Identification of vehicle suspension system using particle swarm optimization with neural network

Abstract

This chapter proposes a novel approach to suppress vibration that causes brake noise is proposed employing a closed-loop feedback control method using an Active Force Control (AFC) based strategy. It is used in conjunction with the classic proportionalintegral- derivative (PID) scheme that is typically incorporated in the outermost positional control loop. The idea is to introduce an active element that dynamically compensates the disturbances through a control mechanism that takes into account the direct measurements and estimation of parameters in the AFC section. A disc brake model is considered and simulated taking into account a number of operating and loading conditions. Results clearly show the superiority of the proposed AFC-based scheme compared to the pure PID counterpart in suppressing the vibration and hence the brake noise. Brake is one of the most important safety components in any automotive vehicle and is almost indispensable. The brake system of an automobile typically consists of the contact metallic solids rubbing against each other, which frequently generates undesirable noise and vibrations. This in turn causes discomfort to the passengers and adversely affects their perceptions of the quality and reliability of the vehicle. Thus, noise generation and suppression have become an important factor to be considered in the design and manufacture of brake components. Indeed, as noted by Abendroth and Wernitz (2000), a large number of manufacturers of brake pad materials spend up to 50% of their engineering costs on issues related to noise, vibration and harshness. Brake noise vibration phenomena are described by a number of terminologies that are sometimes interchangeably used such as squeal, groom, chatter, judder, moan and hum (Kinkaid et al., 2003). Even to this day, there is no precise or conclusive definition of brake squeal that has gained complete acceptance. It is also worth mentioning that since in a vehicle with disc brakes installed at the front wheels while drum brakes at the back wheels, around 70% of the braking action occurs at the front wheels. Thus, it is expected that most of the noise and squeal is coming from the front disc brake system. The main cause of brake noise is due to the effect of negative damping (Shin et al., 2002), in which the friction coefficient reduces with the increase of relative velocity of the pad and the disk. The other factor maybe attributed to mode coupling (Chen et al., 2006). In literature, there are three major methods to study and reduce brake squeal, namely through mathematical modeling, experimental and finite element methods. A recent research study has been carried out for reducing brake noise using finite element (FE) can be found in (Dai and Lim, 2007). They developed a dynamic FE model of the brake system, and based on their analysis, the pad design changes can be made in the FE model to determine the potential improvements in the dynamic stability of the system and also in noise reduction. Wagner et al. proposed a new mathematical rotor based model of a brake system that is suitable for noise analysis (Wagner et al., 2007). A brief description of the previous mathematical models that have been developed by other researchers were explicitly outlined in their study. Besides, there is also an active control method known as dither control which makes use of high frequency disturbance signal for the suppression of the automotive disc brake squeal. Brake squeal control using an active technique 43 Through this scheme, the dither signal stabilizes friction induced self-oscillations in the disc brake using a harmonic vibration, with a frequency higher than the squeal frequency generated from a stack of piezoelectric elements placed in the caliper piston of the brake system. The resulting control vibration was not heard from the brake system if an ultrasonic control signal was activated. This system assumes an open loop control mode in which there is no requirement to detect the presence of squeal and is much simpler in design than the feedback control (Grag, 2000). This paper presents a closed loop control employing system Active Force Control (AFC) with PID element applied to a brake model described in (Hoffmann et al., 2005) in order to suppress the brake noise and squeal. The main advantage of the AFC technique is its ability to reject disturbances that are applied to the system through appropriate manipulation of the selected parameters. In addition, the technique requires much less computational burden and has been successfully demonstrated to be readily implemented in realtime. AFC as first proposed by Hewitt and Burdess (1981) is very robust and effective in controlling a robot arm. Mailah has successfully demonstrated the application of the technique to include many other dynamical systems with the incorporation of artificial intelligence (AI) methods (Mailah, 1998; Mailah and Rahim, 2000).