| 摘要 |
A parking brake is released by a controller and a rotating electric motor is speed-feedback-controlled or position-feedback-controlled to stop and hold an upper rotating body if at least one of arm operation, bucket operation, and travel operation is carried out in a rotating stopped state and with respect to the arm operation and the bucket operation, cylinder thrust of an arm cylinder or a bucket cylinder is greater or equal to a set value. Thereby, a parking brake and a rotating driving part can be prevented from being damaged by rotating external force generated by excavation reaction force or the like and a rotating body can be stopped and held.
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