<p dir="ltr" style="line-height: 1.2; text-align: justify; margin-top: 0pt; margin-bottom: 8pt">With increasing concerns about depleting fossil fuels and many countries bringing in policies to encourage use of cleaner energy sources, there has been a significant push for electrification in the field of Off-Highway mobile machines, especially vehicles in the construction and agriculture segments. Novel architectures such as the Hybrid Hydraulic-Electric&nbsp;Architecture (HHEA) have been proposed as an energy efficient alternative to conventional load-sensing architectures that are on board mobile machines such as Excavators and Wheel-loaders. HHEA leverages the advantages of hydraulic power and electric power to eliminate throttling valves while also improving the energy and control performance of the system. The highly inefficient throttling valves in present-day architectures are replaced by a set of common pressure rails and selector valves that control the input to the Hydraulic Electric Control Modules (HECMs) which further modulate the hydraulic power. Previous work has developed a computationally efficient Lagrange Multiplier approach for determining the optimal pressure rail selections that minimizes the energy losses in the system. The static model used considers only the energy use for each pressure rail selection but not the losses associated with&nbsp; the valves during the transition. This paper presents an approach to including the switching losses in the model and in the optimization procedure. To capture the switching losses, switching events between different rails and at various input and output flow rates were simulated with consideration of valve spool dynamics. A parameterized model that summarizes the losses is then obtained, allowing switching losses to be added to the previous energy. The performance of the switching loss model was compared with reference data obtained from a high-fidelity simulation model. To incorporate the switching losses into optimal control algorithm, an efficient dynamic programming approach that prevents frequent switching is adopted in place of the Lagrange multiplier approach. The overall effect of switching losses on the energy consumption and optimal control decisions will be presented. In general, switching losses contribute to about 5-7% in energy losses.&nbsp;</p>

Incorporating Valve Switching Losses Into a Static Optimal Control Algorithm for the Hybrid Hydraulic-Electric Architecture (HHEA)

Paper Proceedings: https://asmedigitalcollection.asme.org/FPST/FPMC2021/volume/85239

2021 ASME/BATH Symposium on Fluid Power and Motion Control (FPMC2021)

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