Last month we presented five reasons hydraulic is more advantageous than electronic motion. The information was obtained from a white paper, Hydraulic Motion vs. Electric Motion: An Honest Comparison for the Record, which was co-authored by George Kokalis with Servo Kinetics, and Dr. J.F. Sarnicola, P.E., president of Sarnicola Simulation Systems, Inc.
Here is a synopsis of the final eight reasons the authors believe hydraulic motion is more advantageous than electronic motion.
1. Both hydraulic and electric systems are comparable in terms of performance, except for the areas of resolution and losing communications and/or interruptions with the control system and its effects on physical hardware. While electrical systems should conceptually have higher resolution capability they are actually comparable to hydraulic systems due to manufacturing, design and assembly tolerances. In terms of losing communications and/or interruptions with the control systems, electric systems with digital feedback systems often lose their orientation. Hydraulic systems, with analogue feedback systems, don’t lose their spatial orientation. This can be an important factor if frequent power outages are an issue, particularly in applications where very heavy payloads are elevated and power is lost or an E-stop condition is initiated.
2. During E-Stop conditions or power outages, hydraulic systems are inherently safe, as they can either lock-in-place or soft settle, depending on the design. Electrical systems typically lock in position when an E-Stop command is initiated. Slow settle can be achieved through more expensive and complex battery backup schemes. If potential failure cases are not addressed for electrical systems a failure may result in an immediate retraction collapse of the actuators due to the higher efficiency mechanical designs.
3. In hydraulic systems both the motion platform and payload are protected from damage because hydraulic actuators are designed to absorb the total system energy in run-away conditions. Electrical systems rely on a combination of switches and control logic to protect the system. While effective, programming and additional complexity results in a much higher installed cost and potential for system failure, including having the actuator slam into one of the hard stops initiating a lock-up of the actuator.
4. Electric motion platform systems can be noisy and the rushing sound made by the many small moving parts in the actuators can interfere with the programmed content on the moving deck, especially in flight simulation applications. Hydraulic systems are extremely quiet in the equipment space, and noise associated with the HPU is addressed by locating it remotely from the motion platform.
5. Hydraulic systems have installation advantages over electrical systems. First, hydraulic systems only require high voltage service be brought to the HPU location, unlike electrical systems which require that high voltage service be brought to the motion platform system actuators, which are within the personnel space. Second, the leaking and rupturing problems in the pressurized hoses that hydraulic systems use to run each actuator under servo-valve control have been eliminated with modern SAE O-ring, JIC and other fitting configurations.
6. Hydraulic units which can either use standard hydraulic oil, or food grade oils when necessary, are safe in the rare event that an oil leak should occur. Food grade oil has been used in food processing applications for about 100 years with no ill effects. Also, the fittings and connections for servo quality systems commonly use JIC and SAE connections which protect against leakage, unlike industrial and farming systems which use unreliable pipe fitting connections.
7. Hydraulic systems require less maintenance than electric systems. After every 1000 hours of operations, a hydraulic system requires a check on the HPU filter, lubrication per the manufacturer’s instructions, and general clean up and verification of performance responses. Every 80 hours of operation, electrical systems require lubrication, and an inspection of the power wiring and a multitude of limit switches and encoder/resolver operation as well as control logic verification. If any one part of the electric system goes down the system is halted, increasing down time and related expenses.
8. Hydraulic systems have passed the durability test. Most of the older hydraulic motion platform systems have been in operation, with original physical hardware, for over 60 years. Other than servo-valves, the only physical moving parts are the piston/rod combinations in each actuator. Developments in servo-valves over the years have made them very reliable and durable; with operational lives greater than 30 years in most instances. Electric motion systems have been in operation for only approximately 10-15 years. Current electric motion systems mostly use either lead, ball or roller screw mechanisms to affect the rotary to linear motion. If all of these mechanisms are not lubricated properly, the result is component wear and possible system failure.
Servo Kinetics is a full-service hydraulic repair, inspection and rebuild facility that delivers the highest quality standards at the lowest possible cost. We have been serving the needs of the industrial hydraulic aftermarket for over 45 years so our expertise and technical capabilities are second to none. If you need help with industrial hydraulic repair services including flight simulator repair and Beach Russ vacuum pump repair, or are looking for reverse engineering services, or new pumps and motors, we can help. Call us to learn more about our services, we have a lot to share!
All technical and scientific conclusions are included in the white paper which can be found in its entirety at www.servokinetics.com, under the About Us section.