Nonlinear Model Predictive Control of Active Vehicle Suspension Systems
Creators: name: Alshawi, Aymen
Publisher: name: University of Surrey
Year: 2024

description: Active and semi-active vehicle suspension systems have been used for decades in the
description: automotive engineering industry and have been applied to passenger vehicles in pursuit of enhanced
description: occupant comfort, and improved vehicle handling by reducing the tyre load variations
description: induced by road irregularities. A lesser-known use of these suspensions is yaw rate control.
description: This thesis builds on earlier research on the use of active suspension systems for this purpose,
description: and focuses on implementing Nonlinear Model Predictive Control (NMPC) to capitalise on
description: the capabilities of these suspension systems.<br>
description: <br>
description: This study addresses several gaps in the current literature with regards to vehicle state
description: estimation using Unscented Kalman Filters (UKFs) with adaptive covariance matrices. There
description: are also several gaps regarding real-time capable NMPC controllers that target several
description: objective functions simultaneously. The overall aim of this thesis is to develop and enhance
description: vehicle control using active suspensions and NMPC strategies. This was achieved by
description: initially developing an enhanced vehicle state estimator, followed by a multifunctional NMPC
description: controller and subsequently a multifunctional integrated controller that combines an NMPC
description: controller with other types of controllers. In the first part of the study, the objective (1) was
description: to improve vehicle state estimation performance in extreme driving conditions by developing
description: a novel state estimator using a UKF with adaptive covariance matrices. The estimator was
description: tested across a wide variety of high slip scenarios, in both high and low friction conditions.
description: The results show that the proposed estimator provides improved accuracy and robustness in
description: all test cases considered when compared to a well-tuned baseline UKF estimator.<br>
description: <br>
description: In the second part of the study, the objective (2) was to enhance current NMPC controller
description: capabilities in relation to vehicle dynamics control, body motion control and active safety, by
description: developing real-time implementable suspension controllers using the NMPC approach. Two
description: NMPC controllers - one with adaptable cost function weights - governing both semi-active
description: and active suspensions, were initially developed and tested against different performance
description: objectives. The NMPC controllers outperformed several benchmarking controllers in every
description: test considered, with improvements in both body motion control and yaw rate tracking, even
description: in situations at the limit of handling.<br>
description: <br>
description: Finally, in the third part of the study, the objective (3) was to develop a novel integrated
description: control strategy, comprised of NMPC with road profile preview, Skyhook and PID
description: front-to-total anti-roll moment distribution controllers. Working in tandem, this Ride-Blending
description: Controller (RBC) is designed to manage both active suspension and front-to-total torque
description: distribution. It was subsequently assessed against its individual constituent controllers on
description: an experimentally validated simulation model. The developed RBC was shown to improve
description: performance in all test cases considered, across all key performance indicators. The indicators
description: were designed to highlight the multi-faceted ability of the RBC, and thus relate to body
description: motion, ride comfort, active safety and yaw rate control.<br>
description: <br>
description: The novel outcomes developed in the presented study provide enhanced vehicle control
description: solutions and can be directly implemented in the automotive engineering industry.
description: Furthermore, the contribution to knowledge and understanding can be further expanded upon in
description: academia, towards the improved use of active suspension systems and implementation of
description: NMPC controllers.<br>