真空系统中落体做自由下落运动的轨迹重建算法,是进行拟合求解绝对重力测量结果的关键步骤之一.在自主研制小型高精度激光干涉绝对重力仪的过程中,基于目前高速发展的数字测量技术,提出一种自由落体轨迹重建的算法.其基本原理是:首先通过高速采样,得到落体自由下落过程中产生的一系列数字化的激光干涉信号；其次通过数字处理算法提取干涉信号每次过零前后采样点的时间坐标；然后按照相同的下落高度均分这些过零点,得到落体运动轨迹上的“时间-位移”坐标,从而重建落体轨迹.模拟实验表明,该算法时间平均误差在±0.01ns范围以内,由此引入的计算测量重力加速度平均误差为5.2×10-12m/s2,一次完整测量循环的时间为15s,计算时间为2.5s.该结果保证了高精度绝对重力仪研制中对测量速度和计算精度的要求.%Rebuilding the trace of a free-fall body in the vacuum is one of the key steps in finding gravitational acceleration from the sampled fringe signals. This paper proposed an algorithm for rebuilding the trace during the independent process of developing small Laser Interference Absolute Gravimeter. The basic principles are: ① Computing the time of the points before and after zero-crossing of a completely sampled fringe signal, which is generated by a freely falling body, and getting the time coordinates of zero-crossing points; ② Dividing these time coordinates to get the Time-Displacement Coordinates in the body trace using the same displacement interval. In the experiment, we found that it needs 2.5 s to complete one calculation, the average timing accuracy is ±0.01 ns, the induced error is 5. 2×10-12 m/s2, and one complete measurement time is 15 s. The results satisfy the demand of the measurement speed and the accuracy in developing the high precision laser interference absolute gravimeter.
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