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1. Definition 2. Functional Requirements 3. Syntax 4. Semantics

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:

2.1 Confirm actuation results

  • Provide the time of response.
  • Provide achieved vehicle velocity.
  • Provide the brake state (e.g., braking, released, fault).

2.2 Provide actuator‑level physical feedback

The Brake shall report measurements currently available or emerging in modern brake systems:

  • Brake Pressure (hydraulic or actuator pressure) — standard in ABS/ESC modules.
  • Brake Force Applied — available in electromechanical brakes and EMB caliper sensors.
  • Brake Temperature (pad or disc) — sensors now survive 600–825°C.
  • Brake Pad Wear Level — multi‑stage sensors can estimate remaining life.
  • ABS / Traction‑Control Activation State — standard ESC information.

2.3 Support motion‑modelling and stability

  • Wheel Slip Ratio (derived from wheel‑speed sensors).
  • Brake Event Duration (start–stop of braking event).
  • Brake Torque Estimate (when provided by EMB motor current).

2.4 Support fault detection and lifecycle management

  • Error Codes / Diagnostic States
  • Overheat Flags
  • Sensor Degradation Alerts
  • Line Pressure Irregularity Flags

2.5 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

Label Description
Header Brake Response Header – “CAV‑BRR‑Vx.y”.
BrakeID Identifier of the Brake producing the response.
BrakeResponseTime Time at which the Brake issued the response.
VelocityReached Vehicle velocity at BrakeResponseTime.
BrakeState Operational state (e.g., Applied, Released, Fault, Overheated).
BrakePressure Hydraulic or actuator pressure reported by the brake module. Modern ESC/ABS systems include pressure sensors.
BrakeForceApplied Estimated brake force from caliper/actuator sensors, available in Electromechanical Brakes (EMB).
BrakeTemperature Brake disc/pad temperature. Modern sensors tolerate >600°C and up to 825°C.
BrakePadWear Remaining pad life or wear percentage derived from single‑stage or multi‑stage pad wear sensors.
ABSActivation Whether ABS/ESC is currently modulating brake pressure.
WheelSlipRatio Slip ratio derived from wheel‑speed sensors and vehicle‑speed estimation; used for stability control.
BrakeTorqueEstimate Estimated braking torque (e.g., via EMB motor current or force/position models).
BrakeEventDuration Duration (ms) of the braking event from start to response time.
ErrorCode Diagnostic code reporting detected faults or anomalies.
OverheatFlag Boolean indicating thermal limits exceeded.
SensorDegradationFlag Flag for detection of pad wear sensor or temperature sensor deterioration.
LinePressureAnomaly Indicates irregular hydraulic pressure behaviour.
DataExchangeMetadata
DataExchangeMetadatad is needed. Not all DEM fields are required.
Trace Provenance trace providing Source and Time per AIF rules.
DescrMetadata Optional descriptive metadata.