科研之友
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摘要
The objective of our study is to develop a safety measure that ensures smooth control mode switching of an intelligent assist device (IAD)-Skill-Assist for the purpose of effective automotive manufacturing. Smooth switching, i.e., switching without abrupt deceleration, from the hands-off control mode (used for automatic travel) to the hands-on control mode (as typified by a power-assist control mode) is expected to enhance the productivity of IADs. However, the hazardous behaviors, i.e., careless behaviors that disregard an approaching IAD in hands-off control mode might cause collision and serious injuries to a human operator. For safety purposes, we focused on the operator's gesture of reaching for the force sensor of the Skill-Assist. Laser range sensors were employed to recognize the reaching gesture during control mode switching. A reaching gesture recognition algorithm, based on a hidden Markov model, processes characteristic patterns acquired by the laser range sensors, and judges the operator safety. Experimental results suggest that the Skill-Assist to which the proposed safety measure was applied could recognize the reaching gesture of an operator when the control mode was smoothly switched. In an experiment on hazardous behavior, the Skill-Assist could predict that the operator would be unsafe.
Note to Practitioners-IADs are force-control based robotic devices that enable a human operator to handle heavy modules, and they play a valuable role in automobile production lines. IADs can function in both a force control mode, defined as a hands-on control mode, and in an automatic traveling mode, defined as the hands-off control mode. How the unit switches between the hands-off and hands-on control modes has a considerable impact on productivity of automotive manufacturing. Smooth control mode switching, i.e., control mode switching without abrupt deceleration, could be achieved in our previous study. However, safety measures for dealing with the hazardous behaviors, i.e., careless behaviors that disregard an approaching IAD in hands-off control mode, which might cause serious injuries to the operator, were not considered. The objective of our study is to develop a safety measure ensuring smooth control mode switching of an IAD based on the method in our previous study, the use of laser range sensors (LRSs), and a pattern recognition algorithm. The proposed safety measure is expected to allow smooth control mode switching of IADs in practical automobile manufacturing; it can ensure safety monitoring that continuously operates an IAD without the production cycle delay by the frequent abrupt deceleration. This is important for efficient and safe operations of IADs with hands-off and hands-on control modes and will contribute toward effective automobile manufacturing. However, the proposed safety measure adopted the general purpose type LRSs and depended on the relatively large-scaled software for safety purpose. Therefore, LRS with certification by safety standards, and techniques and verification processes for safe software are essentially required for practical application. Moreover, the proposed safety measure was verified by certain foreseeable hazardous behaviors; for further improvement and practical application, it should be verified for other possible behaviors in fields where IADs are used.
- 出版日期2010-10
