The previous crane could also be handled this way.
It consists of a large arm and a small arm.
The connection between the large arm and the car can rotate, and the angle between the small arm and the large arm can be adjusted.
When the small arm extends, the heavy object moves forward.
The small arm carries a pulley, which determines the position of the pulley.
The length of the cable constrained by the pulley determines the height at which the goods are lifted.
One motor controls the pulling of the cable, and another motor controls the movement of the small arm.
Another motor is used to control the rotation of the large arm.
Therefore, this crane can lift heavy objects, control height, rotate, and move back and forth along the direction of the boom.
Hence, it meets the requirements.
Although this structure is rather unconventional, requiring three motors for a crane to achieve these functions, it indeed gets the job done.
