Flexible tube insertion apparatus and flexible tube insertion method

A flexible tube insertion apparatus comprising:

• a flexible tube section that is adapted to be inserted into an insertion target;
• a variable stiffness material that is disposed in the flexible tube section and configured to change a bending stiffness of the flexible tube section;
• a drive actuator configured to drive the variable stiffness material;
• a rotation detection sensor configured to detect rotation of the flexible tube section about a central axis;
• an insertion shape detection sensor configured to detect a curved shape of the flexible tube section;
• and
• a controller configured to control the drive actuator so that a bending stiffness of the variable stiffness material is increased in response to determining that the flexible tube section forms a loop and that the flexible tube section rotates about the central axis, based on rotation information detected by the rotation detection sensor and curved shape information detected by the insertion shape detection sensor;
• wherein the controller is configured to, based on the rotation information and the curved shape information,
• control the drive actuator so that the bending stiffness of the variable stiffness material is reduced in response to determining that the flexible tube section is being pushed, and
• control the drive actuator so that the bending stiffness of the variable stiffness material is increased in response to determining that the flexible tube section is being pulled out based on the rotation information and the curved shape information.