| name | safety-liveness-control-contracts |
| description | Design layered control architectures (LCAs) using safety-liveness decomposition via heterogeneous assume-guarantee contracts. Use when: (1) designing hierarchical control systems with discrete planning + continuous execution, (2) enforcing safety constraints while achieving long-horizon objectives, (3) co-designing multi-layer controllers with formal guarantees, (4) building reference governor bridges between MPC planners and low-level controllers. Based on arXiv:2605.04222.
|
Safety-Liveness Control Contracts
Design hierarchical layered control architectures using the safety-liveness
decomposition framework from arXiv:2605.04222.
Core Architecture
+------------------------------------------+
| Discrete-Time Planner (Liveness) |
| - MPC planner |
| - Long-horizon objectives |
| - Vertical refinement contracts |
+------------------------------------------+
| Reference Governor Bridge |
| - Timing compatibility |
| - Inter-layer coordination |
+------------------------------------------+
| Continuous-Time Executor (Safety) |
| - ISS low-level controller |
| - Invariance enforcement |
| - Safety constraints |
+------------------------------------------+
Safety-Liveness Decomposition
- Safety: enforced by invariance at continuous-time layer
- Liveness: achieved through refinement at discrete-time layer
Assume-Guarantee Contracts
Each layer specifies: (1) Assumptions, (2) Guarantees, (3) Refinement conditions
Vertical Refinement
Discrete planner outputs refined to continuous inputs via timing-compatibility.
Implementation Pattern
class SafetyLivenessController:
def __init__(self, mpc_planner, iss_controller, reference_governor):
self.planner = mpc_planner
self.controller = iss_controller
self.bridge = reference_governor
def step(self, state, goal):
ref_traj = self.planner.plan(state, goal)
safe_ref = self.bridge.filter(ref_traj, state)
control = self.controller.compute(state, safe_ref)
return control
Key Design Principles
- Compositional separation: Each layer designed independently
- Specification preservation: Contracts guarantee properties when interconnected
- Heterogeneous time scales: Discrete + continuous coexist
- No naive input filtering: Use structured refinement
Pitfalls
- Do not use naive input-filtering — breaks compositional guarantees
- Timing compatibility must be verified
- Safety sets must be control-invariant
- Liveness requires progress metrics
