Vinicius Mariano Gonçalves

Parsimonious Kinematic Control of Highly Redundant Robots

When a robot is highly redundant in comparison to the task to be executed, current control techniques are not “economic” in the sense that they demand, most of the time unnecessarily, all the joints to move. Such behavior can be undesirable for some applications. In this direction, this work proposes a new control paradigm based on linear programming that intrinsically provides a parsimonious control strategy, i.e, one in which few joints move. In addition to a formal stability proof, this letter presents simulation and experimental results on the HOAP-3 humanoid robot. Finally, a comparison is made with a least-square method based on the pseudoinverse of the task Jacobian, showing that the proposed method indeed uses fewer joints than the classic one.

An observer for tropical linear event-invariant dynamical systems

This paper presents a sufficient condition to solve the observation problem in tropical linear event-invariant dynamical systems, where a linear functional of the states can be observed in a finite number of steps using only the information from inputs and outputs. Using the residuation theory, this solvability condition can be easily implemented in polynomial time. Moreover, the main results are applied to state feedback control using only the observed states based on the measurements of the original states in the system. Furthermore, the main results are implemented in the perturbation observation problem for tropical linear event-invariant dynamical systems, where the system matrices are perturbed in intervals.

Artificial vector fields for robot convergence and circulation of time-varying curves in n-dimensional spaces

This paper addresses the problem of controlling a single mobile robot to converge smoothly to a pre-specified closed curve. Once in the curve, the robot remains circulating along it. The main motivation for this is the control of unmanned airplanes, where the robot cannot converge to a single point. Our control law is based on an artificial vector field that allows for the generalization to time-varying curves defined in n-dimensional spaces. We also present results that may be used to control mobile robots moving with constant speed. We devise convergence proofs and present simulations that verify the proposed approach.

On the Steady-State Control of Timed Event Graphs With Firing Date Constraints

Two algorithms for solving a specific class of steady-state control problems for Timed Event Graphs are presented. In the first, asymptotic convergence to the desired set is guaranteed. The second algorithm, which builds on from the recent developments in the spectral theory of min-max functions, guarantees Lyapunov stability since the distance between the actual state and the desired set never increases. Simulation results show the efficiency of the proposed approach in a problem of moderate complexity.

Coordination of multiple fixed-wing UAVs traversing intersecting periodic paths

This paper addresses the problem of coordinating the motion of multiple fixed-wing Unmanned Aerial Vehicles (UAVs) following closed intersecting curves. We require that each UAV avoid collisions with its teammates without changing its predefined, periodic path. Also, each robot must keep a minimum speed to avoid stall and a maximum speed determined by its physical constraints. The centralized solution presented in this paper is modeled as a Mixed Integer Linear Programming (MILP) problem. The solution to this problem, which maximizes safeness (in the sense of collision avoidance), determines, for each UAV, the start time and the velocity profile over the curve.

Circulation of curves using vector fields: Actual robot experiments in 2D and 3D workspaces

Different robotic tasks can be solved by controlling a robot to circulate along curves. These include, for example, border inspection and surveillance, multirobot manipulation, and pattern generation. In a previous, work we have proposed a vector field approach for robot convergence and circulation along time-varying curves embedded in N-dimensional spaces. In the present work we instantiate this approach for three-dimensional spaces and, for the first time, show the efficacy of this method to control actual robots. Besides new theoretical analysis when constant speed control is applied, we present experimental results with aerial (quadrotors) and ground (differential-driven) robot

NAVEGAÇÃO DE ROBÔS UTILIZANDO CURVAS IMPLÍCITAS

In several applications in robotics, including monitoring, mapping, and surveillance, robots must follow closed curves with several different shapes determined by the application. In this paper, it is proposed a methodology for robot navigation in tasks where the robot path can be specified by the intersection of level sets of given functions. Besides the path, the control law is also defined by a vector field created using these functions. The main contribution of this work is the computation of n-dimensional vector fields and the proofs that a holonomic robot controlled by this vector field converges and circulates the specified curve. The paper also shows that the resulting field is continuous and can be modified to maintain constant robot speed, an important characteristic for controlling airplane based aerial robots. Finally, it is shown a numerical technique, based on the weighted sum of radial basis functions, for the construction of the functions that determine the robot path. Simulations with a nonholonomic mobile robot subject to localization errors illustrate the potential of the method to drive several types of robots.

On the solution of Max-plus linear equations with application on the control of TEGs

Abstract In this paper, a method is proposed for generating solutions for linear Max-plus equations from a given solution. We have called this method as “Primal method”. The solutions generated by the Primal method have useful properties in the context of control of Timed Event Graph (TEG). In order to illustrate an application of the method, we present a sufficient condition for solving a feedback control problem for a TEG, based on the notion of “Equivalent System”. We can show that the desired feedback matrix is a solution of a Max-plus affine equation, which can be transformed into a linear one, and therefore the Primal method can be applied.