Luiz S. Martins-Filho

Patrol Mobile Robots and Chaotic Trajectories

This paper presents a study of special trajectories attainment for mobile robots based on the dynamical features of chaotic systems. This method of trajectories construction is envisaged for missions for terrain exploration, with the specific purpose of search or patrol, where fast scanning of the robot workspace is required. We propose the imparting of chaotic motion behavior to the mobile robot by means of a planner of goal positions sequence based on an area-preserving chaotic map. As a consequence, the robot trajectories seem highly opportunistic and unpredictable for external observers, and the trajectoriess characteristics ensure the quick scanning of the patrolling space. The kinematic modeling and the closed-loop control of the robot are described. The results and discussion of numerical simulations close the paper.

Optimal On-Off Attitude Control for the Brazilian Multimission Platform Satellite

This work deals with the analysis and design of a reaction thruster attitude control for the Brazilian Multimission platform satellite. The three-axis attitude control systems are activated in pulse mode. Consequently, a modulation of the torque command is compelling in order to avoid high nonlinear control action. This work considers the Pulse-Width Pulse-Frequency (PWPF) modulator which is composed of a Schmidt trigger, a first-order filter, and a feedback loop. PWPF modulator holds several advantages over classical bang-bang controllers such as close to linear operation, high accuracy, and reduced propellant consumption. The Linear Gaussian Quadratic (LQG) technique is used to synthesize the control law during stabilization mode and the modulator is used to modulate the continuous control signal to discrete one. Numerical simulations are used to analyze the performance of the attitude control. The LQG/PWPF approach achieves good stabilization-mode requirements as disturbances rejection and regulation performance.

Locomotion control of a four-legged robot embedding real-time reasoning in the force distribution ☆

Abstract This paper discusses the application of rule-based reasoning to manage in real time the force distribution computation within a locomotion control of quadruped robots. The control uses input–output linearization in the attitude subsystem, and optimal linear control in the overall locomotion system. The force distribution approach provides more adaptability and flexibility to the locomotion control, because the system is capable of fast adaptation to a wide variety of situations. Rules defining the knowledge about how to deal with walk events and feet forces calculation are presented. The rule-based reasoning is made using the KHEOPS system (LAAS).

A methodology for the teaching of dynamical systems using analogous electronic circuits

The behaviour of dynamical systems can be reproduced from analogous electronic circuits, which allows the study of many interesting phenomena associated with them using inexpensive and versatile electronic components easily found on the market. This paper proposes a methodology to develop didactic platforms for the study of dynamical systems based on analogous electronic circuits. Presented here are the design and implementation of three electronic circuits that mimic natural chaotic systems: the forced Duffing system, the Lorenz system and the Rössler system.

Guidance and Control of Position and Attitude for Rendezvous and Dock/Berthing with a Noncooperative/Target Spacecraft

Noncooperative target spacecrafts are those assets in orbit that cannot convey any information about their states (position, attitude, and velocities) or facilitate rendezvous and docking/berthing (RVD/B) process. Designing a guidance, navigation, and control (GNC) module for the chaser in a RVD/B mission with noncooperative target should be inevitably solved for on-orbit servicing technologies. The proximity operations and the guidance for achieving rendezvous problems are addressed in this paper. The out-of-plane maneuvers of proximity operations are explored with distinct subphases, including a chaser far approach in the target’s orbit to the first hold point and a closer approach to the final berthing location. Accordingly, guidance solutions are chosen for each subphase from the standard Hill based Closhessy-Willtshire (CW) solution, elliptical fly-around, and Glideslope algorithms. The control is based on a linear quadratic regulator approach (LQR). At the final berthing location, attitude tracker based on a proportional derivative (PD) form is tested to synchronize the chaser and target attitudes. The paper analyzes the performance of both controllers in terms of the tracking ability and the robustness. Finally, it prescribes any restrictions that may be imposed on the guidance during any subphase which can help to improve the controllers tracking ability.

A Fault-Tolerant Attitude Determination System Based on COTS Devices

In this paper we present a low cost fault-tolerant attitude determination system to a scientific satellite using COTS devices. We related our experience in developing the attitude determination system, where we combine proven fault tolerance techniques to protect the whole system composed only by COTS from the effects produced by transient faults. We detailed the failure cases and the detection, reconfiguration and recovery schemes that assure the fault-tolerant condition. A testbed system was used to inject faults, evaluate the recovery capability of the fault-tolerant system and validate the solution proposed.

Development of an amphibious robotic propulsor based on electroactive polymers

This paper presents the project of a robotic device for propulsion in aquatic environment. The propulsor is a biologically inspired system characterized by efficiency and flexibility for locomotion environment changing: the legs of anuran amphibious. These animals are exceptionally adapted to locomotion in water and land. This type of locomotion requires specific features of the mechanisms that are hardly provided by traditional solutions based on standard electric motors. The proposed approach is based on ionomeric polymers-metal composites drives, constituting a system commonly called artificial muscle. The paper presents the anuran locomotion modeling, a description of the electroactive polymers, the experimental production procedures and results, and also discusses some constructive aspects of a first device prototype.