Design, modeling and analysis of continuum robots as surgical assistants with intrinsic sensory capabilities

New robotic surgical assistants are expected to enable precise dexterous manipulation and provide haptic perception in robot-assisted Minimally Invasive Surgery (MIS). Their implementations in MIS have been shown to further reduce patients' postoperative pain, complications, hospitalization time, etc. This dissertation presents the modeling and analysis for a new type of continuum robots as surgical assistants with intrinsic sensory capabilities. These continuum robots consist of multiple flexible backbones, enhancing dexterity at the distal ends of the surgical assistants, integrating wrench sensing capabilities and possessing inherent flexibility that assures soft and safe interactions with the human anatomy.;This dissertation first presents simplified models for kinematics and statics of these continuum robots. These models are extended from previous works and are based on a ubiquitously accepted assumption that shape of each segment of the continuum robots is circular. This assumption is experimentally validated and some necessary correction factors are introduced.;The simplified models for kinematics and statics can be evaluated in a real-time manner and enable the implementation of the continuum robots in a 16-DoF dual-arm teleoperative robotic system for the throat MIS and in a 17-DoF dual-arm teleoperative robotic system for the Single Port Access (SPA) abdominal surgery. An actuation compensation method for these continuum robots is presented to compensate for the discrepancy between the simplified model and the actual kinematic characteristic of the continuum robots in order to assure manipulation accuracy during the operations. This compensation method uses a tiered hierarchy of two novel approaches in both joint space and configuration space for these remotely actuated continuum robots. Experimental results validate the compensation method by demonstrating suturing and knot tying in confined spaces using these robots under surgeons' control.;The intrinsic wrench sensing capability of these continuum robots is then investigated. This wrench estimation is achieved via monitoring the actuation forces of the joints and is referred to as intrinsic wrench sensing . The essence of this intrinsic wrench sensing is to treat the entire continuum robot as a multiple-axis force sensor and having transducers monitor the loads on the actuation lines. This end-effector-as-sensor approach fulfills the rapidly increasing needs for miniature tools with force sensing capability subject to various limitations in MIS, such as sizes, MRI compatibility, sterilizability, etc. The presented wrench sensing capability is validated through experiments in different scenarios, demonstrating these continuum robots can sense the external wrenches and generate stiffness map of phantom tissues for possible medical applications such as palpation for tumor detection. In order to understand the limitation of the intrinsic wrench sensing, screw theory is used to provide geometric interpretation of the sensible and insensible wrenches. The analysis is based on the Singular Value Decomposition (SVD) of the Jacobian mapping between the configuration space and the twist space of the end effector. Furthermore, in order to quantify how suitable the intrinsic wrench sensing is for different scenarios, a performance index is introduced as an extension of the evaluation index for load cell designs. Evaluations of the performance index for different types of robots in simulation case studies show that this index can serve as an implementation guide for robots that provide force sensing.;These new continuum robots consist of one or more flexible segments. Each segment consists of one primary backbone and multiple secondary backbones. It possesses two degrees of freedom (DoF) via simultaneous actuation of the secondary backbones in a push-pull mode. Actuation redundancy is introduced since three secondary backbones are actuated to carry out a 2-DoF bending motion for each segment.;In the end, a novel and unified analytic formulation for kinematics, statics, and shape restoration of these continuum robots is presented to study the exact shapes of all the backbones. A solution framework based on constraints of geometric compatibility and static equilibrium is derived using elliptic integrals. This framework allows the investigation of the effects of different external loads and actuation redundancy resolutions on the shape variations of these continuum robots. The simulation and experimental validation results show that these continuum robots bend into an exact circular shape for one particular actuation resolution. The simulation results show that these continuum robots have the ability to redistribute loads among their backbones without introducing significant shape variations. (Abstract shortened by UMI.)...