| Popis: |
The topic of this scholarly research is motivated by the need for superior control of vehicle powertrain vibration, commonly accomplished using 3 or 4 passive mounts. However, emerging design trends (such as higher power density powertrains and lightweight structures) necessitate a hybrid approach utilizing active and passive methods to meet more stringent system performance targets. The chief research objective is to acquire fundamental understanding of dynamic interactions among multiple active and passive paths in a powertrain mounting system for improved control of multi-dimensional motion, in the presence of a rigid frame placed on four bushings. All hybrid paths are assumed to be an actuator in series with an elastomeric mount; and discrete linear time-invariant deterministic systems are assumed with small motions, harmonic excitations, steady state behavior, and no kinematic nonlinear effects. Also, passive elements are assumed massless while active elements possess mass. Additionally, passive torque roll axis motion decoupling concepts are explored to enhance active control capabilities given certain practical constraints. Analytical, computational, and experimental methods are utilized though no real-time control is done. First, the torque roll axis motion decoupling concept is studied in a 12 degree of freedom model of a realistic powertrain and coupled frame. Deficiency of prior literature neglecting the need for a physically realizable system is overcome by deriving improved mount compatibility conditions, implemented in new decoupling paradigms to ensure more realistic mount positions. It is mathematically shown that full decoupling is not possible for a practical system, and partial decoupling paradigms are pursued to ensure that only the powertrain roll motion is dominant. This constitutes as a major contribution. The interaction between hybrid paths is studied next as part of a resonating two path source-path-receiver system with 6 degrees of freedom, simplified from a realistic powertrain and frame system. The main contribution of this work is derivation of a performance index (dictated by passive system dynamics) that characterizes this interaction for source mass motion control; two passive system parameters (hybrid path damping and disturbance force location) emerge that drastically change the performance index. Design paradigms are developed for desirable path interactions, and limited experimental validation demonstrates motion control concept at 400 Hz. Finally, a new 24 degree of freedom mathematical model for a coupled powertrain and frame is developed with versatility to select passive only, active only, or hybrid powertrain paths. Additionally, new torque roll axis decoupling paradigms are derived for non-identical powertrain mount properties and orientations, and the new model allows for arbitrary or torque roll axis designed mounts. Improved vibration control is achieved with hybrid mounts over active or passive only, and it is found that a minimum of two actuators should be used for a realistic powertrain mounting system. Future work should include construction of a powertrain and frame experiment to examine hybrid path effectiveness and torque roll axis mounting schemes, examination of active motion control for transient powertrain events, and application of real-time control. |
