TechTalks from event: Technical session talks from ICRA 2012

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Minimally invasive interventions I

  • Design Requirements and Feasibility Study for a 3-DOF MRI-Compatible Robotic Device for MRI-Guided Prostate Intervention Authors: Bohren, Jonathan; Iordachita, Iulian; Whitcomb, Louis
    This paper reports the design requirements, practical challenges, and a preliminary design for a magnetic resonance imaging (MRI) guided, three degree-of-freedom (DOF) transrectal prostate intervention robot. We show the operational space constraints imposed by patient anatomy when performing transrectal prostate procedures in a magnetic resonance (MR) scanner bore, as determined by analyzing data from 12 patient procedures with a device. We also describe practical challenges arising in designing a compact actuated MR compatible needle placement robot for MRI-guided transrectal needle intervention in the prostate. We present a preliminary design which aims to improve upon previous un-actuated and partially-actuated devices with the addition of an actuated needle insertion module. Such an enhancement enables needle driving to take place inside the MR scanner bore and thereby may reduce the overall procedure time -- thus improving patient comfort and reducing likelyhood of needle targeting errors resulting from patient motion. We show that it is feasible to add such actuation while reducing the footprint of the device in accordance with the anatomical and MR scanner constraints and practical design requirements.
  • Visual and Force-Feedback Guidance for Robot-Assisted Interventions in the Beating Heart with Real-Time MRI Authors: Navkar, Nikhil Vishwas; Deng, Zhigang; Shah, Dipan J.; Bekris, Kostas E.; Tsekos, Nikolaos
    Robot-assisted surgical procedures are perpetually evolving due to potential improvement in patient treatment and healthcare cost reduction. Integration of an imaging modality intraoperatively further strengthens these procedures by incorporating the information pertaining to the area of intervention. Such information needs to be effectively rendered to the operator as a human-in-the-loop requirement. In this work, we propose a guidance approach that uses real-time MRI to assist the operator in performing robot-assisted procedure in a beating heart. Specifically, this approach provides both real-time visualization and force-feedback based guidance for maneuvering an interventional tool safely inside the dynamic environment of a heart's left ventricle. Experimental evaluation of the functionality of this approach was tested on a simulated scenario of transapical aortic valve replacement and it demonstrated improvement in control and manipulation by providing effective and accurate assistance to the operator in real-time.
  • Trans-Abdominal Active Magnetic Linkage for Robotic Surgery: Concept Definition and Model Assessment Authors: Di Natali, Christian; Ranzani, Tommaso; Simi, Massimiliano; Menciassi, Arianna; Valdastri, Pietro
    The novel concept of Trans-abdominal Active Magnetic Linkage for laparoendoscopic single site surgery has the potential to enable the deployment of a bimanual robotic platform trough a single laparoscopic incision. The main advantage of this approach consists in shifting the actuators outside the body of the patient, while transmitting a controlled robotic motion by magnetic field across the abdomen without the need for dedicated incisions. An actuation mechanism based on this approach can be comprised of multiple anchoring and actuation units, mixed depending upon the specific needs. A static model providing anchoring and actuation forces and torques available at the internal side of the magnetic link was developed to provide a tool to navigate among the many possibilities of such an open ended design approach. The model was assessed through bench top experiments, showing a maximum relative error of 4% on force predictions. An example of a single degree of freedom manipulator actuated with the proposed concept and compatible with a 12-mm access port is able to provide an anchoring force of 3.82 N and an actuation force of 2.95 N.
  • Cable Length Estimation for a Compliant Surgical Manipulator Authors: Segreti, Sean M.; Kutzer, Michael Dennis Mays; Murphy, Ryan Joseph; Armand, Mehran
    This paper presents a method for estimating drive cable length in an underactuated, hyper-redundant, snake-like manipulator. The continuum manipulator was designed for the surgical removal of osteolysis behind total hip arthroplasties. Two independently actuated cables in a pull-pull configuration control the compliant manipulator in a single plane. Using a previously developed kinematic model, we present a method for estimating drive cable displacement for a given manipulator configuration. This calibrated function is then inverted to explore the ability to achieve local manipulator configurations from prescribed drive cable displacements without the use of continuous visual feedback. Results demonstrate an effectiveness in predicting drive cable lengths from manipulator configurations. Preliminary results also show an ability to achieve manipulator configurations from prescribed cable lengths with reasonable accuracy without continuous visual feedback.
