A Study on Failure Analysis and High Performance of Hydraulic Servo Actuator

Abstract

Hydraulic servo actuator is used as the core actuator in tensile compression fatigue life test equipment as it operates the micro displacement very precisely at a high frequency and can be used continuously for a long period of time. Recently, the life expectancy of automobiles has been extended, the load conditions of accelerated life testing on auto parts have been increased, and the life test time and number of tests have increased significantly in order to secure the reliability of the guaranteed life of produced vehicles. Therefore, hydraulic servo actuators mounted on accelerated life testing equipment for automotive parts are essential for much higher performance and a longer life than those tested. However, small- and medium-sized companies that supply test equipment for the fatigue life of auto often fail to develop technology due to a lack of research personnel and the development budget compared to the capabilities of large automobile manufacturers, resulting in frequent breakdowns due to the technical overload of test equipment. In this study, servo actuators were used to test automotive parts, with a maximum output of 2 ton, a maximum frequency of 3.3 Hz and a maximum displacement of 50 mm. The hydraulic servo actuator, which was installed in the tensile compression fatigue life test equipment, failed to operate normally at the site, and by analyzing it, we realized this resulted from the heat generation of insulation compression due to the accumulation of air and gas into the hydraulic oil and the increase in friction due to the deterioration of flow. A static pressure bearing was adopted as a design change to improve the root cause for this failure mode, and a very high level of geometric concentricity was secured by inserting concentric tubes outside the labyrinth seal type piston. The newly designed and manufactured actuator is the result of research that has achieved a semi-permanent long life and improved performance up to 100 Hz by non-contact operation.

A Review of State of the Art for Accelerated Testing in Fluid Power Pitch Systems

“…For wind turbine pitch cylinders the study by Lee et al [24] is, however, of specific interest as the cylinder is here tested under micro displacement. This is expected to be somewhat similar to the micropitch motions that many pitch cylinders encounter when operating below rated wind speed of the turbines, and where the lubrication film between the seal and housing may be reduced and experience local heating.…”

“…The authors identified the operating stresses to be temperature, pressure and frequency, in which the pressure was set constant to analyze the properties of the other two stresses. Furthermore, another study performed by Lee et al [24] employed a hydraulic servoactuator as it operates micro displacement precisely at high frequency over an extended duration. The hydraulic servo-actuator was installed in a tensile compression fatigue life test.…”

Application of the MEMS Accelerometer as the Position Sensor in Linear Electrohydraulic Drive

“…Various types of distance-measuring sensors are used for positioning electrohydraulic servo drives. The structure of the electrohydraulic servo drive has been described, among others, in [ 1 , 2 ]. The most common are magnetostrictive transducers or linear variable differential transformer (LVDT) sensors.…”

Transformative Use of Additive Technology in Design and Manufacture of Hydraulic Actuator for Fly-by-Wire System

“…Hybrid servos can also be found in aviation onboard systems [11]. Hydraulic actuators ensure the transmission of very high power in relation to their weight [12], surpassing both electromechanical and pneumatic systems in this respect. The power of hydraulic systems is relatively easy to maintain and control, and properly designed and operated hydraulic systems are extremely reliable and safe [13].…”

“…The biggest disadvantages of hydraulic systems include the high costs related to the construction of their installation. They also require regular inspection and maintenance, and breakdowns related to the occurrence of leaks in the hydraulic system are particularly troublesome [12]. Designing actuators for control surfaces requires special consideration of the aspects related to their reliability, operational safety, and long-term operation in unfavorable environmental conditions (e.g., large-amplitude changes in ambient temperature, air pressure, and exposure to vibrations and shocks) [13][14][15].…”