TechTalks from event: Technical session talks from ICRA 2012

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Biomimetics

  • Experimental Validation of locomotion efficiency of Worm-like Robots and Contact Compliance Authors: Zarrouk, David; Sharf, Inna; Shoham, Moshe
    Biological vessels are characterized by their substantial compliance and low friction which present a major challenge for crawling robots for minimally invasive medical procedures. Quite a number of studies considered the design and construction of crawling robots, however, very few focused on the interaction between the robots and the flexible environment. In a previous study, we derived the analytical efficiency of worm locomotion as a function of the number of cells, friction coefficients, normal forces and local (contact) tangential compliance. In this paper, we generalize our previous analysis to include dynamic and static coefficients of friction, determine the conditions of locomotion as function of the external resisting forces and experimentally validate our previous and newly obtained theoretical results. Our experimental setup consists of worm robot prototypes, flexible interfaces with known compliance and a Vicon motion capture system to measure the robot positioning. Separate experiments were conducted to measure the tangential compliance of the contact interface which is required for computing the analytical efficiency. The validation experiments are shown to be in clear match with the theoretical predictions. Specifically, the convergence of the tangential deflections to an arithmetic series and the partial and overall loss of locomotion verify the theoretical predictions.
  • Dynamic Turning of 13 Cm Robot Comparing Tail and Differential Drive Authors: Pullin, Andrew; Kohut, Nicholas Joseph; Fearing, Ronald
    Rapid and consistent turning of running legged robots on surfaces with moderate friction is challenging due to leg slip and uncertain dynamics. A tail is proposed as a method to effect turns at higher yaw frequencies than can be obtained by differential velocity drive of alternate sides. Here we introduce a 100 mm scale dynamic robot - OctoRoACH - with differential-drive steering and a low-mass tail to investigate issues of yaw rate control. The robot without tail is under-actuated with only 2 drive motors and mass of 35 grams including all battery and control electronics. For some surface conditions, OctoRoACH can maintain heading or turning rate using only leg velocity control, and a basic rate-gyro-based heading control system can respond to disturbances, with a closed-loop bandwidth of approximately 1 Hz. Using a modified off-the-shelf servo for the tail drive, the robot responds to turning commands at 4 Hz.
  • A Compliant Bioinspired Swimming Robot with Neuro-Inspired Control and Autonomous Behavior Authors: Stefanini, Cesare; Orofino, Stefano; Manfredi, Luigi; Mintchev, Stefano; Marrazza, Stefano; Assaf, Tareq; Capantini, Lorenza; Sinibaldi, Edoardo; Grillner, Sten; Wallén, Peter; Dario, Paolo
    In this paper the development of a bio-robotic platform is described. The robot design exploits biomechanical and neuroscientific knowledge on the lamprey, an eel-like swimmer well studied and characterized thanks to the reduced complexity of its anatomy. The robot is untethered, has a compliant body, muscle-like high efficiency actuators, proprioceptive sensors to detect stretch and stereoscopic vision. Experiments on the platform are reported, including robust and autonomous goal-directed swimming. Extensive experiments have been possible thanks to very high energy efficiency (around five hour continuous operating) the platform is ready to be used as investigation tool for high level motor tasks.
  • Kinematic Design of an Asymmetric In-phase Flapping Mechanism for MAVs Authors: Park, Joon-Hyuk; Yang, Emily; Agrawal, Sunil
    The thorax of an insect has direct flight muscles that can independently control the flapping amplitude, relative phase, and mean position of its left and right wings. This feature allows insects to modulate lateral dynamics during hovering flight, resulting in high flight maneuverability. This paper introduces the development and characterization of a novel flapping mechanism for MAVs, denoted as AIFM (Asymmetric In-phase Flapping Mechanism), that is capable of achieving controlled, asymmetric in-phase wing flapping as inspired by similar features in insects. The system consists of two 4-bar mechanisms that create basic flapping motions and two RRPR mechanisms that control the asymmetric flapping motion. The kinematics of the mechanism was investigated and optimized in such a way that enables the mechanism to produce reliable, in-phase wing motion during asymmetric flapping flight. The kinematics of the wings was evaluated both computationally and experimentally. It was shown that asymmetric wing flapping can be successfully achieved without affecting the in-phase flapping motion.
