Mauro Speranza Neto

A closed-loop model of a multi-station and multi-product manufacturing system using bond graphs and hybrid controllers

Production plans and production schedules are fundamentally dynamic and may be disturbed by several events. In the manufacturing research domain, however, dynamic models for scheduling and production control usually receive less attention as static models. In this paper, a bond graph model for depicting a multi-product production system with job shop configuration is proposed. A case study based on a real production system is presented to illustrate the modeling process. The state model derived from the pictorial representation (i.e., derived from the bond graphs) is simulated, in order to observe the dynamic response of the system. Also, a hybrid proportional controller (HPC) and a hybrid adaptive proportional controller (HAPC) are proposed. In this sense, this research extends the findings of a previous work reported in the literature, in which constant and proportional controllers were tested. The results demonstrated that the HAPC and the HPC outperforms the mentioned controllers, and that the bond graphs are a viable methodology to represent and study the dynamics of manufacturing systems. This approach is innovative since no other closed-loop model based on bond graphs for multiple products has been previously reported in the literature, nor its combination with a hybrid adaptive controller.

A rough terrain traction control technique for all-wheel-drive mobile robots

Traction control is a critical aspect of mobile robots that need to traverse rough terrain, avoiding excessive slip - which may cause the terrain to collapse locally and trap the robot wheels - and guaranteeing an adequate trajectory and speed control while reducing the power requirements. Traction control of all-wheel-drive robots in rough terrain was originally motivated by space exploration, such as in the case of the Mars Exploration Rovers. However, such technology is also needed in our planet, in particular in the Amazon region. This is the case of the Hybrid Environmental Robot (HER), a 4-wheel-drive mobile robot with independent suspensions, under development at CENPES/PETROBRAS. This robot is susceptible to changing terrain conditions, facing slippery soil and steep slopes. In this work, a new traction control scheme is proposed to allow HER to maintain a desired velocity while minimizing power requirements and slippage, considering motor saturation and avoiding flip-over dynamic instability. The proposed technique is based on a redundant computed torque control scheme, analytically optimized to minimize power requirements. Simulations are performed for rough terrain conditions with 2D-profile, considering the general case of different tire-terrain contact angles at each wheel. It is found that the control scheme is able to analytically predict in real time the ideal torques required by each independent wheel to maintain the desired speed, even on very rough terrain, minimizing when possible the power consumption. The method is applicable to the 3D case as long as the roll angle of the robot chassis does not vary too much compared to the robot pitch angle.

Experiences and perspectives of a non-conventional introduction to engineering course

This paper presents a briefing about the introduction of engineering course of the Center of Science and Technology of the Pontifical Catholic University of Rio de Janeiro, recent tracking, regarding the period from 1997 to 2011, demonstrating the positive background and the obstacles faced during the courses progression, relating all different experiences, from Hands-on to Problem Based Learning (PBL) Methodology.

Analysis of Control Strategies for Autonomous Motorcycles Stabilization and Trajectories Tracking

Autonomous vehicles—defined as vehicles with carrying capacity of persons or property without the use of a human driver—are an interesting and recent problem, with increasing studies in the last 20 years. Regarding this type of vehicles, a less explored option is the motorcycle: apart from the difficulties inherent in making a vehicle move independently, autonomous motorcycles have to be able to remain stable at any speed and trajectory. This work’s main object of study is a small-scale electric motorcycle; represented by a linear model through a multibody approach: its four rigid bodies—wheels, chassis, handlebar and fork—have separately a characteristic behavior and together they influence the dynamics of each other. This approach results in lower order models, easier to simulate and to apply classical or modern control strategies. The two-wheeled vehicle is considered an inverted pendulum with a mobile base and other simplifications are proposed, as constant displacement speed or small steering and yaw angles. Since this vehicle is naturally unstable, to ensure a follow-up course without overturning it is necessary to apply an adjusted control signal; once the autonomous system studied will not have the presence of a mechanical counterbalance, there remains only the steering as a control strategy. Thus, this work analyzes the dynamic characteristics of the zero track vehicles and verifies the validity of different stability and path tracking control strategies of a motorcycle using as input only the steering of the handlebar.

Dynamic Models of Bicycles and Motorcycles using Power Flow Approach

Abstract: This paper presents a procedure for the determination of the analytical form of dynamic models for bicycles and/or motorcycles through the characterization of the power flow between its components (driver, handlebars and frame, suspension and wheels/tires, engine, transmission and brakes) including the influence of gyroscopic effect and the interactions between the longitudinal, lateral and vertical dynamics of those vehicles. From the kinematic relations associated to the velocities of the degrees of freedom of each part of the vehicle (driver, handlebar, frame, power train, suspension mechanisms and tires/wheels) their links are determined. Considering the power flow between the degrees of freedom and also between then and the subsystems elements, the equilibrium relations between the forces and torques are determined. Finally, taking the inertial, stiffness and damping effects of the various system components into consideration, the equations of motion or state equations that characterize the dynamics of the vehicles are analytically obtained, represented in any reference frame, local or global. This procedure is modular and can be applied to smaller model subsystems (e.g. with fewer components and degrees of freedom). These will later be coupled, also through the power flow, to generate the model of a new subsystem representing the dynamic characteristics of the former system and their interactions. This approach adopts the same basis, concepts and elements of the Bond Graph Technique, without its symbolic notation and graphical representation. As an illustration, the procedure is applied for modeling the longitudinal, vertical and lateral coupled dynamics of a motorcycle, with the purpose of analyzing their stability in the vertical and lateral plane.

Fuzzy Shared Semi-Autonomous Control System For Military Vehicles

Semi-autonomous control systems applied to automobiles are Advanced Driver Assistance Systems (ADAS) that have gained importance from similar devices with applications in robotics. The control sharing between humans and automatic controllers is the main characteristic of these systems, and can be accomplished through various different manners. However, the use of Artificial Intelligence (AI) techniques for this purpose remains unexplored. In this paper we propose the design of a semi-autonomous control system applied to military vehicles through the use of Fuzzy Inference Systems for the definition of the controller intervention level. Simulations of a vehicle being operated in highly dangerous situations, represented by the existence of hostile military threats or by unexpected maneuvers that could put the stability of the car at risk were performed. The control system’s level of intervention during the simulations was observed, and we could realize the increase of this variable according to the level of threat that the car was exposed to. The application of the proposed system results in safer operation of the vehicle, which shall be controlled with greater influence of the automatic controller when in greater danger. We present a critical analysis of these results and new directions for the future of this work.