The target of our project is to realise a novel traction control system for an electric vehicle with four independently controlled in-wheel-motors. In each in-wheel-motor, the optimal slip ratio control is implemented beforehand to prevent wheel slip for vehicle stability control. The optimal slip ratio control is achieved by maintaining the slip ratio to the value to give the maximum road friction. This means that the driving force of the vehicle is fixed at its maximum level. As the driving force is affected by highly nonlinear adhesion characteristics between tire and road surface, real-time generation of the optimal slip ratio is necessary while the vehicle is moving. To estimate the adhesion characteristics, only the estimation of the slope of road friction curve is enough. To this aim, in this paper, the driving-force observer is newly designed to detect the road friction coefficient and the fixed-trace algorithm is applied to the slope estimation. The effectiveness of the proposed method is confirmed by simulation and experimental data obtained by laboratory-made electric vehicle "UOT Electric March".

Road condition estimation for traction control in electric vehicle

Estimation of Tire-Road Friction Using Tire Vibration Model

In the context of hybrid anti-lock brake systems (ABS), a closed-loop wheel-acceleration controller based on the observation of the extended braking stiffness (XBS) is provided. Its objective is to improve the system's robustness with respect to changes in the environment (as changes in road conditions, brake properties, etc.). The observer design is based on Burckhardt's tyre model, which provides a wheel acceleration dynamics that is linear up to time-scaling. The XBS is one of the state variables of this model. The paper's main result is an observer that estimates this unmeasured variable. When the road conditions are known, a three-dimensional observer solves the problem. But, for unknown road conditions, a more complex four-dimensional observer must be used instead. In both cases, the observer's convergence is analysed using tools for switched linear systems that ensure uniform exponential stability (provided that a dwell-time condition is satisfied). Both experiments and simulations confirm the convergence properties predicted by the theoretical analysis.

/pdf/extended-braking-stiffness-estimation-based-on-a-switched-4of2d4p119.pdf

Extended Braking Stiffness Estimation Based on a Switched Observer, With an Application to Wheel-Acceleration Control

This work presents a hydraulic anti-lock braking system (ABS) for a motorcycle. The ABS has a hydraulic modulator and an intelligent controller. The hydraulic modulator is analyzed, and then equipped on a scooter for road tests. The intelligent controller controls the hydraulic modulator by estimated vehicle velocity to calculate the slip ratio of the wheels in real time. The performance of the hydraulic modulator and intelligent controller are assessed by the hardware-in-the-loop (HIL) simulations and road tests. In HIL simulation, the ABS is tested for different initial braking velocities on roads with different adhesive coefficients. Furthermore, both HIL simulations and road tests are conducted on a one-phase pavement road and three-phase pavement road.

http://www.j-mst.org/On_line/admin/files/17-J2009-05249_1141-1149_.pdf

Design of a hydraulic anti-lock braking system (ABS) for a motorcycle

The paper reviews and presents which is the envisaged improvement of the active safety of road vehicles arising from the real time measurement of forces and moments at the wheels. There are many researches undertaken in the world attempting to find devices able to measure accurately the forces and the moments at the wheels of road vehicles. In particular, a six-component measuring wheel developed and patented at the Politecnico di Milano is presented. The active safety of road vehicles is related to longitudinal motions (braking, traction control), lateral motions (yaw moment control) and vertical motions (road holding). In each of these three fields the paper briefly reviews the up-to-date controls. Based on such a state-of-the art survey, the weak points of today's controls are highlighted. A proposal of new controls is presented aiming to use all of the information available and provided by six-axis measuring hubs at the wheels. A considerable improvement of the vehicle active safety can be achieved by...

Improving the active safety of road vehicles by sensing forces and moments at the wheels

In this paper, we propose a new control strategy for an antilock braking system (ABS) to maintain the braking force at maximum. The popularization of the ABS that prevents the wheels from locking has resulted in an improvement of the vehicle stability and shortening of the braking distance. Further improvement is anticipated if the maximization of the braking force is realized. We found an interesting phenomenon in which the characteristics of the resonance system composed of the vehicle body and the wheel and road surface reflects the slip condition of the road surface. Using this phenomenon, we realized a control method for maintaining the maximum value of the braking force.

Masuru Sugai

Papers

New Control Technique for Maximizing Braking Force on Antilock Braking System