  • Maintaining Odor Tracking Behavior Using an Established Tracking Direction in a Dynamic Wind Environment Authors: Taylor, Brian; Wu, Dora; Willis, Mark; Quinn, Roger, D.
    The ability to autonomously track a fluid-borne odor has numerous engineering applications and natural occurrences. Engineering systems can use odor-guided navigation in tasks ranging from search and rescue to locating dangerous chemicals. Animals use odors to locate food and mates. For animals in strong unsteady turbulent flow environments where the wind is intermittent and occasionally vanishes, there is an ecological benefit to maintaining wind-driven tracking behavior. This has been shown in experiments performed using moths and cockroaches, where animals that began tracking odor in wind maintained their wind driven tracking behavior and eventually located the source after the wind was shut off during their tracking behavior. Here, we use RoboMoth, a previously developed 3D odor-tracking robot, to replicate these experiments. Our results can aid biologists in understanding how animals track odors in dynamic environments. In engineering, this study provides a first step in a hardware system towards linking odor tracking in strong wind environments to tracking in zero/low flow environments by studying the transition between the two regimes. This can help further engineers’ efforts to design odor-tracking systems capable of negotiating diverse and dynamic environments. Our study of the transition from using the wind as a primary directional cue to relying on odor and an established tracking direction appears to be novel in an engineering context and unique to our work.
  • Brain-inspired Bayesian Perception for Biomimetic Robot Touch Authors: Lepora, Nathan; Sullivan, John C W; Mitchinson, Ben; Pearson, Martin; Gurney, Kevin; Prescott, Tony J
    Studies of decision making in animals suggest a neural mechanism of evidence accumulation for competing percepts according to Bayesian sequential analysis. This model of perception is embodied here in a biomimetic tactile sensing robot based on the rodent whisker system. We implement simultaneous perception of object shape and location using two psychological test paradigms: first, a free-response paradigm in which the agent decides when to respond, implemented with Bayesian sequential analysis; and second an interrogative paradigm in which the agent responds after a fixed interval, implemented with maximum likelihood estimation. A benefit of free-response Bayesian perception is that it allows tuning of reaction speed against accuracy. In addition, we find that large gains in decision performance are achieved with unforced responses that allow null decisions on ambiguous data. Therefore free-response Bayesian perception offers benefits for artificial systems that make them more animal-like in behavior.

Micro - Nanoscale Automation

  • Automated Nanomanipulation for Nano Device Construction Authors: Zhang, Yanliang; Li, Jason; To, Steve; Zhang, Yong; Ye, Xutao; Sun, Yu
    Nanowire field-effect transistors (nano-FETs) are nano devices capable of highly sensitive, label-free sensing of molecules. However, significant variations in sensitivity across devices can result from poor control over device parameters, such as nanowire diameter and the number of electrode-bridging nanowires. This paper presents a fabrication approach that uses wafer-scale nanowire contact printing for throughput and uses automated nanomanipulation for precision control of nanowire number and diameter. The process requires only one photolithography mask. Using nanowire contact printing and post processing (i.e., nanomanipulation inside scanning electron microscope), we are able to produce devices all with a single nanowire and similar diameters at a speed of ~1 min/device with a success rate of 95% (n=500). This technology represents a seamless integration of wafer-scale microfabrication and automated nanorobotic manipulation for producing nano-FET sensors with consistent response across devices.
  • Vision-Based Retinal Membrane Peeling with a Handheld Robot Authors: Becker, Brian C.; MacLachlan, Robert A.; Lobes, Louis A.; Riviere, Cameron
    Peeling delicate retinal membranes, which are often less than five microns thick, is one of the most challenging retinal surgeries. Preventing rips and tears caused by tremor and excessive force can decrease injury and reduce the need for follow up surgeries. We propose the use of a fully handheld microsurgical robot and vision-based virtual fixtures to enforce helpful constraints on the motion of the tool. Our key contribution is using only visual information to reduce and limit forces during vitreoretinal surgery: no force feedback is used in the control system. Utilizing stereo vision and tracking algorithms, the robot activates motion-scaled behavior as the tip nears the surface, providing finer control during the critical step of engaging the membrane edge. A hard virtual fixture just below the surface bounds the total downward force that can be applied. Furthermore, velocity limiting during the peeling helps the surgeon maintain a smooth, constant force while lifting and delaminating the membrane. On a retinal phantom consisting of plastic wrap stretched on top a rubber slide, we demonstrate a reduction of maximum force by 40-70%.