  • Towards a Compact Robotically Steerable Thermal Ablation Probe Authors: Graves, Carmen; Slocum, Alexander; Gupta, Rajiv; Walsh, Conor James
    The focus of this paper is on the design and evaluation of a robust drive mechanism intended to robotically steer a thermal ablation electrode or similar percutaneous instrument. We present the design of an improved screw-spline drive mechanism based on a profiled threaded shaft and nut that reduces the part count and simplifies manufacturing and assembly. To determine the optimal parameters for the profile shape, an analytical expression was derived that relates the tolerance between the nut and shaft to the angular backlash, which was validated using SolidWorks. We outline the forward kinematics of a steering mechanism that is based on the concept of substantially straightening a pre-curved Nitinol stylet by retracting it into a concentric outer cannula, and re-deploying it at a different position. This model was compared to data collected during targeting experiments performed in ex-vivo tissue samples where the distal tip of the stylet was repositioned in ex-vivo bovine tissue and the location of its distal tip was recorded with CT imaging. Results demonstrated that the drive mechanism operated robustly and targeting errors of less than 2mm were achieved.

Force, Torque and Contacts in Grasping and Assembly

  • Object Motion-Decoupled Internal Force Control for a Compliant Multifingered Hand Authors: Prattichizzo, Domenico; Malvezzi, Monica; Wimboeck, Thomas; Aggravi, Marco
    Compliance in multifingered hand improves grasp stability and effectiveness of the manipulation tasks. Compliance of robotic hands depends mainly on the joint control parameters, on the mechanical design of the hand, as joint passive springs, and on the contact properties. In object grasping the primary task of the robotic hand is the control of internal forces which allows to satisfy the contact constraints and consequently to guarantee a stable grasp of the object. When compliance is an essential element of the multifingered hand, and the control of the internal forces is not designed to be decoupled from the object motion, it happens that a change in the internal forces causes the object trajectory to deviate from the planned path with consequent performance degradation. This paper studies the structural conditions to design an internal force controller decoupled from object motions. The analysis is constructive and a controller of internal forces is proposed. We will refer to this controller as object motion-decoupled control of internal forces. The force controller has been successfully tested on a realistic model of the DLR Hand II. This controller provides a trajectory interface allowing to vary the internal forces (and to specify object motions) of an underactuated hand, which can be used by higher-level modules, e.g. planning tools.
  • Robust, Inexpensive Resonant Frequency Based Contact Detection for Robotic Manipulators Authors: Backus, Spencer; Dollar, Aaron
    This paper presents a method for detecting contact on a compliant link utilizing a method to sense changes in the resonant frequency of the link due to external contact. The approach uses an inexpensive accelerometer mounted on or inside the compliant link and a phase locked loop circuit to oscillate the link at its resonant frequency. Using this approach, we are able to reliably sense contact anywhere on the link with a contact force threshold sensitivity of between 0.05 and 0.15 N depending on the contact location.
  • Testing Pressurized Spacesuit Glove Torque with an Anthropomorphic Robotic Hand Authors: Roberts, Dustyn; Kim, Joo H.
    While robotic hands have been developed for manipulation and grasping, their potential as tools for performance evaluation of engineered products - particularly compliant garments that are not easily modeled – has not been broadly studied. In this research, the development of a low-cost anthropomorphic robotic hand is introduced that is designed to characterize glove stiffness in a pressurized environment. The anthropomorphic robotic hand was designed to mimic a human hand in a neutral posture corresponding to the naturally relaxed position in zero gravity, and includes the transverse arch, longitudinal arch, and oblique flexion of the rays. The resulting model also allows for realistic donning and doffing of the prototype spacesuit glove, its pressurization, and torque testing of individual joints. Solid models and 3D printing enabled the rapid design iterations necessary to successfully work with the compliant pressure garment. The performance of the robotic hand is experimentally demonstrated with a spacesuit glove for different levels of pressures, and a unique data processing method is used to calculate the required actuator torque at each finger's knuckle joint. The reliable measurement method confirmed that glove finger torque increases as the internal pressure increases. The proposed robotic design and method provide an objective and systematic way of evaluating the performance of compliant gloves.
