熔化极气体保护焊中弧长系统的改进无模型自适应控制

针对熔化极气体保护焊中电流与弧长非线性时变系统难以建立精确的模型，且在焊接过程中，系统存在各类不确定因素并易受到内外界扰动的问题，提出一种改进的无模型自适应控制方法。首先，设计了带有可测与不可测干扰以及不确定因素的动态线性化泛模型，采用参数估计算法在线估计伪偏导数，引入干扰观测器实时补偿逼近内外界扰动和不确定因素；进而，通过构建准则函数设计出弧长系统的控制律通，在此基础上，得到改进的无模型自适应控制方案；最后，证明了该方法的鲁棒稳定性。仿真结果表明：与现有无模型自适应控制方案相比，所提出方法具有良好的跟踪性能和更快的响应速度；当焊接过程中遇到可测和不可测干扰以及不确定因素时，所提出的控制方法具有更强的鲁棒性，从而确保了焊接过程中弧长的稳定和较好的控制品质。

Improved Model-free Adaptive Control of Arc Length System in Gas Metal Arc Welding

In gas metal arc welding,it is difficult to establish an accurate model of arc length nonlinear systems.Moreover,the system has various uncertainties and is vulnerable to the problem of internal and external disturbance.In this paper,an improved model-free adaptive control method was proposed to address the above issues.First of all,a dynamic linear generalized model with measurable and unmeasurable disturbances and uncertain factors was designed.A parameter estimation algorithm was used to estimate pseudo partial derivative online.Then,the disturbance observer was introduced to compensate the internal and external disturbances and uncertainties in real time. Furthermore,the control law of arc length system was designed by constructing a criterion function.On this basis,a model-free adaptive control scheme was developed.Finally,the robust stability of the method was validated.The simulation results showed that the method had better tracking performance and faster response speed than the existing model-free adaptive control schemes.It also had a stronger robustness when the unmeasured disturbances and uncertain factors are encountered in the welding process,which ensuring the stability of the arc length in welding process and the better control of quality.