Brake-by-wire Simulator Circuit Diagnostic Method
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Solution Overview
Problem
The existing brake-by-wire systems in vehicles are complex and difficult to diagnose, requiring multiple valves and sensors to function correctly, making fault identification challenging.
Innovation Solution
A vehicle braking system with a master cylinder, a simulator circuit, and a brake pressure generator, where a controller establishes a diagnostic circuit to check the relationship between piston retraction and brake fluid pressure, allowing for the isolation of the braking circuit from the simulator circuit and enabling continued operation in brake-by-wire mode by determining if the pressure decrease is within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a full-power brake system (brake-by-wire) is implemented, then the braking force is generated without direct mechanical connection from the brake pedal, but the system complexity increases significantly requiring many valves and sensors
Solution Approach 1:
The patent combines the simulator circuit and braking circuit into a single hydraulic circuit that can operate in different modes. The isolation valve allows the same circuit to function as either a simulator circuit (when closed) or a braking circuit (when open), eliminating the need for separate, redundant circuits and reducing overall system complexity.
Solution Approach 2:
The hydraulic circuit is designed to serve multiple functions: it can operate as a simulator circuit during normal brake-by-wire operation, or be reconfigured as a braking circuit when faults are detected. The isolation valve enables this multi-functionality by allowing the circuit to be dynamically reconfigured between different operational modes.
2Reliability
If multiple valves and sensors are used in the brake-by-wire system, then the braking function is achieved, but fault diagnosis becomes difficult
Solution Approach 1:
The system performs preliminary diagnostic actions by monitoring the relationship between master cylinder pressure and brake pressure during normal operation. The controller continuously checks whether the pressure relationship falls within expected parameters, enabling early detection of faults before they lead to system failure.
Solution Approach 2:
The system uses feedback from pressure sensors to monitor the relationship between master cylinder pressure and brake pressure. When the relationship deviates from expected parameters, the controller receives feedback and can diagnose faults in the braking circuit, enabling proactive maintenance and improving diagnostic capability.
3Ease of repair
If the simulator circuit is isolated from the braking circuit, then fault diagnosis is simplified, but the system cannot continue operating in brake-by-wire mode
Solution Approach 1:
The system dynamically reconfigures the hydraulic circuit based on diagnostic results. When faults are detected in the simulator circuit, the isolation valve opens to reconfigure the circuit as a braking circuit, allowing the system to adapt its structure in real-time to maintain operational reliability while isolating the faulty components.
Solution Approach 2:
The system changes the operational parameters of the hydraulic circuit by switching the isolation valve between closed and open positions. This parameter change transforms the circuit from simulator mode to braking mode, enabling continued operation with modified configuration when faults are detected.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution simplifies fault diagnosis and ensures continued brake-by-wire operation by determining the operational status of the simulator circuit, allowing for effective brake fluid pressure generation and maintaining vehicle safety.
Implementation Method 1
a brake pressure generator, including a strokable piston, separate from the brake pedal
Implementation Method 2
A pressure sensor is operable in at least one vehicle configuration to be in fluid communication with both the simulator circuit and the brake pressure generator
Implementation Method 3
a pedal feel simulator coupled to the master cylinder output side through a switchable simulator valve, the pedal feel simulator providing a reaction force to the brake pedal
Data Source
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AI summary
A vehicle includes a brake pedal, a master cylinder, a braking circuit with a wheel cylinder, and a brake pressure generator with strokable piston. A pedal feel simulator is coupled to the master cylinder through a switchable valve, the simulator providing a reaction force. An isolation valve closes to isolate the braking circuit from the master cylinder and the simulator circuit. A controller is programmed to connect the simulator circuit with an outlet of the brake pressure generator, and to stroke and retract the piston at a designated diagnostic time. The controller observes a pressure decrease as the piston retracts and checks whether the pressure-decrease to piston-retraction relationship is within a predetermined acceptable range for continued operation of a brake-by-wire mode in which the master cylinder is coupled to the simulator circuit and decoupled from the braking circuit.