Optimizing Built-in Tire Pressure Monitoring Sensors

Optimizing Built-in Tire Pressure Monitoring Sensors

The miniature sensors that control automobile performance must be designed to work correctly when mounted directly on moving tires. They must be sensitive enough to measure while moving and durable enough to resist the elements.

Tire pressure is an unsung hero in automobile performance. Tires are in the shape they were designed to be when inflated at the correct pressure. Tires require more energy as air pressure drops. In the daily routine of driving from place to place, drivers can easily forget about maintaining their tire pressure. Unnoticed punctures can occur. It makes a huge difference to have an onboard sensor alerting the driver when more air is needed. Simulators are a great way to find the perfect design for these sensors.

Tire pressure sensors shape driving experience

Low tire pressure can lead to a substantial reduction in fuel efficiency. In addition, vehicles with low tire pressure can emit tons of greenhouse gasses into the atmosphere. Low tire pressure may also cause the vehicle to be difficult to stop or to slide on wet surfaces. Schrader Electronics, the world’s leading tire pressure monitoring company, is required by automakers to install pressure sensors on wheels to alert drivers when a tire pressure falls below the recommended pressure.

Schrader Electronics produces 45 million sensors per year and supplies sensors to major automotive companies such as GM, Ford, and Mercedes. Reliability and durability are essential for a sensor to endure road conditions over the lifetime of a vehicle. When designing the required functions, geometry, and materials, consideration is given to shocks, vibrations, humidity, temperatures, and other dynamic forces. Christabel Evans is an engineer on the Schrader Electronics Mechanical Design Team. She has used finite element simulation (FEA) to create successful and efficient tire sensors.

Designing better sensors with FEA

The Hi-Speed Snap-In tire pressure monitoring sensor, shown in Figure 1, is a product that is frequently used at Schrader. It mounts directly to the wheel assembly. This product measures tire pressure even when the vehicle is moving. The tire pressure is monitored by a sensor that emits a warning when it drops too far. This alerts the driver to stop the car and refill the tire.

Figure 1. Figure 1. Bottom: Amplification by 10x of the stress and deformation of the transmitter housing due to the centrifugal load produced by the rotating wheel.

Schrader Electronics, which has been making sensors for nearly 20 years now, wanted to improve the efficiency of product testing and design. Christabel Evans was able to convince her colleagues that a more modern approach would be better. The simulations were done using FEA, and the iteration process allowed them to reduce experimental costs and evaluate the performance of designs during development. Schrader Electronics discovered that existing FEA options were costly if they wanted it for their entire team. The Structural Mechanics module and the CAD Import module of COMSOL Multiphysics (r) were used. The first step was to compare standardized samples and simulations in order to validate the software.

Improve Sensitivity with Better Simulation Tools

Researchers began to incorporate more parameters in their simulations over time. These included dynamic forces such as centrifugal forces, environmental stresses like temperature changes, and static factors like pressure and crushing load. The Hi-Speed Snap-In TPS is a transmitter consisting of a circuit enclosed in an enclosure, attached to the stem of a valve with a cap. The valve stem is connected to the tire rim, allowing air to pass. The valve geometry of the Hi-Speed-TPMS includes a rib which helps to retain the assembly inside the rim hole.

Schrader Electronics, in Figure 1, measured the stress placed on the enclosure by outside forces such as tire fitting, shock, or vibration caused by road conditions. They also measured the deformation of the device when it was loaded. Figure 2 depicts a component designed to be used in a spin-testing machine. The part rotates at high speeds. This component was analyzed to ensure that the chosen material could handle the required load.


Evans and her team found that by analyzing multiple models at the same time, they were able to find which model worked best and refine their design. They tested different geometries and materials as well as load scenarios.

Schrader researchers could learn COMSOL Multiphysics much faster than other simulation packages. The flexibility of licensing options also made deploying the software throughout the company easier. Evans said that “COMSOL was easy to use and quick to learn. The engineers were able to pick it up immediately.”

Schrader will initially focus on growth and design but also on failure analysis. They hope to improve this development-focused approach by using simulation tools. Each new design strives to improve the driver’s comfort, environmental impact, and road safety.

Schrader Electronics’ Mechanical Engineering Department uses COMSOL by multiple teams. Andrew Herron (left to right), Sam Guist (right), Adam Wright, Christabel Evan, and Russell McKee.

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