  • Holonomic 5-DOF Magnetic Control of 1D Nanostructures Authors: Schuerle, Simone; Peyer, Kathrin Eva; Kratochvil, Bradley; Nelson, Bradley J.
    This paper presents a manipulation system capable of five degree of freedom (5-DOF) control of a magnetic nanoagent (3-DOF position, 2-DOF orientation) implemented on an inverted microscope. Magnetic fields up to 50 mT and gradients up to 5 T/m at frequencies up to 6 kHz can be achieved. The independent generation of field and gradient vectors enables holonomic 5-DOF wireless magnetic manipulation at the nanoscale. Multiple types of motion were investigated for nickel nanowires of different lengths and analyzed using resistive force theory.
  • Interval Analysis for Robot Precision Evaluation Authors: Pac, Muhammed Rasid; Popa, Dan
    The success of assembly and manipulation tasks is highly dependent on the precision of robotic positioners employed. In turn, precision metrics for robots depend on the kinematic design, choice of actuators, sensors, and control system. In this paper, we investigate the effect of parametric uncertainties on the robot precision using interval analysis. The advantage of interval analysis is that it provides rigorous bounds on the effects of errors in terms of interval numbers. Two types of errors are considered: geometric errors due to link and joint parameter uncertainties, and sensing errors due to inaccurate measurement of joint positions. We show that modeling and simulation of these uncertainties using intervals can provide useful insight into the evaluation of manipulator precision for a given task. In particular, simulation results are offered to predict the required tolerances in a peg-in-hole microassembly operation. It is illustrated that the presented approach can replace computationally more expensive Monte-Carlo simulations to estimate the effect of uncertainties.

Multi-Legged Robots

  • Stable Dynamic Walking of a Quadruped "Kotetsu" Using Phase Modulations Based on Leg Loading/Unloading against a Lateral Perturbation Authors: Maufroy, Christophe; Kimura, Hiroshi; Nishikawa, Tomohiro
    We intend to show the basis of a general legged locomotion controller with the ability to integrate both posture and rhythmic motion controls. We respectively used leg loading and unloading for the phase transitions from swingto- stance and stance-to-swing, and showed the following in our previous 3D model simulation study: (a) as a result of the phase modulations based on leg loading/unloading, rhythmic motion of each leg was achieved and leg coordination (resulting in a gait) emerged, even without explicit coordination among the leg controllers, allowing to realize dynamic walking in the low- to medium-speed range (b) but an additional ascending coordination mechanism between ipsilateral leg controllers was necessary to improve the stability. In this paper, we report on experimental results using “Kotetsu” under a lateral perturbation while walking and compare them with the results of our previous simulations.
  • Dynamic Torque Control of a Hydraulic Quadruped Robot Authors: Boaventura, Thiago; Semini, Claudio; Buchli, Jonas; Frigerio, Marco; Focchi, Michele; Caldwell, Darwin G.
    Legged robots have the potential to serve as versatile and useful autonomous robotic platforms for use in unstructured environments such as disaster sites. They need to be both capable of fast dynamic locomotion and precise movements. However, there is a lack of platforms with suitable mechanical properties and adequate controllers to advance the research in this direction. In this paper we are presenting results on the novel research platform HyQ, a torque controlled hydraulic quadruped robot. We identify the requirements for versatile robotic legged locomotion and show that HyQ is fulfilling most of these specifications. We show that HyQ is able to do both static and dynamic movements and is able to cope with the mechanical requirements of dynamic movements and locomotion, such as jumping and trotting. The required control, both on hydraulic level (force/torque control) and whole body level (rigid model based control) is discussed.
