Manipulator

1. A manipulator comprising:

an elongated main portion, a distal end portion disposed at a distal end of the main portion, and a bendable portion provided between the main portion and the distal end portion;

a plurality of linear members that are connected to the distal end portion and that extend to the main portion via the bendable portion;

a power generator that generates power;

a plurality of power transmitters that are provided in the main portion and that transmit, to proximal ends of the linear members, the power generated by the power generator as linear motion in a longitudinal direction of the main portion; and

a linear-member relaxing unit that relaxes the plurality of linear members in which tension is generated between the distal end portion and the power transmitters by pushing and pulling of the linear members in the longitudinal direction by the linear motion transmitted from the power transmitters;

wherein the power transmitters each include

a shaft member that is disposed in the longitudinal direction in the main portion and that is rotated about an axis extending in the longitudinal direction by the power generated by the power generator,

a threaded shaft member that connects the proximal end of the corresponding linear member to the shaft member and that is rotated together with the shaft member, and

a nut member that is engaged with the threaded shaft member and that feeds the rotating threaded shaft member in the longitudinal direction.

2. The manipulator according to claim 1 , wherein the linear-member relaxing unit causes the distal end portion and the plurality of power transmitters to relatively move in the longitudinal direction close to each other.

3. The manipulator according to claim 2 , wherein the linear-member relaxing unit includes a supporting member that simultaneously supports the plurality of power transmitters and that is movable together with the plurality of power transmitters in the longitudinal direction relative to the main portion, and a moving mechanism that moves the supporting member toward the distal end.

4. The manipulator according to claim 2 , wherein the linear-member relaxing unit includes a supporting member that supports a proximal end of the bendable portion, and a moving mechanism that moves the supporting member toward the proximal end.

5. The manipulator according to claim 3 ,

wherein the moving mechanism includes

a rotational-force generator that generates a rotational force, and

a power converter that converts the rotational force generated by the rotational-force generator into linear motion in the longitudinal direction and transmits the linear motion to the supporting member.

6. The manipulator according to claim 4 ,

wherein the moving mechanism includes

a rotational-force generator that generates a rotational force, and

a power converter that converts the rotational force generated by the rotational-force generator into linear motion in the longitudinal direction and transmits the linear motion to the supporting member.

7. A manipulator comprising:

an elongated main portion, a distal end portion disposed at a distal end of the main portion, and a bendable portion provided between the main portion and the distal end portion;

a plurality of linear members that are connected to the distal end portion and that extend to the main portion via the bendable portion;

a plurality of pulling mechanisms provided in the main portion and having connectors that are connected to proximal ends of the linear members, drivers that generate rotational motion, and power converters that convert the rotational motion generated by the drivers into linear motion in a longitudinal direction and transmit the linear motion to the connectors; and

a combination changing mechanism that changes a combination of the linear members and the pulling mechanisms connected to the linear members;

wherein the power converters each include a shaft member that is disposed in a longitudinal direction of the main portion and that is rotated about a central axis thereof by the corresponding driver, a threaded shaft member that is coaxial with the shaft member and that is rotated together with the shaft member, and a movable member that has a thread groove engageable with the threaded shaft member and that is provided at the proximal end of the corresponding linear member in a movable manner in the longitudinal direction, and

wherein each connector is formed of the threaded shaft member and the movable member.

8. The manipulator according to claim 7 , wherein the combination changing mechanism changes the combination of the linear members and the pulling mechanisms by moving the pulling mechanisms relative to the linear members.

9. The manipulator according to claim 8 ,

wherein the main portion includes a tubular outer tube having a first part that is fixed to the bendable portion and a second part that is provided at a proximal end of the first part in a rotatable manner in a circumferential direction relative to the first part and that accommodates the pulling mechanisms, and

wherein the combination changing mechanism moves the pulling mechanisms relative to the linear members by rotating the pulling mechanisms together with the second part.

10. The manipulator according to claim 7 , further comprising:

a fault detector that detects a fault in the pulling mechanisms,

wherein the combination changing mechanism changes the combination of the linear members and the pulling mechanisms when the fault detector detects a fault in the pulling mechanisms.