The 13-mile drive from Victoria crater had taken three years. But the tiny craft had been documenting its progress, stepby step.
从维多利亚陨石坑开始的13英里的路程已经走了3年，但是这个微小的太空船一步一步的记录着它的前行。
2
The control principle of step motor is exposed, drive control of feed system is carried out by use of motion controller, meanwhile, dot motion control of step motor is also carried out by use of PLC.