Fabrizio Leonardi

Modeling and optimal control formulation for manual wheelchair locomotion: The influence of mass and slope on performance

A framework to generate predictive simulations is proposed to investigate the influence of systems mass on manual wheelchair locomotion. The approach is based on a model of wheelchair propulsion dynamics and an optimal control formulation. In this study, predictive simulations of steady-state wheelchair locomotion are generated for different combinations of model mass and uphill slope inclination angle. The results show that the influence of systems mass is negligible in level surfaces in steady-state, a finding which agrees with experimental observations in the literature. On the other hand, the results show that the influence of mass on slopes is critical, with large increases in propulsion effort with systems mass, even for slight inclination angles. This shows the importance of reducing wheelchair mass for improving locomotion performance, particularly in overcoming obstacles and ramps. Decreasing the wheelchairs mass may not be sufficient. Therefore, and on the light of these findings, we propose the reduction of systems apparent mass through the implementation of an impedance control scheme in power-assisted wheelchairs.

An experience of teaching industrial automation for industrial engineering undergraduate students

This paper describes the experience of teaching industrial automation to Brazilian industrial engineering undergraduate students at University Center of FEI based on software tools associated with an integrated manufacturing laboratory. The manufacturing laboratory has got three complete manufacturing cells integrated by computer. At first approach an analytical analysis of the automated process is carried out. In the sequence, the manufacturing laboratory is used, combined with software tools, to provide to the industrial engineering student a powerful analysis capability of how to use these kinds of systems to improve product quality and production performance. To do that, computational models are implemented using software tools like Visual Object Net++, Promodel® and WEB support. It was observed that such strategy has been producing excellent learning results.

Fractional PID Controller Applied to a Chemical Plant with Level and pH Control

Abstract One of the most important processes in the chemical, biological and petrochemical industries is the control of the potential of hydrogen (pH). As it is a multivariable process and non-linear, pH control gives rise to many challenges for designers in both dynamic responses and robustness issues. Despite all this complexity, in many circumstances pH control is performed by using a conventional proportional integral derivative (PID) control, which is very common in industry. This paper proposes using a fractional-order PID to improve the pH control performance of a lab-scale process, as it is more flexible, i. e., there is a higher number of variables to be adjusted. Results from a simulation have been compared to those from both conventional and fractional-order PID controls, which has shown the better performance of the latter related to important metrics such as the control effort and dynamic response of the controlled variables.

Yaw Stability Analysis of Articulated Vehicles Using Phase Trajectory Method

This paper addresses the yaw stability analysis of articulated vehicles using the phase trajectory method. The goal of this work is to ascertain the dynamic conditions that the articulated vehicle can assume without the occurrence of instability events such as jackknife and rollover. The study focuses on the vehicle configuration composed by one tractor unit and a driven unit such as, for instance, a tractor semi-trailer combination. The system consists of a nonlinear tire model and a nonlinear articulated bicycle model with four degrees of freedom. The analysis presented in this paper illustrates the convergence regions of equilibrium points obtained through numerical integration of the equations of motion of the model for different initial conditions in the phase plane. In addition, the changes in the obtained regions are presented as a function of the tractor speed and the position of the articulation point between the two units.

The Influence of Inertial Forces on Manual Wheelchair Propulsion

Both experimental and computational studies have contributed to the understanding of the loads during wheelchair propulsion and the factors leading to the incidence of musculoskeletal disorders. However, few studies have addressed the influence of inertial forces on wheelchair propulsion, which are potentially large as upper limb segments undergo large accelerations along the different phases of the propulsion cycle. This study determines and investigates the influence of inertial forces during manual wheelchair propulsion for a subject at two different locomotion velocities. The isolated influence of inertial as well as gravitational forces is determined using a planar model of the upper extremity and an inverse-dynamics approach. The results show that the inertial forces are preponderant even at lower speeds. These findings evidence that quasi-static models are inappropriate to investigate wheelchair propulsion and show the importance of accurate estimation of anthropometric parameters such as segment masses and moments of inertia, which directly affect inertial force estimations in inverse dynamics-based studies of wheelchair propulsion. The results can also help guide investigations on efficient propulsion techniques, as they show that the radial component of the pushrim forces are, to a large extent, determined by inertial effects rather than by an inefficient propulsion technique.

