‘Electronification’ of Working Hydraulics in Compact Machines
Sampierana employs Rexroth eOC for mini excavators and compact wheel loaders to reduce fuel consumption and improve functionality.
Compact off-highway machines should be as maneuverable, versatile and energy-efficient as possible. Key to achieving these goals is the electronification of the working hydraulics. New mini excavators, wheel loaders and track loaders from the Eurocomach brand, which is part of the Italian Sampierana Group, demonstrates the improvements that can be gained by utilizing electrohydraulic pump control and software.
Sampierana first launched the electronification of its working hydraulics on its six-ton mini excavators. “Our compact construction machines are used for a wide variety of jobs,” said Giuseppe Fabbri, technical manager at Sampierana. “Loading, excavating or digging should be very accurate or quick and productive to perform, as needed, and also support a wide range of tools – from shovels to hammers or mowers.”
Conventional work hydraulics have limited what could be done because their rigidity forces manufacturers to compromise. Because it used to be necessary to specify in advance whether the hydraulic pump was to be controlled by pressure, torque or swivel angle, it was not possible to optimize energy efficiency, flexibility and productivity in equal measure. Once parameters have been defined on the hardware side, they remain unchanged over the entire service life.
Electronic control in an open loop
The eOC (electronic open circuit) architecture from Bosch Rexroth features an electrohydraulic axial piston pump as its central component, operating in an open circuit with a swivel angle sensor and pressure sensors. The eOC pump is electronically controlled in a closed loop so that the required setpoints for torque, pressure or volume flow can be controlled independently of each other precisely and dynamically in the range of milliseconds.
Using the associated BODAS eOC software, parameters such as dynamics and power control can be individually set, changed and combined during operation. The control software communicates via the CAN bus and can be installed either on a BODAS eOC controller from Bosch Rexroth or on a controller from a third-party manufacturer.
For machine optimization, the eOC pumps offer Sampierana a wide range of hydromechanical control functions and mechanical interfaces. They are all transferred directly to the control software, which provides Eurocomach engineers with the following control modes: Pressure or delta pressure control, flow rate and swivel angle control, and torque control. All three control modes each have a predefined set of parameters for optimal behavior of the eOC pump in the hydraulic system, such as load sensing.
Since the BODAS eOC software continuously adapts the hydraulic power to the available engine torque and also compensates for disturbances in the load cycles of the machine, highly dynamic and precise work functions become possible. The overall productivity of the working machine increases while the energy consumption of the entire hydraulic system decreases in favor of fuel consumption and battery usage.
Flow sharing: compact and scalable
In its first project, Sampierana used the eOC architecture to develop the 60ZT and 65TR mini excavators. While the 60ZT has a zero-radius profile with a monolithic boom, the 65TR is equipped with a triple boom, which is particularly suitable for digging, handling and loading operations thanks to its small radius. Both models have benefited from the eOC architecture. While the low-noise axial piston variable displacement pump type A10VO realizes precise performance control, the compact RS12/EH control block ensures flow sharing (LUDV) and, with low pressure losses, in turn contributes to equally high-performance and energy-efficient working hydraulics.
Together with the open and scalable BODAS eOC pump control RC5-6/40 and the BODAS eOC software, the productivity of the machine can be specifically optimized, with the operator interacting directly with the machine’s electronics via joystick and onboard display. Situation-dependent modification of functional parameters such as delta-P, pressure gradient or volume flow allow the mini excavators to work slowly and precisely on the construction site or move larger volumes at a rapid pace.
“Since all control functions are transferred from the hydromechanical controller to the software, the entire range of functions and variability of the pumps is available to our customers,” said Simon Dreher, sales and industry management for mining excavators and construction machinery. In addition, the scalable solution allows manufacturers a step-by-step implementation, according to the Rexroth expert. For example, manufacturers can start with the electrohydraulic eOC pump and then expand the solution to the electrohydraulic main control block or the entire hydraulic system. Depending on requirements, the implementation can be realized with hard-coded individual parameters as well as with a whole range of adjustable digital CAN bus parameters.
More functionality, less fuel
With the help of the eOC BODAS pump control, Sampierana has managed to increase the range of working modes and tools while increasing machine performance. “The working hydraulics can be precisely controlled with short response times,” Fabbri said. “At the same time, we can configure the system parameters very easily. We secure these advantages in the long term because the eOC BODAS system is designed to be open and scalable.”
Sampierana also can point to improvements in terms of sustainability. Less control oil is required because several hydromechanical controller axes for pressure, flow rate and torque have been combined into one. In addition, the dynamic adjustment of the control parameters minimizes the energy consumption of the entire hydraulic system.
“On this basis, we can comply more easily with current regulations regarding ecomobility, emissions and efficiency and support our customers even better in meeting their climate protection targets,” Fabbri said. “This is an important competitive factor.”
As a result of the reduced pump variance, Sampierana also reduces the administrative effort from development to assembly and logistics to service, including spare parts management and aftermarket. Feature updates and troubleshooting are carried out via the BODAS Service Tool, which among other functions includes a detailed guide to pump commissioning.
The electronification of working hydraulics at Eurocomach demonstrates how compact work machines can benefit when complexity is shifted from hardware to software. Following the successful deployment in its mini excavators, Sampierana decided to extend the Bosch Rexroth eOC system to other Eurocomach models.
“Thanks to eOC BODAS, we can now map a wide range of functions with a consistent hydraulic system and adapt it precisely to the type of work to be performed and the operator’s preferences,” Fabbri said. “While we delight our customers on the jobsite, we benefit internally from leaner processes and high degrees of freedom for the coming generations of vehicles.”
This article is based on a Bosch Rexroth submission to SAE Media.