F2008-03-040
Objective and Subjective Evaluation of Vehicle Vibrations
The methods of virtual product design with the aid of computer simulation particularly in the design of road vehicles made a significant progress during the last decade. Virtual prototypes comply very well with reality in vehicle stability domain. However, there are still cases in the product assessment process, in which experiments with human test persons are unavoidable, since objective measures have not been developed yet or simulation models are not enough advanced. Ride comfort counts to such cases despite some approaches for objective measures exist, e.g. ISO 2631-1:1997 / VDI 2057, British Standard BS 6841:1987, or SAE-J 1013. However, the fulfilment of such objective measures does not guarantee in all cases that the vehicle is really subjectively assessed as comfortable by its potential users.
The reasons for the design of comfort cars and trucks are also connected with the safety of the road traffic, because the vehicle vibrations cause tiredness and alertness reduction of the driver.
The goal of the presented research is to develop objective measures for the assessment of the vibration comfort of vehicles. Such methodology has its potential in enabling the comfort evaluation also in free design stages of the vehicle even for the virtual prototypes and in acceleration the assessment of the existing vehicles.
The investigation of vibration comfort is focused on two main areas: (i) analysis of the occupant behaviour in the vehicle, and (ii) comparison of subjective and objective vehicle assessment. Such investigations are necessarily related to numerous field experiments, in which vehicle and/or occupant states are measured. The proposed paper describes the set-up of the experiments and presents some important conclusions from the experimental results.
In order to study the interaction between the vehicle and its occupant, a set of experiments was performed, in which typical ride manoeuvres were took place on a test field and data was collected both from the vehicle on-board sensors and sensors on the human occupant. Together 38 signals describing the vehicle and occupant states were captured; among the others the occupant´s muscular activity was measured with electromyography (EMG) as well as occupant´s motion in the vehicle measured with accelerometers and cameras. One of the objectives of the presented measurements was also to indicate the influence of the visual information on the occupant behaviour.
For the comparison of the subjective and objective vehicle assessment a group of test persons evaluated a set of test vehicles from different OEMs. The subjective evaluation was based on several ride comfort indicators. Furthermore, the group of the test persons was complemented with the professional test drivers. The objective information on the vehicle vibration level was captured with 16 accelerometers together with a special device evaluating comfort on the seat according to the ISO 2631-1. Both evaluations were performed on the same test circuit consisting of typical road profiles ranging from a country road to a motorway.
Poster presentation: Chassis development for passenger cars, trucks and buses