Marco Gubitosa

Vehicle dynamics with LMS Virtual.Lab Motion

LMS Virtual.Lab Motion is a complete and integrated solution to simulate realistic motion and loads of mechanical systems. It permits engineers to quickly analyse and optimize the real-world behavior of the mechanical design, before committing to expensive physical prototype testing. LMS Virtual.Lab Vehicle Motion simulates all types of vehicle ride and handling behavior from passenger cars and motor sport vehicles to multi-axle vehicles like trucks and buses. Through the multi-attribute nature of the LMS Virtual.Lab Solution, different vehicle performances can be balanced and optimized. This allows performing studies for example to improve the road noise while keeping the handling performance untouched. For handling analyses, LMS Virtual.Lab Motion Vehicle includes the possibility to quickly run standardized events. The industry driver ‘IPG-DRIVER’ is integrated in LMS Virtual.Lab Motion, which allows to simulate all the actions a human driver performs while driving a vehicle. The main tire models integrated in LMS Virtual.Lab Motion are the TNO Delft tire models (MF-Tyre and MF–SWIFT) and CDTire. Other tire models can be integrated using the Standard Tire Interface. The interface with Matlab/Simulink and LMS Imagine.Lab Amesim allows the integration of detailed models of electronic as well as hydraulic control systems in order to perform combined simulations to analyze for example the effect of active safety systems on the vehicle dynamics. As such, LMS Virtual.Lab Motion Vehicle provides a complete package to efficiently perform vehicle dynamics studies.

Multi-Disciplinary Optimization of an Active Suspension System in the Vehicle Concept Design Stage

The automotive industry represents a significant part of the economic activity, in Europe and globally. Common drivers are the improvement of customer satisfaction (performance, personalization, safety, comfort, brand values,) and the adherence to increasingly strict environmental and safety regulations, while at the same time reducing design and manufacturing costs and reducing the time to market. The product evolution is dominated by pushing the envelope on these conflicting demands.

Optimized Design Method of Vehicle Suspension Systems Using a Reverse Engineering Approach

Nowadays companies dealing with the automotive market, and in particular product designers, are facing with highly competitive environments though conflicting demands to deliver more complex products with increased quality in ever shorter development cycles. The usage of numerical simulations is therefore a confirmed technique going through the conceptual (1D) modeling towards a detailed digital mock-up to realize complex multibody (3D) simulations. The purpose of this paper is to develop a systematic design method for the suspension systems using CAE (Computer Aided Engineering) tools to investigate different properties which have influence on the ride & handling of a vehicle. Running a reverse engineering approach, the elasto-kinematic characteristics of different types of suspensions can be focused out and exported from a multibody environment (Virtual.Lab Motion has been chosen as example) as look-up tables to be read by a 1D multi-domain software (in the work here presented we used Imagine.Lab AMESim). Combined runs of sensitivity analyses and optimization cycles would then bring to the final goal of understanding the most suitable target behavior of the full system and the weight of different design variables on this, being hence able to directly address modifications of the global configuration.Copyright

Performance Comparison of Real-Time and General-Purpose Operating Systems in Parallel Physical Simulation with High Computational Cost

Real-time simulation is a valuable tool in the design and test of vehicles and vehicle parts, mainly when interfacing with hardware modules working at a given rate, as in hardware-inthe-loop testing. Real-time operating-systems (RTOS) are designed for minimizing the latency of critical operations such as interrupt dispatch, task switch or inter-process communication (IPC). General-purpose operating-systems (GPOS), instead, are designed for maximizing throughput in heavy-load systems. In complex simulations where the amount of work to do in one step is high, achieving real-time depends not only in the latency of the event starting the step, but also on the capacity of the system for computing one step in the available time. While it is demonstrated that RTOS present lower latencies than GPOS, the choice is not clear when maximizing throughput is also critical.

Model Based Actuator Management for a Hydraulic Active Suspension System: Improving Comfort Performance by Advanced Control

Active suspension systems aim at increasing safety by improving vehicle ride and handling performance while ensuring superior passenger comfort. This paper addresses the influence of the actuator management on the comfort performance of a complete hydraulic active suspension system. An innovative approach, based on nonlinear Model Predictive Control, is proposed and compared to a classical approach that employs a steady-state performance map of the actuator. A simulation analysis shows how taking into account actuator dynamics improves the actuator’s force tracking performance, leading to an improvement of the overall vehicle comfort performance.Copyright

A Computer Aided Engineering Approach for the Optimal Design of an Active Suspension System

