This paper presents in details the design and implementation on a low cost target of a high performance clamping force estimation method based on Kalman Filter in a Free RTOS environment. The algorithm presented requires only current and voltage measurements. An optimized method to solve the discrete state equation model of the system reduces memory consumption and calculation time. The presented force estimation algorithm can run on a low cost DSPIC target using a proper RTOS. The results obtained using a microchip DSPIC33F give good satisfactory.

Anti-lock braking systems for the full electric vehicles are characterized by the control structure of higher complexity due to the combined use of actuators with different performance and capabilities. In the discussed research the vehicle prototype is represented by a full electric sport utility vehicle equipped with four individual on-board motors. The study includes problems of (i) integration of the electric and electro-hydraulic brake systems on the vehicle prototype and (ii) development of advanced wheel slip control strategy aimed on the reduction of the stopping distance, enhancement of the driving comfort during the braking, ensuring safe operation and maximal energy recuperation.

The proposed brake system integration is done to realize the combined use of electric and hydraulic brake actuators during the emergency braking situation. In particular, it is aimed at the achievement of the maximal energy recuperation and reduction of the friction brakes use. The proposed wheel slip control approach is based on the PI-controller with the gain scheduling according to the vehicle velocity.

The achieved results showed the reduction of the stopping distance not only on the stage of hardware-in-the-loop system testing, but confirmed enhanced vehicle safety on the vehicle demonstrator. The road tests were performed at the Lommel Proving Ground on the surface with low friction conditions. Besides the developed approach, several ABS configurations were tested on the vehicle. In particular, all results were compared with the serial vehicle of the same type with internal combustion engine, conventional hydraulic brake system and rulebased ABS. Final benchmarking shows significant reduction of the stopping distance and improvements in driving comfort during the emergency braking in the case of developed continuous ABS algorithm.

The proposed brake system architecture shows possible benefits and enhancements, which can be realized by the full electric vehicles with individual wheel torque distribution. Developed ABS control functions showed considerable reduction in the stopping distance and improvement in the driving comfort. The proposed brake system architecture and ABS functions in particular have a huge potential in further use on full electric vehicles.

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.