Measuring the Deformation of a Parallel Kinematics Machine under Dynamic Conditions, by Combining Video and Accelerometers

Parallel structure machines are a means to reach higher acceleration capacities, and thus significant reductions in machining time. But this contribution implies having light structures, leading to significant deformations in dynamic conditions. Based on a prototype built at IFMA and its numerical model, this article shows first the influence of elastic deformations on actuator efforts. In order to validate the numerical model or any other model which takes flexibilities into account, we propose the concept of a dynamic metrology tool, capable of measuring the deformations of the machine's different components during machining movements. This is a hybrid tool built around a camera and an accelerometer. Experimental progress is then described, particularly the work leading to the improvement of camera detection accuracy. The precision obtained to date is 0.02 mm with one target in a field of 300 mm. It can theoretically reach 0.01 mm with three targets instead of one