Steering control for haptic feedback and active safety functions
Doctoral thesis, 2021
The closed-loop architecture, outlined in this thesis, includes a reference model, a feedback controller and a disturbance observer. The feedback controller forms the inner loop and it ensures: reference tracking, hardware impedance compensation and robustness against the coupling uncertainties. Two different causalities are studied: torque and position control. The two are objectively compared from the perspective of (uncoupled and coupled) stability, tracking performance, robustness, and transparency.
The reference model forms the outer loop and defines a torque or position reference variable, depending on the causality. Different haptic feedback functions are implemented to control the following parameters: inertia, damping, Coulomb friction and transparency. Transparency control in this application is particularly novel, which is sequentially achieved. For non-transparent steering feedback, an environment model is developed such that the reference variable is a function of virtual dynamics. Consequently, the driver–steering interaction is independent from the actual environment. Whereas, for the driver–environment transparency, the environment interaction is estimated using an observer; and then the estimated signal is fed back to the reference model. Furthermore, an optimization-based transparency algorithm is proposed. This renders the closed-loop system transparent in case of environmental uncertainty, even if the initial condition is non-transparent.
The steering related active safety functions can be directly realized using the closed-loop steering feedback controller. This implies, but is not limited to, an angle overlay from the vehicle motion control functions and a torque overlay from the haptic support functions.
Throughout the thesis, both experimental and the theoretical findings are corroborated. This includes a real-time implementation of the torque and position control strategies. In general, it can be concluded that position control lacks performance and robustness due to high and/or varying system inertia. Though the problem is somewhat mitigated by a robust H-infinity controller, the high frequency haptic performance remains compromised. Whereas, the required objectives are simultaneously achieved using a torque controller.
Chalmers, Mechanics and Maritime Sciences, Vehicle Engineering and Autonomous Systems
Comparison of Steering Feel Control Strategies in Electric Power Assisted Steering
International Symposium on Advanced Vehicle Control,; (2018)
Paper in proceeding
Design of Haptic Feedback Control for Steer-by-Wire
IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC,; Vol. 21(2018)p. 1737-1744
Paper in proceeding
An approach to develop haptic feedback control reference for steering systems using open-loop driving manoeuvres
Vehicle System Dynamics,; Vol. 58(2019)p. 1953-1976
T. Chugh, F. Bruzelius, M. Klomp and B. Jacobson. Steering feedback transparency using rack force observer
T. Chugh, F. Bruzelius, B. Kulcsár and M. Klomp. Robust H-infinity position control for vehicle steering
In electric power assisted steering and steer-by-wire systems, steering feedback is determined by the control strategy of actuators. It is desirable to control them in a manner that minimizes the influence of mechanical hardware, disconnects the haptic feedback from system dynamics, and manipulates the transparency with a straightforward approach. However, the first two aspects are limited by a performance-stability tradeoff and the last, by a transparency-stability tradeoff. Stability of the steering system must be ensured and it takes precedence over steering feedback performance and transparency regardless of the control method.
The main highlight is driver-environment transparency control. This dictates the performance requirements on both the control algorithms and the estimation of environment interaction. With the proposed solution, steering feedback can be designed by selecting what the driver should and should not haptically sense from the actual tire-road interaction.
In modern passenger vehicles, driving automation functions, such as pilot assist, highway pilot, and lane keeping assistance, intend to take control of the steering wheel. Under those circumstances, the proposed algorithm would provide possibilities in a manner that is consistent with the steering feedback control.
Steer by wire Opportunities, performance and system safety (SWOPPS)
VINNOVA (2017-05504), 2018-03-09 -- 2021-07-01.
Development of Virtual Steering Control and Steering Feel Model Reference
Volvo Cars, 2016-07-01 -- 2022-06-30.
European Commission (EC) (675999), 2016-07-01 -- 2022-06-30.
Areas of Advance
ReVeRe (Research Vehicle Resource)
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4988
Chalmers University of Technology
Room KC, Kemigården 4
Opponent: Dr. David Cole, University of Cambridge, United Kingdom