Thermal and Geometric Error Compensation Approach for an Optical Linear Encoder.

Linear displacement measuring systems, like optical encoders, are widely used in various precise positioning applications to form a full closed-loop control system. Thus, the performance of the machine and the quality of its technological process are highly dependent on the accuracy of the linear encoder used. Thermoelastic deformation caused by a various thermal sources and the changing ambient temperature are important factors that introduce errors in an encoder reading. This work presents an experimental realization of the real-time geometric and thermal error compensation of the optical linear encoder. The implemented compensation model is based on the approximation of the tested encoder error by a simple parametric function and calculation of a linear nature error component according to an ambient temperature variation. The calculation of a two-dimensional compensation function and the real-time correction of the investigated linear encoder position readings are realized by using a field programmable gate array (FPGA) computing platform. The results of the performed experimental research verified that the final positioning error could be reduced up to 98%.

In-depth comparison of conventional glass cutting technologies with laser-based methods by volumetric scribing using Bessel beam and rear-side machining.

With the development of industrial lasers and novel glass processing techniques, which offer high speed, quality and precision, this becomes an attractive alternative to conventional methods, such as mechanical scribing and cleaving, diamond saw and waterjet cutting, commonly used in the industry. However, the emerging techniques lack thorough validation with respect to well-established methods. To this end, we present a detailed comparison of different glass cutting methods, taking into account surface quality, side-wall roughness, residual stresses and flexural strength. In addition, samples were examined after fracture, and the flexural strength was estimated according to the quarter elliptical corner flaws, which were the main reason of glass failure. Two laser glass processing techniques were investigated - the rear-side glass processing with tightly focused nanosecond laser pulses and sub-nanosecond laser volumetric scribing with asymmetrical Bessel beam. Results were compared to mechanical scribing and breaking, diamond saw and waterjet cutting.