Definition
Functional Requirements
Syntax
Semantics
Conformance Testing
Performance Assessment
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/V1.1/data/BrakeResponse.json
4 Semantics
| Header | Brake Response Header – Standard “CAV‑BRR‑Vx.y”. |
| MInstanceID | Identifier of the M-Instance (Virtual Space) associated with this Brake Response. |
| UEnvironmentID | Identifier of the U-Environment (Real Space) associated with this Brake Response. |
| BrakeResponseID | Unique identifier of this Brake Response instance. |
| BrakeResponseTime | Time this Brake Response was produced. |
| BrakeResponseSpaceTime | Space/Time where/when this Brake Response applies. |
| BrakeID | Identifier of the Brake producing this response. |
| BrakeState | Operational state of the Brake (e.g., Applied, Released, Fault, Overheated). |
| VelocityReached | Vehicle velocity (m/s) at BrakeResponseTime. |
| BrakePressure | Hydraulic or actuator pressure reported by the brake module (bar or Pa). |
| BrakeForceApplied | Estimated caliper or actuator force applied (N). |
| BrakeTorqueEstimate | Brake torque estimate derived from caliper force or EMB motor current (N·m). |
| BrakeTemperature | Brake pad or disc temperature (°C). |
| BrakePadWear | Remaining pad life as a fraction from 0.0 (fully worn) to 1.0 (new). |
| ABSActivation | Indicates whether ABS/ESC is currently modulating brake pressure. |
| WheelSlipRatio | Slip ratio derived from wheel-speed sensors and vehicle-speed estimation. |
| BrakeTorqueEstimate | Estimated braking torque via EMB motor current or force/position models (N·m). |
| BrakeEventDuration | Duration (ms) of the braking event from start to response time. |
| ErrorCode | Fault or diagnostic code reported by the brake subsystem. |
| OverheatFlag | Indicates that brake thermal thresholds have been exceeded. |
| SensorDegradationFlag | Indicates degraded pad-wear or brake-temperature sensor behaviour. |
| LinePressureAnomaly | Indicates hydraulic or actuator pressure irregularities. |
| DataXMData | 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 | Human-readable descriptive metadata of the Brake Response (plain text, max 2048 characters). |
5 Conformance Testing
A Data instance conforms with Brake Response (CAV‑BRR) if:
- The Data validates against the Brake Response’s JSON Schema.
- All Data in the Brake Response’s JSON Schema:
- Have the specified type.
- Validate against their JSON Schemas.
- Conform with their Data Qualifiers.
6 Performance Assessment
Not part of this specification.
