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Definition
Functional Requirements
Syntax
Semantics
Conformance Testing
Performance Assessment

1      Definition

A Brake Command is issued by the Motion Actuation Subsystem (MAS) to a Brake of the physical vehicle. It expresses:

  1. The desired target velocity after a specified time, as defined by the MPAI‑CAV standard.
  2. Additional actuator‑level command parameters needed by autonomous‑vehicle braking systems, such as brake pressure targets, brake force/torque targets, ABS‑related constraints, and emergency‑braking flags.

2      Functional Requirements

Brake Command shall enable the MAS to:

  1. Specify the braking objective — provide the target velocity to reach after a specified time and designate which BrakeID should execute the command.
  2. Control actuator characteristics — support additional controllable parameters for modern braking systems (hydraulic, electro‑hydraulic, and electromechanical): BrakePressureTarget, BrakeForceTarget, BrakeTorqueTarget, DecelerationTarget.
  3. Support complex AV braking modes — EmergencyBrakeFlag, RegenerativeBrakeFraction (EVs), ABSAllow.
  4. Improve MAS planning and explainability — provide optional confidence, constraints, priority, and ramp‑time fields.
  5. Support future and hybrid brake‑by‑wire systems — the Command shall be compatible with EMB, hydraulic, and hybrid brake systems.

3      Syntax

https://schemas.mpai.community/CAV2/V1.1/data/BrakeCommand.json

4      Semantics

Table 1 – Semantics of the Brake Command Data Type

Label
Description
Header Brake Command Header – Standard “CAV‑BRC‑Vx.y”.
MInstanceID Identifier of the M-Instance (Virtual Space) associated with this Brake Command.
UEnvironmentID Identifier of the U-Environment (Real Space) associated with this Brake Command.
BrakeCommandID Unique identifier of this Brake Command instance.
BrakeCommandTime Time this Brake Command was produced.
BrakeCommandSpaceTime Space/Time where/when this Brake Command applies.
BrakeID Identifier of the Brake to which this command is addressed.
BrakeCommand[] Set of braking command parameters.
    – TargetVelocity Expected velocity (m/s) at the end of BrakeCommandTime.
    – BrakeCommandTime Time after which TargetVelocity should be reached.
    – BrakePressureTarget Target hydraulic or actuator line pressure (bar or Pa).
    – BrakeForceTarget Target clamp or actuator force (N).
    – BrakeTorqueTarget Target brake torque (N·m).
    – DecelerationTarget Target longitudinal deceleration (m/s²).
    – RegenerativeBrakeFraction Fraction [0..1] of braking to be provided by the regenerative system (EVs).
    – ABSAllow Indicates whether ABS is allowed to intervene during this command.
    – EmergencyBrakeFlag Indicates that this is an autonomous emergency braking (AEB) request.
    – RampTime Ramp-up/down time for achieving braking targets.
DataXMData MPAI-PTF Data Exchange Metadata providing provenance, authorisation, legal, security, and confidence information associated with this Brake Command in a trusted data exchange context.
DescrMetadata Human-readable descriptive metadata of the Brake Command (plain text, max 2048 characters).

5      Conformance Testing

A Data instance conforms with Brake Command (CAV‑BRC) if:

  1. The Data validates against the Brake Command’s JSON Schema.
  2. All Data in the Brake Command’s JSON Schema:
    1. Have the specified type.
    2. Validate against their JSON Schemas.
    3. Conform with their Data Qualifiers.

6      Performance Assessment

Not part of this specification.

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