针对目前扫描隧道显微镜超高精度位移的要求,提出了一种基于神经网络的精密工作台控制方案。在分析微位移机构工作原理的基础上,建立了工作台的数学模型。神经网络辨识器在线辨识工作台的机械参数,神经网络自学习PID控制器代替传统PID控制器,实现了样本的在线采集,有效克服了神经网络控制器需要离线训练的缺点。利用BP网络的自学习和自适应能力,实时调整网络加权值,改变控制器的控制系数,增强了系统的实时控制性能。实验结果表明,相对于传统PID控制算法,参考位移量为10Fm时,达到稳态值的时间从3.8S缩短到1.8S,稳态误差从4.29/6减小到1.99/6。
According to the request of ultra-high precision control for stage of STM, a new control scheme based on neural network is proposed. The mathematical model is set up by analyzing the principle of the actuator. Mechanical parameters are identified on-line by the neural identifier. The traditional PID controller is replaced by a neural network self-learning PID controller. The on-line collection of sample is realized. The disadvantage of controller's off-line training is overcome. The weights of BP network and the parameters of neural net PID controller can be adjusted by the functions of self-learning and adaptability. The performance of real control system is enhanced. The results of experiment show that the response time is shortened from 3.8 s to 1.8 s, and the stable error is reduced from 4.2 % to 1.9 % under a displacement of 10 μm.