TechTalks from event: Technical session talks from ICRA 2012

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Minimally Invasive Interventions II

  • Configuration Comparison for Surgical Robotic Systems Using a Single Access Port and Continuum Mechanisms Authors: Zheng, Xidian; Xu, Kai
    Research on robot-assisted laparoscopic SPA (Single Port Access) surgery and N.O.T.E.S (Natural Orifice Translumenal Endoscopic Surgery) have thrived in the past a few years. A configuration similarity between these surgical robotic slaves is that two robotic arms are extended from the same access port (either a laparoscope or an endoscope) for surgical interventions. However, upon designing such a surgical robotic slave, the structure of the extended robotic arms has not been explored thoroughly based on evaluation of their distal dexterity. This paper presents a simulation-based comparison among three different structures which could be used to form these extended robotic arms. Results presented in this paper could serve as a design reference for surgical robotic slaves which use a single access port and continuum mechanisms.
  • Control of Untethered Magnetically Actuated Tools Using a Rotating Permanent Magnet in Any Position Authors: Mahoney, Arthur; Cowan, Daniel Lewis; Miller, Katie; Abbott, Jake
    It has been shown that when a magnetic dipole, such as a permanent magnet, is rotated around a fixed axis such that the dipole is perpendicular to the axis of rotation, the magnetic field vector at every point in space also rotates around a fixed axis. In this paper, we reformulate this phenomenon using linear algebraic techniques, which enables us to find the necessary dipole rotation axis to make the magnetic field at any desired point in space rotate about any desired axis. To date, untethered magnetically actuated tools (e.g., capsule endoscopes, rolling spheres, and helical-propeller microswimmers) controlled with a single rotating permanent magnet have been constrained to operate in positions where the rotating field behavior is simple and easy to visualize. We experimentally demonstrate that the results of this paper can be used to control a variety of untethered, rotating magnetic devices in any position even while the rotating permanent magnet follows trajectories independent of the devices themselves. This method constitutes a substantial step toward making a great deal of prior laboratory research regarding rotating magnetic microrobots and capsule endoscopes clinically feasible.
  • Integration and Preliminary Evaluation of an Insertable Robotic Effectors Platform for Single Port Access Surgery Authors: Bajo, Andrea; Goldman, Roger E.; Wang, Long; Fowler, Dennis; Simaan, Nabil
    In this paper, we present the integration and preliminary evaluation of a novel Insertable Robotic Effectors Platform (IREP) for Single Port Access Surgery (SPAS). The unique design of the IREP includes planar parallel mechanisms, continuum snake-like arms, wire-actuated wrists, and passive flexible components. While this design has advantages, it presents challenges in terms of modeling, control, and telemanipulation. The complete master-slave resolved-rates telemanipulation framework of the IREP along with its actuation compensation is presented. Experimental evaluation of the capabilities of this new surgical system include bi-manual exchange of rings, pick-and-place tasks, suture passing and knot tying. Results show that the IREP meets the minimal workspace and dexterity requirements specified for laparoscopic surgery, it allows for dual-arm operations such as tool exchange and knot tying in confined spaces. Although it was possible to tie a surgeon's knot with minimal training, suture passing was difficult due to the limited axial rotation of the distal wrists.
  • Constrained Filtering with Contact Detection Data for the Localization and Registration of Continuum Robots in Flexible Environments Authors: Tully, Stephen; Bajo, Andrea; Kantor, George; Choset, Howie; Simaan, Nabil
    This paper presents a novel filtering technique that uses contact detection data and environmental stiffness estimates to register and localize a robot with respect to an a priori 3D surface model. The algorithm leverages geometric constraints within a Kalman filter framework and relies on two distinct update procedures: 1) an equality constrained step for when the robot is forcefully contacting the environment, and 2) an inequality constrained step for when the robot lies in the freespace of the environment. This filtering procedure registers the robot by incrementally eliminating probabilistically infeasible state space regions until a high likelihood solution emerges. In addition to registration and localization, the algorithm can estimate the deformation of the surface model and can detect false positives with respect to contact estimation. This method is experimentally evaluated with an experiment involving a continuum robot interacting with a bench-top flexible structure. The presented algorithm produces an experimental error in registration (with respect to the end-effector position) of 1.1 mm, which is less than 0.8 percent of the robot length.
