Platform Health Management (PHM) - AUTOSAR Adaptive Platform

Supervision Types

Type	How It Works	Detects
Alive	App reports checkpoint periodically; PHM checks regularity	Deadlock, infinite loop, complete process hang
Deadline	PHM measures time between two named checkpoints (A → B); must be within [min, max]	Timing violation, task overrun
Logical	App traverses a defined graph of checkpoints; PHM checks correct ordering	Incorrect control flow, skipped initialisation steps

💡 ASIL Contribution

Each supervision type contributes to the Diagnostic Coverage (DC) metric in the ISO 26262 safety case. Alive supervision achieves ~90% DC for deadlock faults; Logical supervision adds coverage for incorrect execution paths.

Checkpoint Reporting

C++phm_checkpoint.cpp

#include <ara/phm/supervised_entity.h>

ara::phm::SupervisedEntity supervision(
    ara::core::InstanceSpecifier{"SensorApp/SensorSupervision"});

// In main loop — called once per cycle to prove liveness (Alive supervision)
supervision.ReportCheckpoint(
    ara::phm::CheckpointId{1}); // checkpoint ID matches manifest

// For Deadline supervision: report both start and end checkpoints
supervision.ReportCheckpoint(ara::phm::CheckpointId{10}); // start
DoHeavyComputation();
supervision.ReportCheckpoint(ara::phm::CheckpointId{11}); // end

PHM → SM Notification

When a supervision failure is detected, PHM invokes the State Manager's registered RecoveryAction callback. The action type (kRestartProcess, kRestartFunctionGroup, kResetMachine) is declared in the PHM manifest per supervised entity.

JSONphm_manifest_excerpt.json

{
  "supervisedEntities": [
    {
      "shortName": "SensorSupervision",
      "processRef": "SensorApp",
      "aliveSupervision": {
        "expectedAliveIndications": 10,
        "minMargin": 2,
        "maxMargin": 3,
        "aliveReferenceCycle": 100
      },
      "recoveryNotification": {
        "recoveryAction": "kRestartFunctionGroup",
        "functionGroupRef": "SensorFG"
      }
    }
  ]
}

Hardware Watchdog Integration

On safety-relevant ECUs, PHM drives an external hardware watchdog. PHM sends a periodic token (toggle) to the watchdog driver. If any alive supervision failure stops PHM from generating the token, the hardware watchdog triggers a forced ECU reset — a mechanism outside software control.

PHM–Watchdog Architecture

  Application
      │  ReportCheckpoint()
      ▼
  PHM (Adaptive FC)
      │  all supervisions OK → sends watchdog token every 50 ms
      ▼
  WdgIf / WdgDriver (or kernel driver)
      │  token received within window
      ▼
  External Watchdog IC
      │  timeout expired → triggers RESET line
      ▼
  ECU Hardware Reset

Summary

PHM provides the liveness guarantee that safety analyses require. Alive supervision is the minimum viable configuration; Deadline and Logical supervision add precision. Hardware watchdog integration completes the chain from software supervision to hardware-enforced recovery.

🔬 Deep Dive — Core Concepts Expanded

This section builds on the foundational concepts covered above with additional technical depth, edge cases, and configuration nuances that separate competent engineers from experts. When working on production ECU projects, the details covered here are the ones most commonly responsible for integration delays and late-phase defects.

Key principles to reinforce:

Configuration over coding: In AUTOSAR and automotive middleware environments, correctness is largely determined by ARXML configuration, not application code. A correctly implemented algorithm can produce wrong results due to a single misconfigured parameter.
Traceability as a first-class concern: Every configuration decision should be traceable to a requirement, safety goal, or architecture decision. Undocumented configuration choices are a common source of regression defects when ECUs are updated.
Cross-module dependencies: In tightly integrated automotive software stacks, changing one module's configuration often requires corresponding updates in dependent modules. Always perform a dependency impact analysis before submitting configuration changes.

🏭 How This Topic Appears in Production Projects

Project integration phase: The concepts covered in this lesson are most commonly encountered during ECU integration testing — when multiple software components from different teams are combined for the first time. Issues that were invisible in unit tests frequently surface at this stage.
Supplier/OEM interface: This is a topic that frequently appears in technical discussions between Tier-1 ECU suppliers and OEM system integrators. Engineers who can speak fluently about these details earn credibility and are often brought into critical design review meetings.
Automotive tool ecosystem: Vector CANoe/CANalyzer, dSPACE tools, and ETAS INCA are the standard tools used to validate and measure the correct behaviour of the systems described in this lesson. Familiarity with these tools alongside the conceptual knowledge dramatically accelerates debugging in real projects.

⚠️ Common Mistakes and How to Avoid Them

Assuming default configuration is correct: Automotive software tools ship with default configurations that are designed to compile and link, not to meet project-specific requirements. Every configuration parameter needs to be consciously set. 'It compiled' is not the same as 'it is correctly configured'.
Skipping documentation of configuration rationale: In a 3-year ECU project with team turnover, undocumented configuration choices become tribal knowledge that disappears when engineers leave. Document why a parameter is set to a specific value, not just what it is set to.
Testing only the happy path: Automotive ECUs must behave correctly under fault conditions, voltage variations, and communication errors. Always test the error handling paths as rigorously as the nominal operation. Many production escapes originate in untested error branches.
Version mismatches between teams: In a multi-team project, the BSW team, SWC team, and system integration team may use different versions of the same ARXML file. Version management of all ARXML files in a shared repository is mandatory, not optional.

📊 Industry Note

Engineers who master both the theoretical concepts and the practical toolchain skills covered in this course are among the most sought-after professionals in the automotive software industry. The combination of AUTOSAR standards knowledge, safety engineering understanding, and hands-on configuration experience commands premium salaries at OEMs and Tier-1 suppliers globally.