CORRELATION ANALYSIS OF TIRE RADIUS ESTIMATION AND TIRE SLIP AS MEASURED WITH DIFFERENTIAL GPS AND WHEEL ENCODERS

Open Access
Author:
Wan, Mengxiong
Area of Honors:
Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Sean Brennan , Thesis Supervisor
  • Hosam Fathy, Faculty Reader
  • Sean Brennan, Honors Advisor
Keywords:
  • tire radius estimator
  • tire slip detection
  • kinematic model
  • recursive least square
  • encoder
  • GPS
Abstract:
The research in this thesis proposes to enhance the safety of commercial vehicles by detecting when tire slip is occurring on low-friction surfaces. Tire slip is measured by comparing the longitudinal velocity of the vehicle, as measured by a Global Positioning System (GPS), and the kinematic differential drive velocity, as measured by two rear-mounted optical encoders. During tire slip, the wheel encoders can measure a different rotational speed when compared to the longitudinal velocity measured from the GPS. In order to accurately measure the longitudinal velocity of the vehicle, as measured from the wheel encoders, an online tire radius estimator is developed utilizing measurements of longitudinal velocity and yaw rate form the GPS and wheel angular velocities measured by the optical wheel encoders. A simulation of the proposed algorithm is presented to ensure the accuracy of tire radius estimation under noisy data inputs. Experimental tests were conducted on various road conditions at the Larson Transportation Test Track, including the left side tires of the vehicle braking on a low-friction patch to experience slip, and tests on various bumps to verify the accuracy of the tire slip detection algorithm and tire radius estimator. This algorithm has successfully shown that vehicle slip can be detected and changes of tire radius can be observed, thereby potentially improving the safety of commercial vehicles.