Katja Hynynen

Chatter Detection in Turning Processes Using Coherence of Acceleration and Audio Signals

Chatter is an unfavorable phenomenon in turning operation causing poor surface quality. Active chatter elimination methods require the chatter to be detected before the control reacts. In this paper, a chatter detection method based on a coherence function of the acceleration of the tool in the x direction and an audio signal is proposed. The method was experimentally tested on longitudinal turning of a stock bar and facing of a hollow bar. The results show that the proposed method detects the chatter in an early stage and allows correcting control actions before the chatter influences the surface quality of the workpiece. The method is applicable both to facing and longitudinal turning.

Comparison of suboptimal control methods in magnetic levitation system

The use of active magnetic bearings (AMB) is increasing in high-speed applications, because their low friction operation allows higher rotational speeds than the traditional bearings. The inherent instability and complexity of the AMB rotor system with high nonlinearities pose challenges to the controller design. This leads to a problem of robust design. Robustness of LQG and loop-shaping H∞ controllers is compared with the help of the evolutionary algorithm both theoretically and based on experimental measurements.

Commissioning and Control of the AMB Supported 3.5 kW Laboratory Gas Blower Prototype

This paper presents the practical results of the design analysis, commissioning, identification, sensor calibration, and tuning of an active magnetic bearing (AMB) control system for a laboratory gas blower. The presented step-by-step procedures, including modeling and disturbance analysis for different design choices, are necessary to reach the full potential of the prototype in research and industrial applications. The key results include estimation of radial and axial disturbance forces caused by the permanent magnet (PM) rotor and a discussion on differences between the unbalance forces resulting from the PM motor and the induction motor in the AMB rotor system.

Wind turbine adaptive controller modeling

In the time of current trend of increasing energy consumption, the wind-power engineering may compensate considerable part of required electric energy. Rapid wind power engineering development is considered to be one of the important sources of human need satisfaction. Conventional wind turbine control strategies are dedicated to ensure high energy conversion efficiency under varying wind conditions. The challenge in wind power control engineering is to design an adaptive wind turbine control strategy, which provides the dynamic system stability and the effectiveness of energy conversion. Modern vector controlled wind turbine drives allow fast and accurate torque control on a wide speed range. The aim of this paper is to design and implement the control algorithm, which implies the electromagnetic torque control in order to adapt the optimal rotor speed and keep high energy conversion efficiency, taking full advantage of electrical drive performance. Wind turbine operation is considered in the partial-load regime. The stability of the purposed control system is studied using linear control theory concepts. The effectiveness of the wind energy conversion is proved by the simulation results in MATLAB Simulink environment.

Wind resource assessment in southeast Finland

Wind power production in Finland is increasing in near future. Most of the existing and planned wind farms are located in the costal and fell areas where the highest wind speeds occur. The purpose of the present paper is to investigate the inland wind conditions and wind power potential in South-Karelia, southeast Finland, based on wind speed measurements in three locations and several heights. The results show that South Karelia has potential for wind power production with high enough hub heights.

Case study comparison of linear H ∞ loop-shaping design and signal-based H ∞ control

This paper focuses on the design of a linear robust controller for a mechatronic system in the presence of real parametric and non-parametric frequency-dependent uncertainties. An Hinfin loop-shaping control design procedure is compared with a signal-based Hinfin control. The comparison of the robust controllers is carried out in the context of an active magnetic bearing rotor system. Experimental results demonstrate the better robust stability of the signal-based approach. A genetic algorithm is essential to credible comparison of different design approaches.

Audibility of wind turbine noise indoors: Evidence from mixed-method data

The sound of wind turbines occasionally causes annoyance among residents living nearby. A high sound pressure level fa an obvious reason for annoyance. However, there seems to be other explanations for annoyance, since annoyance and sound pressure level are not always fully correlated. In this study, the audibility of wind turbine noise and the factors affecting it are examined by using data collected from two residential areas near operating wind farms. The aims are to develop methods of analyzing the factors affecting the audibility of wind turbine noise and to analyze and compare the impacts of sound pressure levels, as well as wind characteristics and amplitude modulation on the audibility. The results reveal that combining self-reported annoyance levels with measurements of wind and sound characteristics makes it possible to gather versatile information about the audibility of wind turbine sound indoors and the annoyance caused by it. The results show that the sound pressure level is an important factor in the audibility of wind turbine noise, and wind characteristics seem to have some impact on it as well.

Inland Wind Resource Assessment in Southeast Finland

Rapid development of wind power technologies is enabling many nations to increase the share of wind energy in total electricity production. Finland, in common with many other countries, has a target of raising the contribution of wind resources to national energy production. The majority of existing and planned turbines in Finland are located in coastal areas, where the wind resources can provide favorable conditions for wind farms. However, considerable wind potential may exist in inland areas of the country. This paper presents a wind resource analysis of the southeast of Finland. The wind data, consisting of meteorological mast and LIDAR measurements at several heights, were collected in 2009 – 2011. The analysis includes monthly average wind speed, diurnal wind behavior and wind shear assessment. The energy output is estimated for a 3 MW wind turbine based on real wind speed distributions. Capacity factors are calculated to assess 3 MW wind turbine feasibility at the site. The obtained results demonstrate that inland wind conditions have sufficient potential to allow wind energy to thrive.