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Stability Analysis of a Disc Brake with Piezoelectric Self-Sensing Technique
Abstract:
Piezoelectric self-sensing allows to measure frequency response functions of dynamical systems with one single piezoelectric element. This piezoceramics is used as actuator and sensor simultaneously. In this study, a model-based piezoelectric self-sensing technique is presented to obtain potential squealing frequencies of an automotive disc brake.
The frequency-response function of the brake system is obtained during operation by measuring the current flowing through the piezoelectric element while the piezoelectric element is driven by a harmonic voltage signal with constant amplitude. The current flow is composed of the part which is required to drive the piezoelectric element as an actuator and a second part which is the sensor signal that is proportional to the vibration amplitude of the attached mechanical system. Typically the first part is dominant and the influence of the mechanical system is marginal.
With an idealized mathematical model of the piezoelectric element, the admittance can be calculated and the actuator current eliminated from the measured signal. This software-based solution does not require any additional electrical circuits or precise tuning during the measurements.
Potential squealing frequencies which agree with the eigen-frequencies of the brake model can be determined in the recalculated signal. When the brake is heated up, one of these resonances stands out in the measurements, even if the brake does not squeal at that moment. This frequency is the most critical one and it is a very good indicator for potential squealing frequencies of the brake. The proposed technique is therefore helpful especially during the development of new brake systems, where the stability of various brake prototypes must be determined quickly so that the necessary modifications can be carried out.