  • Kinematic Control and Posture Optimization of a Redundantly Actuated Quadruped Robot Authors: Thomson, Travis; Sharf, Inna; Beckman, Blake
    Although legged locomotion for robots has been studied for many years, the research of autonomous wheel- legged robotics is much more recent. Robots of this type, also described as hybrid, can take advantage of the energy efficiency of wheeled locomotion while adapting to more difficult terrain with legged locomotion when necessary. The Micro Hydraulic Toolkit (MHT), developed by engineers at Defence R&D Canada – Suffield, is a good example of such a robot. Investigation into control and optimization techniques for MHT leads to a better understanding of hybrid vehicle control for terrestrial exploration and reconnaissance. Control of hybrid robots has been studied by several researchers during the last decade. The methodology applied in this work uses an inverse kinematics algorithm developed previously for a hybrid robot Hylos, and implements an optimization technique to minimize torques occurring at crucial actuators. As well, some added functionality is incorporated into the control method to implement stepping maneuvers. This paper will present the results obtained via co-simulation using Matlab’s Simulink and a high-fidelity model of MHT in LMS Virtual Lab.
  • Optimally Scaled Hip-Force Planning: A Control Approach for Quadrupedal Running Authors: Valenzuela, Andrés; Kim, Sangbae
    This paper presents Optimally Scaled Hip-Force Planning (OSHP), a novel approach to controlling the body dynamics of running robots. Controllers based on OSHP form the high-level component of a hierarchical control scheme in which they direct lower level controllers, each responsible for coordinating the motion of a single leg. An OSHP controller takes in the state of the runner at the apex of its primary aerial phase and returns desired profiles for the vertical and horizontal forces to be exerted at each hip during the subsequent stride. The hip force profiles returned by OSHP are scaled variants of nominal force profiles based on biological ground reaction force data. The OSHP controller determines the scaling parameters for these profiles through constrained nonlinear optimization on an approximate model of the runner's body dynamics. Evaluation of an OSHP controller for a quadruped model in simulation shows that even with very simple leg controllers, the OSHP controller can accelerate the runner from rest to steady-state running without a pre-defined footfall sequence.
  • Enforced Symmetry of the Stance Phase for the Spring-Loaded Inverted Pendulum Authors: Piovan, Giulia; Byl, Katie
    The Spring-Loaded Inverted Pendulum (SLIP) is considered the simplest model to effectively describe bouncing gaits (such as running and hopping) for many legged animals and robots. For this reason, it is has often been used as a model for robot design. A key challenge in using this model, however, is the lack of a closed-form solution for the equations of motion that define the stance phase of its dynamics. This results in the impossibility of analytically predicting its trajectory. Consequently, developing a practical control strategy to operate on the model is computationally intensive, because accurately predicting the step-to-step dynamics is still an unsolved problem. By adding an actuator in series with the spring, we can develop a control law for actuator displacement which enforces a desired trajectory during stance. In particular, for our specific chosen control law, we can compute an analytical solution for the stance phase trajectory. Furthermore, we give examples of higher level control strategies for foothold placement and for keeping the forward velocity or the apex height constant on rough terrain that employ our low-level control laws, and we illustrate through simulations the performance typical of our strategy.
  • A Behavior Based Locomotion Controller with Learning for Disturbance Compensation in Bipedal Robots Authors: Beranek, Richard; Ahmadi, Mojtaba
    A novel behavior based locomotion controller (BBLC) capable of adapting to unknown disturbances is presented. The proposed controller implements a behavior based control architecture by subdividing the walking control into several task-space controllers such as swing leg control and center of gravity (COG) position control. For each task-space controller, a number of behaviors, which plan the reference task-space trajectories, are designed based on existing stabilizing controllers or strategies inspired by human walking biomechanics. A Q-learning algorithm is used to classify which behavior combinations can compensate for specific disturbances. The controller is implemented on a planar biped simulation with push type disturbances applied on flat and sloped terrain. The results show that stabilization strategies, capable of compensating for these disturbances emerge from the combination of different task level behaviors, without a priori knowledge of the nature of the disturbances.