Antônio Bento Filho

A four legged walking robot with obstacle overcoming capabilities

The paper deals with the four legged walking robot Guará, built with obstacle overcoming capabilities. It was designed as a research robot platform, to be used in indoor environment, walking straight and curved paths and detecting and overcoming known obstacles. Straight paths are done with gait matrix strategy and curved paths are accomplished by the four legs which have differential strokes in inclined paths relatively to the robot longitudinal axis. Obstacle overcoming is done using only information from contact sensors installed on the robots feet. Complex movements and tracking sequences are proposed to be built from a small group of simple movements sequenced according to the contact keys switching sequence. Results include: gait generation for straight and curved paths; integrated movement sequence to go one step up in the floor; and a description of the Guara quadruped robot.

A Divide and Conquer Approach for Obstacles Surpassing of a Legged Robot

Small obstacles are difficult to be detected and having their position precisely established from vision or other stereo obstacle detecting systems thus needing to be treated locally by the robot legs and foot. This work deals with the obstacle overcoming and curved walking capabilities of a four legged walking robot. Obstacle overcoming and avoidance is done using only information from contact sensors installed on the robot’s feet. A divide and conquer approach was used to get over known obstacles. Obstacles considered are going a step up and down, going ramp up and down and overcoming a channel. Results include integrated movement sequence to go one step up in the floor.

Modeling of a Four-Legged Robot with Variable Center of Mass as a Cooperative Multirobot System

A multibody system, such as a multiple legged robot, can be modeled and controlled as a cooperative multirobot system (CMS), since it is expected that the several parts involved in the multibody to have a common purpose, in which they must cooperate in order to achieve success. This paper introduces the modeling of a four-legged robot as a set of five robot manipulators: four legs and one additional torso robot for center of mass change. The body’s trajectory is defined and the legs must move cooperatively in order to keep the movement as defined, and the cooperation factor is used again with the torso compensation. The task of the torso robot is to keep the center of mass inside the supporting polygon composed by (at least) three legs, so that the system can remain stable at all times, and, because of that, must act cooperatively with the legs’ movement. The kinematics are computed and simulated using the presented methodology, with screw theory, Assur virtual chains, graph theory and Davies method.

Series Elastic Actuator: Design, Analysis and Comparison

In general, actuators are built to be as stiff as possible to increase the bandwidth. When a robot works in a structured environment, its automation is easier than in a nonstructured environment in which case its modeling is quite difficult and presents a high computational effort. To overcome this difficulty, series elastic actuator (SEA) has been applied in compliant robotic grasping. Unlike rigid actuators, a SEA contains an elastic element in series with the mechanical energy source. Such an elastic element gives SEAs tolerance to impact loads, low mechanical output impedance, passive mechanical energy storage, and increased peak power output. The spring has to be able to support the loads, but it cannot be too stiff; otherwise, system impedance will be high. This chapter describes a comparison between two types of SEA, an electric series elastic actuator (ESEA) and a hydraulic series elastic actuator (HSEA), for four-legged dynamic robot application. The parameters employed in the comparison are bandwidth, output impedance, time response, power density, and dynamic range. The results indicate that HSEA is a better actuator than ESEA for a weight carrying four-legged dynamic robot because of its higher power density and dynamic ratio with desirable output impe‐ dance, time response, and bandwidth.

Reflexive Behavior for a Four-Legged Mobile Robot Using Fuzzy Logic

This article presents hierarchic control architecture, with stability reflexives behavior for a four-legged mobile robot, by using fuzzy controllers and a dual-axis accelerometer. This article blends the conventional control application with fuzzy logic to get reflexives behaviors which enables the robot to react to the balance instability, improving its performance to navigate.