Diagnostic and control method for a vehicle system

#The present description relates generally to control and diagnostic strategies in a vehicle system. More particularly, the present description relates to techniques for fault monitoring in a driveline system.

#Different sets of vehicle driveline conditions may lead to unintended behaviors. The unintended behaviors may include unwanted changes in vehicle acceleration and other undesirable kinematic behavior. For instance, a number of conditions can cause erroneous clutch settings that may lead to unwanted vehicle braking or movement in an unintended direction. In an attempt to avoid these unwanted behaviors, previous vehicle control and diagnostic systems have guarded against unintended behaviors by verifying actual settings against requested settings. When the mismatch in the settings is too large, actions are taken to discontinue or altogether avoid the unintended behaviors.

#U.S. Pat. No. 7,980,981 B2 to Kawaguchi et al. discloses a vehicle system including an automatic transmission that includes a plurality of clutches and brakes to change the gear ratio of the transmission. The system determines whether or not at least one or more of the clutches is brought into unintended engagement. Said determination is carried out analyzing vehicle deceleration and an intended gear ratio and an actual gear ratio.

#FIG. 1 is a schematic depiction of a vehicle system with a controller.

#FIG. 2 is a flow chart depicting an example control and diagnostic process of a vehicle system.

#FIG. 3 is a flow chart depicting another example control and diagnostic process of a vehicle system.

#The following description relates to a driveline component control strategies and fault diagnostics in a vehicle system. The system uses efficient logic for confident and independent fault diagnosis to reduce the likelihood of undesired driveline and more generally vehicle behaviors. The system uses independent controllers, or processing units, to implement nominal driveline control strategies and diagnostic (e.g., fault detection) strategies. As such, diagnostic routines may be executed independently from nominal control strategies and is not influenced by the nominal control strategies. Thus, a diagnostic controller determines a fault condition of a driveline component and triggers a fault state to operate the driveline component in a fault mode, overriding the nominal control settings of a driveline controller. The separation of control and diagnostic logic allows for independent alteration of control and fault applications, providing increased system adaptability and diagnostic reliability. This adaptability may result in efficient integration of fault diagnostics into an existing control architecture, as well as the ability to independently update or otherwise alter diagnostic and/or control architecture in a wide variety of driveline platforms.

#To achieve the diagnostic efficiency gains, the diagnostic routine compares actual component settings to thresholds that are anticipated to cause unwanted kinematic vehicle behavior (e.g., unintended acceleration/deceleration or vehicle movement in an unintended direction). The thresholds may be stored in a lookup truth table and correspond to values which have a high likelihood of causing the unwanted kinematic behavior. This comparison may disregard intended settings to achieve greater accuracy in the fault diagnosis, using lower computational intensive calculations than previous strategies. The diagnostic system may further determine if a fault duration exceeds a fault tolerance time that may be correlated to the component's reaction time. By using the fault duration in this manner, the diagnostic accuracy may be further increased. Mapping the diagnostic thresholds to values that have a greater chance of causing unwanted vehicle movement to trigger a fault, as opposed to triggering a fault whenever component settings deviate from intended values, drives down the likelihood of incorrect fault generation. Situations where the vehicle is superfluously placed in the fault state, which may impact vehicle performance, may be avoided.

#FIG. 1 illustrates a high-level vehicle system architecture that uses different controllers to execute a nominal control module and a diagnostic module. This configuration allows for diagnostic routines to be executed independently from, and in tandem with, nominal control strategies, resulting in a highly reliable setup that is easily implemented for a variety of driveline setups. FIGS. 2 and 3 depict flow charts illustrating methods for diagnosing mechanical component faults. FIG. 4 shows a lookup truth table for identifying unauthorized clutch conditions. FIG. 5 illustrates ranges of operating conditions that may indicate a mechanical component fault. FIGS. 6 and 7 depict timing diagrams of use-case control and diagnostic strategies for identifying fault conditions and operating a driveline component in a fault state, to avoid unwanted vehicle behavior.