Georg Brasseur

Modelling of high power automotive batteries by the use of an automated test system

In order to estimate the field of application for an electrical energy storage, its performance at different operating conditions has to be measured and evaluated. An automated test system has been designed to speed up measurement and to ensure reproducible measurement conditions. The paper focuses on the performance of this test system and on measured data. Based on this data, a battery model of a NiMH cell is parameterized and the obtained results are discussed.

Design rules for robust capacitive sensors

Capacitive technologies play an increasingly important role in the fields of industrial and automotive sensors. The noncontact working principle, on the one hand, is the main advantage of this technology; on the other hand, the sensor is thus sensitive to electromagnetic disturbances. This paper describes methods to successfully develop capacitive sensors, which can reliably be operated in harsh industrial and automotive environments. A carrier frequency system combined with a ratiometric evaluation algorithm and a frequency hopping strategy can guarantee safe operation of capacitive sensors.

A robust capacitive angular speed sensor

This paper presents a contactless capacitive angular speed sensor for automotive applications. The sensor is based on a passive rotating electrode placed between two mechanically static and electrically active electrodes. The different characteristics of the charge transfer at various sensor positions is utilized as an input for the calculation of the rotational speed. The main advantages of this low cost system are its capability to operate at high temperatures and humidity as well as its insensitivity to vibrations, dirt, dew and moisture deposited on the three sensor electrodes. The mathematical model of the sensor further enables the optimization of the sensor characteristics for specific applications. Experimental results from a prototype designed for the speed-measurement of a steering-wheel show a relative speed error of /spl plusmn/4% at a resolution better than 1/spl deg//s.

A robust capacitive angular position sensor

A noncontacting robust capacitive angular position sensor currently under development for industrial and automotive application is presented. The main advantages of this low-cost system are its simplicity, high accuracy (/spl plusmn/0,2/spl deg/) and resolution (/spl plusmn/0,04/spl deg/) over the range of up to 360/spl deg/, excessive temperature operating capability, insensitivity to dirt, moisture and dew on the sensor electrodes and fast measurement speed. The paper describes the working principle, derives the required relationships for computing the rotor position and discusses the sensors properties in relation to those of established encoder principles. The sensitivity of the sensor to mechanical errors like radial and axial axis offset, tilted axis, and tilted electrodes is explained. Finally the sensor electronics and its realization is discussed and data obtained from prototype sensors is presented.

A Feasibility Study on Autonomous Online Condition Monitoring of High-Voltage Overhead Power Lines

For electric power transmission, high-voltage overhead power lines play an important role, as the costs for power transmission are comparatively low. However, the sag of the conductors (e.g., due to temperature variations, aging, or icing of conductors as a result of extreme weather conditions) may increase safety margins and limit the operability of these power lines. Furthermore, heavy loads due to icing or vibrations excited by wind streams increase the risk of line breakage. With online condition monitoring of power lines, critical states can be detected early, and appropriate countermeasures can be applied. In this paper, we investigate possibilities for monitoring devices that are directly mounted onto a conductor. The feasibility of powering the device from the electric field, protection of electronic circuitry from strong electric fields, and data transmission by means of a wireless link is demonstrated, as well as its operability during the presence of strong magnetic fields due to high currents and transient signals due to partial and spark discharge events.

A Combined Inductive–Capacitive Proximity Sensor for Seat Occupancy Detection

This paper presents a simple and efficient seat occupancy detector. A seat occupancy detector is an integral part of the airbag safety system and, in its simplest form, provides the (occupied or vacant) status of the seat to the airbag control unit. Although the occupancy sensing methods based on a capacitive principle are efficient, they typically require electrodes to be placed in the surface layer of the sitting and backrest areas of the seat. The proposed sensor uses a simple electrode structure, and it is placed below the seat foam in the sitting area of the seat. These features promise a less-expensive sensor as it can be easily manufactured and installed in a seat. The new sensor combines inductive and capacitive proximity sensing principles. The sensor detects the presence of an occupant exploiting the shielding effect of the electric field while its inductive proximity feature senses the presence of conductive objects (e.g., laptop) that may be placed in the seat and helps to achieve reliable occupancy sensing. The measurement system uses a signal conditioning unit based on a carrier frequency principle. A prototype sensing system has been built, and its application as a seat occupancy sensing system in a vehicle has been verified. The developed system successfully senses human proximity and distinguishes it from other conductive objects.

Inertial tracking for mobile augmented reality

Augmented Reality applications require the tracking of moving objects in real-time. Tracking is defined as the measurement of object position and orientation in a scene coordinate system. We present a new combination of silicon micromachined accelerometers and gyroscopes which have been assembled into a six degree of freedom (6 DoF) inertial tracking system. This inertial tracker is used in combination with a vision-based tracking system which will enable us to build affordable, light-weight, fully mobile tracking systems for Augmented Reality applications in the future.

Seat Occupancy Detection Based on Capacitive Sensing

This paper presents a simple yet efficient seat occupancy detection scheme based on a capacitive sensing principle. Parameters such as the presence, position, and type of the occupant of the seat are essential for successful air-bag control in vehicles. Without this information, during a collision, the air bag may be inflated to an empty seat (ES), wasting it and, hence, leading to allied repair and reinstallation. Also, if deployed, it can cause fatal injuries to infants in rear-facing infant seats. The proposed capacitive sensor system detects the presence of an occupant and provides information about the occupants position. A prototype occupancy detection system has been developed, and the feasibility of the new method has been validated through practical tests. The developed system takes 200 mus to complete a measurement and, hence, promises real-time operation of the air-bag system. The presented method employs a carrier-frequency method and lock-in-amplifier technique to measure the capacitances. Thus, the influence of external electromagnetic fields on the final result is kept low.

Digital-to-analog conversion by pulse-count modulation methods

Three low-cost digital-to-analog converters (DACs) are described and compared. These designs can easily be implemented in an integrated circuit: the conventional pulse-width modulation (PWM) DAC, the new pulse-count modulation (PCM) DAC and the first-order noise shaping (FONS) DAC. All three methods control the ratio of the sum of all pulse durations to the constant total period. As the pulse durations are integral multiples of a unit pulse, all three can be classified as pulse-count modulation methods. Block diagrams of all three DACs consisting of a simple digital circuit and a low-pass filter are presented. For a constant digital input value the worst case ripple of the filter output is used to calculate the cutoff frequency of the low-pass filter. Approximations for the 3 dB cutoff frequency of first-order, second-order and fourth-order Butterworth low-pass filters are given. The dynamic properties are analyzed in the time domain (settling time) and in the frequency domain (unfiltered output spectrum of a full-scale sine wave input). The main influences on the static accuracy are analyzed. A case study demonstrates the abilities of PCM and FONS.

Capacitive sensor for relative angle measurement

Based on a capacitive angle/angular speed sensor a sensor measuring the relative angle between two rotating shafts has been developed. Two rotatable grounded electrodes are placed between two sensor plates. The relative angle between the two rotors and the absolute position of the rotor blades are calculated from measurements of the capacitive coupling between different transmitting stator segments. A prototype of this sensor has been developed with a range of the relative angle of /spl plusmn/7.5/spl deg/ with a resolution of 0.1.