  • Learning Grasping Force from Demonstration Authors: Lin, Yun; Ren, Shaogang; Clevenger, Matthew; Sun, Yu
    This paper presents a novel force learning framework to learn fingertip force for a grasping and manipulation process from a human teacher with a force imaging approach. A demonstration station is designed to measure fingertip force without attaching force sensor on fingertips or objects so that this approach can be used with daily living objects. A Gaussian Mixture Model (GMM) based machine learning approach is applied on the fingertip force and position to obtain the motion and force model. Then a force and motion trajectory is generated with Gaussian Mixture Regression (GMR) from the learning result. The force and motion trajectory is applied to a robotic arm and hand to carry out a grasping and manipulation task. An experiment was designed and carried out to verify the learning framework by teaching a Fanuc robotic arm and a BarrettHand a pick-and-place task with demonstration. Experimental results show that the robot applied proper motions and forces in the pick-and-place task from the learned model.
  • Revised Force Control Using a Compliant Sensor with a Position Controlled Robot Authors: Lange, Friedrich; Jehle, Claudius; Suppa, Michael; Hirzinger, Gerd
    A different way of force control is presented, that is especially advantageous for position controlled robots. Instead of usual force control laws we rely on the well tuned position control loop and just use the force sensor to measure the target pose or to predict the desired trajectory. In combination with a compliant sensor we introduce an inherently stable framework of force control which almost inhibits all control errors. After an unexpected impact the force error is reduced independently from the sensor's bandwidth or delays in signal processing. Thus the (inevitable) impact force is more significant than the measured force control errors. The special case of a sensor that is mounted far away from a vertex-face contact is discussed, too.
  • Force Controlled Robotic Assembly without a Force Sensor Authors: Stolt, Andreas; Linderoth, Magnus; Robertsson, Anders; Johansson, Rolf
    The traditional way of controlling an industrial robot is to program it to follow desired trajectories. This approach is sufficient as long as the accuracy of the robot and the calibration of the workcell is good enough. In robotic assembly these conditions are usually not fulfilled, because of uncertainties, e.g., variability in involved parts and objects not gripped accurately. Using force control is one way to handle these difficulties. This paper presents a method of doing force control without a force sensor. The method is based on detuning of the low-level joint control loops, and the force is estimated from the control error. It is experimentally verified in a small part assembly task with a kinematically redundant robotic manipulator.

Hybrid Legged Robots

  • Passive Dynamic Walking of Viscoelastic-Legged Rimless Wheel Authors: Asano, Fumihiko; Kawamoto, Junji
    imit cycle walking including passive-dynamic walkers is mathematically modeled as a nonlinear hybrid dynamical system with state jumps in general. The generated motion is natural and energy efficient, but it is still pointed out that there are many differences between limit cycle walking and human walking. Non-existence of the period of double-limb support in the former comes from the assumption of instantaneous inelastic collision and is one of the biggest differences from the latter. In human walking, the period of double-limb support accounts for more than 10% of one cycle, and this must have significant effects on the gait stability and efficiency. Also in robot walking, utilizing the effects of double-limb support is essential to achieve more flexible, adaptive and human-like behavior. This paper then develops a novel mathematical model of a passive rimless wheel that emerges double-limb support by using the leg viscoelasticity, and numerically investigates the fundamental properties.
