Rahizar Ramli

Multi-body co-simulation of semi-active suspension systems

Abstract This paper describes the development and use of a multi-body co-simulation approach for predicting the dynamic response of a vehicle containing magnetorheological (MR) semi-active dampers. The approach is used to investigate the effects of various local and global control strategies on the load histories of suspension components for the purpose of assessing their likely impact on fatigue life. The approach adopted aims to exploit the capability of a multi-body system (MBS) code and a mathematical simulation code, by integrating the MBS vehicle models with selected semi-active damper/controller models. Various MBS vehicle models are developed of increasing complexity using MSC.visualNastran, which are linked to three local, two-state switchable, control algorithms and also two global controllers, each developed in MATLAB/Simulink. The control strategies are implemented within the vehicle model using an MR damper model derived from experimental test data. Road inputs, including both bump/pothole and random road excitation, and the tyre model are also implemented within MATLAB/Simulink. Ultimately, the aim is to develop an approach which would allow concurrent structural optimization and controller optimization to enable lighter and more durable suspension components to be produced.

A review on electromagnetic suspension systems for passenger vehicle

This paper discussing all the design literature review for electromagnetic suspension systems for passenger vehicle. Electromagnetic suspension is the alternative for existing conventional suspension system that uses passive suspension system. Generally, linear motor is used in the design of the suspension. This is due to the behavior of the motor that can exert linear force directly to the attached load. In addition, the linear force from linear motor is controllable. This paperreview with the effects of all types of electromagnetic suspension systems to the passengers comfort. The reliability of fully active suspension system for vehicle also highlighted in this paper. A quarter-car model is used to assess the vehicle body vibration. This paper also deals with regenerative properties of linear motor that can improve the performance of lightweight vehicle.

A review on control strategies for passenger car intelligent suspension system

The main function of a suspension system is to reduce/isolate vibration caused by road irregularities to improve comfort, reliability and road holding of the vehicle. In this paper, various control aspects in controllable suspension are reviewed focusing on suspension performance criteria, control strategies and control methodologies. This includes the implementation of software-in-the-loop (SIL) and hardware-in-the-loop (HIL) simulations. Based on these reviews, a study on a suspension system control strategy with implementation of the HIL and SIL simulations approach is proposed for future works.

Identification of vehicle suspension parameters by design optimization

The design of a vehicle suspension system through simulation requires accurate representation of the design parameters. These parameters are usually difficult to measure or sometimes unavailable. This article proposes an efficient approach to identify the unknown parameters through optimization based on experimental results, where the covariance matrix adaptation–evolutionary strategy (CMA-es) is utilized to improve the simulation and experimental results against the kinematic and compliance tests. This speeds up the design and development cycle by recovering all the unknown data with respect to a set of kinematic measurements through a single optimization process. A case study employing a McPherson strut suspension system is modelled in a multi-body dynamic system. Three kinematic and compliance tests are examined, namely, vertical parallel wheel travel, opposite wheel travel and single wheel travel. The problem is formulated as a multi-objective optimization problem with 40 objectives and 49 design parameters. A hierarchical clustering method based on global sensitivity analysis is used to reduce the number of objectives to 30 by grouping correlated objectives together. Then, a dynamic summation of rank value is used as pseudo-objective functions to reformulate the multi-objective optimization to a single-objective optimization problem. The optimized results show a significant improvement in the correlation between the simulated model and the experimental model. Once accurate representation of the vehicle suspension model is achieved, further analysis, such as ride and handling performances, can be implemented for further optimization.

A new multi-objective optimization method for full-vehicle suspension systems

The conventional approach in vehicle suspension optimization based on the ride comfort and the handling performance requires decomposition of the multi-performance targets, followed by lengthy iteration processes. Suspension tuning is a time-consuming process, which often requires the benchmarking of competitors’ vehicles to define the performance targets of the desired vehicle by experimental techniques. Optimum targets are difficult to derive from benchmark vehicles as each vehicle has its own unique vehicle set-up. A new method is proposed to simplify this process and to reduce significantly the development process. These design objectives are formulated into a multi-objective optimization problem together with the suspension packaging dimensions as the design constraints. This is in order to produce a Pareto front of an optimized vehicle at the early stages of design. These objectives are minimized using a multi-objective optimization workflow, which involves a sampling technique, and a regularity-model-based multi-objective estimation of the distribution algorithm to solve greater than 100-dimensional spaces of the design parameters by the software-in-the-loop optimization process. The methodology showed promising results in optimizing a full-vehicle suspension design based on the ride comfort and the handling performance, in comparison with the conventional approach.

