Staying within the nullcline boundary for vehicle envelope control using a sliding surface

TLDR

Envelope control has been used in aircraft for decades and, with advances in sideslip and friction estimation, is now applicable to automotive vehicles. The paper aims to analyze the physical factors for envelope selection and present a specific envelope defined by the yaw‑acceleration nullcline and maximum rear‑slip limits. The authors implement a sliding‑surface controller that, based on full state estimation of yaw rate and sideslip angle, keeps the vehicle inside the defined envelope of the yaw‑acceleration nullcline and rear‑slip limits. Experimental results confirm that the steer‑by‑wire sliding‑surface controller successfully maintains the vehicle within the envelope. Keywords: vehicle dynamics, vehicle control, stability, sliding surface control, envelope control, acknowledgements to NISSAN MOTOR Co., Ltd., project team members, and the Dynamic Design Laboratory at Stanford University.

Abstract

Abstract Envelope control has been implemented successfully in aircraft for over a decade to assist pilots in stabilising their planes. With current advances in sideslip angle and friction coefficient estimation, envelope control can now be applied to the automotive industry as well. Using full state estimation of yaw rate and sideslip angle, stability controllers can assist the driver by keeping the vehicle within a safe region of the planar state space. This paper discusses the physical phenomena that must be taken into account when choosing an envelope and details a specific choice of envelope comprised of the yaw acceleration nullcline and the maximum rear slip angle limits. The vehicle is kept within the envelope using a computationally simple sliding surface control scheme. Experimental data show the success of the controller, which is implemented on a vehicle through the use of steer-by-wire. Keywords: vehicle dynamicsvehicle controlstabilitysliding surface controlenvelope control Acknowledgements The authors thank the NISSAN MOTOR Co., Ltd. as well as project team members Yoshitaka Deguchi, Shinichiro Joe, and Takuro Matsuda for sponsoring this research. We also thank the other members of the Dynamic Design Laboratory at Stanford University, especially Craig Beal, for help with vehicle testing.