  • Control of Dynamic Locomotion for the Hybrid Wheel-Legged Mobile Robot by using Unstable-Zeros Cancellation Authors: Suzumura, Akihiro; Fujimoto, Yasutaka
    In this paper, a new method of center of mass trajectory planning using the zero-phase low pass filter is proposed. This method is based on a table-cart model which simply describes the relationship between center of mass and zero moment point. Generally, zero moment point should be controlled to realize dynamic motion. This method can easily generate the center of mass trajectory which realizes the desired zero moment point. In our study, this method is applied to wheel-legged locomotion. We will show the result that zero moment point can be sufficiently controlled even if quadruped wheel-legged mobile robot is apploximated to a table-cart model. The effectiveness of the idea is validated by simulation and experiment.
  • Comparison of Cost Functions for Electrically Driven Running Robots Authors: Remy, C. David; Buffinton, Keith; Siegwart, Roland
    In this work we apply optimal control to create running gaits for the model of an electrically driven one legged hopper, and compare the results obtained for five different objective functions. By using high compliant series elastic actuators, the motions of joint and motor are decoupled, which allows the exploitation of natural dynamics. Depending on the cost function, this exploitation varies. Energy is injected at different points of time, the amplitude of actuator action changes significantly, and the optimal gear ratios differ by a factor of two. Variations are, however, comparable over a wide range of hopping heights and running velocities. Purely force-based cost functions prove to be ill-suited for such non-conservative systems, and it is shown that thermal electrical losses, in contrast to common belief, do not dominate energy expenditure. The numerical results are corroborated by detailed analytical considerations which give general insights into optimal excitation with electric actuators.
  • A Reduced-Order Dynamical Model for Running with Curved Legs Authors: Jun, Jae Yun; Clark, Jonathan
    Some of the unique properties associated with running with curved legs or feet (as opposed to point-contact feet) are examined in this work, including the rolling contact motion, the change of the leg's effective stiffness and rest length, the shift of the effective flexion point along the leg, and the compliant-vaulting motions over its tiptoe during stance. To examine these factors, a novel torque-driven reduced-order dynamical model with a clock-based control scheme and with a simple motor model is developed (named as torque-driven and damped half-circle-leg model (TD-HCL)). The controller parameters are optimized for running efficiency and forward speed using a direct search method, and the results are compared to those of other existing dynamical models such as the torque-driven and damped spring-loaded-inverted-pendulum (TD-SLIP) model, the torque-driven and damped two-segment-leg (TD-TSL) model, and the TD-SLIP with a rolling foot (TD-SLIP-RF) model. The results show that running with rolling is more efficient and more stable than running with legs that involve pin joint contact model. This work begins to explain why autonomous robots using curved legs run efficiently and robustly. New curved legs are designed and manufactured in order to validate these results.
  • FastRunner: A Fast, Efficient and Robust Bipedal Robot. Concept and Planar Simulation Authors: Cotton, Sebastien; OLARU, IONUT MIHAI CONSTANTIN; bellman, matthew; van der ven, tim; Godowski, Johnny C; Pratt, Jerry
    Bipedal robots are currently either slow, energetically inefficient and/or require a lot of control to maintain their stability. This paper introduces the FastRunner, a bipedal robot based on a new leg architecture. Simulation results of a Planar FastRunner demonstrate that legged robots can run fast, be energy efficient and inherently stable. The simulated FastRunner has a cost of transport of 1.4 and requires only a local feedback of the hip position to reach 35.4 kph from stop in simulation.
  • Zero-Moment Point Based Balance Control of Leg-Wheel Hybrid Structures with Inequality Constraints of Dynamic Behavior Authors: An, Sang-ik; Oh, Yonghwan; Kwon, Dong-Soo
    This paper discusses an unified method of the tracking and balancing controls for leg-wheel hybrid structures in an effort to improve the mobility over hard, flat surfaces. Preliminarily, we analyzed the contact constraint to formulate a dynamically decoupled model in the task space. Then, inequality constraints were determined to restrict the dynamic behavior of the system within the given bounds for the dynamic stability and the actuator saturation. The inequality constraints were applied to the reference control input that was designed for the mechanism to traverse the desired trajectories without the constraints. To find the constrained control input, a quadratic objective function was proposed to minimize the modification error of the control inputs. We tested the effectiveness of the proposed algorithm by comparing simulation results with our previous research.