Ludmila Corrêa de Alkmin e Silva

Measurement of wheelchair contact force with a low cost bench test.

In mechanical engineering, it is well established that contact between the tire and the ground is a key parameter in characterizing the dynamic behavior of vehicles and an important factor in design control. Therefore, it is an important part of dynamic simulation models for vehicles, including wheelchairs. This work presents a bench test designed to experimentally monitor and measure the forces transmitted to the ground by a moving wheel. The test bench is composed of a table and a track with a fixed wheel structure and powertrain system. The table is an integrated structure that measures the longitudinal and lateral forces produced by tire contact. This table allows characterization of the tire and tests the tire under varying loads at different slip and camber angles. Additionally, the test bench can also be used to evaluate other tires, such as caster tires. The performances of the new device are illustrated, and the results show the differences between tires, which are related to the dynamic behaviors of wheelchair model. Finally, preliminary experiments performed using the test bench have shown that it is able to monitor and measure the forces generated by the contact between the tire and the ground.

A study of battery power for a different electric vehicle propulsion system

This paper presents a simulation of an electric vehicle propulsion system. The simulation assumes BLDC motors combined with a proportional-integral controller and batteries. Regarding the longitudinal dynamics of electric vehicles (EV), models of different components and configurations are introduced and simulated. The simulations show the potential of each configuration according to the battery size. Thus, the objective is to find the best configuration (batteries size and propulsion system setup), keeping the original drivability. Six different configurations will be analyzed using the standard Brazilian urban driving cycle NBR6601. A rule-based method is used in the power management strategy that indicates the batteries states. This information aids the decision on the correct specification of the battery for each simulated configuration according to some restrictions.

Modeling a Hands-Free Controlled Power Wheelchair

This paper will present a study of the dynamics of the contact between the tire of a wheelchair and the ground. The model of the contact between road and tire has been implemented using a mathematical concept in a 2D multibody program, creating a laboratory. With this laboratory, it is possible to see the behavior of the wheelchair with different input sources. In this work the input is taken care of by a program called HaWCoS which allows the user to control a wheelchair without the need to use the hands. The results make it possible to develop new products for people with special needs and to develop better control systems by taking the dynamic behavior of wheelchairs into consideration.

Gear shifting multi-objective optimization to improve vehicle performance, fuel consumption, and engine emissions

ABSTRACT In the present work, the Adaptive-Weight Genetic Algorithm was employed in order to determine the gear shifting strategies that allow an automobile to work in the best compromise among fuel consumption, engine emissions, and vehicle performance. For the assessment of each of the three objective functions, a simulation model based on engine data and on the well-established equations of the longitudinal dynamics was developed. The driving cycle chosen for the calculations was the FTP-75, which takes into account both cold and hot starts, meaning that the transient operation during the warm-up of the catalyst is also considered.

Study of Different Electric Vehicle Propulsion System Configurations

This paper presents a study of an electric vehicle (EV) with two different drive systems and three available electric motors (EMs) configurations. The EMs are BLDC (Brushless Direct Current) motors combined with a proportional-integral controller (PI). The vehicle power demand is divided between the drive systems through rules based vehicle power management control (PMC) that aims to reduce the lithium-ion battery discharges during the Brazilian urban driving cycle NBR6601. The results indicate the potential of each simulated configuration and the combination drive system/EM in which present the lower battery discharge. Each EV configuration is compared and the best configuration is defined.

Gear Shifting Strategy to Improve the Parallel Hybrid Vehicle Fuel Consumption

The hybrid electric vehicle (HEV) is an alternative to reduce the engine fuel consumption due to the extra electrical power addition in the system that allows changing the engine operation point for a better efficiency region. The gear shifting strategy is a way to modify the engine operation point and it can be combined with the power management strategy to reach a better operational condition. The aim of this study was to analyze the influence of the gear shifting strategy in the HEV configuration, comparing a conventional 1.0L vehicle with a parallel HEV.

A lateral dynamics of a wheelchair: identification and analysis of tire parameters

In vehicle dynamics studies, the tire behaviour plays an important role in planar motion of the vehicle. Therefore, a correct representation of tire is a necessity. This paper describes a mathematical model for wheelchair tire based on the Magic Formula model. This model is widely used to represent forces and moments between the tire and the ground; however some experimental parameters must be determined. The purpose of this work is to identify the tire parameters for the wheelchair tire model, implementing them in a dynamic model of the wheelchair. For this, we developed an experimental test rig to measure the tires parameters for the lateral dynamics of a wheelchair. This dynamic model was made using a multi-body software and the wheelchair behaviour was analysed and discussed according to the tire parameters. The result of this work is one step further towards the understanding of wheelchair dynamics.

Canceling interference caused by tremors in joystick controller: study case in a power wheelchair

People with disabilities such as Parkinsons, Holmess or other disease have difficulty operating conventional joysticks because of the tremor. This paper will present a study of the joystick control for the minimization of this tremor. For this minimization, different types filter and control were study and compared. These controls were tested in a wheelchair laboratory to see the behavior of the wheelchair with diferents inputs. Simulation results were presented to show the tremor cancel as well as the performance of the control development. With this results is possible to develop new products for people with special needs and to develop better controls for people with tremor hand.

Application of Pattern Recognition for the Mitigation of Systematic Errors in an Optical Incremental Encoder

The accuracy and reliability in the measurement of the instantaneous angular speed (IAS) by incremental encoders are fundamental for speed and torque control systems. An error in the acquisition of this variable may cause instabilities or even render the system unfeasible. Many works deal with this problem, which in some cases is caused by the imperfections in the disk manufacturing or also shaft misalignments. Due to the systematic character of these type of error, in this work an error pattern in the encoder signal of a vehicle dynamometer was identified by means of a calibration process and detected along the experiment by minimizing the total variation of the corrected angular speed curve. By making use of this procedure, not only the measurement became more accurate, but also the direction of rotation and angular position of the rotary system could be detected with only one channel of the encoder sensor being acquired. After the application of this method, the measurement error was reduced by 84.22%, even in transient conditions, without the application of further filtering methods, which may unwantedly lead to phase shifting in the IAS signal.

Powertrain Optimization to Improve Vehicle Performance and Fuel Consumption

The available gearbox transmission ratios associated with gear shifting strategies influence the vehicle performance and fuel consumption because it changes the powertrain inertia and the engine operation point. However, the best configuration for the vehicle powertrain, according to a specific driving condition, is difficult to be determined. Therefore, this paper presents an Interactive Adaptive-Weight Genetic Algorithm to optimize the vehicle powertrain gear ratios and the gear shifting strategies to allow the vehicle to operate in the best compromise among fuel consumption and performance in the urban driving scenario provided by the FTP-72 cycle. The optimization process results in a fuel saving of 10.61% and 50.12% improvement in the vehicle performance when using the best-compromised configuration.