Koditschek, Daniel E
Email Address
ORCID
Disciplines
Acoustics, Dynamics, and Controls
Artificial Intelligence and Robotics
Control Theory
Controls and Control Theory
Dynamic Systems
Electro-Mechanical Systems
Ordinary Differential Equations and Applied Dynamics
Robotics
Systems and Integrative Engineering
Artificial Intelligence and Robotics
Control Theory
Controls and Control Theory
Dynamic Systems
Electro-Mechanical Systems
Ordinary Differential Equations and Applied Dynamics
Robotics
Systems and Integrative Engineering
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Position
Faculty Member
Introduction
I am a robotics researcher with interests in applications of dynamical systems to intelligent machines using bioinspired designs.
Research Interests
Collection
260 results
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Now showing 1 - 10 of 260
Publication Exact Robot Navigation Using Artificial Potential Functions(1992-10-01) Rimon, Elon; Koditschek, Daniel EWe present a new methodology for exact robot motion planning and control that unifies the purely kinematic path planning problem with the lower level feedback controller design. Complete information about the freespace and goal is encoded in the form of a special artificial potential function - a navigation function - that connects the kinematic planning problem with the dynamic execution problem in a provably correct fashion. The navigation function automatically gives rise to a bounded-torque feedback controller for the robot's actuators that guarantees collision-free motion and convergence to the destination from almost all initial free configurations. Since navigation functions exist for any robot and obstacle course, our methodology is completely general in principle. However, this paper is mainly concerned with certain constructive techniques for a particular class of motion planning problems. Specifically, we present a formula for navigation functions that guide a point-mass robot in a generalized sphere world. The simplest member of this family is a space obtained by puncturing a disc by an arbitrary number of smaller disjoint discs representing obstacles. The other spaces are obtained from this model by a suitable coordinate transformation that we show how to build. Our constructions exploit these coordinate transformations to adapt a navigation function on the model space to its more geometrically complicated (but topologically equivalent) instances. The formula that we present admits sphere-worlds of arbitrary dimension and is directly applicable to configuration spaces whose forbidden regions can be modeled by such generalized discs. We have implemented these navigation functions on planar scenarios, and simulation results are provided throughout the paper.Publication Averaged Anchoring of Decoupled Templates in a Tail-Energized Monoped(2015-01-01) De, Avik; Koditschek, Daniel EWe refine and advance a notion of parallel composition to achieve for the first time a stability proof and empirical demonstration of a steady-state gait on a highly coupled 3DOF legged platform controlled by two simple (decoupled) feedback laws that provably stabilize in isolation two simple 1DOF mechanical subsystems. Specifically, we stabilize a limit cycle on a tailed monoped to excite sustained sagittal plane translational hopping energized by tail-pumping during stance. The constituent subsystems for which the controllers are nominally designed are: (i) a purely vertical bouncing mass (controlled by injecting energy into its springy shaft); and (ii) a purely tangential rimless wheel (controlled by adjusting the inter-spoke stepping angle).We introduce the use of averaging methods in legged locomotion to prove that this “parallel composition” of independent 1DOF controllers achieves an asymptotically stable closed-loop hybrid limit cycle for a dynamical system that approximates the 3DOF stance mechanics of our physical tailed monoped.We present experimental data demonstrating stability and close agreement between the motion of the physical hopping machine and numerical simulations of the (mathematically tractable) approximating model. More information: http://kodlab.seas.upenn.edu/Avik/AveragingTSLIPPublication Rigid body visual servoing using navigation functions(2000-12-12) Cowan, Noah J; Lopes, Gabriel A. D.; Koditschek, Daniel EVisual servo controllers in the literature rarely achieve provably large domains of attraction, and seldom address two important sensor limitations: (i) susceptibility to self-occlusions and (ii) finite field of view (FOV). We tackle the problem of global, occlusion-free visual servoing of a fully actuated rigid body by recourse to navigation functions on a compact manifold which encode these restrictions as control obstacles. For occlusion free rigid body servoing, the manifold of interest is the "visible" set of rigid body configurations, that is, those for which the feature points are within the field of view and unoccluded by the body. For a set of coplanar feature points on one face of a convex polyhedron, we show that a slightly conservative subset of the visible set has a simple topology amenable to analytical construction of a navigation function. We construct the controller via a closed form coordinate transformation from our problem domain into the topological model space and conclude with simulation results.Publication Event