Development of Active Heave Compensator

升沉补偿器用于隔离悬浮在浮体上的仪器和结构，使其免受升沉运动的影响。在深海中，由于无法通过超声波等手段进行直接和实时的测量，因此对升沉运动的检测是非常困难的。本文研究了一种由加速度计和作动器组成的主动运动补偿系统。在该系统中，利用浮体平均位置保持平均水位的知识，消除了漂移。首先设计FIR数字滤波器，对加速度进行双积分，去除漂移、高频和低频噪声；在微处理器上进行数值计算。在测试过程中可以明显看出，浮体位置的计算对信号的任何虚假波动都非常敏感，例如低幅值稳态和与真实信号的极低频率偏移。通过旁路低通滤波器，可以检测到噪声的低频成分并成功地从信号中去除。该滤波器可以检测到带宽相对较窄的升沉运动。通过仿真和实验验证了该滤波器的功能。其次，针对更精确的滤波，提出了另一种基于顺序最小二乘算法的滤波方法。该算法能够在不损失实时性的前提下识别噪声成分。为了保证算法的永久运行和防止参数发散，还采用了周期重置的方法。该算法能准确地检测出升沉运动，无漂移和相位延迟。该算法在升沉过程中也很稳定。在伺服控制的摆动台上，用升沉补偿器对该算法进行了实验验证。

Heave compensator is used to isolate instruments and structures, which are suspended from the floating body, from heave motion. In deepsea, heave motion detection is very difficult because the direct and realtime measurement by ultra sound and so on are impossible. In this research an active motion compensator system, which consists of accelerometer and actuator, has been developed. In this system, drift is removed by using the knowledge that average pisition of floating body stays mean water level.Firstly FIR digital filter was designed to double integrate the acceleration and remove the drift, high frequency and low frequency noise. The calculation is done numerically in a microprocessor. It became obvious during testing that the calculation of floating body position is extremely sesitive to any false fluctuation of signal, such as low-amplitude steady-state and very low frequency offsets from the true signal. With bypassed Low Pass Filter, low frequency component of noise is detected and successfully removed from the signal. This filter can detect heave motion of relatively narrow bandwidth. Simulation and experiment were performed and the function of the filter was confirmed.Secondly aiming more precise filter, another type of filter with sequential least square algorithm was developed. This algorithm enable to identify noise component without loss of realtimeness. Periodical reset is also employed to ensure the algorithm works permanently and to prevent divergence of parameters. With this algorithm heave motion is accurately detected without drift and phase delay. This algorithm also stable when initiated during the heaving. This algorithm was successfully tested by experiment with heave compensator on the servo-controlled oscillating stage.