Definition
Functional Requirements
Syntax
Semantics
Conformance
Performance
1 Definition
Brake Response is the information produced by a physical Brake and transmitted to the Motion Actuation Subsystem (MAS) of a Connected Autonomous Vehicle (CAV). In autonomous‑vehicle operation, Brake Response carries not only the result of executing a Brake Command but also additional physical‑system measurements required for:
- motion‑prediction and route replanning,
- safety monitoring and hazard response,
- diagnostic and maintenance scheduling,
- subsystem explainability.
2 Functional Requirements
The Brake Response shall enable the Motion Actuation Subsystem to:
- Confirm actuation results — provide the time of response, the achieved vehicle velocity, and the brake state (e.g., braking, released, fault).
- Provide actuator‑level physical feedback — report Brake Pressure (hydraulic or actuator pressure), Brake Force Applied, Brake Temperature (pad or disc), Brake Pad Wear Level, and ABS/Traction‑Control Activation State.
- Support motion‑modelling and stability — provide Wheel Slip Ratio, Brake Event Duration, and Brake Torque Estimate.
- Support fault detection and lifecycle management — provide Error Codes, Overheat Flags, Sensor Degradation Alerts, and Line Pressure Irregularity Flags.
- Support explainability — all fields shall be available to higher‑level AIMs for explainability and trace generation.
3 Syntax
https://schemas.mpai.community/CAV2/V2.0/data/BrakeResponse.json
4 Semantics
Table 1 specifies the semantics of the Brake Response Data Type.
| Label | Type | Req. | Description |
|---|---|---|---|
| Header | string (CAV-BRR-V2.0) | Yes | Brake Response Header – Standard CAV-BRR-Vx.y |
| MInstanceID | string | Identifier of the M-Instance (Virtual Space) associated with this Brake Response. | |
| UEnvironmentID | string | Identifier of the U-Environment (Real Space) associated with this Brake Response. | |
| BrakeResponseID | string | Yes | Unique identifier of this Brake Response instance. |
| BrakeResponseTime | Simple Time | Time this Brake Response was produced. | |
| BrakeResponseSpaceTime | Simple Time | Space/Time where/when this Brake Response applies. | |
| BrakeID | string | Yes | Identifier of the Brake producing this response. |
| BrakeState | Brake States | Yes | Operational state of the Brake (e.g., Applied, Released, Fault, Overheated). One of: Normal, WheelStopped, Braking, Released, Hold, EmergencyBraking, ABSActive, TractionControlActive, RegenerativeBraking, Overheated, Degraded, Fault, Unavailable, PreCharge, PressureBuildUp, PressureDecay, HydraulicSaturation, LowBrakeFluid, PadWearLimit, CaliperStuck, LinePressureAnomaly, ElectronicActuatorFault, SelfTest, ServiceMode. |
| VelocityReached | number | Vehicle velocity (m/s) at BrakeResponseTime. | |
| BrakePressure | number | Hydraulic or actuator pressure reported by the brake module (bar or Pa). | |
| BrakeForceApplied | number | Estimated caliper or actuator force applied (N). | |
| BrakeTorqueEstimate | number | Brake torque estimate derived from caliper force or EMB motor current (N·m). | |
| BrakeTemperature | number | Brake pad or disc temperature (°C). | |
| BrakePadWear | number | Remaining pad life as a fraction from 0.0 (fully worn) to 1.0 (new). | |
| ABSActivation | boolean | Indicates whether ABS/ESC is currently modulating brake pressure. | |
| WheelSlipRatio | number | Slip ratio derived from wheel-speed sensors and vehicle-speed estimation. | |
| BrakeEventDuration | number | Duration (ms) of the braking event from start to response time. | |
| OverheatFlag | boolean | Indicates that brake thermal thresholds have been exceeded. | |
| SensorDegradationFlag | boolean | Indicates degraded pad-wear or brake-temperature sensor behaviour. | |
| LinePressureAnomaly | boolean | Indicates hydraulic or actuator pressure irregularities. | |
| ErrorCode | string | Fault or diagnostic code reported by the brake subsystem. | |
| DataXMData | Data Exchange Metadata | MPAI-PTF Data Exchange Metadata providing provenance, authorisation, legal, security, and confidence information associated with this Brake Response in a trusted data exchange context. | |
| DescrMetadata | string | Human-readable descriptive metadata of the Brake Response (plain text, max 2048 characters). |
5 Conformance Testing
Data conform to the Brake Response Data Type when they validate against its schema. If the schema references other schemas, data referencing a secondary schema shall also validate against that schema, if present, and conform with the Qualifier, if present.
