Arm with a combined shape and force sensor

#Aspects of the invention relate to a system for using a sensor to monitor both the shape of an arm as well as an external force applied to that arm. Some aspects of the invention are particularly suited for monitoring flexible guide tubes and articulated arms used in robotic surgery.

#There has been considerable effort in developing systems for performing minimally invasive surgery. One area of particular interest is robotically assisted surgery.

#In robotically assisted surgery, the surgeon typically operates a control device at a location that is remote from the patient to control the motion of surgical instruments at the patient's surgical site. The control device typically includes one or more manually operated input devices, such as multiple degree of freedom master tool manipulators, joysticks, exoskeletal gloves, or the like, which are coupled to the surgical instruments via servo motors for articulating the instruments at the surgical site. During the surgical operation, the control device controls a surgical robotic manipulator that provides mechanical articulation and functional control of a variety of surgical instruments, such as tissue graspers, needle drivers, electrosurgical cautery probes, etc., that each perform various functions for the surgeon, e.g., holding or driving a needle, grasping a blood vessel, dissecting, cauterizing, or coagulating tissue.

#FIG. 1 is a diagrammatic view that illustrates a bask inventive concept.

#FIG. 2 is a diagrammatic view of elements of an arm and the associated forces that will be calculated in accordance with an aspect of the subject invention.

#FIG. 3 is diagrammatic view of one embodiment of the subject invention.

#Arms, including instruments and structures used to support and move such instruments, may be substantially rigid or flexible. Flexible instruments may be classified into two types: (i) continuously flexible arms that do not have discrete joints (i.e., infinite degrees of freedom), and (ii) arms that have a series of two or more short links interconnected by joints having at least one degree of freedom (the number of degrees of freedom being sufficient to provide the required flexibility). Many medical devices, such as catheters and small diameter minimally invasive instruments, have such a continuously flexible property. Many other medical devices, such as relatively large diameter endoscopes that include one or more working channels for minimally invasive instruments, are made of such a series of short, interconnected links. It is possible to have a hybrid flexible arm that includes at least one continuously flexible portion and at least one link portion. Arms with both rigid and flexible (continuous, linked, or hybrid) portions are also possible.

#Such arms may be actuated to move by various methods that provide a necessary actuation force. One exemplary method is actuation with one or more tendons (e.g., cables) that run along the length of an arm. A pulling force (tension) in one or more of the tendons bends the arm or a segment in the arm. Actuation force may be provided from various sources, such as manual crank or a servomotor. Other mechanical actuation methods, such as providing pushing force (compression) on tendons, using gears, etc. are known and may be used.

#An arm may include a passive stiffening element that applies a restoring force to a default pose for the arm. Stiffening elements may be of various forms, such as an internal spring that runs inside the flexible arm or an external sheath that surrounds the flexible arm. When no bending forces are applied to such an arm, the stiffening element enforces a minimum energy shape or kinematic configuration. If a bending force is applied to the arm, the stiffening element opposes the bending force on the portion of the arm that is being moved.