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PublicationDesign of Body-Grounded Tactile Actuators for Playback of Human Physical Contact(2011-06-01) Kuchenbecker, Katherine J; Stanley, Andrew AWe present four wearable tactile actuators capable of recreating physical sensations commonly experienced in human interactions, including tapping on, dragging across, squeezing, and twisting an individual’s wrist. In seeking to create tactile signals that feel natural and are easy to understand, we developed movement control interfaces to play back each of these forms of actual human physical contact. Through iterative design, prototyping, programming, and testing, each of these servo-motor-based mechanisms produces a signal that is gradable in magnitude, can be played in a variety of temporal patterns, is localizable to a small area of skin, and, for three of the four actuators, has an associated direction. Additionally, we have tried to design toward many of the characteristics that have made high frequency vibration the most common form of wearable tactile feedback, including low cost, light weight, comfort, and small size. Bolstered by largely positive comments from naive users during an informal testing session, we plan to continue improving these devices for future use in tactile motion guidance. PublicationFast Image Segmentation(1989-07-01) Corke, Peter I; Anderson, Helen IImage segmentation remains one of the greatest problems in machine vision. The technique described here takes an image and a geometric description of the object required, determines multiple binary thresholds to segment the image, and combines the information from the appropriate thresholds. By utilizing region-growing hardware it is possible to achieve segmentation in less than 2 seconds. PublicationMulti-Modal Control of Systems with Constraints(2001-12-04) Koo, T. John; Pappas, George J; Sastry, ShankarIn multi-modal control paradigm, a set of controllers of satisfactory performance have already been designed and must be used. Each controller may be designed for a different set of outputs in order to meet the given performance objectives and system constraints. When such a collection of control modes is available, an important problem is to be able to accomplish a variety of high level tasks by appropriately switching between the low-level control modes. In this paper, we propose a framework for determining the sequence of control modes that will satisfy reachability tasks. Our framework exploits the structure of output tracking controllers in order to extract a finite graph where the mode switching problem can be efficiently solved, and then implement it using the continuous controllers. Our approach is illustrated on a robot manipulator example, where we determine the mode switching logic that achieves the given reachability task. PublicationBayesian Regularization and Nonnegative Deconvolution for Time Delay Estimation(2004-12-13) Lin, Yuanqing; Lee, Daniel DBayesian Regularization and Nonnegative Deconvolution (BRAND) is proposed for estimating time delays of acoustic signals in reverberant environments. Sparsity of the nonnegative filter coefficients is enforced using an L1-norm regularization. A probabilistic generative model is used to simultaneously estimate the regularization parameters and filter coefficients from the signal data. Iterative update rules are derived under a Bayesian framework using the Expectation-Maximization procedure. The resulting time delay estimation algorithm is demonstrated on noisy acoustic data. PublicationCCSR: A Calculus for Communicating Shared Resources(1990-03-12) Gerber, Richard; Lee, InsupThe timing behavior of a real-time system depends not only on delays due to process synchronization, but also on the availability of shared resources. Most current real-time models capture delays due to process synchronization; however, they abstract out resource-specific details by assuming idealistic operating environments. On the other hand, scheduling and resource allocation algorithms used for real-time systems ignore the effect of process synchronization except for simple precedence relations between processes. To bridge the gap between these two disciplines, we have developed a formalism called Communicating Shared Resources, or CSR. This paper presents the priority-based process algebra called the Calculus for Communicating Shared Resources (CCSR), which provides an equational characterization of the CSR language. The computation model of CCSR is resource-based in that multiple resources execute synchronously, while processes assigned to the same resource are interleaved according to their priorities. CCSR possesses a prioritized strong equivalence for terms based on strong bisimulation. The paper also describes a producer and consumer problem whose correct timing behavior depends on