Back massaging device and its controlling method of massage route

A back massaging device, comprising:

• a seat back having a back rest portion for supporting a human back;
• a linear rack gear fixedly disposed on the seat back and extending in a vertical direction of the seat back;
• a frame body slidably disposed on the seat back;
• a gear shaft having a first rotation axis passing through the back rest portion;
• at least one main gear pivotally disposed at one surface of the frame body through the gear shaft;
• a massage member comprising a support arm and a massage protrusion, the support arm that is fixedly connected to the massage protrusion and the gear shaft, and the massage protrusion that is deviated from the first rotation axis of the gear shaft;
• a first motor assembly directly or indirectly meshed with the main gear for driving the main gear to rotate about the first rotation axis so as to rotate the massage protrusion by a predetermined angle;
• a second motor assembly directly or indirectly meshed with the linear rack gear for driving the frame body to vertically move along the vertical direction so as to control a height position of the massage protrusion;
• and
• a control unit disposed on the frame body, and electrically connected to the first motor assembly and the second motor assembly,
• wherein when one of trajectory scripts is executed, the control unit sequentially calculates rotation angle values and vertical movements that the massage protrusion is instructed to be moved, and controls the first motor assembly and the second motor assembly to operate synchronously, so that the massage protrusion is allowed to outline a trajectory pattern corresponding to the one of the trajectory scripts.