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- A novel monolithic silicon sensor for measuring acceleration, pressure and temperature on a shock absorberPublication . Ferreira, C.; Ventura, P.; Grinde, C.; Morais, R.; Valente, A.; Neves, C.; Reis, M.J.C.S.; Henriques Ferreira, Carlos Daniel; Neves, CarlosA fabricated micro-mechanical sensor to assess the condition of automotive shock absorbers is presented. The monolithic sensor, measures the oil temperature, acceleration and internal pressure of the shock absorber. A dual mass accelerometer with optimized beam geometry is used for acceleration readout. In addition, a 23.1 μm thickness square membrane and two buried resistors are used for pressure and temperature sensing respectively. The proposed miniaturized sensor can be effectively integrated with standard single- and dual-tube shock absorbers. The data acquired during normal vehicle operation can be continuously used to monitor the condition of the shock absorbers, allowing shock absorbers to be replaced before their degradation significantly reduce the comfort, performance and safety of the vehicle.
- Sensing methodologies to determine automotive damper condition under vehicle normal operationPublication . Ferreira, Carlos Daniel Henriques; Ventura, Paulo; Morais, Raul; Valente, António L.G.; Neves, Carlos; Reis, Manuel C.Vehicles rely on the efficiency of dampers to dissipate energy from the motion of vehicle body and wheels, maintaining the vehicle more stable, and improving the contact between tires and the road surface. To achieve an effective monitoring of dampers (or shock absorbers), two different methodologies, capable of assessing, under vehicle normal operation, the condition of the automotive dampers are presented. The proposed methodologies are based in acceleration, temperature and pressure sensing to determine the shock absorber condition, and are therefore suitable for future implementation in low cost fabrication technologies. The results shown that it is possible to have an effective monitoring device, installed in the damper body, capable of continuously determining shock absorber status, and therefore enabling real time diagnosis. Such a diagnosis system can reduce the number of vehicles riding with defective suspension systems and increase the overall vehicle safety.
- Study of the driver’s behavior when cornering and characterization of safe speed perceptionPublication . Brás, M.; Ferreira, Carlos Daniel Henriques; Neves, CarlosRecently, there has been a growing interest in research towards autonomous vehicles, aiming to improve efficiency, safety, comfort and to eliminate human errors. However, a question arises: what should set the speed of the vehicle? The road legal limit, the maximum possible given the traffic conditions, the road critical speed or any other matter? Moreover, it has been mentioned in literature that drivers feel unsafe when using cruise control systems, namely in cornering conditions. Therefore, to study the driver’s behaviour when cornering, a test vehicle was equipped with a dedicated data acquisition system to acquire the vehicle dynamics and the driver heart rate. Trials with volunteers were carried out on a 22 km selected route, consisting of multiple types of roads, from city roads to highways. Based on the field results, we propose a control strategy for the vehicle speed when cornering relating the curve radius with the centrifugal acceleration. The proposed control strategy could be easily adopted by advanced driver assistance systems and autonomous vehicles. The reproduction of a human-like behavior will enhance the perception of safety and comfort of both the driver and occupants.
- Autonomous Wireless Sensor with a Low Cost TEG for Application in Automobile VehiclesPublication . Costa, A.; Costa, D.; Morgado, J.; Santos, Helder; Ferreira, Carlos Daniel HenriquesThe present work consists in the development of an autonomous, low cost, reliable, energy scavenger sensor for automotive applications. Thermoelectric generators typically exhibit low efficiency but high reliability, making them suitable for autonomous, low average energy consumption, applications. A prototype sensor was developed for mounting in the engine exhaust pipe using a step-up voltage converter, a microcontroller, temperature and pressure sensing elements, conditioning electronics and a wireless transceiver, all powered by a low cost TEG (Peltier module TEC1-12706), through the scavenging of exhaust gases thermal energy. During the tests the prototype was able to sustain a regular signal transmission throughout the engine operation. The sensor was installed directly at the measuring point eliminating wired cables to hot and vibrating parts, thus, simplifying the installation of components and improving the reliability of the vehicle systems.
- High Sensitivity Micro-machined Piezoresistive Strain SensorPublication . Caseiro, D.; Santos, S.; Ferreira, Carlos Daniel Henriques; Neves, CarlosThis paper presents a micro-machined piezoresistive sensor capable of measuring very small strains. The sensor design, based on piezoresistive sensing technology, was optimized by the numerical method using Finite Element Method (FEM) to enhance sensibility. The high sensibility is achieved through a reduction of section and through the action of the bending moment. As a result, a sensor with a sensitivity of 569.4608 μV/V/με, which can be fabricated by the SensoNor MultiMEMS process, is proposed. Furthermore, practical essays with macro prototypes confirmed and validated the numerical analysis. Such a sensor can be a direct replacement for the strain gauges and its very high sensitivity opens the door to many other applications, that otherwise would not be possible.