In this work, we present the conceptual design of a 3.5mm outside diameter cable-driven hyper-redundant robotic manipulator with an attached micro-force sensor at the tip for application in transurethral palpation of any targeted area of the bladder interior wall tissue. The stain-gauge based micro-force sensor is designed using finite element analysis (safety factor > 3.5 and load capacity of 0.8N) and subsequently prototyped using additive manufacturing. Sensor components were prototyped using additive and traditional manufacturing, assembled and characterized using a data acquisition environment. The performance of the finite element and prototyped sensor was almost identical. The characterized sensor was used to evaluate tissue properties. The concept of a hyper-redundant 10-joint 6-DOF manipulator comprising of a 5-DOF rigid and a 5-DOF continuum segment is presented along with the forward and inverse kinematics analyses. The inverse kinematics is performed using a Jacobian based formulation to limit the possibilities of singularities. Studies employing the proposed inverse kinematics analysis demonstrated the ability of the manipulator to engage with any area in the bladder and especially the difficult to reach trigone area while attaining a normal pose at the point of contact. A normal pose is required for properly interrogating the tissue with the uniaxial force sensor. The proposed manipulator and force sensor system as presented suggest a probable solution for quantitatively evaluating localized biomechanical properties of the bladder interior wall tissue as a means towards improving treatment and providing better patient care. An initial limited functionality prototype demonstrates capabilities of the proposed concept and provides confidence for further research to fully realize the proposed concept.
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Minimally invasive procedures employ continuum manipulators, however internal human anatomy presents challenges relating to size, dexterity, and workspace for these manipulators. This manuscript presents modeling, kinematic analysis, prototyping, and characterization of a micro-robotic manipulator for transurethral palpation of bladder tissue. The proposed micro-robot consists of two subsystems: a tendon-driven continuum segment with an elastic tube encompassing each joint for compliance and structural integrity, and a hyper-spherical joint ensuring higher dexterity and manipulability with a comprehensive actuation and modeling approach. The forward kinematics follow the Denavit-Hartenberg formulation. A developed differential Jacobian inverse kinematics formulation prevents motion singularities for desired poses while operating in the confined space. The simulated kinematic results confirm the dexterity and reach of the proposed micro-robot. A strain energy quasi-static model is developed for a single continuum module. The model is evaluated for tension-bend angle relationships as function of tube material and geometry, and joint length. Limited functionality continuum modules (4mm outside diameter) with four different joint lengths, (3, 6, 9, 12) mm, are prototyped for tension-bend angle characterization using a computer vision outfitted experimental setup. An equivalent shear modulus relationship for the elastic tube for selected joint length values and bend angles is developed using experimental results. The tension-bend angle response is nonlinear and function of tube properties, joint geometry, and their interactions. The comparison of the experimental and quasi-static model results shows high fidelity for use in predicting the robot continuum segment behavior.
We present the conceptual design and limited functionality prototype and characterization of a system for application in transurethral palpation of any targeted area of the bladder interior wall tissue consisting of a robotic manipulator and a micro-force sensor attached at its tip all less than 3.5mm in diameter. A hyper-redundant 10-joint 6-DOF manipulator (5-DOF rigid and 5-joint continuum segments) is presented along with the forward and inverse kinematics analyses based on a Jacobian formulation to prevent configuration singularities. Simulated motion studies demonstrate the ability of the proposed manipulator to attain a desired pose (normal to the tissue) with any area in the bladder including the difficult to reach trigone area. A strain gauge-based micro-force sensor is designed using finite element analysis (safety factor >3), prototyped using additive manufacturing, and characterized. The characterized sensor was used to acquire in vivo measurements to evaluate human palm tissue viscoelastic properties. A single module of the continuum segment is designed and prototyped using additive manufacturing, and used to characterize its tension-bend angle behavior. Finite element analysis is used to improve structurally weak regions of the vertebra. A 3-joint 4-vertebrae prototype was successfully actuated to reach a bend state using tendons. The developed robot and sensor prototypes demonstrate capabilities of the proposed concept which could be a possible solution to quantitatively evaluate localized biomechanical properties of the bladder tissue to improve treatment and provide better patient care.
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