Abstract:

Objective The detaching roller is the core mechanism of the comber. In the process of combing, it needs to complete a high-speed periodic motion that follows the "rise-return-dwell" pattern. Thus, there are stringent requirements on kinematics and dynamics performances of the transmission mechanism of the detaching roller. The conventional mechanical driving mode can generate a large impact and vibrations, and it is difficult to further improve its speed. Therefore, it is particularly important to overcome the shortcomings of the existing drive mode, including long drive chain, high vibration and noise.

Method The paper analyzed the separation and jointing process of comber, and put forward the key points in movement of detaching roller. The segmented fitting method was adopted to fit them, yielding the optimal movement law of detaching roller. The number of teeth of each gear in the system was optimized based on the dynamic analysis of the gear transmission system of detaching roller. Combined with kinematics analysis and relevant requirements, the motions of two servo motors were then planned and the speed curves of the servo motors were determined. The theoretical expectation was verified by software simulation and test evaluation.

Results The curve of displacement of the detaching roller conformed to the "rise-return-dwell" pattern with the maximum error being 0.30 mm, which satisfied the requirements of flock detachment and overlap. The velocity and acceleration at the starting and terminal points were zero, and the detaching roller did not produce rigid or a flexible impact (Fig. 2). Therefore, the fitting results of the motion curve for the detaching roller were ideal. It can be seen from transmission system that, after optimization, the vibration acceleration of most of gears was reduced to varying degrees, and the sum of root mean square vibration accelerations of all gears in the transmission system was reduced by 18.21% compared with the original, achieving the effect of vibration reduction. Vibration accelerations of some gears in the transmission system showed that the speed of the servo motor connected to the sun gear s is always positive, and the speed of the servo motor connected to gear 1 was always negative, that is, both servo motors operate in one direction. Therefore, the motion planning of the servo motor meets the design requirements. In addition, through the results of ADAMS simulation, it can be seen that the detaching roller motion curve obtained by simulation was basically consistent with the motion curve obtained by theoretical calculation. Therefore, the detaching roller drive system designed can make the movement of the detaching roller meet the process requirements. Finally, according to the experimental results, it can be seen that the overall errors between the displacement curve of the detaching roller obtained from the experiment and the theoretical calculation and simulation results was very small, which verified that the detaching roller drive system can replace the conventional mechanical structure, overcome the problems of its long transmission chain and large vibration noise, and complete the drive of the detaching roller. From displacements of different detaching rollers, displacement curves can be obtained by changing the motion law of the servo motor, verifing that the hybrid drive mode of the detaching roller can make the detaching roller meet different process requirements.

Conclusion In this paper, the hybrid drive system of the detaching roller is studied. The driving system can render the motion of the detaching roller flexible. It solves the problems of the long drive chain of the existing detaching roller drive mechanism and the difficulty in adjusting the motion law of the detaching roller. However, this study still needs to be improved. For example, this study considered only the degrees of freedom in the torsional direction in the dynamic model of the driving system of the detaching roller, which is sufficient for engineering. In future research, more factors should be considered to build a dynamic model with multiple degrees of freedom to better reflect the empirical situation.

Key words: comber, detaching roller, hybrid drive, gear transmission system, dynamic