An Integrated Self-Powered Wheel- Speed Monitoring System Utilizing Piezoelectric–Electromagnetic-Triboelectric Hybrid Generator

In the intelligent vehicle systems, vehicle speed information is collected and transmitted by wheel speed sensors, which is related to the safety, energy efficiency, and comfort of the vehicle. This work proposes an integrated self-powered wheel-speed monitoring system (SWMS), which can achieve real-time sensing and wireless transmission multifunction by employing an integrated piezoelectric–electromagnetic-triboelectric hybrid generator (PETHG) for harvesting the mechanical energy from rotating wheels. In particular, the triboelectric generation unit in SWMS includes an energy-channel (E-TENG) and a sensing-channel (S-TENG), the E-TENG was used for harvesting the rotational energy of the wheel, and the S-TENG was used for monitoring the rotation speed of the wheel. In the experimental test, the output performance of the hybrid generator was assessed using a rotating electrical motor to simulate different wheel speed inputs. At 600 rpm, the instantaneous power of the hybrid generator reached 168.2 mW, which can power the low-power microcontrol unit (MCU) and waveform conversion circuit in the established wheel speed monitoring system. The wheel speed recorded by MCU was compared with actual rotation speed yielding an average error rate of only 1.9%. This work offers a solution for self-powered sensors for intelligent driving.

I. Introduction

The Internet of Things (IoT) approach has gained momentum in connecting everyday objects to the Internet and facilitating machine-to-human and machine-to-machine communication with the physical world. The wireless sensor network is the core of the IoT [1]. In recent years, intelligent networked vehicles have been able to share and monitor information, such as road conditions and vehicle driving status through IoT technology, in which sensors play a major role [2], [3], [4]. In vehicle systems, the monitoring of wheel speed is related to the safety, energy saving, and comfort of the automobiles. For example, in the anti-lock braking system of the car, it is necessary to automatically adjust the pressure of the brake pump according to the wheel speed information detected by the wheel speed sensor to avoid wheel locking and improve the safety role of the car [5]. In addition, wheel speed information is required for the operation of the automotive dynamic control system (ADCS), automotive electronic stability program (ESP), and automatic transmission control system, so it is very important to accurately detect the wheel speed of the vehicle in real time for the control and monitoring of the vehicle. However, the traditional wheel speed sensors should be supplied by the additional battery, and other power-consuming modules are required to work during data transmission, which makes the chemical battery need to be replaced periodically and cannot provide a more continuous power source to supply the sensing system. Therefore, it is necessary to build a self-powered wheel speed monitoring system that monitors the wheel speed of automobiles in real time.