Optimal Control of an Electric Vehicle for Competitions in Energy Efficiency

This work proposes a methodology in open loop for driving a vehicle with electric traction in energy efficiency competitions. The optimal voltage is obtained by solving an optimal control problem that includes physical constraints and requirements of the competition. The vehicle model is related to the longitudinal dynamics and allow variable slope along the track. The influence of cornering is considered by means of a constraint on the maximum centripetal acceleration tolerated by the tire. The methodology transforms the optimal control problem in a nonlinear optimization problem. The methodology was applied to basic tracks and reveals solutions such as allowing velocity reduction during positive slopes and acceleration through the action of the weight force during negative slopes. The methodology was also applied to the conditions of an energy efficiency competition. The results suggest that both the design and driving strategy are very relevant to the energy consumption, but the procedure may not be easily converted into a set of driving rules, i.e., to ensure maximum energy efficiency, it is important to formulate and solve an optimal control problem.

Optimal Control of the Wheelchair Wheelie

The wheelchair wheelie is a maneuver employed to overcome obstacles and descend ramps, for instance. The task is similar to the stabilization problem of an inverted pendulum that is extensively described in the control theory literature. However, in this case, the goal is to maintain the user and the wheelchair in equilibrium on wheels, which is achieved when the center of mass of the system is aligned with the rear axle in the vertical direction. This work investigates a controller to perform the wheelie in power-assisted wheelchairs using optimal control theory and a model of the user and wheelchair system. The proposed approach leads to a controller capable of rising the wheelchair, which is able to reject perturbations and which is robust to typical parameter uncertainties.

A Comparison of Different Assistance Strategies in Power Assisted Wheelchairs using an Optimal Control Formulation

Power assisted wheelchairs are a promising solution to overcome problems associated with manual wheelchair propulsion, such as the incidence of upper limbs injuries and muscle fatigue. However, there are still open questions regarding the most appropriate assistance strategy. The main goal of this paper is to compare three different types of assistance in power assisted wheelchairs: constant force, proportional force and a novel type of assistance inspired on the impedance control theory. The comparison was performed using a simple model and an optimal control formulation that searched for optimal user actuation and controller parameters so as to minimize the user effort. The fairness of the comparison was ensured by imposing an upper bound on the energy consumption by the motors. The results show that the proportional and impedance controlbased strategies are the most appropriate steady state conditions. In typical daily activities such as obstacle avoidance, the impedance control has advantage as it permits a faster system’s response.

Active Learning Concepts Applied on a Automotive Mechatronic System

Nowadays, managing the combustion engines by the usage of electronics, has become indispensable. Without the electronics in this management system, would not be possible, for example, achieving the low emissions required by the environmental agencies, and meet, at the same time, the torque and performance requirements, imposed by the vehicles manufacturer. Study how the electronic management controls, the entire cycle of the engine operation, in different operating conditions, is a major challenge. To become this task easier, some small individual control loops are engaged (air intake, fuel injection and spark ignition), providing a support to the macro engine control. This paper aims to demonstrate a detailed procedure, step by step, to design a controller using the classical concepts of control systems, applied on a gas pedal + throttle body + electronic system, known as drive-by-wire system (DBW). The study proposed here becomes an important tool to support management engine classes and also classic control classes, for the students of Technology and Engineering Automotive, Mechatronics or Electric courses, because it demonstrates a practical application of mechatronic systems concepts involving multidisciplinary topics.

State Feedback Controller - An Alternative Approach Applied to Unmanned Aerial Vehicle

The primary goal of this work is to propose an alternative methodology as a first approach in the design of control systems by means of a feedback state gain. The proposed method is detailed and an application is presented. The results show relevant aspects regarding the state feedback gain, especially in regard to variation in the parameters of the plant.