priority. PublicationVideo Rate Visual Servoing for Robots(1989-02-01) Corke, Peter I; Paul, Richard PThis paper presents some preliminary experimental results in robotic visual servoing, utilizing a newly available hardware region-growing and moment-generation unit. A Unix-based workstation in conjunction with special purpose video processing hardware has been used to visually close the robot position loop at video field rate, 60Hz. The architecture and capabilities of the system are discussed. Performance of the closed-loop position control is investigated analytically and via step response tests, and experimental results are presented. Initial results are for 2 dimensional servoing, but extensions to 3 dimensional positioning are covered along with methods for monocular distance determination. Finally some limitations of the approach and areas for further work are covered. PublicationActive Sensing for Dynamic, Non-holonomic, Robust Visual Servoing(2014-05-01) De, Avik; Bayer, Karl S.; Koditschek, Daniel EWe consider the problem of visually servoing a legged vehicle with unicycle-like nonholonomic constraints subject to second-order fore-aft dynamics in its horizontal plane. We target applications to rugged environments characterized by complex terrain likely to perturb significantly the robot’s nominal dynamics. At the same time, it is crucial that the camera avoid “obstacle” poses where absolute localization would be compromised by even partial loss of landmark visibility. Hence, we seek a controller whose robustness against disturbances and obstacle avoidance capabilities can be assured by a strict global Lyapunov function. Since the nonholonomic constraints preclude smooth point stabilizability we introduce an extra degree of sensory freedom, affixing the camera to an actuated panning axis mounted on the robot’s back. Smooth stabilizability to the robot-orientation-indifferent goal cycle no longer precluded, we construct a controller and strict global Lyapunov function with the desired properties. We implement several versions of the scheme on a RHex robot maneuvering over slippery ground and document its successful empirical performance. For more information: Kod*Lab PublicationA leg configuration sensory system for dynamical body state estimates in a hexapod robot(2003-09-14) Lin, Pei-Chun; Komsuoglu, Haldun; Koditschek, Daniel EWe report on a novel leg strain sensory system for the autonomous robot RHex [Saranli U. et al., 2001] implemented upon a cheap, high performance local wireless network [H. Komsuoglu, 2002]. We introduce a model for RHex's 4-bar legs [E.Z. Moore, 2001] relating leg strain to leg kinematic configuration in the body coordinate frame. We compare against ground truth measurement the performance of the model operating on real-time leg strain data generated under completely realistic operating conditions. We introduce an algorithm for computing six degree of freedom body posture measurements in world frame coordinates from the outputs of the six leg configuration models, together with a priori information about the ground. We discuss the manner in which such stance phase configuration estimates will be fused with other sensory data to develop the continuous time full body state estimates for RHex. PublicationFlying Hot Potatoes(2002-05-08) Mishra, Pradyumna; Pappas, George JOptical communication networks and air traffic management systems share the same fundamental routing problem as both optical packets and aircraft must continuously move within the network, while avoiding conflicts. In this paper, we explore the use of hot potato and deflection routing algorithms, which are established routing methods in optical communication networks, in the conflict-free routing of air traffic. Hot potato algorithms allow the incorporation of conflict resolution constraints into the routing problem, in contrast to most approaches that decouple the optimal routing problem from the conflict resolution problem. PublicationRobust Invariants From Functionally Constrained Motion(1998-07-01) Hicks, Andrew R.; Daniilidis, Kostas; Bajcsy, Ruzena; Pettey, DavidWe address in the problem of control-based recovery of robot pose and the environmental lay-out. Panoramic sensors provide us with an 1D projection of characteristic features of a 2D operation map. Trajectories of these projections contain the information about the position of a priori unknown landmarks in the environment. We introduce here the notion of spatiotemporal signatures of projection trajectories. These signatures are global measures, like area, characterized by considerably higher robustness with respect to noise and outliers than the commonly applied point correspondence. By modeling the 2D motion plane as the complex plane we show that by means of complex analysis our method can be embedded in the well-known affine reconstruction paradigm.