From test bench to test track – ika relies on WheelWatch

Ever since cars have been built, engineers have worked on the design and development of various chassis components to enhance vehicle comfort and at the same time improve active safety. The Chassis Division at the Institute for Motor Vehicles (ika) of the RWTH Aachen University is also committed to these working principles. Since 2013 the ika has successfully deployed WheelWatch for their examinations of the driving dynamics of vehicles.

In cooperation with car manufacturers and their suppliers, the Institute for Motor Vehicles (ika) of the RWTH Aachen University focuses on specific issues, making an acknowledged contribution to finding solutions to present-day challenges. Its engineers master all steps of chassis development: from design and simulation through to detail design, prototype construction as well as functional and endurance testing in test drives and on different test benches. fka Forschungsgesellschaft Kraftfahrwesen mbH Aachen is a research institute founded by ika. For more than 30 years it has been conducting research for international OEMs and suppliers, and offers consulting, construction, simulation, design, prototyping and experimental testing from a single source. Both institutes work closely together.

To further develop the measurement technology used, an optical high-speed measurement system was required which could provide all important measurements for determining axle parameters such as track, camber inclination and shifts in the coordinate system of a vehicle. The system had to be appropriate both for test track and test bench, as well as for any other measuring tasks required. Today, ika uses the AICON measurement system WheelWatch for these tasks.

Non-contact measurement of high speed wheel motion on the test track

The impact of different types of bearings on both axles and wheel positions as well as drivability is for example one of the questions that can be answered by an effects analysis. To do so, a variety of maneuvers are driven where for example the vertical dynamics are examined through straight exits on bad roads. To measure the lateral dynamics, standardized driving maneuvers such as the VDA (German Automobile Industry Alliance) lane change (according to ISO 3888-2) are performed, but also open-loop maneuvers such as stationary circle and sinusoidal steering.

To do so, an axle is fitted with the WheelWatch system. A camera is mounted on each wheel to be measured which simultaneously captures the fender as a stationary reference system and the wheel as a second rigid body. Specially coded measurement targets on the bodywork identify the vehicle coordinates system. The wheel is signalized with an adapter in lightweight construction (CRP). The complete setup including referencing, wheel axis calibration and system setup takes less than one hour per vehicle axle.

In addition to the WheelWatch system, the test vehicle has more measurement equipment on board: for example, sensors which record forces and acceleration; a steering robot and centrifugal platforms are often also deployed. The different sensors are connected via various interfaces (such as CAN, Ethernet, analog) to the data acquisition system and measurement data are synchronously merged and stored centrally, in real-time or post-processing, according to need.

Kinematic analysis on the test bench

The kinematics and elastokinematics of vehicles and axis modules are measured on the kinematic and compliance test rig of ika: wheel behavior, wheel loads, track, camber inclination, longitudinal, lateral and vertical forces as well as the shifting of wheel contact points are some of the values recorded. The analyses also address the question of the impact which individual components have on the axle. A loaded condition of the vehicle is simulated, i.e. the vehicle is placed in a defined spring travel position. The tests are performed with a mechanical wheel replacement system and WheelWatch.

Parallel to the measurement, ika also works with WheelWatch on the test bench with its own recording system of forces and travels. A measuring computer controls the test bench. The 6D data (X, Y, Z, 3 rotations) captured by WheelWatch are sent in real time via the Ethernet interface to the central data recording system. Extensive post processing is therefore not required. This makes the work with WheelWatch and the integration of the system into more complex measuring processes simple and convenient.

New system - new comfort

Thomas Horrmann, manager Benchmarking and Function Development, supervises the work with WheelWatch. He is extremely happy with the decision in favor of AICON: "We have integrated the WheelWatch system very well into our existing testing environment. The fast setup allows us to save 30% time compared to our previous measurement system. WheelWatch makes test drives much easier to implement; now we can determine absolute track and camber angles, and not only relative values as before. What's more, the new system is very stable."

WheelWatch is the system with the highest available accuracy for static and dynamic vehicle parameter monitoring on the market. In driving tests, the system impresses with its robustness and reliability in data acquisition even under harsh environmental conditions. WheelWatch is part of AICON's modular MoveInspect Technology system concept that can be adapted to any individual measurement task. The system will therefore also be used in the future for the measurement of other components and parts. For the ika and fka research teams, the WheelWatch system has proved itself today as a long-term solution for universal  measurement tasks.

We thank the Institute for Motor Vehicles (ika) of RWTH Aachen University and fka Forschungsgesellschaft Kraftfahrwesen mbH for their kind support!