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We describe work-in-progress toward a nonlinear image-based rigid body dynamic triangulator which we believe tracks a moving target from “essentially all” initial conditions (all initial conditions except a set of measure zero). The dynamic triangulator depends on the goal state only through its image plane position and velocity and requires a navigation function, imposed directly upon image features, to serve as a regressor for a gradient-like state update law.

We report on our recent empirical success in the study of a two-link brachiating robot. The “target dynamics” controller developed in our previous work (1997) is implemented on a physical system in our laboratory. The swing locomotion and swing-up behavior of the robot as well as continuous locomotion have been successfully attained. The experimental results illustrate the effectiveness of our control strategy.

We propose a new family of controllers for multi-jointed planar monoped runners, based on approximate but accurate models of the stance phase dynamics of a two degree of freedom “SLIP” leg. Unlike previous approaches, the new scheme gives control over all parameters of the system including the hopping height, forward speed and duty cycle. The control laws are “deadbeat” in nature, derived by computing the inverse of an approximate return map and corrected by integral compensation. We use the expressions obtained in this way to control the original SLIP leg as well as radically different, more realistic four degree of freedom legs. In each case, the performance of the deadbeat scheme in controlling forward running velocity is compared to a modified Raibert control strategy, whose experimental stability properties have been analyzed carefully in the low degree of freedom setting.

This paper explores the possibility of using vector fields to design and implement reactive schedules for safe cooperative robot patterns on graphs. The word “safe” means that obstacles – designated illegal portions of the configuration space – are avoided. The word “cooperative” connotes situations wherein physically distributed agents are collectively responsible for executing the schedule. The word “pattern” refers to tasks that cannot be encoded simply in terms of a point goal in the configuration space. The word “reactive” will be interpreted as requiring that the desired pattern be asymptotically stable: conditions close but slightly removed from those desired remain close and converge toward the desired pattern. We consider Automated Guided Vehicles (AGV’s) operating upon a predefined network of pathways, contrasting the simple cases of locally Euclidean configuration spaces with the more topologically intricate non-manifold cases. The focus of the present inquiry is the achievement of safe cooperative patterns by means of a succession of edge point fields combined with a circulating field to regularize collisions at non-manifold vertices.

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We present a system for generation and recognition of oscillatory gestures. Inspired by gestures used in two representative human-to-human control areas, we consider a set of oscillatory (circular) motions and refine from them a 24 gestures lexicon. Each gesture is modeled as a dynamic system with added geometric constraints to allow for real time gesture recognition using a small amount of processing time and memory. The gestures are used to control a pan-tilt camera neck. The gesture lexicon is then enhanced to include non-linear in parameter (“come here”) gesture representations. An enhancement is suggested which would enable the system to be trained to recognized previously unidentified yet consistent human generated oscillatory motion gestures.

We characterize equilibrium gaits of a small knee monoped in terms of manifest parameters by recourse to approximate closed form expressions. We first eliminate gravity during stance and choose a very special model of potential energy storage in the knee. Next, we introduce simple closed form approximations, motivated by the mean value theorem, to the elliptic integrals arising in the more general case. In so doing, we derive a conjectured generalization applicable to small knee monopeds with an arbitrary knee potential. Finally, we introduce a new closed form perturbation intended to adjust the approximate coordinate transformations to the presence of gravity. Simulation data is offered as evidence for the efficacy (to within roughly 5-10% accuracy) of both the proposed generalization across knee potentials and the proposed perturbation for the presence of gravity during stance.

We report on our preliminary studies of a new controller for a two-link brachiating robot. Motivated by the pendulum-like motion of an ape’s brachiation, we encode this task as the output of a “target dynamical system”. Numerical simulations indicate that the resulting controller solves a number of brachiating problems that we term the “ladder”, “swing up” and “rope” problems. Preliminary analysis provides some explanation for this success. We discuss a number of formal questions whose answers will be required to gain a full understanding of the strengths and weaknesses of this approach.

This paper presents some preliminary results from a research collaboration concerning the modeling and control of color xerography. In this first communication of our work, we describe our efforts to develop a model for a monochrome marking engine. We adopt the technique of principal component analysis for choice of output coordinates and demonstrate preliminary experimental evidence suggesting that this procedure yields accuracy in data reconstruction superior to present industry practice. Preliminary analysis of the experimental evidence suggests that the process has a nonlinear component that we seek to model using a mixture of physical and empirical insight.

We present a simplified state-space model of a once-through supercritical boiler turbine power plant. This phenomenological model has been developed from a greatly simplified application of the first principles of physical laws. When we fit our model to a far more complex and physically accurate simulation model commissioned by EPRI for operator training, we find that the input-output responses are surprisingly close.

Encouraged by this initial success, we describe some initial steps toward a design method for supercritical boiler control suggested by the geometric structure arising from the simplified model. Preliminary simulation results suggest that this approach may offer a closed loop response considerably improved relative to that achieved by the linear controllers presently in place in typical industrial settings.

We present a working implementation of a dynamics based architecture for visual sensing. This architecture provides field rate estimates of the positions and velocities of two independent falling balls in the face of repeated visual occlusions and departures from the field of view. The practical success of this system can be attributed to the interconnection of two strongly nonlinear dynamical systems: a novel triangulating state estimator; and an image plane window controller. We detail the architecture of this active sensor, provide data documenting its performance, and offer an analysis of its soundness in the form of a convergence proof for the estimator and a boundedness proof for the manager.