Online efficiency maximization of drivetrains using a calorimeter in the loop

Energy efficiency is a critical aspect in the design and operation of motion systems. In mobile applications, a minor reduction in the drivetrain losses can have a worthwhile impact on battery life and vehicle range. Loss reduction is important for stationary machines as well, as manufacturing processes have a considerable share in the industry’s energy consumption. Classically, the losses of a motion system or sub-component are minimized offline during design by using models, e.g. using Finite Element Analysis for electrical machines, electro-thermal models of battery systems, equivalent circuits for power electronics, motion simulation for mechanics, etc. Accurately modelling losses is challenging, especially if they depend on thermal aspects. Hence, the resulting optimal design is limited by the accuracy of the used models. Although certain design choices cannot be changed after prototype construction, several settings can still be optimized during testing, e.g. the drive’s switching frequency, cooling pump settings, DC voltage, motion profile, control settings, etc. These could be optimized iteratively to ensure true minimum losses, but that requires an accurate loss measurement in the optimization loop. Two common techniques are available for accurate loss measurement, i.e. input-output or calorimetry. Compared to input-output, a calorimetric measurement has a greater accuracy, but is slow as it takes time to reach thermal equilibrium.