在这情况，用比较小的体积焊接关节是更有利的。

In this case, welded joint with smaller volume are more favorable.

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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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各关节驱动电机的选择满足了机器人本体本身的重量尺寸大和负载有限对电机输出力矩大、重量轻、体积小的要求。

Because of the large size and weight, limited payload of the body, the joint-driving motors have to be powerful, small in size and light in weight.

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