Chapter 21 Suppression of Multiple Order Friction Torque Fluctuations with Modulated Actuation Pressure Osman Taha Sen, Jason T. Dreyer, and Rajendra Singh Abstract The goal of this article is to examine the effect of modulated actuation pressure on the friction torque response of a disc brake system. First, a dynamic friction experiment, consisting of a flywheel, shaft and brake assembly, is built and instrumented accordingly. The actuation pressure is modulated with a solenoid valve located in the hydraulic line. During the experiment, the modulation frequency is kept intact, and the shaft torque is measured as the system slows down; an amplification of the dynamic torque is observed as the system passes through the resonance. Second, a nonlinear mathematical model of the brake experiment is developed, and the dynamic torque response is numerically calculated for various modulation schemes, such as with constant frequency and sweeping modulation frequency with single harmonic content. Predicted results are compared with measurements. Finally, the outcome of this study is related to the brake judder problem, and some solutions for the reduction of dynamic torque are briefly discussed. Keywords Friction-induced vibration • Modulated actuation pressure • Experimental dynamics • Transient vibration • Brake judder 21.1 Introduction Friction-induced vibrations are observed in automotive disc brake systems and cover a wide range of frequencies. Dynamic instability and noise at higher frequencies (1–16 kHz) are usually linked to the brake squeal phenomenon [1]. Several active control strategies have been proposed [2–4]. For instance, piezoceramic actuators are placed between the brake piston and brake pad to suppress high frequency noise. In the lower frequency range (say up to 500 Hz), the source of brake vibration problems is assumed to be the distortions in the disc surface [5–8]. Motion excitations due to disc surface distortions generate variations in brake pressure and friction torque (Tf (t)); this excitation is non-stationary with frequencies proportional to wheel speed. Due to multiple distortion orders of comparable amplitudes, Tf (t) may have multiple dominant frequencies at a given time [5–7], and it generates variations in dynamic responses such as in the shaft torques (T(t)). Furthermore, dynamic amplifications of T(t) can occur at multiple speeds due to path resonances. For the active control of T(t), Duan and Singh [8] proposed the modulation of actuation pressurep(t) and numerically illustrated a significant reduction inT(t) for a single order rotor surface distortion profile. However, pressure modulation methods are yet to be experimentally and computationally investigated in detail. Accordingly, the specific objectives of this study are: (1) Design a laboratory experiment with a modulated actuation pressure at constant frequency, collect relevant measurements, and examine the effect of modulation on p(t) and T(t); and (2) Develop a nonlinear mathematical model of the experiment, and find numerical solutions for several modulation schemes. O.T. Sen ( ) Department of Mechanical Engineering, Istanbul Technical University, Istanbul 34437, Turkey e-mail: senos@itu.edu.tr J.T. Dreyer • R. Singh Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA e-mail: dreyer.24@osu.edu; singh.3@osu.edu G. Kerschen (ed.), Nonlinear Dynamics, Volume 2: Proceedings of the 32nd IMAC, A Conference and Exposition on Structural Dynamics, 2014, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-04522-1__21, © The Society for Experimental Mechanics, Inc. 2014 223
RkJQdWJsaXNoZXIy MTMzNzEzMQ==