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High-redundancy actuation (HRA) is a new approach to fault-tolerant control in the area of mechanical actuation. ==Overview== The basic idea is to use a lot of small actuation elements, so that a fault of one element has only a minor effect on the overall system. This way, a High Redundancy Actuator can remain functional even after several elements are at fault. This property is also called graceful degradation. Fault-tolerant operation in the presence of actuator faults requires some form of redundancy. Actuators are essential, because they are used to keep the system stable and to bring it into the desired state. Both requires a certain amount of power or force to be applied to the system. No control approach can work unless the actuators produce this necessary force. So the common solution is to err on the side of safety by over-actuation: much more control action than strictly necessary is built into the system. For critical systems, the normal approach involves straightforward replication of the actuators. Often three or four actuators are used in parallel for aircraft flight control systems, even if one would be sufficient from a control point of view. So if one actuator fails, the remaining actuator can always keep the system operation. While this approach certainly successful, it also makes the system expensive, heavy and ineffective. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「High-redundancy actuation」の詳細全文を読む スポンサード リンク
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