Method of detecting low tire pressure by comparing wheel speeds
First Claim
1. A method of operation for a vehicle low tire pressure warning system based on tire speed comprising the steps of:
- measuring tire speeds and periodically determining a current pattern of relative tire speeds;
determining raw offset values by aggregating the current patterns of relative tire speeds determined during an initial period of operation;
after a given number of said current patterns of relative tire speeds have been aggregated, initiating a convergence period of operation in which said raw offset values are adjusted based on the current pattern of relative tire speeds determined during said convergence period, and low tire pressure is detected when a computed difference between a determined current pattern of relative tire speeds and the adjusted offset values exceeds a first under-inflation threshold amount;
after said adjusted offset values stabilize, storing said adjusted offset values as final offset values, and initiating a monitoring period of operation during which low tire pressure is detected when a computed difference between a determined current pattern of relative tire speeds and the stored final offset values exceeds a second under-inflation threshold amount which is lower than said first under-inflation threshold amount; and
issuing a low tire pressure warning based on the detection of low tire pressure.
2 Assignments
0 Petitions
Accused Products
Abstract
Relative speeds of wheels are measured in different speed ranges when tires are properly inflated to learn offsets due to parameters not related to pressure. The offsets are used during leak monitoring to detect a wheel speed pattern which is abnormal due to pressure drops. During learning periods, monitoring for large pressure drops only is permitted using preliminary offset values. When learning is complete in a given speed range high sensitivity monitoring is invoked. Special sensitivity of large pressure drops shortly after vehicle start up allows a brief period of flat detection. A plurality of leak events for a given wheel are accumulated to signal a warning, with large pressure drops accumulating faster than small drops for progressive sensitivity and greater robustness.
72 Citations
8 Claims
-
1. A method of operation for a vehicle low tire pressure warning system based on tire speed comprising the steps of:
-
measuring tire speeds and periodically determining a current pattern of relative tire speeds; determining raw offset values by aggregating the current patterns of relative tire speeds determined during an initial period of operation; after a given number of said current patterns of relative tire speeds have been aggregated, initiating a convergence period of operation in which said raw offset values are adjusted based on the current pattern of relative tire speeds determined during said convergence period, and low tire pressure is detected when a computed difference between a determined current pattern of relative tire speeds and the adjusted offset values exceeds a first under-inflation threshold amount; after said adjusted offset values stabilize, storing said adjusted offset values as final offset values, and initiating a monitoring period of operation during which low tire pressure is detected when a computed difference between a determined current pattern of relative tire speeds and the stored final offset values exceeds a second under-inflation threshold amount which is lower than said first under-inflation threshold amount; and issuing a low tire pressure warning based on the detection of low tire pressure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
Specification