Luiz Carlos Gertz

Dynamic torque measurement for automotive application

This work presents a system for the measurement and monitoring of the torque transmitted to the wheel of a moving vehicle. The transducer was built on the aluminum alloy wheel and the electronic system installed right on the center of the wheel assembly. The whole system spins with the tire, commanded by the power sent by the engine. The designed beam load cell was milled on an aluminum radial spoke and strain gauges were attached to the points of maximum deformation. The signal from the strain gauge bridge, was amplified and filtered. Then it was sent to an analog to digital converter built on a wireless ZigBee transmission module. The receptor ZigBee module was connected to a notebook inside the vehicle. A static calibration has been conducted with calibration weights and the results show features like linearity, sensibility and noise rejection. Finally, preliminary dynamic experiments run on a flat road, have shown so far, that the device is able of measuring and monitoring the direct torque developed on the vehicles wheel during real conditions on the road.

Avaliação da Força de Atrito em máquina de musculação durante exercícios de extensão de joelho

During exercises performed in weight training machines, the friction force (FF) between its mechanical components can influence the magnitude of the overload offered by the machine on force of the exercise. However, little is known about how to measure this friction and what its real effect. Thus the objectives of this study were (i) describe a technique for measuring FF in weight training machines, and (ii) exemplify the technique, by quantifying the FF of the weight training machine at different exercise speeds and loads. For this, a subject performed repetitions of the exercise in different loads and speeds. The loads evaluated were 3 kg, 6 kg and 9 kg; and the speeds were 30°/s, 60°/s and 120°/s. The FF, normalized by selected load, increased significantly with the increasing of the speed and decreased with increasing of the load. Results for friction force around 40% found for highest speed and lowest load show that take the FF in count its an important factor to consider during muscle equipment choice and maintaining.

Estudo de um motor CC brushless aplicado no acionamento de um carro elétrico de pequeno porte

This work presents the study of an electric motor, which was used to drive a small electric car. The aim was to select a motor with characteristics of suited operation to drive the electric car at a speed range from 12 to 20 km/h. Tests were carried out on the electric car with the purpose of determining its dynamic behavior. The test results allowed to select a DC (Direct Current) brushless electric motor of 12 V and 5.9 A with 77% of maximum efficiency. A theoretical study was developed to determine the best relation of the movement transmission from the motor to the car. By doing that, it was possible to determine the characteristics of the operation of the motor in which it developed its maximum efficiency, when the electric car was started up. The speed ratio value resulted in 64:1. The study showed that to operate a 20 km/h speed, the car requires a mechanical power of 58 W from its electric motor.