The primary purpose of this study is to provide a comprehensive experimental analysis of how various popular semiactive control methods perform when used with magneto rheological dampers. Specifically, the performance of five different skyhook control methods is studied experimentally, using a single suspension test rig. The control methods that are analyzed include: skyhook control, groundhook control, hybrid control, displacement skyhook, and relative displacement skyhook. For a MR damper, this paper provides an in-depth analysis of how these semiactive control methods perform at the sprung and unsprung mass natural frequencies, using the single suspension test rig. Upon evaluating the performance of each control method in frequency domain for various conditions, they are compared with each other as well as with passive damping. The results indicate that no one control method outperforms others at both the sprung and unsprung mass natural frequencies. Each method can perform better than the other control methods in some respect. Hybrid control, however, comes close to providing the best compromise between different dynamic demands on a primary suspension. The results indicate that hybrid control can offer benefits to both the sprung and unsprung mass with control gain settings that provide equal contributions from skyhook control and groundhook control.
This study intends to identify the behavior of MR fluid subject to high rates of shear and high flow velocities. A high shear rheometer is built which allows for the high velocity testing of MR fluids. The rheometer is capable of fluid velocities ranging from 1 m/s to 37 m/s, with corresponding shear rates ranging from 0.14x105 s-1 to 2.5x105 s-1. Fluid behavior is characterized in both the off-state and the on-state. In the off-state, the MR fluid was shown to exhibit nearly Newtonian post-yield behavior. A slight thickening was observed for growing shear rates. This slight thickening can be attributed to the behavior of the carrier fluid. The purpose of the on-state testing was to characterize the MR effect at high flow velocities. MR fluid was run through the rheometer at various flow velocities and a number of magnetic field strengths. The term "dwell time" is introduced and defined as the amount of time the fluid spends in the presence of a magnetic field. Two active valve lengths were considered, which when coupled to the fluid velocities, generated dwell times ranging from 12 ms to 0.18 ms. The yield stress was found from the experimental measurements and the results indicate that the magnitude of the yield stress is sensitive to fluid dwell time. The results from the on-state testing imply that high velocity applications may be subject to diminished controllability for falling dwell times.
The primary purpose of this paper is to investigate the response time of magnetorheological (MR) dampers and the effect of operating parameters. Rapid response time is desired for all real-time control applications. In this experimental study, a commercially available MR damper was tested and the response time was found for various operating conditions. The parameters considered include operating current, piston velocity, and system compliance. The authors define the response time as the time required to transition from the initial state to 63.2% of the final state, or one time constant. Using a triangle wave to maintain constant velocity across the damper, various operating currents ranging from 0.5 Amps to 2 Amps were applied and the resulting force was recorded. The results show that, for a given velocity, the response time remains constant as the operating current varies, indicating that the response time is not a function of the applied current. To evaluate the effect of piston velocity on response time, velocities ranging from 0.1 in/s to 3 in/s were tested. The results show that the response time decreases exponentially as the velocity increases, converging on some final value. Further analysis revealed that this result is an artifact of the compliance in the system. To confirm this, a series of tests were conducted in which the compliance of the system was artificially altered. The results of the compliance study indicate that compliance has a significant effect on the response time of the damper.
Conference Committee Involvement (6)
Active and Passive Smart Structures and Integrated Systems VI
12 March 2012 | San Diego, California, United States
Active and Passive Smart Structures and Integrated Systems V
7 March 2011 | San Diego, California, United States
Active and Passive Smart Structures and Integrated Systems IV
8 March 2010 | San Diego, California, United States
Active and Passive Smart Structures and Integrated Systems III
9 March 2009 | San Diego, California, United States
Active and Passive Smart Structures and Integrated Systems II
10 March 2008 | San Diego, California, United States
Active and Passive Smart Structures and Integrated Systems
19 March 2007 | San Diego, California, United States
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