Steering control for haptic feedback and active safety functions
Doktorsavhandling, 2021

Steering feedback is an important element that defines driver–vehicle interaction. It strongly affects driving performance and is primarily dependent on the steering actuator's control strategy. Typically, the control method is open loop, that is without any reference tracking; and its drawbacks are hardware dependent steering feedback response and attenuated driver–environment transparency. This thesis investigates a closed-loop control method for electric power assisted steering and steer-by-wire systems. The advantages of this method, compared to open loop, are better hardware impedance compensation, system independent response, explicit transparency control and direct interface to active safety functions.

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.

position control

haptic feedback

transparency

state estimation

torque control

steering system

passivity

active safety

coupled stability

uncoupled stability

Room KC, Kemigården 4
Opponent: Dr. David Cole, University of Cambridge, United Kingdom

Författare

Tushar Chugh

Chalmers, Mekanik och maritima vetenskaper, Fordonsteknik och autonoma system

Comparison of Steering Feel Control Strategies in Electric Power Assisted Steering

International Symposium on Advanced Vehicle Control,; (2018)

Paper i 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 i 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

Artikel i vetenskaplig tidskrift

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

The sensation of touch that human experiences upon interacting with a machine is haptic feedback. Its performance and quality depend on how well the user can sense the environment, which is subsequently defined as transparency. A higher degree of transparency is important for human operated task completion, such as in remote surgeries, simulators, and telerobotics. The driver-steering interaction falls under the same category. In general, steering feel is a culmination of the information flow from different feedback channels: haptic, motion, visual, and audio. The haptic part of the steering feel is defined as steering feedback. This is one of the main elements that define driver-vehicle interaction and consequently, it affects driving performance.

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.

Europeiska kommissionen (EU) (675999), 2016-07-01 -- 2022-06-30.

Styrkeområden

Transport

Infrastruktur

ReVeRe (Research Vehicle Resource)

Ämneskategorier

Farkostteknik

Robotteknik och automation

Reglerteknik

ISBN

978-91-7905-521-9

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4988

Utgivare

Chalmers tekniska högskola

Room KC, Kemigården 4

Online

Opponent: Dr. David Cole, University of Cambridge, United Kingdom

Mer information

Senast uppdaterat

2021-10-04