Title page for ETD etd-05122009-140123

Type of Document Master's Thesis
Author Reader, Daniel Martin
URN etd-05122009-140123
Title Nonlinear Mr Model Inversion for Semi-Active Control Enhancement With Open-Loop Force Compensation
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Southward, Steve C. Committee Chair
Ahmadian, Mehdi Committee Member
Taheri, Saied Committee Member
  • Magneto-Rheological Damper
  • Skyhook
  • Control
  • Inverse MR Damper
Date of Defense 2009-04-27
Availability unrestricted
The increased prevalence of semi-active control systems is largely due to the emergence of cost effective commercially available controllable damper technology such as Magneto-Rheological (MR) devices. Unfortunately, MR dampers exhibit highly nonlinear behavior, thus presenting an often over-looked complexity to the control system designer. With regards to controlling dampers, the well-known Skyhook Damping control algorithm has enjoyed great success for both fully active and semi-active control problems. The Skyhook design strategy is to create a control force that emulates what a passive linear damper would create when connected to an inertial reference frame. Skyhook control is device independent since it generates a desired control force command output that must be produced by the control system.

For simplicity, MR dampers are often assumed to have a linear relationship between the current input and the force output at a given relative velocity. Often this assumption is made implicitly and without knowledge of the underlying nonlinearity. This thesis shows that the overall performance of a semi-active Skyhook control system can be improved by explicitly inverting the nonlinear relationship between input current and output force. The proposed modification will work with any semi-active control algorithm, such as Skyhook, to insure that the controller performance is at least as good as the performance without the proposed modification. This technique is demonstrated through simulation on a quarter-vehicle system. Hysteretic damping effects are incorporated into the modification by application of simple open loop force compensation. Laboratory testing of the hysteretic inversion process was performed with the goal of emulating an ideal linear damper without hysteresis. These results are compared with the implicit assumption thus providing a basis for validating the benefits of the improved methodology.

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