  • Real-Time Control Architecture of a Novel Single-Port Laparoscopy Bimanual Robot (SPRINT) Authors: Niccolini, Marta; Petroni, Gianluigi; Menciassi, Arianna; Dario, Paolo
    This paper presents a novel master-slave teleoperated robotic platform designed for Single Port Laparoscopy. The SPRINT (Single-Port lapaRoscopy bimaNual roboT) is composed of two high-dexterity 6 Degrees of Freedom (DOFs) robotic arms, a stereoscopic camera and a dedicated console for the robot control by the surgeon. Along with a short summary of the hardware features of the system, this paper describes the real-time control architecture of the SPRINT. Particular attention was given to the kinematic coupling between the master and the slave manipulators, as well as to the inverse kinematics algorithm. Tests performed to validate the performance of the robot in terms of accuracy are satisfactory, thus positioning the SPRINT as a candidate for the next generation of robots for Single Port Laparoscopy.
  • Remote Centre-Of-Motion Control Algorithms of 6-RRCRR Parallel Robot Assisted Surgery System (PRAMiSS) Authors: Moradi Dalvand, Mohsen; Shirinzadeh, Bijan
    In this paper a 6-RRCRR parallel robot assisted minimally invasive surgery/microsurgery system (PRAMiSS) is introduced. Remote centre-of-motion (RCM) control algorithms of PRAMiSS suitable for minimally invasive surgery and microsurgery are also presented. The programmable RCM approach is implemented in order to achieve manipulation under the constraint of moving through the fixed penetration point. Having minimised the displacements of the mobile platform of the parallel micropositioning robot, the algorithms also apply orientation constraint to the instrument and prevent the tool tip to orient due to the robot movements during the manipulation. Experimental results are provided to verify accuracy and effectiveness of the proposed RCM control algorithms for minimally invasive surgery.

Biologically Inspired Robotics II

  • Approximating the Stance Map of the SLIP Runner Based on Perturbation Approach Authors: Yu, Haitao; Li, Mantian; Cai, Hegao
    The Spring-Loaded Inverted Pendulum (SLIP), or monopedal runner, is widely used to depict running and hopping in mammalian and human locomotion, which is also serving as a template for running robot design. This classic model describes quite a simple mechanical system. Nevertheless issue of seeking the accurate analytic solution revealing the characteristics of the motion during stance remains unsettled due to the nonintegrable terms contained in the system equations. Moreover, several existing analytic approximations by simply ignoring or linearizing the gravitational force can not reveal the entire dynamical behavior of nonlinear system as well as can be breakdown rapidly when applied to a non-symmetric motion case. In this paper, a novel method with perturbation technique is proposed to obtain analytic approximate solutions to the SLIP dynamics in stance phase with considering the effect of gravity. The perturbation solution achieves higher accuracy in predicting the apex trajectory and stance locomotion by comparing with typical existing analytical approximations. Particularly, our solution is validated for non-symmetric case in a large angle range. Additionally, the prediction for stance trajectory is also verified through numerical evaluation.
  • Analysis of Dynamics and Planar Motion Strategies of a Swimming Microorganism -- Giardia Lamblia Authors: Chen, Jun; Lenaghan, Scott; Zhang, Mingjun
    We studied the dynamics associated with planar swimming in the microorganism Giardia lamblia. Giardia parasitizes the small intestine of humans and other animals, and has evolved a robust attachment and swimming mechanism to survive this harsh environment, which provides potential bio-inspiration for microrobot design. In this paper, a 2D dynamic model of flagella-body-fluid interaction was developed to analyze the actuation of the flagellum, energy supply and dissipation, and thrust along the flagellum. We found that to achieve the observed flagella motion, the required actuation bending moment decreases in magnitude from the proximal to the distal end, and that energy only needs to be supplied to the proximal half portion of the flagellum. The supplied energy is dissipated to the fluid continuously along the flagellum, with almost linearly increasing magnitude towards the distal end. Consistently, thrust mainly comes from the posterior portion of the flagellum. We also analyzed the kinematics of the flagella. The characteristics of the forward and turning motion are revealed through simulation. These results may help the gait planning and actuation for energy efficient propulsion in swimming micro-robotic design.