Within companies dealing with the automotive market, and in particular for product designers, the usage of numerical simulations is a well established technique to help achieving faster development cycles. Focusing on the very first phase of the design development chain conceptual (ID) modeling software is better suited. Furthermore considering the multiphysics nature of vehicle subsystems, a multidisciplinary system modeling tool is required, which has to be enriched with optimization capabilities in order to produce a suitable design of complex systems involving multiphysics functionalities (for instance for active safety and energy management). The purpose of this paper is to summarize a procedure that has been applied for the optimal design of an active suspension with hydraulic actuation, governed by a general control strategy based on the sky-hook approach, to be manufactured by Tenneco. A 15 Degrees of Freedom (DOF) vehicle model, built in a commercially available 1D simulation environment, has been validated as a first step towards achieving a good correlation with experimental results obtained on the test tracks. As a next step, the sky-hook based control strategy was implemented to take into account the active behavior of the system, and to define the load profiles acting on the suspension dampers while the vehicle is virtually tested on ride roads. Optimization loops were performed in a nested architecture in order to define the optimal gains needed to meet certain performance requirements dictated by the vehicle manufacturer. A detailed model of the damping system was implemented in LMS Imagine.Lab AMESim capturing its multidisciplinary nature including mechanical, hydraulic and electrical aspects. The mission profiles (force-velocity couples at the dampers) were used as input to the simulations to investigate the damping system design parameters considering performance achievement and energy efficiency goals. The results of this project have been used by Tenneco as guidelines for the physical prototype implementation of the active suspension system.Copyright

Real-Time and Real-Fast Performance of General-Purpose and Real-Time Operating Systems in Multithreaded Physical Simulation of Complex Mechanical Systems

Physical simulation is a valuable tool in many fields of engineering for the tasks of design, prototyping, and testing. General-purpose operating systems (GPOS) are designed for real-fast tasks, such as offline simulation of complex physical models that should finish as soon as possible. Interfacing hardware at a given rate (as in a hardware-in-the-loop test) requires instead maximizing time determinism, for which real-time operating systems (RTOS) are designed. In this paper, real-fast and real-time performance of RTOS and GPOS are compared when simulating models of high complexity with large time steps. This type of applications is usually present in the automotive industry and requires a good trade-off between real-fast and real-time performance. The performance of an RTOS and a GPOS is compared by running a tire model scalable on the number of degrees-of-freedom and parallel threads. The benchmark shows that the GPOS present better performance in real-fast runs but worse in real-time due to nonexplicit task switches and to the latency associated with interprocess communication (IPC) and task switch.

Integrating Vehicle Body Concept Modelling and Flexible Multi-Body Techniques for Ride and Handling Simulations

This paper deals with the integration of a vehicle body concept modeling methodology, based on reduced models of beams, joints and panels, with flexible Multi-body (MB) representation of the chassis of a passenger car. The aim is to enable ride and handling simulations in the initial phases of the vehicle design process, where the availability of predictive Computer Aided Engineering (CAE) tools is a key factor to steer design choices such that a faster convergence of the vehicle development cycle towards improved products is achieved.The proposed approach is demonstrated on an industrial case study, involving a commercial passenger car, for which a detailed chassis and suspension model for MB simulations is developed in LMS Virtual.Lab Motion. A flexible concept model of the vehicle’s Body In White (BIW) is created as well and included in the MB model to enable fast investigations on how ride and handling performance of the full vehicle are affected by body modifications.To demonstrate the validity of the resulting concept model, a number of standard handling manoeuvres and ride excitations are simulated by using both the flexible MB model described above and a rigid MB model of the vehicle, which is derived from the same FE model. The numerical results are compared to allow assessing the influence of body flexibility on the predicted handling and ride behaviour of the vehicle.Copyright

A system engineering approach for the design optimization of a hydraulic active suspension

A procedure for the optimal design of an active suspension with skyhook control scheme is presented. A 15 Degrees of Freedom vehicle model has been implemented and, once correlated with test data, the control strategy has been plugged in and tuned in function of the vehicle manufacturer target requirements. Achievable performances of the vehicle equipped with active components have been estimated through the implementation of the “quarter car model”, successively extended towards the full controlled vehicle. The active damper system, to be manufactured by Tenneco, has been separately modeled and the suspension design definition has been optimized with reference to performance achievements and power consumption requirements.

Parameters Identification Strategy for a Generalized Vehicle Concept Model for Ride and Handling Analysis

In this paper we propose a structured approach for the parameters identification of a multibody vehicle concept model to be used for the combined analysis of vertical and longitudinal dynamics. The model here proposed adopts eight degrees of freedom in the space. The wheels are connected to the sprung mass in an equivalent trailing arm configuration thus enabling to reproduce the squat and dive phenomena. This conceptual suspension representation allows determining the dynamic response of the vehicle during longitudinal acceleration or braking maneuvers. The identification procedure here suggested evaluates the unknown parameters of the model, being the global stiffness and damping coefficients of the suspensions and the positions of the pivot points of the trailing arms. The identification algorithm is based on non-linear least square costs that can be computed by having as reference the signals of a measurement campaign which is conducted on a real vehicle as well as on a virtual predecessor model. The results here shown make use of virtually measured quantities coming from ride maneuvers performed by means of a high fidelity multibody model of a passenger car. The presented concept model, showing good correlation with respect to the reference signals, is suggested as a reliable prediction and optimization tool in the early stage of the design phase of new vehicles.Copyright