Calculations

Calculations

• On-delay timer

  The elapsed time and output of a TON block.

  ET = min(now − t₀, PT); Q = ET ≥ PT

  Controller standard functions and integer types std.js Every app
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• Up counter

  The count and output of a CTU block.

  CV ← CV + 1 on a rising edge while CV < 32767; Q = CV ≥ PV

  Controller standard functions and integer types std.js Every app
  Exact

• Round to nearest, ties to even

  The rounding used when a real is converted to an integer.

  nearest whole number; a tie goes to the even neighbor

  Controller standard functions and integer types std.js Every app
  Exact

• Arithmetic functions

  ABS, SQRT, LN, LOG, EXP, the trigonometric functions, MIN, MAX, LIMIT, TRUNC, SHL and SHR.

  SQRT, LN, LOG, EXP, SIN and the rest from Math; SHL: x × 2ⁿ; SHR: ⌊x ÷ 2ⁿ⌋; TRUNC toward zero

  Controller standard functions and integer types std.js Every app
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• Type conversions

  REAL_TO_INT, INT_TO_REAL, BOOL_TO_INT, TIME_TO_REAL and the other A_TO_B functions.

  to an integer type: round to nearest (ties to even), then wrap; to a real type: unchanged

  Controller standard functions and integer types std.js Every app
  64-bit

• Probability of a basic event

  The probability of an event from a fixed value, a failure rate and time, a test interval, or repair data.

  failed by t: 1 − e^(−λt); tested every τ: 1 − (1 − e^(−λτ)) ÷ (λτ), or λτ ÷ 2 below 1e-9; repairable: MTTR ÷ (MTTF + MTTR)

  Fault trees and reliability block diagrams logic.js Every app
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• At least k of n events

  The probability that k or more of a set of independent events occur.

  the distribution of the count, built one event at a time, summed from k up

  Fault trees and reliability block diagrams logic.js Every app
  64-bit

• AND, OR and voting gates

  The probability of a gate from its inputs when no event is repeated.

  AND: Π pᵢ; OR: 1 − Π (1 − pᵢ)

  Fault trees and reliability block diagrams logic.js Every app
  64-bit

• Top event with repeated events

  The probability of the top event when the same event appears in several places.

  P = p_x × P(tree | x occurs) + (1 − p_x) × P(tree | x does not)

  Fault trees and reliability block diagrams logic.js Every app
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• Cut set probabilities and bounds

  The probability of each minimal cut set and two bounds on the top event.

  rare event: min(1, Σ P(cut set)); upper bound: 1 − Π (1 − P(cut set))

  Fault trees and reliability block diagrams logic.js Every app
  64-bit

• Importance measures

  How much each event matters to the top event.

  Birnbaum = P(top | p = 1) − P(top | p = 0); Fussell–Vesely = (P − P₀) ÷ P; RAW = P₁ ÷ P; RRW = P ÷ P₀

  Fault trees and reliability block diagrams logic.js Every app
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• Reliability of a component

  The chance a block still works at the mission time.

  R = e^(−λt); Weibull: R = e^(−(t ÷ η)^β)

  Fault trees and reliability block diagrams logic.js Every app
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• Block diagram reliability

  The reliability of series, parallel and k-of-n arrangements.

  series = OR of failures; parallel = AND; reliability = 1 − P(failure)

  Fault trees and reliability block diagrams logic.js Every app
  64-bit

• Mean time to failure

  The mean life of a system that is not repaired.

  MTTF = ∫ R(t) dt by Simpson's rule, 4000 steps, to the time R ≤ 1e-9

  Fault trees and reliability block diagrams logic.js Every app
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• Common-cause split

  The independent and the shared part of a failure rate.

  independent = λ (1 − β); common = λ β

  Fault trees and reliability block diagrams logic.js Every app
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• Gamma function

  Γ(x), used for the mean life.

  Lanczos approximation, g = 7, 9 coefficients; reflection below 0.5

  Weibull life data weibull.js Every app
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• Weibull distribution functions

  Failure probability, reliability, density, hazard, quantile, mean and B-life.

  F = 1 − e^(−(t ÷ η)^β); quantile = η (−ln(1 − F))^(1 ÷ β); mean = η Γ(1 + 1 ÷ β)

  Weibull life data weibull.js Every app
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• Log-likelihood

  How well a shape and scale explain the failure and suspension times.

