Development of Control Logic for Common Pressure Rail Architecture in Hybrid Excavators

The use of mobile machinery is widespread across all industrial sectors; however, their low energy efficiency, primarily due to hydraulic architecture, presents a significant problem. The hydraulic excavators available on the market predominantly adopt the Load Sensing architecture, which offers good operational capabilities but exhibits very low energy efficiency, with the net work of the actuators amounting to only 4% of the chemical energy of the fuel. The causes of these energy losses lie in various components of the circuit, such as the internal combustion engine, the hydraulic pump, and the actuators, but the main contribution is attributable to the hydraulic distributor. The objective of this thesis was the creation of a model of a hydraulic excavator based on the Common Pressure Rail architecture, an architecture studied over the past decades that has proven to be highly advantageous in terms of fuel consumption. Specifically, the focus of the thesis was the development of the control system for the Common Pressure Rail architecture, capable of managing the access of the actuator chambers to the different pressure lines and determining the modulation of the proportional valve located upstream of each actuator based on external system conditions. This ensures the execution of the digging cycle and the generation of movement of the linear actuators and the hydraulic motor based on the inputs provided by the operator via joystick. The optimization of this controller and the proper design of the hydraulic components for a 9-ton excavator resulted in a 50% reduction in fuel consumption compared to the Load Sensing architecture. Furthermore, the performance of the controller achieved a maximum error of 5% in the displacements of the actuators relative to the joystick inputs. In conclusion, the Common Pressure Rail architecture has proven to be valid and effective, offering lower energy consumption and reduced economic costs compared to other solutions. With some architectural modifications, it can achieve performances similar to the traditional counterpart, offering a significant advantage and proving to be competitive.