  • Against the Flow: A Braitenberg Controller for a Fish Robot Authors: Salumae, Taavi; Rano, Inaki; Akanyeti, Otar; Kruusmaa, Maarja
    Underwater vehicles do not localise or navigate with respect to the flow, an ability needed for many underwater tasks. In this paper we implement rheotaxis behaviour in a fish robot, a behaviour common to many aquatic species. We use two pressure sensors on the head of the robot to identify the pressure differences on the left and right side and control the heading of the fish robot by turning a servo-motor actuated tail. The controller is inspired by the Braitenberg vehicle 2b, a simple biological model of tropotaxis, that has been used in many robotic applications. The experiments, conducted in a flow pipe with a uniform flow, show that the robot is able to orient itself, and keep the orientation, to the incoming current. Our results demonstrate that guidance of a fish robot relative to a flow can be implemented as a simple rheotaxis behaviour using two sensors and a Braitenberg 2b controller.
  • Simplified Motion Modeling for Snake Robots Authors: Enner, Florian; Rollinson, David; Choset, Howie
    We present a general method of estimating a snake robot’s motion over flat ground using only knowledge of the robot’s shape changes over time. Estimating world motion of snake robots is often difficult because of the complex way a robot’s cyclic shape changes (gaits) interact with the surrounding environment. By using the virtual chassis to separate the robot’s internal shape changes from its external motions through the world, we are able to construct a motion model based on the differential motion of the robot’s modules between time steps. In this way, we effectively treat the snake robot like a wheeled robot where the bottom-most modules propel the robot in much the way the bottom of the wheels would propel the chassis of a car. Experimental results using a 16-DOF snake robot are presented to demonstrate the effectiveness of this method for a variety of gaits that have been designed to traverse flat ground.
  • Conical Sidewinding Authors: Gong, Chaohui; Hatton, Ross; Choset, Howie
    Sidewinding is an efficient translation gait used by snakes and snake robots over flat ground, and resembles a helical tread moving over a core cylindrical geometry. Most sidewinding research has focused on straight-line translation of the snake, and less on steering capabilities. Here, we offer a new, geometrically intuitive method for steering this gait: Tapering the core cylinder into a cone, such that one end moves faster than the other, changing the heading of the robot as it drives forward. We present several design tools for working with this cone, along with experimental results on a physical robot turning at different rates.
  • Altitude Feedback Control of a Flapping-Wing Microrobot Using an On-Board Biologically Inspired Optical Flow Sensor Authors: Duhamel, Pierre-Emile; Perez-Arancibia, Nestor O; Barrows, Geoffrey; Wood, Robert
    We present experimental results on the controlled vertical flight of a flapping-wing flying microrobot, in which for the first time an on-board sensing system is used for measuring the microrobot's altitude for feedback control. Both the control strategy and the sensing system are biologically inspired. The control strategy relies on amplitude modulation mediated by optical flow. The research presented here is a key step toward achieving the goal of complete autonomy for flying microrobots, since this demonstrates that strategies for controlling flapping-wing microrobots in vertical flight can rely on optical flow sensors.

Underactuated Robots

  • Trajectory Generation for Underactuated Control of a Suspended Mass Authors: Schultz, Jarvis; Murphey, Todd
    The underactuated system under consideration is a magnetically-suspended, differential drive robot with a winch system articulating a suspended mass. A dynamic model of the system is first constructed, and then a nonlinear, infinite-dimensional optimization algorithm is presented. The Lagrangian mechanics based system model uses the principles of kinematic reduction to produce a mixed kinematic-dynamic model that isolates the modeling of the system actuators from the modeling of the rest of the system. In this framework, the inputs become generalized velocities instead of generalized forces facilitating real-world implementation in an embedded system. The optimization algorithm automatically deals with the complexities introduced by the nonlinear dynamics and underactuation to synthesize dynamically feasible system trajectories for a wide array of trajectory generation problems. Applying this algorithm to the mixed kinematic-dynamic model, several example problems are solved and the results are tested experimentally. The experimental results agree quite well with the theoretical showing promise in extending the capabilities of the system to utilize more advanced feedback techniques and to handle more complex, three-dimensional problems.
