Magnetic springs: fast energy storage for reciprocating industrial drivetrains

Abstract

Industrial machines with reciprocating (oscillating) motion such as weaving looms tackle primarily high inertial loads, conventionally operating within frequency ranges of 5-15 Hz with relatively large strokes. Recent trends of individual electrification of parts of weaving loom drivetrains for reasons of increased flexibility of use make this problem even worse, as the inertial loads are less averaged out. Adding springs to such oscillating drivetrains can allow to improve the energy efficiency and downsize the actuators. To get an estimation of energy sinks and peak power consumption in a reciprocating drivetrain of a weaving loom, a spring assisted demonstrator available at Flanders Make has been modelled using a 1D multiphysical dynamic model. Next to energy requirements, industrial machines have strict lifetime demands. Target lifetime of 50 000 hours results in over 1E9 spring cycles. Mechanical spring design and fatigue modelling for this number of cycles is a difficult design problem with high levels of uncertainty. Therefore, magnetic springs are proposed instead of mechanical springs as a technological novelty with benefits of no material fatigue and additional flexibility in design. In the developed drivetrain model the mechanical spring is replaced by an off-the-shelf magnetic spring in order to perform a first estimation of the impact on the dynamic behavior. Concept: Spring assisted drivetrain Bio-inspired concept developed in robotics for quasi-static loads[1] Electrical drive downsizing-cost efficient Averaged power reduces losses in electrical drive Challenge: Robustness weaving machine drivetrain Control(trajectory) robustness –Dominant, dynamically sensitive, inertial load(high speeds 5-15Hz) Mechanical robustness –Mechanical complexity is an issue –Spring is the critical component Conclusions and further steps Although experimental validation is still needed, initial models show that the magnetic spring technology provides a promising alternative solution to mechanical springs in spring assisted drivetrains for this specific operational range. In order to estimate the industrial applicability of magnetic spring technology to a wider range of specifications, accurate scaling laws for magnetic and mechanical springs yet need to be developed and compared. Improved losses analysis based on measurement and models is required for a more refined final comparison of the two technologies described on this poster.