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Multi-Body Simulation of Mechanical Adjuster for Air Disc Brakes

Bergwall, Louise LU (2020) MMEM01 20201
Machine Elements
Abstract
An important component of air disc brakes for heavy-duty vehicles is an adjusting mechanism, abbreviated 'adjuster', that regulates the clearance between the brake pads and the brake disc. The clearance is important to control as it affects the brake capacity. Normally, adjusters operate to decrease the clearance to compensate for wear of the brake pads. Recently, Haldex Brake Products AB developed a purely mechanical adjuster, capable of both increasing and decreasing the clearance. Increasing the clearance is desirable to avoid drag which causes uncontrollable heating of the brake disc.

During development, physical testing of the adjuster and its subsystems has been performed by Haldex Brake Products AB. However, they lacked a... (More)
An important component of air disc brakes for heavy-duty vehicles is an adjusting mechanism, abbreviated 'adjuster', that regulates the clearance between the brake pads and the brake disc. The clearance is important to control as it affects the brake capacity. Normally, adjusters operate to decrease the clearance to compensate for wear of the brake pads. Recently, Haldex Brake Products AB developed a purely mechanical adjuster, capable of both increasing and decreasing the clearance. Increasing the clearance is desirable to avoid drag which causes uncontrollable heating of the brake disc.

During development, physical testing of the adjuster and its subsystems has been performed by Haldex Brake Products AB. However, they lacked a satisfactory simulation model for better understanding of the behaviour of the adjuster, and to study the effect of tolerance deviations of its components in an efficient way. The aim of this thesis was therefore to develop such a model.

A multi-body simulation model of the whole system was made in MotionView, and was then validated against test data. The model was thereafter used to perform a sensitivity analysis aiming to capture the relative behaviour changes due to tolerance deviations of the adjuster components. The sensitivity analysis was conducted as a DoE using four of the subsystems as design variables. Based on the sensitivity analysis result, a study investigating whether one of the subsystems could be omitted was conducted. Finally, a second multi-body model aiming to more correctly capture the movements of the adjuster was created.

The validation against test data showed that the model replicated the general behaviour well; pre-setting was captured nearly perfectly while the de-adjustment level was assumed to be greater than correct. This is assumed to be the result of lack of friction in the model due to modeling limitations in the software, but the error is believed to be systematic. Then, the sensitivity analysis showed that two of the subsystems had little or no effect on the adjustment and stable clearance level. This result suggests that a wider tolerance range could be used for components in these subsystems or that one of the subsystems even could be omitted. Simulations with the subsystem disconnected was made and showed promising results. Furthermore, the test identified the subsystem with the greatest impact on the adjustment. The second model of the adjuster validated that assumptions made for the sensitivity analysis model had not influenced the result.

The study only considers the de-adjustment and clearance level and does not predict other possible effects of tolerance intervals or removal of subsystems. Omitting one of the subsystems could possible lower the complexity and cost of the adjuster but needs to be investigated further. The work resulted in both better understanding of influence of component tolerances on the adjuster performance, and a multi-body simulation model useful for future studies. (Less)
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author
Bergwall, Louise LU
supervisor
organization
course
MMEM01 20201
year
type
H2 - Master's Degree (Two Years)
subject
keywords
MBS, air disc brake, adjusting mechanism, break performance
language
English
id
9008988
date added to LUP
2020-05-19 08:21:51
date last changed
2020-05-19 08:21:51
@misc{9008988,
  abstract     = {An important component of air disc brakes for heavy-duty vehicles is an adjusting mechanism, abbreviated 'adjuster', that regulates the clearance between the brake pads and the brake disc. The clearance is important to control as it affects the brake capacity. Normally, adjusters operate to decrease the clearance to compensate for wear of the brake pads. Recently, Haldex Brake Products AB developed a purely mechanical adjuster, capable of both increasing and decreasing the clearance. Increasing the clearance is desirable to avoid drag which causes uncontrollable heating of the brake disc.

During development, physical testing of the adjuster and its subsystems has been performed by Haldex Brake Products AB. However, they lacked a satisfactory simulation model for better understanding of the behaviour of the adjuster, and to study the effect of tolerance deviations of its components in an efficient way. The aim of this thesis was therefore to develop such a model.

A multi-body simulation model of the whole system was made in MotionView, and was then validated against test data. The model was thereafter used to perform a sensitivity analysis aiming to capture the relative behaviour changes due to tolerance deviations of the adjuster components. The sensitivity analysis was conducted as a DoE using four of the subsystems as design variables. Based on the sensitivity analysis result, a study investigating whether one of the subsystems could be omitted was conducted. Finally, a second multi-body model aiming to more correctly capture the movements of the adjuster was created.

The validation against test data showed that the model replicated the general behaviour well; pre-setting was captured nearly perfectly while the de-adjustment level was assumed to be greater than correct. This is assumed to be the result of lack of friction in the model due to modeling limitations in the software, but the error is believed to be systematic. Then, the sensitivity analysis showed that two of the subsystems had little or no effect on the adjustment and stable clearance level. This result suggests that a wider tolerance range could be used for components in these subsystems or that one of the subsystems even could be omitted. Simulations with the subsystem disconnected was made and showed promising results. Furthermore, the test identified the subsystem with the greatest impact on the adjustment. The second model of the adjuster validated that assumptions made for the sensitivity analysis model had not influenced the result.

The study only considers the de-adjustment and clearance level and does not predict other possible effects of tolerance intervals or removal of subsystems. Omitting one of the subsystems could possible lower the complexity and cost of the adjuster but needs to be investigated further. The work resulted in both better understanding of influence of component tolerances on the adjuster performance, and a multi-body simulation model useful for future studies.},
  author       = {Bergwall, Louise},
  keyword      = {MBS,air disc brake,adjusting mechanism,break performance},
  language     = {eng},
  note         = {Student Paper},
  title        = {Multi-Body Simulation of Mechanical Adjuster for Air Disc Brakes},
  year         = {2020},
}