Abstract
KEYWORDS – Anti-lock Braking, load based control, force based ABS, experimental investigation, load-sensing bearing ABSTRACT
Research objective: Anti-lock braking algorithms use either/both wheel deceleration and wheel slip to obtain a stable limit cycle around the friction peak to guarantee vehicle steerability and to minimize braking distance. However, both control variables pose several well-known issues regarding ABS control. The usage of wheel loads, for instance estimated based on bearing deformation, could provide a solution to these control variable related difficulties. In this paper, a wheel load based method to control wheel slip is presented and implemented in a novel Anti-lock Braking algorithm. Due to the fundamentally different approach to tackle the issue, numerous well known pitfalls of traditional Anti-lock Braking Systems can be avoided.
Methodology: A mathematical derivation of the quarter car model provides the conditions in which wheel load measurement allows for determination of the derivative of wheel slip. Based on this theory, a novel ABS algorithm is proposed. It consists of two operational phases to control the wheel slip derivative and a phase switching mechanism, all based solely on wheel loads. Furthermore a methodology of wheel load estimation based on bearing deformation measurement is proposed. Finally, an experimental on-road investigation of the load estimation and proposed algorithm is carried out using an instrumented test vehicle.
Results: An on-road investigation with a test vehicle demonstrates the accuracy of wheel load estimation based on bearing deformation. The estimated loads are used in a novel ABS algorithm to demonstrate the feasibility and advantages of load based ABS control.
Limitations of this study: Only straight-line braking is considered as the method of load estimation is currently unable to provide the required bandwidth on estimation of loads when steering.
What does the paper offer that is new in the field: Current research in the field of ABS algorithms is primarily focused on wheel slip and/or wheel deceleration control. The presented study investigates a fundamentally different approach by the use of a novel sensor.
Conclusion: Based on a mathematical derivation a novel load-based ABS algorithm is proposed. Furthermore a methodology of load sensing by the use of instrumented bearings is presented. The performance of both load sensing and the Anti-lock braking algorithm has been checked via experimental testing using an instrumented test vehicle.