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Abstract-Engine knock is among the most relevant limiting factors in the improvement of the operation of spark ignited engines. Due to an abnormal combustion inside the cylinder chamber, it can cause performance worsening or even serious mechanical damage. Being the result of complex local chemical phenomena, knock turns out to have a significant random behaviour but the increasing availability of new on-board sensors permits a deeper understanding of its mechanism. The aim of this paper is to exploit in-cylinder pressure sensors to derive a knock estimator, based on the logistic regression technique. Thanks to the proposed approach it is possible to explicitly deal with knock random variability and to define the so-called margin (or distance) from the knocking condition, which has been recently proven to be an effective concept for innovative knock control strategies. In a model-based estimation fashion, two modelling approaches are compared: one relies on well-known physical mechanisms while the second exploits a principal component analysis to extract relevant pressure information, thus reducing the identification effort and improving the estimation performance.

In this paper, a cascade control architecture for a brake-by-wire system suitable for motor racing applications is described. The system is composed of an electromechanical actuator, i.e., an electric motor, a transmission, a master cylinder, and a traditional hydraulic brake (pipe and caliper). Starting from a control-oriented model, a cascade control is proposed. An inner-loop controls the position; an outer the pressure. The outer loop features an adaptation mechanism to cope with the intrinsic time-varying nonlinearity of the position–pressure relationship. The stability and robustness of the pressure loop are proven. Extensive experimental validation, conducted on an instrumented motorbike on a test circuit by a professional rider, shows the performance of the system