The influence of specifying a roll moment distribution to effect the handling dynamics of automobiles has long been appreciated by conventional automotive designers. With the advent of active suspension systems, it is now possible to actively vary the roll moment distribution via feedback control. Nonlinear vehicle dynamics are developed to describe the effect of roll moment distribution. Controllers based on feedback linearization and intuition are developed and simulated. Based on favorable simulation results, the intuitive nonlinear controller was implemented on a passenger automobile and results of its performance are included.
In practice most active vehicle suspension work can be traced to two sources, Lotus' modal control and Karnopp's skyhook damper. A model is developed which allows comparison of different active suspension control algorithms. The Lotus modal control algorithm is reviewed, and compared with Karnopp's skyhook damper. It is shown that a tight inner closed loop allows the Lotus algorithm to achieve the inertial damping described by Karnopp for a single comer or quarter car. It is suggested that to achieve simultaneously high inertial damping and good disturbance rejection an inner force loop is desirable. A vehicle control scheme is presented which combines the Lotus modal decomposition with Karnopp's skyhook damper, allowing nearly optimal ride and simultaneously permitting modification of vehicle handling properties.
TRW has recently launched an electrically powered, computer-controlled enhancement to commercial vehicle steering systems. ColumnDrive, the new component, precisely controls torque feedback to the driver, resulting in a synthetic or artificial steering feel. Synthetic torque feedback is most effective at masking non-linearities in the steering system that degrade the on-centre lane-keeping properties of the vehicle, as well as providing an unprecedented level of speed proportionality so that parking efforts can be optimized independently of on-centre stability. The new ColumnDrive and existing electrical powersteering control architectures are compared, and actual vehicle performance data are presented.
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