Grip device and controlling method thereof

A grip device comprising:

• a first finger comprising a groove formed as a plurality of inclined surfaces on a gripping surface of the first finger;
• a second finger facing the first finger;
• a middle member comprising a protrusion region inserted into the groove on the gripping surface of the first finger, the middle member covering the gripping surface of the first finger, a first surface of the middle member facing the gripping surface of the first finger, a second surface of the middle member being opposite to the first surface;
• a plurality of mono-axial force sensors, each mono-axial force sensor being respectively positioned on an inclined surface of the plurality of inclined surfaces and configured to detect a force only in one direction, the one direction being normal to the inclined surface, and the force being applied to the middle member by an object gripped between the first finger and the second finger,
• wherein the middle member is formed of a rigid material configured to transmit the force to the plurality of mono-axial force sensors without loss;
• a driving motor configured to adjust a gripping force of the first finger and the second finger;
• and
• a processor configured to:
• calculate a force vector applied to the middle member based on the forces detected by each of the plurality of mono-axial force sensors in the direction normal to each inclined surface, using sensing values received from the plurality of mono-axial force sensors, and
• based on a first force component of the force vector in a direction parallel to the second surface of the middle member being less than a preset value when the first finger and the second finger grip an object by a first gripping force, control the driving motor such that the first finger and the second finger grip the object by a second gripping force that is greater than the first gripping force.