  • Planning in High-Dimensional Shape Space for a Single-Wheeled Balancing Mobile Robot with Arms Authors: Nagarajan, Umashankar; Kim, Byungjun; Hollis, Ralph
    The ballbot with arms is an underactuated balancing mobile robot that moves on a single ball. Achieving desired motions in position space is a challenging task for such systems due to their unstable zero dynamics. This paper presents a novel approach that uses the dynamic constraint equations to plan shape trajectories, which when tracked will result in optimal tracking of desired position trajectories. The ballbot with arms has shape space of higher dimension than its position space and therefore, the procedure uses a user-defined weight matrix to choose between the infinite number of possible combinations of shape trajectories to achieve a particular desired trajectory in position space. Experimental results are shown on the real robot where different motions in position space are achieved by tracking motions of either the body lean angles, or the arm angles or combinations of both.
  • Integrated Planning and Control for Graceful Navigation of Shape-Accelerated Underactuated Balancing Mobile Robots Authors: Nagarajan, Umashankar; Kantor, George; Hollis, Ralph
    This paper presents controllers called motion policies that achieve fast, graceful motions in small, collision-free domains of the position space for balancing mobile robots like the ballbot. The motion policies are designed such that their valid compositions will produce overall graceful motions. An automatic instantiation procedure deploys motion policies on a 2D map of the environment to form a library and the validity of their composition is given by a gracefully prepares graph. Dijsktra's algorithm is used to plan in the space of these motion policies to achieve the desired navigation task. A hybrid controller is used to switch between the motion policies. The results of successful experimental testing of two navigation tasks, namely, point-point and surveillance motions on the ballbot platform are presented.
  • Differentially Flat Design of a Closed-Chain Planar Under-Actuated 2 DOF System Authors: Zhang, Chengkun; Franch, Jaume; Agrawal, Sunil
    This paper investigates when a 2 degree-offreedom PRRRP closed-chain system with a single actuator is both strongly accessible and feedback linearizable. It is demonstrated that for certain choices of mass distribution and addition of springs, an under-actuated 2 DOF PRRRP system is static feedback linearizable, i.e., also differentially flat.
  • Design of Energy Efficient Walking Gaits for a Three-Link Planar Biped Walker with Two Unactuated Degrees of Freedom Authors: Ortiz Morales, Daniel; La Hera, Pedro
    We consider the example of a three-link planar biped walker with two passive links. The main objective is to design symmetric periodic gaits in flat ground, that can be exponentially stabilized by feedback control. To this end, we apply recent advances in nonlinear control, to propose a systematic procedure to the problems of gait synthesis and control design. The core of the method lays on a nontrivial coordinate transformation, in order to approach the problem in a state-dependent form. For gait synthesis, such procedure allows a reduction of the search space, with the feasibility of considering energetic performance for optimization. For control design, this allows to apply concepts of transverse linearization, to design a nonlinear feedback control law, which performance is studied by numerical simulations.
  • Biped Walking Stabilization Based on Gait Analysis Authors: Hashimoto, Kenji; Takezaki, Yuki; Motohashi, Hiromitsu; Lim, Hun-ok; Takanishi, Atsuo
    This paper describes a walking stabilization control based on gait analysis for a biped humanoid robot. We have developed a human-like foot mechanism mimicking the medial longitudinal arch to clarify the function of the foot arch structure. To evaluate the arch function through walking experiments using a robot, a walking stabilization control should also be designed based on gait analysis. Physiologists suggest the ankle, hip and stepping strategies, but these strategies are proposed by measuring human beings who are not "walking" but "standing" against force disturbances. Therefore, first we conducted gait analysis in this study, and we modeled human walking strategy enough to be implemented on humanoid robots. We obtained following two findings from gait analysis: i) a foot-landing point exists on the line joining the stance leg and the projected point of CoM on the ground, and ii) the distance between steps is modified to keep mechanical energy at the landing within a certain value. A walking stabilization control is designed based on the gait analysis. Verification of the proposed control is conducted through experiments with a human-sized humanoid robot WABIAN-2R. The experimental videos are supplemented.