CERES Gimbal Performance on Terra

The Terra satellite has been operating in orbit for 20 years. The Terra satellite is also called the flagship earth-observing satellite. The two Clouds and the Earth’s Radiant Energy System CERES instruments on board continue to function nominally. Their expected mission lifetime was 7 years. Critical to their performance is the longevity of the scanning gimbals. This can be traced to the performance of the fluid-lubricated bearings. Two metrics are used to estimate their lifetime and health. Both lend themselves to readily available data and ease of interpretation. One is predicting the evaporative lubricant loss. This analysis indicates that the lubricant supply is adequate for the continual life of the gimbals. The second is trending the torque with time. Torque precursors are sampled quarterly. These data are converted to torque. Two types of torque behavior were examined. Contrasting torque data have supported the conclusion that the gimbals are operating nominally. This can be partially attributed to the design choices for the bearings and lubricant. The aim of this paper is to quantitatively describe the present health and expected life of the CERES gimbals on the Terra satellite.

Experimental Verification of Rubber Clutch Spring Damper Torque Behavior in Time-Dependent Manner and System Optimization Using Simulated Annealing Algorithm Integrated With 1-D Modeling

Automobile components are subjected to high dynamic loads and vibrations under operational conditions which needs detailed system analysis for work properly. The torque generated in the engine creates oscillations, and this case occurred at different levels of frequencies. Clutch is one of the important part of automobile powertrain system with torque transmission controlling and vibration damping properties. Metallic helical springs are widely preferred within the clutch discs with their durable mechanic properties against dynamic variables on an automobile. This study develops the novel approach on the time-based investigation of rubber clutch springs, and system optimization for torsional vibration damping using the simulated annealing algorithm method. In this purpose, the torque behavior of the rubber spring instead of the helical spring was investigated by experimentally in time-dependent manner. Rubbers consist of polymer chains which are highly sensitive to dynamic variables such as operation time, frequency and thermal load. The clutch disc which includes rubber damper spring made of NBR (Nitril rubber) is experimentally tested with functional torque measurement at different compression cycle times to observe rubber damper spring viscoelastic time-based behavior. As the next step, 1-D modeling of powertrain system, including rubber clutch damper springs, were subjected to vibration optimization with simulated annealing (SA) algorithm. Thus, the simulated annealing (SA) algorithm was developed, and integrated run is provided with 1-D modeling for optimization in Python script. This methodology accelerates the powertrain system optimization using both rubber and metallic damper types with eliminating many of real vehicle testing and saving cost and time before the production phase. Also, results give an idea on the importance of 1-D simulation before design modeling of rubber clutch damper system based on time-dependent conditions.

Static Torsional Stiffness Computation of Circumferential Arc Spring Dual Mass Flywheel

The iterative formulas of spring forces for Circumferential Arc Spring Dual Mass Flywheel (DMF-CS) were derived by discrete method, involving friction forces. The computation program was designed, and the curves illustrating transmitted torques over deformation angles of the outer and inner arc springs were plotted, which showed linear torque behavior. Thus two stages of torsional stiffness of DMF-CS were figured out to be 465.9923Nm/rad and 631.7980Nm/rad. The two stages of torsional stiffness without friction forces were calculated by this method, which were 434.6408Nm/rad and 591.3652Nm/rad. The experiment of static torque characteristic of DMF-CS was completed, obtaining the experimental torsional stiffness, which were 455.9923Nm/rad and 620.9412Nm/rad. Comparing the above values of torsional stiffness, the values with friction forces show more precise than ones without friction forces, and the values without friction forces are smallest. The results show that the friction forces contribute to the torsional stiffness of DMF-CS.