In mechanical engineering, not every task can be solved with the same technology, explained Steffen Haack, Senior Vice President of Industrial Applications Bosch Rexroth AG at this week’s Hannover Fair. Hydraulics have a clear advantage when it comes to power density and robustness. They withstand impact and vibration and also fit into tight installation spaces due to their compact design. Electromechanical systems are traditionally closely connected to control development and have sophisticated functions for high flexibility. The electronification of hydraulics preserves the physical advantages of fluid technology and increases their attractiveness with the possibilities of software-based automation.
That’s reason enough for young engineers, who often come from the software side of things, to get to know the special capabilities of hydraulics, Haack said. This doesn’t mean configuring valve systems or plunging yourself into the basics of fluid mechanics but rather recognizing where hydraulics offer economic and technical benefits. The automated implementation of movements is then done using software, as with electric drives.
New systems teaming electronics and hydraulics use the same control assemblies and logic as electric drives. Using open standards such as multi-Ethernet interfaces, they can be added to horizontally and vertically network machine architectures—in terms of automation there is no difference. Electro-hydraulic axes are configured with the same engineering tools as electric drives—with two distinctions: First, a wizard logically guides the technician through the commissioning of hydraulic axes and suggests parameterization values that lead to a suitable result. Second, best-in-class controllers intelligently compensate for the special features of fluid technology in the background. Technicians don’t need any specific knowledge of hydraulics for this.
“There’s no need to be scared of the characteristics of hydraulics, but rather their suitability should be evaluated and automation implemented in the usual way. With digital intelligence, networkable hydraulics can now be seamlessly integrated into multi-technology and Industry 4.0 concepts, meaning they are and will remain an important component of modern mechanical engineering. In recent years, almost all motion patterns and special features of fluid technology have been modeled in modular software. Even specific characteristics such as transmission kinematics or controlled synchronism are taken into account here. Engineers don’t have to be ‘baptized by oil’ to know that electronified hydraulics offer unique power density and robustness—and otherwise the design, parameterization, commissioning, operation and diagnostics using software are just as convenient as for other drive technologies,” Haack concluded.
Bosch Rexroth engineers are taking these concepts to heart. Due to cost pressures and the shortest possible development periods, machine builders are looking for ways to freely combine electromechanical and electrohydraulic motion axes and scale them to application requirements without the need for major software revisions. Rexroth offers electrohydraulic controls with the same open programming standards and engineering tools used for electromechanical axes.
Multi-Ethernet interfaces and standards, such as OPC-UA, guarantee the seamless networking of the electrified hydraulics. Thus, they can be integrated independently of the control unit into different automation architectures in IIoT/Industry 4.0 environments.
The single- and multi-axis controls for hydraulic actuators can close the control loop in a decentralized manner and unburden the higher-level control system, according to the company. Rexroth reportedly is the only manufacturer using identical control hardware platforms as well as integrated software standards based on IEC 611331-3 and identical engineering tools for all intelligent drives. This provides machine manufacturers with wide design freedom, with minimum cross-technology software programming, and the option to provide varying numbers of drives in their concepts to meet customer-specific requirements. Programs which have been written once can be simply transferred to all motion controls.
Rexroth software automatically considers the non-linearity of fluid technology and compensates it. With respect to higher-level control systems, hydraulic drives thus show the same behavior as electro-mechanical drives. For this purpose, Rexroth has transferred previously purely hydromechanical functions into the software. Such controllers can regulate position, speed, path/force, synchronize several cylinders or provide path-dependent braking. Wizard-supported commissioning does not require any deep knowledge in hydraulics.
For the design and configuration of electrohydraulic axes, Rexroth provides virtual images of the motion controls and their hydraulic actuators. With them, machine and system manufacturers can validate their concepts on the computer and avoid under- or over-dimensioning without having to build a prototype first. In addition, the control simulation enables the programming and validation of movements before or during the machine assembly. This significantly reduces time to market and the engineering costs.
According to Rexroth, “intelligent,” connectible hydraulics offer all physical advantages of fluid technology, with the same automation freedom and comfort offered by their electromechanical counterparts.