A Toolbox for Sensor Data Fusion in Industrial Automation

Abstract: 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.