The largest sector of fluid power technology is in mobile equipment used in agriculture, construction, mining, rail maintenance, firefighting and waste management. The principles of hydraulics have been driving heavy equipment for 140 years. The very first excavator to use hydraulic technology was built in 1882 by Sir W. G. Armstrong & Company in England, where it was used in construction of the Hull docks. Unlike today's excavators that use hydraulic fluid, Armstrong’s system used water to essentially follow the principles of current hydraulic systems.
Fast forward to today, many hydraulic systems incorporate electronic controls and sensors that automate equipment, increasing machine productivity and efficiency. Integrating electronics and software into hydraulics systems is advancing the efficiencies of almost every component in heavy equipment and industrial machines with the advent of IIoT (the Industrial Internet of Things).
According to Terry Hershberger, Director, Sales Product Management & Systems at Bosch Rexroth, “The core vision of IoT for mobile machines is about implementing digital technology to capture actionable data about the performance of mobile machine systems autonomously, do it in real time and deliver it to machine end-users and OEM suppliers so they can maximize the uptime and flexibility of their machines,”
However, with all the updates in electronic and sensor technology, the base hydraulics cannot be ignored. When designing, installing or updating electronics, the hydraulic or mechanical system may require updating too. Simply designing or updating electronics in the system will not always address hydraulic or mechanical problems.
Thinking through the integration of electronic and hydraulic components early in the design process fosters system efficiency and reliability downstream. If designing in electronics for a new system, the usual hydraulics, such as certain pumps, cylinders, motors or even hose and fittings may not meet the same specifications as a similar system without electronic controls. Design engineers must be cognizant of the additional power the electronics will bring to the system and select mechanical components accordingly. When updating a system with electronic controls, mechanical and maintenance engineers must keep in mind the potential limitations of the existing hydraulics.
Consider These Scenarios
· Increase the number of coolers:
If a hydraulic system is overheating, the electronics won’t reduce the heat-- but they will signal the problem and likely the origin. This may indicate the necessity to add additional coolers. If a system already has one tank for the closed loop section and another for the auxiliary, and there is still overheating, a third tank may be worth considering. If the system overheats, seals will start to break down and the oil will degrade, leading to contamination. The coolers in a hydraulic system not only keep it from overheating but helps preserve cleanliness by maintaining system temperatures.
- Motors in creep mode provide low-speed high-torque: When there is low-speed operation or mechanical transmission, failure creep mode can be used to drive the vehicle. In this case, a temperature compensation control strategy of the creep mode should be considered to ensure there is not an increased flow loss due to temperature variation while in creep. This is because a common hydraulic system problem.
However, some low-speed high-torque motors may not provide the necessary efficiencies. Torque ripple and speed fluctuations can occur if operating below the manufacturer’s specified speed, which can be dangerous to the operator, people in the vicinity and to the system. These cannot be programed out with software, but rather proper selection of the components.
- Double or triple gear pumps: Gear pumps are typically used to pump high viscosity fluids such as oil, resins, paints or foodstuffs (honey, cooking oil, etc.) Some hydraulic systems require multiple pumps that operate independently of one another, but in the pump´s center section they share a common suction port. In addition, a hydraulic integrated circuit manifold can be used, allowing operators to regulate the flow of fluid between pumps, actuators and other components of the system. And Overheating may be reduced while improving overall performance and efficiency through use of a single pump in conjunction with a flow-sharing circuit and priority on demand in a custom hydraulic integrated circuit.
- Contamination: Hydraulic systems must be designed to allow maintenance personnel easy access to filters so they can be quickly changed. Though an electronic control system can notify maintenance that a filter is clogged and in need of replacement, it cannot clean the filter.
- Single-acting cylinders: Often used because they are less expensive than a double-acting cylinder, yet electronic programming cannot fully control gravity down, load holding, load drop and ensure system safety.
Pascal’s Law taught us the basic principle of a hydraulic system: that pressure applied anywhere to a body of fluid causes a force to be transmitted equally in all directions. By following that law, we have employed modern hydraulic systems that are comprised of pumps, cylinders, hoses, fittings and other components. However, today’s technological advancements with actuators, solenoid valves and the integration of the entire system with electronic controls is the biggest leap since the discovery of hydraulic principles. Hydraulic components have been adapted with electronics for intelligent motion and sensors for gathering operating data values. This data is key for condition monitoring, predictive maintenance, and machine-to-machine communication.
Current electronic technology and the mechanical components of hydraulics cannot live independently. Each relies on the other to increase efficiency and reduce consumption of power and fuel, ultimately leading to a decrease in costs and increase in ROI.