Technical session talks from ICRA 2012
TechTalks from event: Technical session talks from ICRA 2012
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Biologically Inspired Robotics II
Approximating the Stance Map of the SLIP Runner Based on Perturbation ApproachThe 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 LambliaWe 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 RobotUnderwater 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 RobotsWe present a general method of estimating a snake robotâ€™s motion over flat ground using only knowledge of the robotâ€™s shape changes over time. Estimating world motion of snake robots is often difficult because of the complex way a robotâ€™s cyclic shape changes (gaits) interact with the surrounding environment. By using the virtual chassis to separate the robotâ€™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 robotâ€™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 SidewindingSidewinding 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 SensorWe 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.