Blocked Forces

Operational TPA (OTPA) is typically used as a tool for path ranking of different noise sources in a troubleshooting phase. OTPA has the advantage of not requiring laborious impact campaigns but lacks the possibility to predict receiver noise levels from testbench measurements. In this paper, we derive an OTPA method offering this "testbench to vehicle" capability.

This study focuses on quantifying road noise performance using complex power (structural) on the main body connection points of rear axle of an SUV. It shows how this quantity can be calculated using measured data. The power in mechanical systems is calculated by the product of forces and velocity. The compatibility of the forces/ body velocities are achieved by the application of the virtual point transformation.

Operational TPA (OTPA) is typically used as a tool for path ranking of different noise sources in a troubleshooting phase. OTPA has the advantage of not requiring laborious impact campaigns but lacks the possibility to predict receiver noise levels from testbench measurements. In this paper, we derive an OTPA method offering this “testbench to vehicle” capability. This novel, component-based OTPA method will be compared to the blocked force TPA method in a numerical test case.

An exciting new development is the mixed indicator Blocked Force determination, which uses both acceleration-based measurements and force gauges as indicators for the Blocked Force calculation. This study focuses on comparing the acceleration-based in-situ and new mixed indicator Blocked Force determination methods using measurements of an artificially excited electric power steering (EPS). 

Many OEMs use dedicated test bench setups for testing and developing of components separately from their vehicle platforms. Relating these results to full-vehicle assemblies is not immediately possible, because of the difference in boundary conditions and incompatibility between test bench and vehicle measurement points. This study focuses on the use of tire noise test benches in the engineering of full-vehicle NVH. We show how virtual points, easily obtained using DIRAC, ensure compatibility between various test assemblies.

The goal of this paper is to provide a method for airborne source description of the EC and to determine the airborne sound contribution at the driver’s ear. The radiation of the EC was approximated by six acoustic monopoles emitting a volume acceleration. The characterization was conducted with the help of noise transfer functions (NTFs) and operational measurements in an anechoic chamber. Volume acceleration sources were used to measure the NTFs. The validation of the source identification was performed in a changed environment and a vehicle.

Before performing a transfer path analysis (TPA), the engineer needs to think about the right modeling of the source’s interface with the receiver. In practice, the vibration transfer from the source to the receiver is often modeled with three translational forces in each connection point. Mechanically this corresponds to a ball joint connection, which cannot transfer any moments. This study compares different complexities of interface descriptions on the industrial example of an electro-magnetic roll control (ERC) in a passenger car.

This thesis is the result of a 4-year collaboration between the Technical University of Munich and the BMW Group. The goal was to apply substructuring methods to the Noise Vibration Harshness (NVH) engineering needed for integrating electric climate compressors in upcoming vehicles. Specifically, the aim was to simulate the compressor noise in the cabin for different, virtual design variants of the isolation concept. Therefore, the methods from two broader fields were applied: First, the excitation of the compressor was modeled with component transfer path analysis (TPA) methods. Second, the full transfer path from the compressor to the driver’s ear is assembled from multiple subcomponent models, via dynamic substructuring (DS).

Due to the lack of masking noise from combustion engines in electric vehicles, the noise of auxiliary components is becoming a relevant topic. One of these components is the electric refrigerant compressor (ERC). This paper addresses the airborne sound transmission of the compressor, using the methods of component-based transfer path analysis (TPA).

Currently two ISO standards are proposed for source characterisation. In this paper it is shown how the different approaches can be derived and compared using the general framework for Transfer Path Analysis (TPA).

This paper presents a practical study on popular Experimental Dynamic Substructuring topics. A series of substructures is designed of such complexity to fit in right between “real life” structures and “academic” structures.

This paper presents a Transfer Path Analysis (TPA) method to predict the transmission of steering gear vibrations of BMW vehicles in a multi-kHz range. The blocked-force TPA concept is used.

Component-based Transfer Path Analysis allows us to analyse and predict vibration propagation between an active source and passive receiver structures. The forces that characterise the active source are determined using sensors placed on the connected passive substructure.

Sound and vibration have a defining influence on our perception of product quality. They are especially well-known aspects in the automotive industry. While traditional combustion engines are gradually getting replaced by hybrid or full-electric drive-lines, other electromechanical (so-called mechatronic) systems make their entrance. As a consequence, the sound experience shifts from low-frequent engine roar to high-frequent humming and whining – a yet unfamiliar experience that calls for redefinition of the soundscape. This thesis presents techniques that aim to implement measurements of structural dynamics and active vibration sources into development processes. This simulation is facilitated by use of Experimental Dynamic Substructuring: a methodology that determines structural dynamic aspects of complete products based on individually measured components.

Transfer Path Analysis (TPA) designates the family of test-based methodologies to study the transmission of mechanical vibrations. Since the first adaptation of electric network analogies in the field of mechanical engineering a century ago.

This paper presents a comparison of two component Transfer Path Analysis methods to predict the transmission of steering gear vibrations into the vehicle.

This thesis deals with new methods, which can determine the dynamic response of a complex system identified in operation, based on the knowledge of its subsystem dynamics and excitation.