fore-and-aft, or longitudinal, vehicle acceleration transients are reviewed. It is found that the wide variability in type of study and form of results does not allow conclusive statements to be made regarding passenger acceptability of any specific acceleration—jerk profile in a given transportation system.
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High-quality material manufacture requires the improvement of the computer numerical control (CNC) machine performance. Such task can be achieved by considering the tool trajectory, in which it is important to minimize the acceleration and jerk levels. Previous research works are focused on providing smooth movements at most with C2 continuous trajectories, and the results of using C3 continuity in the trajectory are not evaluated. The contribution of this study is the design of a methodology for obtaining C3 tool trajectories while acceleration and jerk levels are constrained through adaptive feed-rate. C3 and C2 trajectories are executed in a CNC machine. Speed, acceleration, and jerk are monitored in order to validate the proposed methodology and to analyse and quantify the differences between using C2 and using C3 trajectories.
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Machine tool
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A novel algorithm based on NURBS curve is addressed for acceleration/deceleration of CNC machine tools by combining quartic polynomial velocity planning and filtering, aiming at vibration of CNC caused by sharp acceleration and jerk. Its validity has been proved theoretically. By connecting a filter after the routine results, continuous acceleration and jerk are further smoothed. Experiment shows that this is a simple and effective algorithm to achieve further smoothing of continuous acceleration and jerk, thereby reducing machine vibration and achieving high speed, high efficiency and high precision machining.
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Smoothing
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The machine flexible impact was due to step change of the jerk,this paper proposed a method,In this method,the machining parameters were set reasonably.It could limit the jerk and smooth handling the jerk by selecting the appropriate filter.It could effectively reduce the CNC machine flexible impact because of step change in jerk.The machining parameters of the package was designed in the HEIDENHAIN iTNC530 system platform.This package was developed according to the parts processing requirements.The package was divided into four machining processing modes.The machining parameters were refined set for each processing modes.The machining experimental results shown that,The different machining parameters could be called in the CNC machining process according to different processing conditions.It could reduce secondary machining time and improve the machining efficiency with in the allowable range in the accuracy.
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Machine tool
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Aiming at the CNC machine tools vibration due to unsmoothed velocity and jerk during starting/stopping stage,A new s-curve acceleration and deceleration algorithm is proposed combining the cubic polynomial model with the moving average filtering technique.Theoretical analysis of the velocity model,acceleration model,and jerk model shows that the method can ensure the continuity of velocity acceleration and jerk.Practical application on CNC system shows the effectiveness of the method.
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Acceleration time
Look-ahead
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