Driven Parts Moving in 2D Endogenuous Environments(2000-04-01) Karagoz, C. Serkan; Bozma, H. Isil; Koditschek, Daniel EThis paper is concerned with the parts’ moving problem based on an event-driven planning and control. We are interested in developing feedback based approaches to the automatic generation of actuator commands that cause the robot to move a set of parts from an arbitrary initial disassembled configuration to a specif ed final configuration. In the Phase I of this project, a composite algorithm that reactively switches between different feedback controllers has been shown to induce a noncooperative game being played among the parts being manipulated. This paper describes experimental results with EDAR - Event-Driven Assembler Robot - developed for moving parts based on feedback techniques. For more information: Kod*LabPublication Active 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*LabPublication Hybrid Zero Dynamics of Planar Biped Walkers(2003-01-01) Westervelt, E. R.; Grizzle, J. W.; Koditschek, Daniel EPlanar, underactuated, biped walkers form an important domain of applications for hybrid dynamical systems. This paper presents the design of exponentially stable walking controllers for general planar bipedal systems that have one degree-of-freedom greater than the number of available actuators. The within-step control action creates an attracting invariant set—a two-dimensional zero dynamics submanifold of the full hybrid model—whose restriction dynamics admits a scalar linear time-invariant return map. Exponentially stable periodic orbits of the zero dynamics correspond to exponentially stabilizable orbits of the full model. A convenient parameterization of the hybrid zero dynamics is imposed through the choice of a class of output functions. Parameter optimization is used to tune the hybrid zero dynamics in order to achieve closed-loop, exponentially stable walking with low energy consumption, while meeting natural kinematic and dynamic constraints. The general theory developed in the paper is illustrated on a five link walker, consisting of a torso and two legs with knees.Publication Integration of Local Geometry and Metric Information in Sampling-Based Motion Planning(2018-02-25) Pacelli, Vincent; Arslan, Omur; Koditschek, Daniel E.The efficiency of sampling-based motion planning algorithms is dependent on how well a steering procedure is capable of capturing both system dynamics and configuration space geometry to connect sample configurations. This paper considers how metrics describing local system dynamics may be combined with convex subsets of the free space to describe the local behavior of a steering function for sampling-based planners. Subsequently, a framework for using these subsets to extend the steering procedure to incorporate this information is introduced. To demonstrate our framework, three specific metrics are considered: the LQR cost-to-go function, a Gram matrix derived from system linearization, and the Mahalanobis distance of a linear-Gaussian system. Finally, numerical tests are conducted for a second-order linear system, a kinematic unicycle, and a linear-Gaussian system to demonstrate that our framework increases the connectivity of sampling-based planners and allows them to better explore the free space. For more information: Kod*lab.Publication Analysis of A Simplified Hopping Robot(1991-12-01) Koditschek, Daniel E; Buehler, MartinThis article offers some analytical results concerning simplified models of Raibert's hopper. We represent the task of achieving a recurring hopping height for an actuated "ball" robot as a stability problem in a nonlinear discrete dynamical control system. We model the properties of Raibert's control scheme in a simplified fashion and argue that his strategy leads to closed-loop dynamics governed by a well-known class of functions, the unimodal maps. The rich mathematical literature on this subject greatly advances our ability to determine the presence of an essentially globally attracting fixed point-the formal rendering of what we intuitively mean by a "correct" strategy. The motivation for this work is the hope that it will facilitate the development of general design principles for "dynamically dexterous" robots.Publication High Gain Feedback and Telerobotic Tracking(1987-01-15) Koditschek, Daniel EAsymptotically stable linear time invariant systems are capable of tracking arbitrary reference signals with a bounded error proportional to the magnitude of the reference signal (and its derivatives). It is shown that a similar property holds for a general class of nonlinear dynamical systems which includes all robots. As in the linear case, the error bound may be made "arbitrarily" small by increasing the magnitude of the feedback gains which stabilize the system.Publication Strict Global Lyapunov Functions for Mechanical Systems(1988-06-01) Koditschek, Daniel EA novel Lyapunov function is introduced. The author treats the PD compensated mechanical system, which is defined on a configuration space which admits a trivial tangent bundle. Previous results are derived in a simpler form, namely, that such systems are exponentially stable, hence BIBO stable, and steady-state ouptut magnitudes are proportional to input magnitudes with a constant of proportionality depending in a simple fashion on the PD gain magnitudes. For more information: Kod*Lab