Estimation of Vehicle Speed for Low Curvatures Assuming Ideal Steering Behaviour

Abstract

In the current scenario, the vehicle is integrated with advanced sensors, infotainment maps and a telematics module, which provide extensive information regarding the terrain and dynamic state, including the radius of curvature (R). The transportation authority had imposed guidelines regarding the range of allowable vehicle speeds for low curvatures (e.g. [15 25] MPH for R = 18.4m), but a unique optimal speed for a definite curvature was not investigated. The maximum allowable speed for R = 8.34m (U-turn) is 6.7 m.s−1, whereas for R = 42.57m (cloverleaf interchange) is 11.17 m.s−1. Therefore, in this article, the concept of Ideal Steering Behavior (ISB) was utilised to estimate a unique speed for a definite R. The functionality of ISB was formulated with steering parameters [Speed, Lateral acceleration, Yaw rate, R] whose boundary conditions were derived from real-time analysis. The test vehicle 2019 Cadillac Escalade provided by General Motors Inc., was driven by four drivers on the test track with R = 18.4m, and in this research, historic driver data under normal driving conditions were utilized to adapt “human-like” driving behaviour. Basic convex optimization and polynomial interpolation techniques were adopted to generate the empirical quadratic function correlating the parameters speed and R. The optimal speed for the test track R = 18.4m was estimated using by known statistical methods which resulted in a similar value of 7.485 m.s−1, and similar procedure was adopted for R = [8.34 42.57] m. The validation of the results was performed by comparing the roll and slip coefficients for the drivers and estimated speed. Traversing the vehicle with the estimated speed is safer as it falls in the recommended range, reflects ISB, and achieves optimal lateral dynamics.