系统主要由主电机、辅助电机、差动的行星机构、蜗轮蜗杆传动以及控制器组成。
The driven system is including a main motor, auxiliary motor, differential planet gear structure, worm driven and controller.
排气气门（5）借助于一包括一 液压气门辅助控制单元（12）的机械的连接机构（7，8）与凸轮轴相连 接。
The exhaust valve (5) is connected with a camshaft by means of a mechanical connecting mechanism (7, 8) including an hydraulic valve auxiliary control unit (12).
但是PMA还需要其他辅助机构才能构成关节和手臂，使用中增加了体积、重量，也给结构设计和控制带来不便。
However, assistant devices are needed to construct joint or arm with PMA, which increases the volume and weight. This makes the structure bigger and the control more difficult.
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