Definition
Functional Requirements
Syntax
Semantics
Conformance
Performance
1 Definition
A Brake Command is issued by the Motion Actuation Subsystem (MAS) to a Brake of the physical vehicle. It expresses:
- The desired target velocity after a specified time, as defined by the MPAI‑CAV standard.
- 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:
- Specify the braking objective — provide the target velocity to reach after a specified time and designate which BrakeID should execute the command.
- Control actuator characteristics — support additional controllable parameters for modern braking systems (hydraulic, electro‑hydraulic, and electromechanical): BrakePressureTarget, BrakeForceTarget, BrakeTorqueTarget, DecelerationTarget.
- Support complex AV braking modes — EmergencyBrakeFlag, RegenerativeBrakeFraction (EVs), ABSAllow.
- Improve MAS planning and explainability — provide optional confidence, constraints, priority, and ramp‑time fields.
- 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/V2.0/data/BrakeCommand.json
4 Semantics
Table 1 specifies the semantics of the Brake Command Data Type.
| Label | Type | Req. | Description |
|---|---|---|---|
| Header | string (CAV-BRC-V2.0) | Yes | Brake Command Header – Standard CAV-BRC-Vx.y |
| MInstanceID | string | Identifier of the M-Instance (Virtual Space) associated with this Brake Command. | |
| UEnvironmentID | string | Identifier of the U-Environment (Real Space) associated with this Brake Command. | |
| BrakeCommandID | string | Yes | Unique identifier of this Brake Command instance. |
| BrakeCommandTime | Simple Time | Time this Brake Command was produced. | |
| BrakeCommandSpaceTime | Simple Time | Space/Time where/when this Brake Command applies. | |
| BrakeID | string | Yes | Identifier of the Brake to which this command is addressed. |
| BrakeCommand[] | object [] | Yes | Set of braking command parameters. |
| BrakeCommand[]. |
number | Yes | Expected velocity (m/s) at the end of BrakeCommandTime. |
| BrakeCommand[]. |
Simple Time | Yes | Time after which TargetVelocity should be reached. |
| BrakeCommand[]. |
number | Target hydraulic or actuator line pressure (bar or Pa). | |
| BrakeCommand[]. |
number | Target clamp or actuator force (N). | |
| BrakeCommand[]. |
number | Target brake torque (N·m). | |
| BrakeCommand[]. |
number | Target longitudinal deceleration (m/s²). | |
| BrakeCommand[]. |
number | Fraction [0..1] of braking to be provided by the regenerative system. | |
| BrakeCommand[]. |
boolean | Indicates whether ABS is allowed to intervene during this command. | |
| BrakeCommand[]. |
boolean | Indicates that this is an autonomous emergency braking (AEB) request. | |
| BrakeCommand[]. |
Simple Time | Ramp-up/down time for achieving braking targets. | |
| DataXMData | Data Exchange Metadata | 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 | string | Human-readable descriptive metadata of the Brake Command (plain text, max 2048 characters). |
5 Conformance Testing
Data conform to the Brake Command 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.
