This paper presents control and coordination algorithms for groups of vehicles. The focus is on autonomous vehicle networks performing distributed sensing tasks where each vehicle plays the role of a mobile tunable sensor. The paper proposes gradient descent algorithms for a class of utility functions which encode optimal coverage and sensing policies. The resulting closed-loop behavior is adaptive, distributed, asynchronous, and verifiably correct.

Coverage control for mobile sensing networks

Matrix Differential Calculus with Applications in Statistics and Econometrics

In this paper, we survey the field of robotic grasping and the work that has been done in this area over the last two decades, with a slight bias toward the development of the theoretical framework and analytical results in this area.

Robotic grasping and contact: a review

A mobile robot is one of the well-known nonholonomic systems. The integration of a kinematic controller and a torque controller for the dynamic model of a nonholonomic mobile robot has been presented (Fierro and Lewis, 1995). In this paper, an adaptive extension of the controller is proposed. If an adaptive tracking controller for the kinematic model with unknown parameters exists, an adaptive tracking controller for the dynamic model with unknown parameters can be designed by using an adaptive backstepping approach. A design example for a mobile robot with two actuated wheels is provided. In this design, a new kinematic adaptive controller is proposed, then a torque adaptive controller is derived by using the kinematic controller.

Adaptive tracking control of a nonholonomic mobile robot

A Treatise on the Analytical Dynamics of Particles and Rigid Bodies: THE GENERAL THEORY OF ORBITS

There are many examples of mechanical systems that require rolling contacts between two or more rigid bodies. Rolling contacts engender nonholonomic constraints in an otherwise holonomic system. In this article, we develop a unified approach to the control of mechanical systems subject to both holonomic and nonholonomic constraints. We first present a state space realization of a constrained system. We then discuss the input-output linearization and zero dynamics of the system. This approach is applied to the dynamic control of mobile robots. Two types of control algorithms for mobile robots are investigated: trajectory tracking and path following. In each case, a smooth nonlinear feedback is obtained to achieve asymptotic input-output stability and Lagrange stability of the overall system. Simulation results are presented to demonstrate the effectiveness of the control algorithms and to compare the performane of trajectory-tracking and path-following algorithms.

/pdf/control-of-mechanical-systems-with-rolling-constraints-2r1potds5j.pdf

Control of Mechanical Systems With Rolling Constraints: Application to Dynamic Control of Mobile Robots

In this paper, we present an experimental study of strategies for maintaining end-to-end communication links for tasks such as surveillance, reconnaissance, and target search and identification, where team connectivity is required for situational awareness. Our main contributions are threefold: (a) We present the construction of a radio signal strength map that can be used to plan multi-robot tasks, and also serve as useful perceptual information. We show how a nominal model of an urban environment obtained by aerial surveillance, is used to generate strategies for exploration. (b) We present reactive controllers for communication link maintenance; and (c) we consider the differences between monitoring signal strength versus data throughput. Experimental results, obtained using our multi-robot testbed in three representative urban environments are presented with each of our main contributions. © 2008 Wiley Periodicals, Inc.

/pdf/maintaining-network-connectivity-and-performance-in-robot-ztoypstybf.pdf

Maintaining network connectivity and performance in robot teams

In this paper, we formulate a semi-implicit time-stepping model for multibody mechanical systems with frictional, distributed compliant contacts. Employing a polyhedral pyramid model for the friction law and a distributed, linear, viscoelastic model for the contact, we obtain mixed linear complementarity formulations for the discrete-time, compliant contact problem. We establish the existence and finite multiplicity of solutions, demonstrating that such solutions can be computed by Lemke's algorithm. In addition, we obtain limiting results of the model as the contact stiffness tends to infinity. The limit analysis elucidates the convergence of the dynamic models with compliance to the corresponding dynamic models with rigid contacts within the computational time-stepping framework. Finally, we report numerical simulation results with an example of a planar mechanical system with a frictional contact that is modelled using a distributed, linear viscoelastic model and Coulomb's frictional law, verifying empirically that the solution trajectories converge to those obtained by the more traditional rigid-body dynamic model.

/pdf/a-semi-implicit-time-stepping-model-for-frictional-compliant-4zgkywpis1.pdf

A Semi-Implicit Time-Stepping Model For Frictional Compliant Contact Problems

We address the problem of planning the motion of a team of mobile robots subject to constraints imposed by sensors and the communication network Our goal is to develop a decentralized motion control system that leads each robot to their individual goals while keeping connectivity with the neighbors We present experimental results with a group of car-like robots equipped with omnidirectional vision systems

/pdf/decentralized-motion-planning-for-multiple-robots-subject-to-4be5grcd1w.pdf

Decentralized motion planning for multiple robots subject to sensing and communication constraints

The stiffness of a rigid body subject to conservative forces and moments is described by a tensor, whose components are best described by a 6X6 Cartesian stiffness matrix. We derive an expression that is independent of the parameterization of the motion of the rigid body using methods of differential geometry. The components of the tensor with respect to a basis of twists are given by evaluating the tensor on a pair of basis twists. We show that this tensor depends on the choice of an affine connection on the Lie group, SE (3). In addition, we show that the definition of the Cartesian stiffness matrix used in the literature [1,2] implicitly assumes an asymmetric connection and this results in an asymmetric stiffness matrix in a general loaded configuration. We prove that by choosing a symmetric connection we always obtain a symmetric Cartesian stiffness matrix. Finally, we derive stiffness matrices for different connections and illustrate the calculations using numerical examples.

https://repository.upenn.edu/cgi/viewcontent.cgi?article=1045&context=meam_papers

R. Vijay Kumar

Papers

Control of Mechanical Systems With Rolling Constraints: Application to Dynamic Control of Mobile Robots

Maintaining network connectivity and performance in robot teams

A Semi-Implicit Time-Stepping Model For Frictional Compliant Contact Problems

Decentralized motion planning for multiple robots subject to sensing and communication constraints

A Geometrical Approach to the Study of the Cartesian Stiffness Matrix