激光金属沉积堆高闭环控制研究

Research of Closed-Loop Control of Deposition Height in Laser Metal Deposition

激光金属沉积(LMD)传统上多采用固定的工艺参数进行扫描堆积成形,每层的实际堆积高度一般是固定且不可控的。为提高成形稳定性和成形件的精度,补偿堆高误差,开发了一种可实时变化工艺参数的堆高闭环控制系统。通过反馈实际堆高与设定期望层高之间的误差,控制实际堆高达到设定值。设计P和PI两种控制器,分别以扫描速度和激光功率作为输入参量来控制实际堆高。结果表明,变扫描速度控制优于变激光功率控制,实际层高的最佳稳态波动范围可达±0.015mm;PI控制器可使总堆高达到期望值;当送粉速率发生突变时,P控制系统具有良好的鲁棒性;P控制器的阶跃响应曲线与成形件剖面纹理显示的堆高变化一致。该系统为堆高的可控和堆高误差补偿提供了新方法。

In laser metal deposition （LMD）, fixed process parameters are mostly used during the deposition. The actual deposition height of each layer is generally fixed and uncontrollable. In order to improve forming stability and accuracy of the forming parts, and compensate the error of deposition height, a real time closed-loop control system of deposition height with variable process parameters is development. The actual deposition height is controlled by means of the feedback of the error between actual deposition height and the set desired layer height. Both P- controller and Pl-controller are designed, and scanning speed and laser power as input variables are implemented respectively to control the actual deposition height. The experimental results indicate that the variable scanning speed control is better than variable laser power control. The best fluctuation range of the actual deposition height is ±0. 015 mm. The total deposition height can achieve the desired total layer height using PLcontroller. If the powder feeding rate changes abruptly, the P-control system has a nice robustness. The sectional view of cladding layer texture shows the variable deposition heights, which are in accord with the step response curve of P-controller. The system provides a new method to control deposition height and to compensate deposition error.