基于多轴同步控制的微尺度双向加载实验系统

针对目前微细成形中材料屈服、强化行为实验研究的不足，提出通过建立多轴同步控制的微尺度双向加载实验系统，实现超薄板在复杂加载路径下的性能表征测试。双向加载实验系统基于四轴独立驱动的硬件组成和上、下位机分布式控制策略，采用数字散斑测量（DIC）计算实验过程的应变。通过建立交流永磁同步电机（PMSM）控制模型，辨识了速度闭环控制参数。在非线性PID控制方法实现单轴位置闭环控制的基础上，基于虚拟主轴法实现了不同位移/载荷比例条件下的四轴同步运动。双向加载实验结果表明:同步控制精度满足位移小于等于0.02 mm、载荷小于等于0.05 kN的要求，可用于超薄板微尺度屈服和强化行为的实验研究。 

Micro-scaled biaxial loading test system based on multi-axis synchronous control

Aimed at the currently insufficient experimental condition for the research on yielding and hardening behavior in microforming of ultrathin sheets, a micro-scaled biaxial loading test system was presented, which can achieve complex loading paths. The system is characterized with four independent driving axes in hardware, coupled with separated upper computer and lower computer in software structure. The digital image correlation (DIC) method is adopted to capture deformation strain in the biaxial tension process. The control model of permanent magnet synchronous motor (PMSM) was first established, and the control parameters of speed closed loop were identified. The control accuracy of single-axis position closed-loop is significantly improved by using the nonlinear PID control method, and the four-axis synchronous control under diverse displacement/load ratios is realized on the basis of virtual axis method. The biaxial loading experiment reveals that the system satisfies the requirements of displacement synchronization error within 0.02 mm and load synchronization error within 0.05 kN. The developed system can thus be used for experimental research on yielding and hardening behavior of ultrathin sheet.