KA-RacIng Team of the Karlsruhe Institute of Technology KA-RacIng Team of the Karlsruhe Institute of Technology | HBM

Smart Chassis: Cornering at a Higher Speed Due to Force Sensors Integrated Into the Pushrod

KA-RaceIng uses torque vectoring to be able to always operate a vehicle at its limit. The torque fed to each wheel is varied and adjusted to the maximum tyre force that can be transmitted in the respective situation. To achieve this, a self-developed control system ensures permanent driver assistance. Implementing such a control system requires knowledge of the tyres’ behaviour as well as determining the influencing factors that enable the software to detect the current driving status. Here, the vehicle's wheel loads play a crucial role. The change in the vertical forces to the wheel, which occur when the vehicle is moving, is very important in determining the tyre’s potential. The greater the wheel load, the more force a tyre can transfer to the tarmac. Therefore, it is very important to have precise values for the wheel loads to ensure a well-functioning control system. The use of U9C load cells in the vehicle's pushrods allows the forces transferred via the vehicle's spring-damper system to be determined precisely. These forces can be used to determine the so-called elastic proportion of the wheel loads in any driving situation and convert it into absolute wheel loads based on an accurate vehicle model. This precise measuring method enables the vehicle to always deliver its maximum performance. Please find below two photos of the installation at the vehicle and an example plot of the pushrod force (in N) over time.

Installation
Copyright: Patrick Wintermantel
Installation
Copyright: Patrick Wintermantel
Pushrod force plot (in N)
Rear axle aero map

Fundamental changes to the overall vehicle in the 2020 season have all been aimed at significantly improving aerodynamics. Therefore, the entire aerodynamics concept was simulated using computational fluid dynamics (CFD). To validate this simulation using real-world values, the so-called aero maps are created from the values gathered from the simulation and the measured values. These aero maps compare the vehicle's geometric properties with its aerodynamic properties. The U9C load cells provide the values for calculating the balance of the rear axle, which are shown in the aero map below.

Other sensors used in a wide range of applications

Furthermore, ultra-thin sensors such as the KMR/20kN force washer enable the implementation of a concept for continuous force-controlled recuperation. It involves measuring the force applied by the foot directly behind the holder for the ball of the driver's foot and, thus, allows to benefit from the great advantage of an electric vehicle—recuperation—with the lowest possible weight of the brake pedal.

To determine the stiffness of the vehicle as a whole and validate the stiffness of the individual components, we examine component assemblies in different levels of detail. The chassis stiffness can be determined using a semi-vehicle test bench. Using the KMD/50kN, all suspension components combined are loaded and measured in the direction of toe and camber.

About KA-RaceIng

As we know, racing always aims at being faster, lighter, and more innovative.

As a Formula Student team of the Karlsruhe Institute of Technology, KA-RaceIng has been following this approach since 2006 and is now developing the 15th generation of racing cars.

Monitoring the entire product life cycle through sensors is enormously important and helpful, especially for building prototypes in the context of Formula Student: from implementing the concept idea through validating it on various test benches to supporting the driver on the track.  For this reason, we use various HBM force transducers such as the U9C force sensors, the 20kN force washer and the 50kN force sensor.

Thank you for your support and cooperation, even at special times!

Copyright: FSG Schulz

 

For more information, visit the website of the KA-RaceIng team at: https://www.ka-raceing.de/