Application of Capacitive Pressure Sensing Technology in Automobile Testing

Innovative sensing technology has indeed accelerated the development of the entire automotive industry. With the emergence of a wide range of advanced sensing technologies, while enhancing the driver or passenger experience, the most important issue is still automotive safety and reliability. In this regard, capacitive touch pressure sensing technology may be helpful. This technology can accelerate the process of automotive testing and development in many ways.

Brake pedal test

A Japanese automaker uses a static test method in the research process of automobile brake pedals. The automaker uses capacitive touch pressure sensing technology in the Pressure Profile Systems (PPS), divides the brake friction pad into two parts, and adheres a capacitive pressure sensor at the joint.

Through this method, automakers have discovered that the brake pressure distribution in a stopped vehicle is completely different from the brake pressure distribution in a moving vehicle after applying the same braking force. This is due to the difference in torque applied to the brake caliper by the centrifugal rotor when the vehicle is moving/stationary.

Unlike resistive sensors (based on heat), capacitive pressure sensors work based on external forces, which means they can withstand greater shear stress than resistive sensors during operation. Based on this feature, capacitive pressure sensors can be installed in real vehicles for further testing.

Undoubtedly, the data obtained from real vehicle testing is more valuable, but a new problem arises. The researchers found that as the temperature of the brake caliper rises, it will be impossible to obtain correct test data because each sensor has a certain degree of thermal sensitivity. They embedded a heat compensation system in the thermocouple center of the capacitive sensor to solve this problem.

Tire tread measurement

Before a tire is actually equipped on a car, it needs to undergo a lot of safety and technical index tests. Through capacitive pressure sensing technology, tire and car manufacturers can conduct more comprehensive dynamic testing of tires, which is more effective than any traditional method currently used.

A piston is installed at each of the four wheels of the car. The four pistons push the tire up and down through a hydraulic device to simulate bumpy road conditions in reality. During the elastic dynamic test, the capacitive tread pressure sensor can collect data on subtle changes in tread performance during the simulated test and take high-resolution images through related equipment; while the traditional tire tread testing method can obtain high-resolution images, its efficiency is low and it is more suitable for static tread testing.

The Pressure Curve System detects tread changes at a frequency of 220 Hz using nearly 2,000 sensors distributed across the tread. This configuration retains the resolution of traditional tread sensors and improves the resolution rate, allowing for more accurate detection of tread performance in bumpy and rapidly changing road conditions.

Tire pressure detection

From brake pedal testing and tread performance testing, we can see that capacitive touch pressure sensing technology is widely used in automotive testing. But in addition, it can also directly benefit consumers, such as when it is used for tire pressure testing.

Capacitive touch pressure sensing devices can be installed in garages or vehicle safety inspection stations. When a car passes the corresponding sensing device, the system calculates whether the tire pressure is normal based on the pressure distribution when the tire contacts the device. When the tire pressure is too high, the sensor in the middle of the sensing device will be under greater pressure, and when the tire pressure is too low, the sensors at both ends will be under greater pressure. Related technical applications can also be seen in the four-wheel alignment of the vehicle.

Whether it is tire pressure detection or positioning detection, its accuracy is directly related to the fuel economy of the vehicle, and the car owner will also be affected by it. The above three examples all show that the application of capacitive touch pressure sensing technology in automobiles will bring great benefits.