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A Toolbox for Sensor Data Fusion in Industrial Automation
Linköping University, Department of Physics, Measurement Technology, Biology and Chemistry. Linköping University, The Institute of Technology.
1999 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work is focused on measurement for support in industrial automation and especially around industrial robots. The main thread in the work is the combination (fusion) of information from different sensors. The applications are disassembly of electrical motors, sensor fusion in industrial safety applications and a new method for calibration of industrial robots.

When working with worn out products e.g. electrical motors, there are many different sources of uncertainty. To be able to perform operations on the products a method that can work under uncertainty are needed. It can be hard to decide which method works best in a specific situation. To make it easier a sensor fusion toolbox including different methods can be used. Typical data are tested by the toolbox and the method giving the best result is then used in the specific situation. One possible method is fuzzy measures: statistics and operator knowledge are combined forming possibility measures. These are then fused to give a decision regarding which operation to perform.

In the work with disassembly of electrical motors we have studied both commercial sensors, such as vision, accelerometers, current probes and speed counters, and sensors developed at the department, i.e. eddy current probes. One part of the work has been to make the different sensors co-operate, both with each other and with the rest of the system.

Safety is important when working with industrial automation. However, a problem with the safety systems of today is that they reduce the flexibility in the work cell. To avoid that we use new sensing methods, which can monitor the critical area and combine their output by sensor fusion. When an intruder is entering the working area, the speed of the equipment is reduced and when the intruder is close to the equipment it will stop.

To make general off-line programming of industrial robots possible there is a need of high absolute accuracy. Absolute accuracy here means that different robots reach the same position with sufficient precision when the same robot program controls them. The industrial robots of today have a good relative accuracy, in the sense that a specific robot always reaches the same position as before when controlled by the same program. However, the absolute accuracy is not so high due to insufficient robot mechanics. ABB Robotics has, in co-operation with the division of measurement technology, worked with a concept based on a calibration stick equipped within clinometers and a LVDT. The stick measures, from a carefully determined point in the floor and to different robot positions, the distance using a LVDT, and the angle of inclination using inclinometers.

Place, publisher, year, edition, pages
Linköping: Linköping University , 1999. , p. 89
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 601
National Category
Other Engineering and Technologies
Identifiers
URN: urn:nbn:se:liu:diva-181866Libris ID: 7624378ISBN: 9172195568 (print)OAI: oai:DiVA.org:liu-181866DiVA, id: diva2:1620806
Public defence
1999-10-15, Schrödinger (E324), Fysikhuset, Linköpings universitet, Linköping, 13:15
Opponent
Note

All or some of the partial works included in the dissertation are not registered in DIVA and therefore not linked in this post.

Available from: 2021-12-16 Created: 2021-12-16 Last updated: 2025-02-10Bibliographically approved
List of papers
1. Recycling of electrical motors by automatic disassembly
Open this publication in new window or tab >>Recycling of electrical motors by automatic disassembly
2000 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 11, no 4, p. 350-357Article in journal (Refereed) Published
Abstract [en]

This paper presents a robotized workstation for end-of-life treatment of electrical motors with an electrical effect of about 1 kW. These motors can. for example, be found in washing machines and in industry. There are two main steps in the work. The first step is an inspection whereby the functionality of the motor is checked and classification either for re-use or for disassembly is done. In the second step the motors classified for disassembly are disassembled in a robotized automatic station. In the initial step measurements art, performed during a start-up sequence of about 1 s. By measuring the rotation speed and the current and voltage of the three phases of the motor classification for either reuse or disassembly can be done. During the disassembly work, vision data are fused in order to classify the motors according to their type. The vision system also feeds the control system of the robot with various object co-ordinates, to facilitate correct operation of the robot. Finally, tests with a vision system and eddy-current equipment are performed to decide whether all copper has been removed from the stator.

Keywords
eddy currents, vision, eddy-current measurement, current probes, voltage divider, classification system, industrial recycling, robotics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-49769 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2021-12-16
2. A fusion toolbox for sensor data fusion in industrial recycling
Open this publication in new window or tab >>A fusion toolbox for sensor data fusion in industrial recycling
2002 (English)In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 51, no 1, p. 144-149Article in journal (Refereed) Published
Abstract [en]

Information from different sensors can be fused in various ways. It is often difficult to choose the most suitable method for solving a fusion problem. In a measurement situation, the measured signal is often corrupted by disturbances (noise, etc.). It is, therefore, meaningless to compare crisp values without the corresponding uncertainty intervals. This paper describes a toolbox including nine different fusing methods. All methods are applied on training data, and the most suitable method is then used for solving the real fusion problem. In the example, fusion is performed on data for classification in an industrial recycling operation. The data is from different vision systems and an eddy current system. The fusion methods included in the toolbox are fuzzy logic with triangular and Gaussian shaped membership functions, fuzzy measures with triangular and Gaussian shapes, Bayes' statistics, artificial neural networks, multivariate analysis (PCA), a knowledge-based system, and a neuro-fuzzy system.

Keywords
AC motors, DC motors, Fuzzy logic, Fuzzy neural networks, Neural networks, Robot vision systems
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47112 (URN)10.1109/19.989918 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2021-12-16
3. A dynamic safety system based on sensor fusion
Open this publication in new window or tab >>A dynamic safety system based on sensor fusion
2000 (English)In: Journal of Intelligent Manufacturing, ISSN 0956-5515, E-ISSN 1572-8145, Vol. 11, no 5, p. 475-483Article in journal (Refereed) Published
Abstract [en]

Machines in industry, including industrial robots, have in many cases dramatically reduced the man-made work and improved the work environment. New machines introduce, however, new risk factors. Traditionally machines are safeguarded by means that more or less rigidly separates the machines from the personnel. This works well in many traditional areas, i.e., where industrial robots are involved. There is however a risk that the safety system limits the valuable flexibility of the robot, which can be considered as a quality that tends to become even more valuable in the progress of programming possibilities and sensor technology. This article shows an example how a safety system can be designed to achieve increased flexibility in co-operation between human and production safety strategy. The proposed safety system is totally based on sensor information that monitors the working area, calculate the safety level and improve the system dynamically, e.g., reduce the robot capability in conjunction to the system safety level. The safety system gain information from the sensors and calculates a risk level which controls the robot speed, i.e., the speed is reduced to achieve a sufficiently low risk level. The sensor data is combined with fuzzy-based sensor fusion and fuzzy rules. The safety system is based on sensor information, hence it automatically adjusts to changes in the guarded area as long as the functionality of the sensors is maintained. Finally, we present a system implementation in an industrial robot application.

Keywords
safety system; sensors; sensor data fusion; fuzzy logic
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-53570 (URN)10.1023/A:1008922330419 (DOI)
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2021-12-16
4. A new calibration method for industrial robots
Open this publication in new window or tab >>A new calibration method for industrial robots
2001 (English)In: Robotica (Cambridge. Print), ISSN 0263-5747, E-ISSN 1469-8668, Vol. 19, p. 691-693Article in journal (Refereed) Published
Abstract [en]

This paper presents a new calibration method for industrial robots. The calibration method is based on a combination of inclinometer and LVDT measurements and is very simple to use. The inclinometers measure the deviation from the gravity direction of a measurement rod and the LVDT sensor measures the length of the rod. The inclinometers can be used without any pre-calibration and the whole equipment is inexpensive, portable and robust.

Keywords
robot calibration, kinematics, robot accuracy, off-line programming, position measurements, inclinometer, LVDT
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-49045 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2021-12-16

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