Narrow tilting vehicles offer an opportunity to tackle both traffic congestion and carbon emissions having a small footprint, low weight and small frontal area. Their narrow width requires that they tilt into corners in order to maintain stability; this may be achieved by means of an automated tilt control system.
A three-wheeled tilting vehicle prototype, known as the Compact Low Emission Vehicle for uRban transport (CLEVER), was constructed at the University of Bath in 2006. The vehicle was equipped with a direct tilt control system in which a pair of hydraulic actuators applied a moment between the cabin and a non-tilting base. This tilt control system provided satisfactory steady state performance but limited transient stability. High tilt rate demands associated with rapid steering inputs would lead to large tilting moments being applied to the non-tilting rear engine module; this, combined with the engine module’s own propensity to roll out of the bend, could cause the inside wheel to lift and the vehicle to capsize.
This thesis details the implementation of a Steering Direct Tilt Control (SDTC) system, whereby the front wheel steer angle is used to generate some of the tilting moment, on the prototype CLEVER Vehicle. Simulation and experimental results are presented which show a 40% reduction in load transfer across the rear axle during a transient ramp steer manoeuvre. The influence of the SDTC system, and associated steer angle alteration, on the vehicle trajectory is considered. A human driver is found to be capable of adapting their steer inputs such that they can follow their chosen path.
Finally, a feed-forward control strategy is shown to reduce the load transfer across the rear axle by an additional 30% in transient situations, but only if the steer input signal is sufficiently free of noise.
|Date of Award
|29 Apr 2014
|Jos Darling (Supervisor) & Andrew Plummer (Supervisor)
- Active Steering
- Steering Direct Tilt Control
- Narrow Tilting Vehicle
- Vehicle Dynamics