Test bench for calculating the longitudinal acceleration of a motor vehicle

Abstract

Test bench with torque transducers for measuring torques and a test bench control system, characterized in that the test bench control system is configured to execute a method for calculating the longitudinal acceleration of a motor vehicle with the following features: - The drivetrain, body and axles of the motor vehicle are modeled as a spring-mass system, - the body, axles and drivetrain components are represented as the massed bodies of the system, and the bearings of the components and subframe of the motor vehicle are represented as the springs connecting the bodies, - On the test bench, torques are measured at the wheels of at least one axle of the drivetrain, - a force exerted on the axle at the measured torques along the length of the motor vehicle is calculated and - The longitudinal acceleration of the body resulting from excitation of the system with the force is determined.

Description

[0001] The present invention relates to a test bench for calculating the longitudinal acceleration of a motor vehicle. State of the art

[0002] For measurements on the PiL or R2R test bench, longitudinal accelerations are calculated based on the measured wheel torques. Wheel torques are converted into a longitudinal force using the Pacejka or another suitable tire model. This longitudinal force is then converted into the longitudinal acceleration of the vehicle using the known mass.

[0003] However, during road measurements, drivetrain-induced excitations, such as transient behavior due to clutch binding, are transmitted via the axles to the subframe and body. This transmission behavior cannot currently be modeled with sufficient accuracy; in particular, transient states are hardly represented.

[0004] There are known approaches to addressing this problem through physical excitation using actuators, but their application is limited to complete vehicle test benches (R2R) and cannot be transferred to powertrain test benches. Furthermore, such methods involve significant setup and calibration costs.

[0005] AT514006A2 discloses a method for vehicle load simulation when driving onto or off a curb, wherein a roller test stand with at least one test stand roller is used for the vehicle load simulation, the angle of rotation of a wheel of the vehicle located on the test stand roller is determined, the position of the wheel on a virtual curb is calculated as a function of the angle of rotation, a curb load moment corresponding to this position is formed and a road load moment acting on the wheel is supplemented by the curb load moment.

[0006] The document “Dynamics of Motor Vehicles” (Mitschke, Manfred; Wallentowitz, Henning; 5th edition; Springer, Wiesbaden, pp. 547–559, 2014, ISBN 978-3-658-05067-2) discloses a method for calculating the longitudinal acceleration of a motor vehicle with the following steps: i) the drivetrain, body, and axles of the motor vehicle are modeled as a spring-mass system; ii) a force exerted on the axle along the length of the motor vehicle is calculated, and the longitudinal acceleration of the body resulting from excitation of the system with the force is determined.

[0007] Document DE 103 34 043 A1 discloses a test rig for the stationary testing of vehicles. In this rig, rollers are connected to a load machine, and the load or drive power is measured by a force or torque measuring device located between the load machine and at least one roller. Furthermore, the load machine is integrated into the roller or one of the rollers. An internal part of the roller is designed as an annular rotor of a self-excited electric machine. Coaxially to this annular rotor, an equally annular stator with rotating field windings is arranged inside the roller. This stator is pivotally mounted on a rotating shaft of the roller and is supported against a support frame via the force measuring device.

[0008] Document US 5,447,060 A describes a chassis test rig specifically designed for road simulation. A torque sensor is integrated into the roller assembly so that the torque signal is not affected by bearing friction. The outer element of the torque sensor is rigidly connected to the roller, while the inner element is rigidly connected to the roller shaft. Disclosure of the invention

[0009] The invention provides a test bench for calculating the longitudinal acceleration of a motor vehicle according to the claim.

[0010] A fundamental idea of ​​the invention lies in the development of a model that transmits the excitation of the drive via the axle to the body with sufficient accuracy, and also takes into account other vibration-prone systems in the body.

[0011] One advantage of this solution is that it allows for easy integration into the test bench control system and is completely independent of the test bench manufacturer. Furthermore, within the context of left-handed development, it also enables application on PiL test benches, ensuring continuous validation of drivability. It also eliminates the need for calibration and setup on the test bench and allows for more efficient use of test bench resources.

[0012] The use of a method not according to the invention is possible on both complete vehicle (R2R) and powertrain-in-the-loop (PiL) test benches. It allows for a significant increase in the accuracy of the representation of longitudinal acceleration in transient states (see Fig. 3).

[0013] This approach makes it possible, for example, for the first time to transfer the validation of shift quality from the road to the test bench. Longitudinal acceleration serves as the primary evaluation criterion. Beyond validating shift quality, this approach also enables a significantly more precise validation of drivability on the test bench, e.g., engine and transmission applications. Brief description of the drawings

[0014] An embodiment of the invention is described in Fig. 4 is shown and is described in more detail below. Fig. 1 and Fig. Figures 2 show a comparison of the longitudinal accelerations due to preloaded clutches between test bench (11) and road (12). Fig. Figure 3 shows the longitudinal acceleration in unsteady states according to the inventive method (10), conventional calculation (11) and driving test (12). Embodiments of the invention

[0015] According to the invention, the drivetrain, body and axles of the motor vehicle are simplified and modeled as a spring-mass system. How Fig. As illustrated in Figure 4, the body, axles and assemblies - i.e., transmission and engine - of the drive train are represented as bodies with mass, while the bearings of the assemblies and subframe of the motor vehicle are represented as singular spring / damper systems connecting these bodies of the resulting three-mass oscillator, the parameterization of which requires in-depth knowledge of the vehicle.

[0016] During test bench operation, torques are measured at the wheels of at least one axle of the drive train, the force exerted on the axle along the length of the vehicle at the measured torques is calculated, and the longitudinal acceleration of the body resulting from the excitation of the system with the force is determined.

Claims

[1] Test bench with torque transducers for measuring torques and a test bench control system, characterized by , that the test bench control is configured to execute a procedure for calculating the longitudinal acceleration of a motor vehicle with the following characteristics: - The drivetrain, body and axles of the motor vehicle are modeled as a spring-mass system, - the body, axles and drivetrain components are represented as the massed bodies of the system, and the bearings of the components and subframe of the motor vehicle are represented as the springs connecting the bodies, - On the test bench, torques are measured at the wheels of at least one axle of the drivetrain, - a force exerted on the axle at the measured torques along the length of the motor vehicle is calculated and - The longitudinal acceleration of the body resulting from excitation of the system with the force is determined.

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