TU Darmstadt Racing Team e.V. – Mobile Data Acquisition Using Strain Gauges and the QuantumX From HBM

The TU Darmstadt Racing Team (DART) is a group of university students from the Technical University of Darmstadt that have been participating in the Formula Student international design competition since 2005. Students from various disciplines have been independently working on developing and producing an electrically powered Formula racing car and have been competing against other teams from all over the world year after year.

Driven by the passion for motorsport, a new racing car will also be developed in the 2020 season. In September of 2019, DART, with the support of HBM, launched a project to validate and analyze the chassis using HBM equipment. To detect the forces acting in the wishbones and tie rods during driving, strain gauges (SG) were installed and the test vehicle was equipped with appropriate electronics. Future developments and the optimization of the chassis will be based on the collected data.


Strain Gauges

Type XY7 strain gauges were used for the tests and connected in a Poisson half-bridge to allow the absorption of tensile and compressive forces while ensuring temperature compensation. These types of wishbones and tie rods are designed exclusively for the absorption of tensile and compressive forces. After their installation, the strain gauges were wired with special measuring leads and calibrated by a Darmstadt-based institute. The strain gauges were protected using the SG250 covering agent by HBM and a cable from HBM (order no.: 4-3301.0151) was selected as the measuring cable. Furthermore, the strain gauges were provided with strain relief and protected with masking tape. 


Measurement Electronics

The MX1615B Quantum X module and the CX22 data recorder were used to acquire and record the data. The modules were fixed in the vehicle and synchronized with each other via Firewire. A total of 13 channels were used in parallel.


Results

After the setup and commissioning of all the hardware and software, test runs were carried out on an airfield where different test tracks were set up. To test as closely as possible to the conditions given by Formula Student and to identify the maximum loads, chicanes with fast load changes as well as wide curves were driven.

For example, the maximum forces recorded during the test in the right-hand tie rod were equivalent to 1702 N for tensile force and 961 N for compressive force. Comparing the data obtained by the measurements to those provided by the camera allowed the evaluation of which load case these values corresponded to. The maximum tensile force was measured during oversteering in a fast left-hander and the maximum compressive force in a wide right-hander at high speed.

 

The forces were also recorded when steering while stationary, with a maximum force of 1300 N being measured.

Due to the support of HBM, DART was able to collect further measurement data which are considered as the basis for further development. In the coming season, these results will be used, for example, to optimize all the wishbones and tie rods and design a steering actor for autonomous driving for the Formula Student Driverless competition.

Prospects

More tests using HBM equipment are planned for the future. For example further optimization iterations on the wishbones and tie rods, the development of completely new concepts with wishbones made of composite materials, and the strain or deformation analysis of other chassis parts are conceivable.

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