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rail-signalling

rail signalling

ETCS, CBTC

SystemTechniques · 14Primitives · 48 rail-signalling Clock synchronizationdistributed · medium: Estimate a clock's offset from four timestamps, filter out queueing noise, and steer the clock smoothly; NTP gets about a millisecond, PTP with hardware timestamps under a microsecond.›Fault tree analysisembedded · medium: Write the unwanted top event as AND/OR logic over component failures, reduce it to minimal cut sets, then compute its probability and each failure's share.›Model checking and formal proofembedded · medium: Exhaustively explore a model's reachable states (or prove its invariants with a solver or proof assistant) to find rule violations with a shortest counterexample trace.›Interlocking logicembedded · medium: Railway route setting, locking, flank protection and release as verified boolean logicMovement authority braking curvesembedded · medium: Train supervision: compute braking curves from movement authority and enforce speed limitsSafety-critical coding standardsembedded · medium: Which rule sets (MISRA C, CERT C, JPL Power of Ten, Rust lint subsets) apply when software must not fail, what they forbid, and how to enforce them in CI.›Safety monitor architectureembedded · medium: Independent doer/checker safety monitor that forces a safe state when the main channel misbehavesBFS and DFSgraphs · low: The two basic graph traversals; BFS gives hop distances and levels, DFS gives discovery/finish order for cycles, components and topological order.›Redundancy votingembedded · low: N-modular redundancy and MooN voting (2oo3, TMR) with discrepancy detectionEnd to end protection e2eembedded · low: Per-message counter, ID and CRC over a black channel to detect loss, repetition, corruption, delayWatchdog timerembedded · low: A hardware down-counter that resets the chip unless software proves, in time and in a plausible pattern, that it is still healthy.›Time triggered schedulingembedded · low: Static cyclic schedules where every task and message has a precomputed time slotKalman filterrobotics · low: Optimal recursive estimator for a linear system with Gaussian noise: fuses a motion model with noisy measurements into a state estimate plus its covariance.›Message authentication codes (HMAC,…security · low: A keyed short tag proving a message is unmodified and came from a key holder; pick HMAC, CMAC, KMAC or a one-time polynomial MAC by what primitive you already have.›Hierarchical state machinesystems · low: Nest states so a substate inherits its parent's reactions and only overrides what differs, with ordered entry and exit actions along the path.›PID controllerrobotics · low: Drive a measured value to a setpoint with three terms on the error: proportional, integral, derivative. The default feedback loop for motors, heaters, drones and gimbals.›Phase-locked loop (digital)signal-processing · low: Feedback loop that locks a local oscillator to the phase and frequency of an input tone; the core of carrier recovery, clock recovery and GNSS tracking.›Robust statisticsstatistics · low: Location and scale estimates (median, MAD, trimmed mean, Huber M-estimator) that stay correct when a minority of the data is garbage.›Binary decision diagramsoptimization · low: A reduced ordered BDD stores a Boolean function as a shared DAG that is unique per variable order, so equivalence is one integer compare and counting is one pass.›Swiss tabledata-structures · low: Open-addressing hash table that filters 8-16 slots at once with 1-byte hash tags and SIMD, giving fast lookups at 87.5 % load.›Fixed-rate control loopembedded · low: Run a controller at an exact period using absolute deadlines and a fixed dt, so jitter never accumulates and the math stays valid.›Spline interpolationnumerics · low: Linear, bilinear/trilinear and cubic spline interpolation on grids and tablesVelocity motion profilesrobotics · low: Trapezoidal and S-curve (jerk-limited) velocity profiles for point-to-point moves+ 7 more techniques+ 32 more primitives

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