The Nightmare of Hydraulic Maintenance
Many companies today are working diligently to create new technologies aimed at replacing outdated, costly, inefficient hydraulic systems in heavy machinery. RISE™Robotics is one of those companies. With the successful market debut of their first commercial product, the fluid-free RISE™Cylinder packaged within Anthony Liftgate's Re-Gen Railtrac, RISE™ is quickly setting themselves apart and proving that they are the TRUE hydraulic cylinder alternative, "ticking all of the boxes" of a hydraulic application.
Modern hydraulic systems are not only incredibly power-dense but also very robust, safe, and generally well suited for their applications. While a handful of existing non-hydraulic technologies might appear to meet the requirements, they have all been shown to come with inadequacies, limitations, and concerns.
Traditional integrators use hydraulic cylinders and other modern, effective alternatives, such as the compliant rack and pinion, ball screw, and roller screw. RISE™Robotics' revolutionary fluid-free belt technology provides a substantial competitive advantage over these technologies. It demonstrates superior performance, reliability, durability, cost-effectiveness, safety, and predictability while being environmentally friendly. A look at the competitive technology landscape emphasizes all of this.
The core of the comparison between these different technologies lies in linear actuation efficiency, which impacts everything from material use to operating cost of running and owning a machine and the capital cost of the machine itself.
M. Vukovic, R. Leifeld and H. Murrenhoff, “Reducing fuel consumption in hydraulic excavators,” Energies, 10, 687, 2017.
Current centralized hydraulic systems may run with between 10 to 40% efficiency, with more sophisticated electro-hydraulic actuators running in the 50 to 60% range. Both have to contend with motor losses across the spectrum, pump losses, small valve and hose losses, as well as losses associated with ports due to temperature and oil viscosity.
With only motor and gearbox losses to contend with, the RISE™Cylinder can deliver a full system efficiency between 70 and 85%.
Volumetric power density is another point of comparison. While hydraulics' volumetric power density is second to none, RISE™Technology is far superior in mass power density.
Close up of a Roller-Screw Nut
A roller screw, in particular, employs a set of rolling threaded contact mechanics within a nut and screw arrangement; these devices can achieve a high load density due to the large number of contact patches on a roller screw. The belts on which RISE™Technology is based can exert pressures of over 1,000 PSI between the belt and the pulley, also allowing for a high load density.
Despite the comparable levels of volumetric power density, roller screws fall short here in that the nut arrangement and supporting bearings used to create the blocks on either side of the rotating screw element are typically very long, resulting in a significant length addition factor. In the case of hydraulic cylinders, the cylinder itself is only marginally longer than the stroke. And while it is not as compact as a hydraulic cylinder, the RISE™Cylinder comes very close.
In addition to the screw technology's naturally longer length, the motor and gearbox must also be considered, which makes packaging more difficult. One advantage of hydraulic systems is that the motor and pump can be located remotely, allowing lines to be routed to the action. Of course, the disadvantages of this lie in the maintenance and pressure losses through hoses.
Like a hydraulic power unit, the RISE™Robotics' system can route the belt from the linear unit across short lengths to a more convenient location for the belt power unit, substantially simplifying packing issues.
Also, due to their design, hydraulic cylinders and the RISE™Cylinder are not only compact but easily scalable and capable of achieving nearly any stroke imaginable. In contrast, both ball screw and roller screw systems must contend with critical speed restrictions. This critical speed depends on the size of the screw, its length, and the relative rigidity of the blocks that mount it to a fixed point. Typically, a screw can not be run faster than around 70% of that critical speed. As a result, the screw's net stroke is typically limited to one or two meters in length for high speed applications.
Shock tolerance and side-impact tolerance are two other areas to consider in this competitive technology landscape. One high-shock event is all it takes to ruin a system, and it is nearly impossible to avoid with cylinders in a wide range of mobile hydraulic applications.
Hydraulics are notoriously good at dealing with shocks as no metal surfaces under Hertzian contact are being loaded due to direct axial shock. RISE™Robotics' RISE™Cylinder is also able to add shock tolerance and side-impact tolerance to its list of competitive advantages.
RISE™Cylinder utilizes belts that are somewhat elastic, allowing them a small amount of give and take. Under full load, the belts typically stretch around 0.5%, similar to how fluids behave when loaded and unloaded. RISE™Cylinder's linear drive has similar levels of inherent shock tolerance. When combined with methods of shock prevention and shock assistance applied directly to individual sections of belt, a quite resilient system emerges.
Hertzian Contact Visualization
Screw systems, on the other hand, use direct Hertzian metal-on-metal mechanics that, when overloaded with an impact load during axial compression, may damage the bearings and, once brinelled, are no longer serviceable.
Last but not least, RISE™Technology and its hydraulic alternatives shine regarding environmental impact. By entirely doing away with hydraulic oil and relying on solid-state components, RISE™Cylinder eliminates environmentally destructive and wasteful mishaps.
Example of a Ball-Screw
Furthermore, by using the least amount of materials during production, RISE™Cylinder is the lightest linear actuation solution on the market today, and thanks to the fact that its revolutionary technology wastes the least amount of energy, it is also the most efficient machine on the market - both of these distinctions resulting in significant financial and environmental savings.
With this impressive list of product features in its technology, RISE™Robotics is electrifying the competitive landscape and redefining what linear actuators can do for heavy machinery. RISE™Technology is being proven capable of meeting or exceeding traditional hydraulic standards, and has garnered the attention of investors, engineering teams, and potential partners with its revolutionary fluid-free belt system, which can outperform, outlast, and outshine the competition.
