Automation of mobile construction and agricultural equipment has gained wide acceptance based on increases in productivity, safety, and precision; while also helping upskill operators. On construction equipment, after-market automation of earthmoving crawler dozers and graders has driven a conversion of machines to electro-hydraulic (EH) implement control and integration into digital worksites. Unlike the aforementioned machines, conversion of the excavator into a semi or fully autonomous machine presents significant challenges due to kinematics, variable loads, non-linear multi-function of implements, safety, and robustness. The present work demonstrates the retrofit of a pilot-operated 21-ton excavator and development of automated controls to address these challenges. The operator pilot joysticks and existing hydraulic system were retained, while adding capability for autonomous functionality with integrated hardware, controls, and kinematic solvers within a production viable environment. Autonomous features for path planning, multi-function actuator velocity control, EH controls, and safety were developed to prove the value of precise and low latency control hardware for EH excavator operation.

This paper discusses the potential of centralized or decentralized electro-hydraulic (EH)-drives in comparison to conventional hydraulic systems. The systems are presented in diagrams covering the major electric and hydraulic components for an exemplary application, but also include specific technical data like the sizing of the components according to power, pressure, rotational speeds etc. In a second step, all systems are compared and evaluated based on criteria like design effort, energy saving potential, controllability, and servicing and maintenance of the machine. The resulting effects on fuel consumption are summarized as well. Finally, an evaluation of the potential of EH-drives in construction machinery and a derivation of the demands for future customization of electro-hydraulic linear drives is given on the basis of a SWOT-analysis from the point of view of a construction machinery OEM.

The hydraulic system in a fighter aircraft is not fully utilised during large parts of the flight mission were more electrical power is needed. To better utilise the hydraulic power the current Auxiliary Hydraulic Pump (AHP) and the Emergency Hydraulic Pump (EHP) can be exchanged to an Electro Hydraulic Energy Converter (EHEC). The EHEC has the possibility to provide hydraulic power to the system, but also convert hydraulic power into electric power. The control for such a unit can be implemented in different ways. A literature study was performed to decide a suitable architecture for use in a fighter aircraft application. A simulation model representing the resulting architecture was created. The simulation model was successful in describing the basic behaviour of the hydraulic system, but lacks a realistic representation of hydraulic consumers.  Different control strategies were created and tested on the simulation model with several test scenarios based on real flight data from tests performed on the aircraft. The control strategies were compared and suitable candidates were presented based on their relative performance and compared with the current hydraulic system behaviour. An architecture consisting of a variable displacement pump with over-center capabilities combined with a permanent magnet synchronous machine (PMSM) was decided to be used. A PI-controller with a feedforward on consumer flow was the best performing controller for use in emergency operation of the EHEC. For the case when regenerating electrical power a PI-controller with load pressure feedback is desired initially during start up. When reaching steady state a PI-controller without load pressure feedback is then advantageous.