How New Products Can Ease Electro-Hydraulic Integration and Improve Flexibility

How New Products Can Ease Electro-Hydraulic Integration and Improve Flexibility

image   imageBy David Follebout, Application Engineer and Michael Lindemann, Software Engineer


The integration of electronics and hydraulic systems may have initially created visions of a mysterious “black box” for traditional users, but the numerous benefits of EH (electro-hydraulic) integration have erased the doubts of many skeptics. Improved reliability of hydraulic systems, along with more flexibility, efficiency, and diagnostic capabilities, has helped EH integration become a way of life, rather than a futuristic concept.

As electronics have become more advanced and miniaturized, machines have become increasingly controlled by some form of electronic controller. Acceptance of EH integration has grown to the point where it is now commonplace, rather than novelty.

Reliable Electronics

Part of the increased acceptance of EH systems has come from the reliability of onboard electronics. While early efforts at EH integration focused on external valve driver cards and external closed loop controllers, more advanced designs feature controllers built into the hydraulic component, as in Eaton’s AxisPro®  valve, shown in Figure 1.

Figure 1 Eaton's AxisPro Valve features on-board electronics
Figure 1: Eaton’s AxisPro Valve features on-board electronics.

With an on-board amplifier and axis controller, the proportional AxisPro valve provides more precise levels of control than older valves. Operations that used to be controlled by a programmable logic controller (PLC), such as closed loop control of an actuator, have been moved onto the valve itself. 

Instead of requiring a separate amplifier card linked to a solenoid to operate the valve, the more integrated approach on the AxisPro valve brings the  hydraulics, electronics, axis loop closure, and even the PLC together as a unit. With the embedded electronics and pre-programmed  control modes, much of the programming work which would have previously been done in the PLC is now incorporated into the valve and is user configurable.

Easier Programming

With both onboard electronics and PLC-driven devices, modern hydraulic components have maintained a high degree of configurability. Some devices are even designed to allow users to develop custom applications specific to their equipment and operations. The AxisPro valves, for example, can be ordered with white space programming capability to allow users to write their own logic code onto the valve.  The programming space available is based on the open architecture development environment CODESYS, which complies with the international industrial standard IEC-61131-3. This programming environment supports multiple languages, including: IL (Instruction list), ST (Structured text), LD (Ladder diagram), FBD (Function block diagram), SFC (Sequential function chart) and CFC (Continuous function chart). Any user with familiarity with one of these programming interfaces can add functionality to that already available with the device.

Custom applications can be developed to control the actuator being driven by the valve or to monitor system parameters such as temperature, pressure, and control deviation.  One valve with white space programming can also be used  to control other Axis Pro valves using the CANopen communication capability of the valves.

Eaton has developed software tools to support users with integrating their advanced hydraulic and electronic components into a system.  Eaton’s Pro-FX®  Configure software is used to set the desired operating parameters in advanced devices such as the AxisPro valves mentioned above.   Eaton’s Pro-FX® Control software expands on the CODESYS capabilities to enable distributors and end users to create custom applications for controlling hydraulic components such as pumps and valves, as well as peripheral devices such as joysticks and pedals. The software  includes libraries and tools that can be used by customers to build their own applications running on Eaton’s family of HFX programmable controllers and VFX programmable displays as well as the programmable white space of the AxisPro valves.

More Flexibility

The combination of advanced electronics and programmability provides more flexibility for end users. Once implemented, programmability allows users to change parameters on the fly.  For example, if a customer had a machine with an AxisPro valve doing velocity control on a particular axis and they decided that they would like to do pressure control as well, they could simply add a pressure transducer, connect it to the valve, and reconfigure the valve to perform a P/Q function which is velocity control with pressure control override.

Distributors working with customers also gain flexibility.  Distributors work with many customers on many different applications with various requirements of control.  These smart valves provide for user configuration of the command signal and spool feedback signal as well as the type of control to be used and the control parameters.  This allows them to stock just a few valve models that can be configured to be used in multiple types of systems which reduces inventory costs and provides faster solutions for their engineering and sales teams.

Upgrades are also easier with advanced electronics. With the onboard electronics on the AxisPro valve, an older system can be upgraded to a closed-loop system, without purchasing a new PLC. If a customer has an open-loop-control system on a particular axis and wants to upgrade to a closed-loop-control system, they can simply add the proper feedback sensor to their system, install an AxisPro valve, connect the feedback sensor to the valve, and configure the valve as required.  The valve will close the loop on the actuator in response to the command signal provided.

Better Diagnostics

Diagnostics and troubleshooting have also benefited from EH integration. With advancements in circuitry, sensors and other devices, software can help identify where failures occur and prevent future failures. A good diagnostic system can detect failures in electronic components, as well as failures in hydraulic components. Examples include broken or shorted wires, excess current, controller faults, and communication failures.

Custom applications can also be developed to aid in diagnostics and troubleshooting. For example, consider an AxisPro valve performing control on a particular machine axis where the load was the same on each machine cycle.  If the valve was equipped with the on-board pressure sensors and temperature sensor these parameters, along with valve spool opening, solenoid current, and other available parameters could be monitored with user-developed logic . This logic could be either incorporated into the user PLC or the available white space on the valve. A change in these monitored parameters could be used to predict things like cylinder seal leakage or wear in the machine guides or to provide indication of process changes that may affect the quality of the end product.

Eaton is continually developing new products and technologies to help aid EH integration into machines that currently have outdated EH systems or no EH systems at all as well as for new machines that may still be in the design phase.  No matter what category your system falls into, the trend for smarter and more flexible hydraulic components and systems will continue to be an important part of getting and keeping your competitive advantage.