Haptic assistance to mitigate damaging vertical accelerations of small fast ships in head waves

Abstract

Crew of small fast ships often experience exces- sive vertical accelerations when sailing in waves, leading to discomfort and injuries. In an attempt to avoid this, in good visibility experienced operators reduce speed voluntarily when they anticipate that the next vertical peak acceleration will be unacceptably large. However, at night and during excessive spray, the operator can hardly see the environment which makes it almost impossible to anticipate wave driven events. On top of that, this approach carries the risk of operator misjudgment due to loss of concentration or fatigue. In this paper, the potential of haptic feedback to support the operator in preventing dangerously large vertical accelerations is inves- tigated. A stochastic based approach was used in combination with a high end ship simulator to construct a haptic algorithm which gives a maximum advisable propeller speed setting based on an estimate of the current sea state. In order to test the effectiveness of this approach, a human-in-the-loop experiment was conducted using a within-subject design with 24 conveniently sampled participants. In this experiment the effect of haptic assistance is compared to manual control under both good and reduced visibility conditions. A key advantage of implemented haptic feedback algorithms is that the human remains in the control loop and can continuously decide to overrule the haptic advice. From the experiment it is found that the workload experienced by the operators is significantly decreased when using haptic feedback. However, no significant decrease in the number of excessive vertical accelerations was found using the current setup. A possible explanation for this result is the lack of motion cues and the inexperience of the participants. Therefore, it is recommended to extend the setup with a motion platform and conduct future experiments with experienced operators.