A Two Degree of Freedom, Lumped Inertia Model for Automatic Transmission Clutch-to-Clutch Shift Dynamics

Abstract

This paper presents a methodology to represent automatic transmission clutch-to-clutch shift dynamics with a two degree of freedom, lumped inertia model. The method of reducing the automatic transmission to a lumped, two inertia model as a function of shift and input shaft acceleration is detailed using a full kinematic representation of the automatic transmission. For a given clutch-to-clutch shift maneuver there are two dependent equations that utilize the two lumped inertias and represent the response of the transmission system from input to output shaft. Applicability of the method is shown for planetary automatic and layshaft dual clutch transmissions. Typical clutch-to-clutch shift maneuvers are illustrated with the two inertia model for power on upshifts and downshifts. The simplification of automatic transmission shift dynamics using this method enables rapid synthesis of a given transmission powerflow for estimation of shift quality potential, required clutching torques, inertia phase engine torque intervention and output torque through all phases of a shift event.

Performance Characterization of Automatic Transmission Upshifts with Reduced Shift Times

“…A lumped, four inertia model of an automatic transmission is used to represent the dynamics of the torque and inertia phases of an upshift as proposed by [7]. This approach greatly simplifies the required calculations to synthesize the performance attributes of a given transmission design during a shift event when compared to other methods presented by [8,9,10,11,12].…”

“…Initial and final torque phase, t TP,i and t TP,f , respectively clutch torques and transmission output torque are functions only of net transmission input torque, gear ratio, GR, and clutch lever ratio with respect to the input shaft, R c , as defined by [7,10]. If net input torque remains constant through the torque phase the clutching torques and output torque profiles will be linear with respect to time.…”

“…Simultaneously, the oncoming clutch torque required to achieve the desired acceleration rate of the shift given the T net,trans,in determined using Eq. (6) can be computed using, (7) The variable R c represents the lever ratio of the oncoming clutch and is the ratio of torque at the clutch of interest to input torque to the transmission. For a planetary automatic transmission, the value of R c is a function of the powerflow arrangement of gearsets and clutches and with typical values ranging between 0.2 and 1.5 depending on the details.…”

“…The lumped inertias I 3 and I 4 for the automatic transmission are a property of a given transmission's architecture, powerflow and torque capacity rating which determines the relative size of the rotating components. The values of the lumped transmission inertia are computed using the methodology described by [7] for any possible clutch-to-clutch shift for the automatic transmission of interest. The other system inertias, I 1 and I 2 , are upstream of the transmission and represent the combined inertia of the engine, accessory drive and primary inertia of the launch device, I 1 , and separately the secondary inertia of the launch device directly coupled to the input shaft(s) of the transmission, I 2 .…”

Tribodynamics of a New De-Clutch Mechanism Aimed for Engine Downsizing in Off-Road Heavy-Duty Vehicles

“…Analytical models for clutches have been presented in the literature to investigate their tribodynamics characteristics. Dynamics models typically comprise two degrees of freedom with lumped inertias in their most rudimentary form [4]. The accuracy of the model increases, when including the inertia of all rotating components inside the clutch pack [5].…”