Commercial vehicle testing under toughest conditions

Simulating global operating conditions

“Apt sensor technology plays an essential role in accurate load detection for the tuning and quality control of our vehicles,” states one of the manufacturer’s test engineers. Each vehicle prototype undergoes a rigorous testing program. “It starts on our test track for measuring vibration behaviors. Here we can simulate a wide variety of conditions to reflect those around the world.”

The vehicle is driven over a wide range of diverse road types, surfaces and obstacles including speed bumps, potholes, railroad crossings or cobblestones. Through inclines, declines, curves including wet and slippery road sections, all sections and maneuvers get evaluated for maximum permissible stress loads.

Vibration loads are recorded at critical points across the vehicle. The aim is both to check whether actual loads come within the scope of calculations and to obtain reference data for subsequent operational load reproduction tests in the company’s testing lab. Inertial sensors from ASC record exact accelerations and directions, rotational movements, maximum speeds and reversal points. From that, further relevant forces and complex mechanical stress loads are calculated, to which components get exposed intensively on the test bench later, over extended periods.

ASC 5525MF: the ‘all-round accelerometer’

“The sensors we use must be extremely robust and versatile,” states the engineer. Triaxial capacitive accelerometers of the ASC 5525MF (Medium Frequency) range are particularly suitable. With measuring ranges from ±2 to ±200g and a wide frequency response from 0 to 7 kHz (±3 dB), they accurately capture low and medium frequencies.

As many typical maneuvers performed by commercial vehicles require measuring ranges up to a maximum of 100 Hz. “Without the ability to accurately capture low frequency responses, we wouldn’t be able to replicate real-world conditions and loads during test drives.”

The robust ASC 5525MF design ensures strong resistance to repeated shock loads of up to 6,000g. It comes embedded in a reliable stainless-steel housing of protection class IP67. All this and its flexible installation options make the analog accelerometer ideal for accurate data acquisition under highly variable, sometimes unexpected and adverse terrain, environmental and climatic conditions.

Weeks of fine-tuning with capacitive measurement technology

After the test drives have been completed, the vehicles undergo a second phase of thorough testing on test benches. To simulate continuous loads over their entire service life, they get “shaken” for weeks on servo-hydraulic test rigs. This replicates the movements and loads that will impact the vehicle in real-world use.

“In so-called operational load reproduction tests, innovative sensors are used to mirror the actual operating profile,” explains the head of the manufacturer’s measurement and calibration laboratory. “From these test series, the overall stress on individual components and the entire vehicle gets extrapolated to thousands of additional miles.” Which saves the producer a lot of time and wear, personnel, fuel and other costs.

These automated 24/7 reproduction tests can take up to 400 hours and beyond. Based on the insights, the material strength of critical components is optimized and the effectiveness of suitable measures to reduce the impact of stress and increase service life – such as vibration damping measures – gets analyzed and adjusted.

Inertial sensors of outstanding precision and stability

The accurate measurement of linear acceleration is critical for the valid recording and evaluation of stress events. “We need precise accelerometers that are easy to handle and install,” says the measurement expert. “They must be robust and deliver stable results over the long term. Water, dust or dirt must not affect these sensors.”

ASC 5525MF accelerometers meet the requirements of intense vehicle testing exceptionally well. Their compact design facilitates quick installation and removal – a fundamental advantage in NVH (noise, vibration, harshness) and test bench applications.

Based on proven MEMS technology and the capacitive measurement principle, they enable the detection of even the smallest acceleration forces in three degrees of freedom across a wide frequency response. This ensures maximum accuracy and stable long-term results. The ASC 5525MF series is, therefore, popular for use in test settings, vehicle and road surface monitoring and diverse additional applications.