Using gear mechanism in vehicle suspension as a method of altering suspension characteristic

A passive vehicle suspension has constant spring and damper properties that compromise either ride or road holding ability, depending on whether the suspension is designed to be hard or soft. This study examines the implementation of a gear mechanism in a vehicle suspension system to alter its suspension characteristic while keeping the same spring and damper properties. In the study, a rack-and-pinion mechanism was used to modify the suspension force which acted between the sprung and unsprung masses of a quarter vehicle model. The system with proposed suspension layout was modeled mathematically and solved to obtain the vehicle response due to step excitation for various gear ratios. Results indicated that the use of such a mechanism was capable of changing the equivalent suspension force of the system. It was noted that different gear ratios would amplify or reduce the equivalent suspension force, hence emulating a harder or softer suspension setting compared to that of the original suspension. Additionally, it was found that with optimized gear ratio and gear mass, the implementation was capable of overcoming the compromise between the ride and road holding ability associated with conventional passive suspensions, as simultaneous improvement on both criteria was observed.

Improving the dynamic characteristics of body-in- white structure using structural optimization

The dynamic behavior of a body-in-white (BIW) structure has significant influence on the noise, vibration, and harshness (NVH) and crashworthiness of a car. Therefore, by improving the dynamic characteristics of BIW, problems and failures associated with resonance and fatigue can be prevented. The design objectives attempt to improve the existing torsion and bending modes by using structural optimization subjected to dynamic load without compromising other factors such as mass and stiffness of the structure. The natural frequency of the design was modified by identifying and reinforcing the structure at critical locations. These crucial points are first identified by topology optimization using mass and natural frequencies as the design variables. The individual components obtained from the analysis go through a size optimization step to find their target thickness of the structure. The thickness of affected regions of the components will be modified according to the analysis. The results of both optimization steps suggest several design modifications to achieve the target vibration specifications without compromising the stiffness of the structure. A method of combining both optimization approaches is proposed to improve the design modification process.

Optimized suspension kinematic profiles for handling performance using 10-degree-of-freedom vehicle model

In an effort to reduce cost involving repetitive prototype build–test cycles, it is inevitable that simulation on full vehicle will be carried out during the product development stage. Desired suspension kinematic profiles of a given vehicle parameter are often unknown at the initial design stage. This paper demonstrates a simple methodology to obtain optimized kinematic characteristics against quality of handling performance using this model as predictive model in earliest design stage. A full vehicle model that is inclusive of suspension kinematic profiles and nonlinear damper profiles has been derived to enable the engineer to study the characteristics of the nonlinear elements against the vehicle performance when only limited vehicle data are available in the initial stage. Results suggest that the handling characteristics of a vehicle are sensitive to the changes in suspension kinematic profile. Additionally, the proposed vehicle model is able to provide satisfactory handling objective when measured in transient handling and frequency response compared to other vehicle models. A robust prediction model of the vehicle responses in frequency domain is proposed. It is coupled with the vehicle model employed as predictive model to optimize front toe angle profile against vehicle quality of handling performance measured in frequency domain.

Impact of aluminium addition on the corrosion behaviour of Sn–1.0Ag–0.5Cu lead-free solder

The effect of Al on the corrosion resistance behaviour of Pb-free Sn–1.0Ag–0.5Cu–xAl solder (x = 0.2 wt%, 0.5 wt% and 1.0 wt%) in 5% NaCl solution was investigated by using potentiodynamic polarization and salt spray exposure. Passivation behaviour was evident in all the solder formulations containing Al, compared to the base SAC solder. FESEM and XRD results revealed that more dense passive films were formed on the solder containing Al, compared to the base solder. These passivation films contained intermetallic compounds such as Al2O3, AlCuO4, SnO and SnO2 served to prevent further reaction on the material surface. Polarization studies showed that the corrosion rate was 30% and 6% lower for alloys with 0.5 wt% and 0.2 wt% Al content, respectively, even though the corrosion potential shifted towards more negative values. The Al-added solder alloys exhibit more refined surface after exposure in the salt spray chamber and revealed no visible infiltration of aggressive ions at the solder–substrate joint. This work suggests a corrosion mitigation strategy for SAC 105 solder through doping of Al.

Parametric modelling of flexible plate structures using continuous ant colony optimization

This paper presents parametric modelling of flexible plate structures using ant colony optimization (ACO). The global optimization technique of ACO is utilized to obtain a dynamic model of a flexible plate structure based on one-step-ahead prediction. In this paper a proposed ACO with roulette wheel selection known as ACO2 is compared with a previous modified ACO which is denoted as ACO1. The comparison is to recognize the optimum performance and to enhance the fast convergence. The flexible plate structure is subjected to random disturbance signal types. Fitness function for the ACO optimization is the mean-squared error between the measured and estimated output of the plate. The validation of the algorithm is presented in both time and frequency domains. Simulation results show that the proposed approachis better and has a fast convergence rate than ACO1. The developed ACO modelling approach will be used for active vibration control systems design and development in future work.