Improvement of velocity measurement
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Improvement of velocity measurement
IHC Hydrohammer® has been widely used in on- and offshore pilling projects. To precisely control the energy delivering level during the pilling process, it is essential to calculate correctly the kinetic energy before impact, which means measuring accurately the instantaneous velocity of the ram weigh inside of the hydrohammer housing when it is about to impact the pipe. This is realized by two inductive sensors mounted in the hydrohammer housing. These two sensors are mounted in sequence on the moving direction of the ram weight. Hence, the instantaneous velocity could be calculated as dividing the distance between two sensors, by the activation time differences of them.
However, due to the construction limitation of inductive sensors, the cone of the sensing range always has a deviation which in ideal situation is supposed to be a central symmetric paraboloid shape. With this deviation, the distance and activation time difference used for the velocity calculation does not correspond to each other, which leads to an inaccurate result.
This project, assigned by IHC IQIP B.V., aimed at improving the accuracy of ram weight velocity measurement using inductive sensors. It focuses mainly on designing a mechatronic calibration tool for the inductive sensors. This calibration tool has to be able decrease the deviation of the distance between the two sensors until it is lower than 0,26 [mm].
Delft Design Method was used as the guidance for conducting the entire project. It consists of four phase. The actions that have been taken and the outputs of each phase are:
- Analysis phase: by analyzing the problem with interviews, experiments, process tree, and system decomposition, a list of design specifications for the final calibration tool and a list of evaluation criteria for choosing integral ideas in the next phase were made.
- Idea phase: with the help of a brainstorm meeting, a morphological chart, and the evaluation criteria, ideas of designing the calibration tool were sketched and categorized. Four integral ideas were created, and two best ones were selected to be further defined in the next phase.
- Concept phase: The two integral ideas were further defined into concepts and were proved feasible. Based on the evaluation criteria, the best one was chosen to be materialized.
- Materialization phase: The chosen concept was developed in detail, which can be categorized as purchase part ordering, machined part modeling, electrical schematic designing and programming. In the end of this phase, the calibration tool was successfully designed, and a prototype was built. This calibration tool calibrates the sensor by finding the symmetry axis of the sensing range which always exists no matter if the sensing range is central symmetric or not. After calibration, when two sensors are both mounted with the symmetry axis perpendicular to the moving direction of the metal object, the distance between two sensors and the activation time difference of them will correspond. Hence, the velocity measurement error could be diminished.