  Σ failures ln f(t) + Σ suspended ln R(t)

  Weibull life data weibull.js Every app
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• Maximum-likelihood fit

  Shape, scale and their confidence bounds from failure times, with suspensions.

  g(β) = Σ tᵝ ln t ÷ Σ tᵝ − 1 ÷ β − mean ln t = 0; η = (Σ tᵝ ÷ r)^(1 ÷ β)

  Weibull life data weibull.js Every app
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• Median ranks

  The plotting position of each failure, adjusted for suspended units.

  F = (rank − 0.3) ÷ (n + 0.4); rank increment = (n + 1 − previous rank) ÷ (1 + units at or after this one)

  Weibull life data weibull.js Every app
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• Rank regression fit

  Shape and scale from a straight line on the Weibull plot.

  β = S_xy ÷ S_xx on (ln t, ln(−ln(1 − F))); η = e^(−a ÷ β)

  Weibull life data weibull.js Every app
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• Duration drawn for a task

  One trial's duration of a task given as minimum, most likely and maximum.

  u < f: min + √(u (max − min)(mode − min)); else max − √((1 − u)(max − min)(max − mode)); duration = round(v)

  Schedule risk (Monte Carlo) simulate.js Every app
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• Finish percentiles, mean and spread

  The finish day at each confidence level over all trials.

  P = sorted[⌈p × n⌉ − 1]; mean = Σ ÷ n; sd = √(Σ (x − mean)² ÷ n)

  Schedule risk (Monte Carlo) simulate.js Every app
  64-bit

• Criticality and sensitivity

  The share of trials in which a task was critical, and the correlation of its duration with the finish.

  criticality = times critical ÷ n; sensitivity = Σ (d − d̄)(F − F̄) ÷ √(Σ (d − d̄)² × n × sd²)

  Schedule risk (Monte Carlo) simulate.js Every app
  64-bit

• Source signals

  Step, ramp, sine and pulse sources as functions of time.

  sine: offset + amp × sin(2π f t + phase); ramp: v₀ + (v₁ − v₀)(t − t₀) ÷ (t₁ − t₀)

  Lumped system models model.js Every app
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• Resistive element laws

  The flow through a resistor, damper, orifice, diode or user law for a given difference across it.

  resistor: i = v ÷ R; orifice: i = v ÷ √(K √(v² + ε²)); diode: i = Is (e^(v ÷ nVt) − 1), a straight line above 40 nVt

  Lumped system models model.js Every app
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• Storage elements

  Capacitors, masses, tanks, inductors and springs: what they store and how it enters the equations.

  capacitive: i + d(C v)/dt = 0; inductive: v + d(L i)/dt = 0; spring: L = 1 ÷ k

  Lumped system models model.js Every app
  64-bit

• Reported flow through an element

  The current, heat flow, flow or force reported for an element.

  the element's law at the solved state; diode: Is (e^(min(v, 40 nVt) ÷ nVt) − 1)

  Lumped system models model.js Every app
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• Dense linear solve

  Solves the Newton step.

  Gaussian elimination with partial pivoting

  Lumped system models solve.js Every app
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• Newton iteration

  Finds the state that satisfies the equations at one time.

  J_ij = (F_i(x + h e_j) − F_i(x − h e_j)) ÷ 2h, h = 1e-7 × max(|x_j|, 1); stop when |Δxᵢ| ≤ rtol |xᵢ| + atol + 1e-11 × max(1, largest |x|)

  Lumped system models solve.js Every app
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• Operating point

  The steady state, or the state set by the given initial values.

  one Newton solve from zero

  Lumped system models solve.js Every app
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• One time step

  The state one step later.

  trapezoid: (2 ÷ h)(S − S₀) − Ṡ₀ + g = 0; backward Euler: (1 ÷ h)(S − S₀) + g = 0

  Lumped system models solve.js Every app
  64-bit

• Step-size control

  Chooses the time step from an estimate of the error, when adaptive stepping is on.

  err = max |x(two half steps) − x(one step)| ÷ (rtol |x| + atol), ÷ 3 for the trapezoid; h ← h × clamp(0.9 err^(−1/3), 0.2, 5)

  Lumped system models solve.js Every app
  64-bit

• Value between stored times

  A node value at a time between two computed points.

  y = y₀ + (y₁ − y₀)(t − t₀) ÷ (t₁ − t₀)

  Lumped system models solve.js Every app
  64-bit

• Parameter expressions

  The value of a parameter written as an expression, such as 2*3.3e3.

  numbers, parameters, + − × ÷ ^, brackets, pi

  Lumped system models modelica.js Every app
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• Thermal conductance to resistance

  A thermal conductor from a model file as the engine's thermal resistance.

