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.