Thomas L Lagö

On physical experiments and individual assessment of laboratory work in engineering education

It is obvious that our society needs more engineers. It is also true that mankind must live in symbiosis with nature and focus on sustainability and understanding. Thus, engineers must be able to design products and services which are in line with the principles of nature and the only way to become familiar with these principles is to perform many physical experiments. A way to use instructional laboratories more effectively and offer more hours in the laboratories for students without significant increased cost per student is opening them for remote access. Hands-on experiments are indispensable but remote mouse-cursor-on ones can supplement them. The VISIR (Virtual Instrument Systems in Reality) Open Laboratory Platform offers an open standard for online workbenches enabling students not only to perform physical experiments 24/7 but also to practice laboratory work. Learning objectives of laboratory work, free access to laboratory resources, and individual assessment of such work should be important key elements in an education delivering engineers with a solid documented laboratory experience.

Analog versus Digital Control of Boring Bar Vibration

In workshops where metal cutting is performed, the machining processes frequently introduces productivity degrading vibration problems and annoying sound, sometimes almost at unbearable levels. Besides producing disturbing noise, the vibrations affect the surface finish of the workpiece and the tool life. Two different approaches based on feedback control are investigated, both applied for the control of an active boring bar. The first approach is based on a digital adaptive feedback controller; the feedback filtered-X LMS algorithm. The second approach is based on an analog controller; a feedback controller with gain and phase orthogonally adjustable, thus flexible for the control of systems with different dynamic properties. Based on open loop frequency response function estimates, robustness and stability of both the digital and the analog feedback control system are discussed. A comparison of the two controllers concerning their boring bar vibration attenuation performance shows that the analog controller attenuates the vibration in same order of magnitude as the digital controller which is approximately by up to 40 dB.

Active vibration reduction in a light weight high speed train bogie

Abstract Active control of vibration-induced noise in light weight train cars is of great interest since low weight trains are more economic but also have higher internal noise levels. This paper describes an approach to isolate bogie vibrations in such a way that the noise inside the car is reduced. An active control system with four inertial mass actuators fitted to the bogie were used to control bogie vibrations and noise inside the car. The tests were performed on an experimental light weight bogie fitted to a test car, in both lab environment and in foil scale tests on track at full speed.

Modeling a Clamped Boring Bar using Euler‐Bernoulli Beam Models with Various Boundary Conditions

This paper addresses modeling of a clamped boring bar using Euler‐Bernoulli beam theory. Euler‐Bernoulli beams with a number of different boundary conditions were used to model a clamped boring bar. Estimates of the boring bar’s natural frequencies and mode shapes were produced with each of the boring bar models. The estimates produced by the distributed‐parameter system models are compared with eigenfrequencies and mode shapes estimated based on experimental modal analysis of the actual boring bar clamped in a lathe.

Actual accuracy in flight data collection and analysis

In aerospace applications it is often vital to understand what is happening when analyzing sound and vibration data and what total accuracy one receives. The tradition has been to spend money on ye ...

Using MATLAB for Advanced Noise and Vibration Analysis

Commercial tools for measurement and analysis of noise and vibration signals have traditionally been very expensive. In the last decade, however, multi-channel measurement systems have become relat ...

Multiple peak count analysis for increased spectral resolution, a non-linear filtering method

In applications for acoustic profiling, an analysis of current versus depth is key. By analyzing the Doppler frequency variation in the backscattering signal, it is possible to calculate the mean current versus depth. However, due to turbulence in the water creating simultaneous currents and layers, the current direction could change rapidly, making the data non-stationary and difficult to analyze. The transmitted pulse is very short, and the volume where the current should be estimated is typically small. Also, the water volume can contain multiple Doppler responses due to turbulence and other phenomenon. When using this innovative non-linear filtering method, Multiple Peak Count Analysis, these effects can become visible, and the method shows superior performance as compared to classical methods. Classical 3-dimensional spectral plots of the data, does not use a-priori information. In this case, there is a particular interested in finding multiple peaks in the data, a-priori information. A non-linear pre-filtering method has thus been developed where the peaks are extracted in the spectra. A short-time FFT has been used to find the spectral content, where a small time data block is processed using a much larger time analysis block size. The paper describes this new method and compares the result with a classical analysis. Advantages with this new method, and suggestions where the method can perform better are also discussed. This approach can also be used in other applications for sound and vibration, despite this methods main current use being under water.

Nonlinear modeling of the forward path in a mechanical active control system

In most active control applications the estimate of the forward path is closely related to the performance of the controlled system. Nonlinearities in the forward path are most likely to degrade the performance. In the active control of machine tool vibration in a lathe, the plant under control principally consists of two physical parts: amplifier and a tool holder construction with integrated actuators. One applicable actuator type was used and it was based on highly magnetostrictive material. However, these types of actuators generally have nonlinear behavior. To obtain deeper understanding on the dynamic properties of the plant under control and thereby obtain a solid base for the feedback control of the machine tool vibration, nonlinear modeling of the forward path was proposed. Two methods were used: The approach of neural networks and the reverse multiple‐input single‐output by Bandat have been used in order to describe the forward path as accurately as possible. In the active control system of mach...