Georg F. Mauer

A fuzzy logic controller for an ABS braking system

Anti-blocking system (ABS) brake controllers pose unique challenges to the designer: a) For optimal performance, the controller must operate at an unstable equilibrium point, b) Depending on road conditions, the maximum braking torque may vary over a wide range, c) The tire slippage measurement signal, crucial for controller performance, is both highly uncertain and noisy, d) On rough roads, the tire slip ratio varies widely and rapidly due to tire bouncing, and e) The braking system contains transportation delays which limit the control system bandwidth. A digital controller design was chosen which combines a fuzzy logic element and a decision logic network. The controller identifies the current road condition and generates a command braking pressure signal, based on current and past readings of the slip ratio and brake pressure. The controller detects wheel blockage immediately and avoids excessive slipping. The ABS system performance is examined on a quarter vehicle model with nonlinear elastic suspension. The parallelity of the fuzzy logic evaluation process ensures rapid computation of the controller output signal, requiring less time and fewer computation steps than controllers with adaptive identification. The robustness of the braking system is investigated on rough roads and in the presence of large measurement noise. This paper describes design criteria, and the decision and rule structure of the control system. The simulation results present the systems performance on various road types and under rapidly changing road conditions.

On-line cylinder fault diagnostics for internal combustion engines

The ability to continuously monitor internal combustion engines for the existence and location of faults can improve engine reliability and reduce operating costs. The diagnostics method is based on recording the engine speed fluctuations at the flywheel and at the front end of the engine over one combustion cycle. From the speed fluctuations, the cylinder-to-cylinder variations of the net engine torque are computed. The performance deterioration of an individual cylinder is detected as a drop of computed torque. The diagnostic hardware consists of a digital engine speed data acquisition system and an embedded controller and is suited for in-vehicle installation. The method, suited for any multicylinder engine, detects the location and severity of faults during normal engine operation. Adjustments for individual engines of the same class are not required. >

An end-effector based imaging proximity sensor

A two-dimensional array of small capacitive sensors detects the distance between each sensor tip and the target object. When touching the surface or operating at close distance, an image of the surface contour is obtained. Each capacitive sensor consists of a thin short lead (line capacitance) embedded in a hard ceramic substrate. The sensor array is rugged and can, due to its small size, be configured to almost any desired shape in order to examine even hard-to-reach surfaces. An electronic circuit converts the capacitance variations into voltage signals. The sensing process is controlled by a microcomputer, which addresses the sensors in serial order through a multiplexer, samples the data and linearizes them according to the calibration curve. When compared to resistive touch sensors, the capacitive sensing method offers potentially higher package density and image resolution; another advantage is the capability to detect the presence of objects while approaching, before physical contact is made. A proximity sensor array mounted on a robot end effector can determine geometrical parameters such as edges of surfaces, hole center locations, and the end effector pose (angle of alignment between end effector and target surface).

Vision-based autonomous robot control for pick and place operations

Typical robotic pick and place operations involve sensors such as touch and vision attached to the robot. In the presence of ionizing radiation this approach becomes difficult because most customary sensors degrade over time due to radiation exposure. The alternative is the placement of multiple cameras outside the radiation zone, and to identify and infer the location and dimensions of parts within the robots workspace through image analysis. The paper describes strategies for the reliable and flexible control of the material handling robots inside a hot cell by means of automated stereo vision systems. Since the cameras can be positioned outside the hot cell, such systems would have significant advantages over sensors inside the hot cell, resulting in potentially reduced system maintenance and increased system reliability.

Combustion Engine Performance Diagnostics by Kinetic Energy Measurement

The diagnostic technique described in this paper is based on measuring the instantaneous angular speed of both the front end and the flywheel on internal-combustion engines, recording more than 400 speed measurements per engine cycle. The results from measurements on an eight-cylinder diesel engine with various cylinder faults show that reduced cylinder performance produces a drop of kinetic energy for the faulty cylinder. An engine performance criterion evaluates the performance of each cylinder, based on its contribution to total engine kinetic energy

On-line performance diagnostics for internal combustion engines

An online diagnostics algorithm and measurement system for automotive engines is described. Both front-end and flywheel engine speeds are measured digitally by time interval detection between encoder pulses, using a single-board computer for data collection and processing. Based on a lumped parameter crankshaft model, the torque contribution of each cylinder is computed. Those cylinders contributing less than a predetermined threshold value are identified as faulty. A series of tests with various engines and fault conditions have shown that the diagnostic system provides for reliable online determination of cylinder fault locations, as well as an estimate of the fault severity, which is determined from the magnitude of the performance index. An estimate of the maximum engine torque is derived from snap acceleration tests. The diagnostics system can be applied to all engines of the same type without requiring training data.<<ETX>>

Mobile Robot Design in an Introductory Engineering Course

The course ‘Introduction to Engineering Design’ is aimed at freshmen students entering Mechanical and Aerospace engineering. The course was restructured from its previous 3-credit lecture format to a 2 credit lecture coupled with a new 1 credit design laboratory. The laboratory project aims at giving the students experience in professional design, engineering practice, and teamwork. While the lecture presents an overview of the engineering profession and its practices, small student teams conduct a structured hands-on design project in the lab. The team assignment is the design, programming, and testing of autonomous mobile ‘Sumo’ robots. Each team develops and builds an autonomous robot, which will compete against the other teams’ robots at the end of the semester. Students find the robot project highly motivating and spend voluntarily several afternoons weekly working in the lab. Student enrollment has increased more than five-fold since course inception six years ago. The course is also being taught regularly to seniors at local high schools through distance education, further broadening the pool of future engineering students. The paper describes the lab course structure, organization, and student learning outcomes.Copyright

Design and Evaluation of Multi-Axis Vibration Shaker Concepts

Multi-axis shaker systems for the mechanical testing of components up to 2 kHz generally exhibit multiple resonances within their operating range of frequencies. Equipment testing requires the control of the shaker’s power density spectra in all axes of shaker motion. The paper describes the results of a 4-year ongoing project to develop a predictive model of 6-axis shaker dynamics, and presents a comparison between the computer model and a series of experiments on a small 6-DOF electrodynamic shaker, employing computed and experimentally recorded power density and coherence spectra, as well as modal analyses. Modifications of the shaker’s structural stiffness and damping are shown to be correctly predicted and validated by the experiments.© 2007 ASME

An Imaging Proximity Sensor for Robotic Inspection and Assembly

A two-dimensional array of small capacitive sensors detects the distance between each sensor tip and the target object. When touching the surface or operating at close distance, an image of the surface contour is obtained. Capacitive gauging is used because of its high sensitivity for the measurement of small distances. Each capacitive sensor consists of a thin short lead (line capacitance) embedded in a hard ceramic substrate. The sensor array is rugged and can, due to its small size, be configured to almost any desired shape in order to examine even hard-to-reach surfaces. An electronic circuit converts the capacitance variations into voltage signals. The sensing process is controlled by a microcomputer, which addresses the sensors in serial order through a multiplexer, samples the data and linearizes them according to the calibration curve. Experimental results with an imaging sensor arranged in a 4x4 matrix are reported. When compared to resistive touch sensors, the capacitive sensing method offers potentially higher package density and image resolution; another advantage is the capability to detect the presence of objects while approaching.