  R = 1 ÷ G

  Lumped system models modelica.js Every app
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• Center, radius and sweep of a bulge arc

  The circle an arc segment lies on, from its two end points and its bulge.

  θ = 4·atan(b); k = (c ÷ 2) ÷ tan(θ ÷ 2); center = midpoint + k × left normal; r = |p − center|

  Arcs from bulges and three points geom.js

  • TakeoffCraft
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• Arc through three points

  The bulge of the arc that starts at one point, passes through a second and ends at a third.

  center = circumcenter(p, m, q); sweep = atan2(q − center) − atan2(p − center) ± 2π; b = tan(sweep ÷ 4)

  Arcs from bulges and three points geom.js

  • TakeoffCraft
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• Segment lengths of a run and their sum

  The length of each segment of an open run, and the run's total.

  L = Σ segLength(pᵢ₋₁, pᵢ, bᵢ₋₁)

  Arcs from bulges and three points geom.js

  • TakeoffCraft
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• Snap to the nearest 45° direction

  Moves a picked point onto the nearest of the eight 45° directions from the point before it, keeping its distance along that direction.

  u = round(cos, sin of k·45° to 12 decimals); p′ = base + u × ((p − base)·u)

  Arcs from bulges and three points geom.js

  • TakeoffCraft
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• Circle as two half-circle arcs

  Stores a drawn circle as two points on opposite sides of the center, each starting a half-circle arc.

  r = |edge − c|; points (c.x + r, c.y) and (c.x − r, c.y), b = 1 each

  Arcs from bulges and three points takeoffcraft.js

  • TakeoffCraft
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• Arc reshaped by dragging its middle

  Recomputes a segment's bulge when its arc handle is dragged.

  Arcs from bulges and three points takeoffcraft.js

  • TakeoffCraft
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• Length and area shown while drawing

  The length of the last segment, the run so far, the area and perimeter so far, or a circle's radius and area, shown in the status line as the pointer moves.

  length = L × k; area = A × k²; circle preview = π·r²

  Arcs from bulges and three points takeoffcraft.js

  • TakeoffCraft
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• Check distance between two points

  The real distance between two picked points, in feet-inches, decimal feet and meters.

  ft = |b − a| × k; m = ft × 0.3048

  Arcs from bulges and three points takeoffcraft.js

  • TakeoffCraft
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• Dropping repeated points when a mark is finished

  Removes a point that sits on the one before it, as a double-click adds.

  drop pᵢ when |pᵢ − previous kept point| ≤ 2 ÷ zoom

  Arcs from bulges and three points takeoffcraft.js

  • TakeoffCraft
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• Arcs broken into chords

  Replaces each arc of a run or outline by points on the arc, at most one step apart.

  k = max(2, ⌈|θ| ÷ step⌉); pⱼ = center + r·(cos tⱼ, sin tⱼ), tⱼ = a₀ + θ·j ÷ k

  Outline checks: inside, crossing, cut-outs geom.js

  • TakeoffCraft
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• Point inside an outline

  Whether a point lies inside a closed outline.

  Outline checks: inside, crossing, cut-outs geom.js

  • TakeoffCraft
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• Two segments cross or touch

  Whether two straight segments cross or touch.

  d₁ = (d − c) × (a − c), …; cross when d₁, d₂ lie beyond ±s on opposite sides and d₃, d₄ too

  Outline checks: inside, crossing, cut-outs geom.js

  • TakeoffCraft
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• Outline crosses itself

  Whether a closed outline crosses itself.

  Outline checks: inside, crossing, cut-outs geom.js

  • TakeoffCraft
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• Outline that cannot be measured

  Refuses an outline with too few points, one that crosses itself, or one with no area.

  Outline checks: inside, crossing, cut-outs geom.js

  • TakeoffCraft
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