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| 2. |
- Andrén, Linus, et al.
(author)
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Active Control of Boring Bar Vibrations Using the Leaky Feedback Filtered X-LMS
- 2003
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Conference paper (peer-reviewed)abstract
- The boring operation is a cumbersome manufacturing process marred by noise and vibration related problems. The manufacturing industry is having trouble with these kinds of metal cutting operations. There exist several approaches to reduce the vibrations in cutting operations in general. Passive tuned dampers in boring bars have been commercially available for some time. An active solution is likely to be more robust to changes in the spectral content, where the passive counterpart have a small operable area, the active solution is able to adapt to these kinds of changes. Active vibration control in boring operations has been proven to be feasible. The algorithm used in the successful experiments was the feedback filtered X-LMS algorithm. This algorithm does however not guarantee a stable behavior, but incorporating a leakage factor will make the algorithm more robust. Power spectral density of boring bar vibration of real cutting experiments show that the leaky filtered X-LMS algorithm is a possible candidate to be a suitable control algorithm. Nyquist diagrams of the controller during operation show that the stability is increased significantly.
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| 3. |
- Andrén, Linus, et al.
(author)
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Active Noise Control Experiments in a Fork-lift Truck Cabin
- 2004
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Conference paper (peer-reviewed)abstract
- High comfort for the driver in working vehicles is an important feature as well as a demand from the drivers. Low noise level is an essential factor for the manufacturer to maintain a high standard and comfort of vehicles. In many cases the noise inside the cabin can be related to the engine orders. Hydraulic pumps and fans are also related to the engine but not necessarily integers of the engine order. Passive absorbers are not suitable for the lowest frequencies and one approach is to use an active noise control system to solve the noise problem at low frequencies. In the present experiment loudspeakers were mounted inside the cabin of a fork lift-truck to produce the secondary noise field. To sense the residual noise, microphones were installed close to the driver's head. The aim is to create a zone of reduced noise around the head. Since a large portion of the noise inside the cabin can be related to the engine, an active control system based on a feedforward solution is possible. Experimental results from a feedforward solution of active noise control in a fork-lift truck cabin show that the noise level in the low frequency region can be reduced significantly.
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| 4. |
- Andrén, Linus, et al.
(author)
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Actuator placements and Variations in the Control Path estimates in the Active Control of Boring Bar Vibrations
- 2004
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Conference paper (peer-reviewed)abstract
- A classical example of chatter prone machining is the boring operation. Turning under conditions with high vibrations in the cutting tool deteriorates the surface finish and may cause tool breakage. Severe noise is also a consequence of the high vibration levels in the boring bar. Active control is one possible solution to the noise and vibration problem in boring operations. In boring operations the boring bar usually have vibration components in both the cutting speed and the cutting depth direction. The introduction of the control force in different angles in between the cutting speed and the cutting depth directions have been investigated. Furthermore, control path estimates produced when the active boring bar was not in contact with the workpiece and during continuous cutting operation are compared. Experimental results indicate that the control force should be introduced in the cutting speed direction. Although the vibrations are controlled in just the cutting speed direction the vibrations in the cutting depth direction are also reduced significantly.
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| 5. |
- Andrén, Linus, et al.
(author)
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Performance Evaluation of Active Vibration Control of Boring Operations Using Different Active Boring Bars
- 2003
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Conference paper (peer-reviewed)abstract
- Vibration and noise in boring operations are ubiquitous problems in the workshop. In boring operations, the boring bar is subjected to forces from both the cutting speed and the cutting depth direction. To solve the vibration problem using active techniques would normally require two actuators in order to enable the control of both directions. By mounting one actuator in between the cutting speed and the cutting depth direction it is possible to achieve an active control solution with one actuator. Using only one actuator not only simplifies the control algorithm and saves extra equipment but is also favourable in terms of modifications of the boring bar. The harsh environment in a lathe more or less requires that both sensors and actuators are embedded and sealed into the boring bar. Since the forces that are to be controlled are large, the space needed for the actuator is substantial. Thus using only one actuator will keep the modified boring bar stiffer than a two actuator design. Three boring bars with the actuator mounted at different angles between the cutting speed and the cutting depth directions have been tested. Results from cutting experiments show that the one actuator solution has good potentials to the vibration problem in boring operations.
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| 7. |
- Bai, Guohua
(author)
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A Sustainable Information System for e-home Services
- 2004
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Conference paper (peer-reviewed)abstract
- E-home related home-services (including homecare and home healthcare) in China is urgently needed. The population of aged people over 80 is increasing 5% every year in China, and to year 2050, one fourth of whole population or 0.4 billions people in China are aged staying at home. Meanwhile the government cannot afford with a national elderly care system like most western countries as Sweden. This is because China has had one-child/one-family policy since 1970’s, and this radical policy has made China step in aged society very quickly within only 20 years, while the same process took 40-80 years in western countries. Even worse, China becomes aged society when the country is still poor and under developing with GDP per capita less than 1000$, comparing to western countries with 5000 – 10000 $ when they became aged society. E-home provides China with a unique, and maybe the most effective solution to the problem. By applying effective IT&C at home, elder people are facilitated to manage their own daily life. If needed, they can always call help from their collective service centre that is located in their resident area and the collective service centre can provide with both homecare (cleaning, shopping, reparation, baby care etc.) and home healthcare (legitimate medical care). Elder people can be also monitored (if wished by all partners) both at home and out door by bearing sensors that can send singles directly to related care providers (including their children and relatives if wished). E-home will greatly increase the security of elder people, release great worry from both their children and elder people themselves, and can be afford by most people. However, e-home is more than just a technical problem, and it needs a systemic way and social-psychological study how to design e-home system. In the end, e-home system must provide with needed services to residents. I will introduce IMIS project ´Integrated Mobile Information System for Home Healthcare’ financed by Swedish Agency for Innovative Systems (VINNOVA). This project will continue to 2006, and one of the outputs will be a sustainable software platform which is based on a systemic study of social psychological factors involved in the home healthcare. I will provide with some Swedish experiences and the so called ‘Scandinavia Approach’ in conducting such complex system to my colleagues in China, and I hope the IMIS project will be also developed in China based up on some feasibility and desirability studies with some Chinese colleagues.
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| 8. |
- Bai, Guohua
(author)
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Activity System Theory Approach to Healthcare Information System
- 2004
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Conference paper (peer-reviewed)abstract
- Healthcare information system is a very complex system and has to be approached from systematic perspectives. This paper presents an Activity System Theory (ATS) approach by integrating system thinking and social psychology. First part of the paper, the activity system theory is presented, especially a recursive model of human activity system is introduced. A project ‘Integrated Mobile Information System for Diabetic Healthcare (IMIS)’ is then used to demonstrate a practical application of the Activity System Theory especially in constructing healthcare information system. Our conclusion is that the activity system model can provide the service system designers with a comprehensive and integrated framework for designing healthcare information system in specific, and for designing various kinds of service systems in general.
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