Low-Level Control of Hybrid Hydromechanical Transmissions for Heavy Mobile Working Machines

Abstract

Fuel efficiency has become an increasingly important property of heavy mobile working machines. As a result, Hybrid Hydromechanical Transmissions (HMTs) are often considered for the propulsion of these vehicles. The introduction of hybrid HMTs does, however, come with a number of control-related challenges. To date, a great focus in the literature has been on high-level control aspects, concerning optimal utilization of the energy storage medium. In contrast, the main topic of this article is low-level control, with the focus on dynamic response and the ability to realize requested power flows accurately. A static decoupled Multiple-Input-Multiple-Output (MIMO) control strategy, based on a linear model of a general hybrid HMT, is proposed. The strategy is compared to a baseline approach in Hardware-In-the-Loop (HWIL) simulations of a reference wheel loader for two drive cycles. It was found that an important benefit of the decoupled control approach is that the static error caused by the system’s cross-couplings is minimized without introducing integrating elements. This feature, combined with the strategy’s general nature, motivates its use for multiple-mode transmissions in which the transmission configuration changes between the modes.

Adaptive Smoothing Power Following Control Strategy Based on an Optimal Efficiency Map for a Hybrid Electric Tracked Vehicle

“…Meanwhile, the controlled object model was The optimal efficiency map is the core of this module. The problem of searching the optimal efficiency map can be converted into a problem of searching the optimal curves under different input torques of the hydraulic pump by using Equation (30). The consumed torque of the hydraulic pump can be calculated by Equation (19).…”

“…Research on the hybrid loader control strategy has also paid attention to the discrimination of operating conditions and to making rules according to the characteristics of the load. The power consumed by a loader's hydraulic system and the impact on the powertrain's dynamic response have often been taken into account to design the strategy [30]. In most studies, the load of the operating system was incorporated into the energy management of the hybrid loader by measuring the outlet pressure of its hydraulic pump [31].…”