Environmental and economic factors have driven the advancements in fluid power technologies over the last two decades. Gradual development has been made over time on the state-of-the-art fluid power technology; however, there has been no major advancement leading to radical improvement on systems’ efficiencies. Displacement-controlled (DC) actuation has been under investigation by the authors’ group since its conception in 1998 as a highly efficient alternative to its valve controlled counterpart, demonstrating fuel economy improvements of up to 40% and the possibility for engine downsizing of up to 50% for an excavator truck-loading cycle. Through the installation of a variable displacement hydraulic pump/motor per actuator, DC actuation entirely eliminates the losses due to resistive control and allows for the recuperation of energy from overriding loads. The one-pump-per-actuator requirement however represents the technology’s largest obstacle due to the increased machine production costs. For this reason the authors’ group proposed the idea of pump switching wherein a reduced number of hydraulic units is connected to the actuators in a multi-actuator machine through a distributing manifold. The idea relies on proper design of the distributing manifold and enabling controls to realize machine operability. Work by the authors’ group has demonstrated that the pump-switching idea is feasible on the actuator level, achieving seaming-less switching transitions while retaining the basic fuel savings demonstrated for DC actuation. This paper presents the first formal attempt to create a supervisory controller for a DC multi-actuator machine with pump switching. The controller is based on priority levels geared towards the maximization of the number of available actuator combinations. Implementation on a DC hydraulic hybrid excavator prototype show the feasibility of the control approach as well as the limitations and further improvements.

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