Parking Brake Valve Functional Test via Redundant Actuation
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Solution Overview
Problem
In vehicle assemblies with pressure medium-actuated actuators, undetected errors in redundant pressure medium valves can lead to critical states due to unintentional actuation, despite redundant design, necessitating a method to reliably detect such errors.
Innovation Solution
A method where one pressure medium valve is controlled to occupy the pressure supply position while the other is not, with monitoring for reactions to determine correct or improper operation, and alternating functional tests are conducted from ignition cycle to ignition cycle, generating error messages or blocking actuation as necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two redundant pressure medium valves are provided to increase operational reliability, then the reliability of assembly actuation is improved, but undetected errors in the valves can lead to critical states due to lack of error detection
Solution Approach 1:
The patent implements preliminary error detection by performing functional tests of the pressure medium valves before critical failures can occur. The control unit alternately actuates each valve during ignition cycles to detect stuck valves in advance, preventing critical states from developing.
Solution Approach 2:
The system incorporates feedback mechanisms where the control unit monitors the response of the assembly to valve actuation. By detecting whether the assembly moves when a valve is actuated, the system receives feedback about valve functionality and can identify errors through the absence of expected responses.
2Measurement precision
If functional tests are performed on redundant pressure medium valves to detect errors, then error detection capability is improved, but the complexity of the control system increases
Solution Approach 1:
The control unit performs multiple functions: it normally controls the assembly actuator and simultaneously performs functional tests of the pressure medium valves. The same control unit and actuator are used for both operational control and diagnostic testing, eliminating the need for separate dedicated test hardware.
Solution Approach 2:
The system performs self-diagnosis by using its own components (control unit, actuators, pressure medium) to test the functionality of the pressure medium valves. The assembly itself serves as the test object and the response to actuation provides the diagnostic information, without requiring external testing equipment.
3Ease of operation
If alternating functional tests are performed from ignition cycle to ignition cycle, then driver perception of testing is minimized, but the time available for testing is limited
Solution Approach 1:
The functional tests are performed periodically at alternating ignition cycles rather than continuously or at fixed intervals. This periodic approach allows the system to complete tests during normal vehicle operation cycles while minimizing disruption and driver perception, as tests are distributed across multiple ignition events.
Data Source
AI summary
A method is provided for the operation of an assembly of a vehicle, whereas the assembly is transferable from an unactuated position into an actuated position by a pressure medium-actuated actuator if two redundant pressure medium valves both occupy a pressure supply position. For the functional test of one of the valves, a first valve is controlled to occupy the pressure supply position, and the second valve is controlled so as not to occupy the pressure supply position. If, upon this control of the two valves at the pressure medium-actuated actuator or at the assembly to be operated by the pressure medium-actuated actuator, no reaction is detected, there is a correct operation at a proper second valve. If, despite this control of the two valves, at the pressure medium-actuated actuator or at the assembly to be operated by the pressure medium-actuated actuator, a reaction is detected, there is an improper operation at a defective second pressure medium valve.