Aerodynamic Forces And Moments — Robotics/Aerodynamics
Robotics/Aerodynamics/Aerodynamic_Forces_And_Moments · 4 input / 2 output port(s) at insert · exports to Python, MATLAB, Java, Rust, C, C++, VHDL, Verilog, SystemVerilog, PLC Structured Text
Description#
The block's own DESCRIPTION_HTML, rendered verbatim — the same text the config dialog's info panel and the library navigator show. Fix a wrong sentence in the block's .cpp (R-D9), never here.
Aerodynamic Forces and Moments
Robotics / Aerodynamics
Turns non-dimensional aerodynamic coefficients into body-axis forces and moments about the centre of gravity:
F = q̄·S·[CX; CY; CZ]
M = q̄·S·[b·Cl; c̄·Cm;
b·Cn] + F × (CG − CP)
The coefficients are taken about the centre of pressure CP; the cross product carries the moment over to the centre of gravity CG, which is where the equations of motion want it. The order is F × d with d = CG − CP – the other order negates the whole transfer term.
Ports
- C – the six coefficients, a [6,1] column [CX; CY; CZ; Cl; Cm; Cn]: three force coefficients then three moment coefficients, all in body axes.
- qbar – the dynamic pressure q̄, [1,1]. A Dynamic Pressure block makes it from the velocity and density.
- CG – the centre of gravity, [3,1], in body axes.
- CP – the centre of pressure, [3,1], in the same axes and units as CG.
- F – the forces, [3,1], body axes.
- M – the moments about CG, [3,1], body axes.
Parameters
- Reference Area – S, the wing reference area.
- Reference Span – b, which scales the rolling and yawing moments Cl and Cn.
- Reference Length – c̄, the mean aerodynamic chord, which scales the pitching moment Cm.
- Sampling Time (s) – zero or less inherits the solver's rate; a positive value runs the block at that period.
Any consistent unit system works: S in m² with q̄ in Pa gives newtons, and so on. The block computes rather than judges, so a negative q̄ or reference value is used as given.
Code export
All ten targets: Python, MATLAB, Java, Rust, C, C++, VHDL, Verilog, SystemVerilog and PLC Structured Text. S, b and c̄ are inlined as constants.
The three HDL targets are genuinely synthesizable Q16.16: multiplies and adds only. Mind the range: q̄·S is the scale of every force, and a full-size aircraft's forces in newtons leave the ±32767 a Q16.16 word holds, so scale them before they arrive.
Simulink bridge
Import and export, mapped to Aerospace Blockset's
aerolibadyn/Aerodynamic Forces and Moments (drawn on two lines, and
its library name ends in a space – the path carries both). Reference
Area → S, Reference Span → b,
Reference Length → c̄ (cbar). The three
axis settings are fixed at Body (inputAxes,
outputForceAxes, outputMomentAxes): any other choice gives
the Simulink block a fifth input port, the body velocity, which this block does
not have, so such a block is reported on import rather than brought in with the
wrong ports. The Simulink block defines no SampleTime (measured), so a
positive Sampling Time (s) stays on this side and is reported.
Notes
- Algebraic and stateless: every output depends on this sample alone.
- Not linear – products of two inputs – so there is no state space, and model reduction correctly declines to merge it.
- Verified against R2026a: at C = [0.3 −0.2 0.5 0.04 −0.07 0.02], q̄ = 1234.5, CG = [0.4 −0.1 0.2], CP = [0.9 0.05 −0.15], S = 2.5, b = 3.1, c̄ = 0.7, both blocks give F = [925.875 −617.25 1543.125] and M = [398.12625 −1246.845 −256.15875].
Code facts#
| Fact | Value |
|---|---|
| registered type | Robotics/Aerodynamics/Aerodynamic_Forces_And_Moments |
| family | Robotics/Aerodynamics |
| solver environment class | ICoreBlock_0_Robotics_1_Aerodynamics_2_Aerodynamic_Forces_And_Moments |
| source | src/ICoreBlocks/ICoreBlockLibrary/Blocks/Robotics/Aerodynamics/Aerodynamic_Forces_And_Moments/ICoreBlock_0_Robotics_1_Aerodynamics_2_Aerodynamic_Forces_And_Moments.cpp |
| header | src/ICoreBlocks/ICoreBlockLibrary/Blocks/Robotics/Aerodynamics/Aerodynamic_Forces_And_Moments/ICoreBlock_0_Robotics_1_Aerodynamics_2_Aerodynamic_Forces_And_Moments.h |
| default size on canvas | 150 × 110 px |
| ports at insert | 4 in, 2 out |
| code generators implemented | Python, MATLAB, Java, Rust, C, C++, VHDL, Verilog, SystemVerilog, PLC Structured Text |
Ports#
| # | Direction | Signal type | Description label |
|---|---|---|---|
| 1 | in | ICoreDouble | C |
| 2 | in | ICoreDouble | qbar |
| 3 | in | ICoreDouble | CG |
| 4 | in | ICoreDouble | CP |
| 5 | out | ICoreDouble | F |
| 6 | out | ICoreDouble | M |
Ports the constructor creates. A block whose port list changes with its configuration adds or removes ports at load time; the count above is the one a freshly inserted block has.
Configuration variables#
| Config variable | Default | Simulink parameter |
|---|---|---|
Reference Area | 1 | S |
Reference Span | 1 | b |
Reference Length | 1 | cbar |
Every block also carries Sampling Time (s) from ICoreBlockSolverEnvironment: zero or less inherits the solver's rate, a positive value runs the block at that period.
Simulink bridge#
| support | Support::Both |
| Simulink path | aerolibadyn/Aerodynamic\nForces and Moments |
| port-count rule | PortsParam::None |
SampleTime parameter | no — the counterpart defines none; the rate stays on the ICore side |
| always set | inputAxes = Body, outputForceAxes = Body, outputMomentAxes = Body |
| ICore config | Simulink parameter | Value translation |
|---|---|---|
Reference Area | S | passes through |
Reference Span | b | passes through |
Reference Length | cbar | passes through |
Caveat (shown to the user): C, qbar, CG and CP are the four ports in Simulink's order. The three axis settings are fixed at Body: any other choice adds a fifth input port (the body velocity) that this block does not have, so such a block is reported on import. The Simulink block defines no SampleTime (measured), so the rate stays on the ICore side
Catalog contract: src/ICoreBlocks/ICoreCoder/ICoreCommandSystem/SimulinkBridge/ICoreSimulinkBlockCatalog.h
Description vs code#
The checker has a blind spot here — it could not resolve something (a grouped port bullet, a computed config name), which is reported and never counted as a pass. A reader has to settle it:
B0no sample under docs/generated/samples/ — nothing to cross-check (P8.1)
The verdict above is
tools/docs/check_block_descriptions.py(P7.1), which compares LISTS. It cannot read a sentence: "stateless" on a block with a state, an initial-value semantic the recursion does not implement, a "not synthesizable" caveat the HDL banner contradicts. That is the agent audit (P7.3) on BLOCK_DESCRIPTION_AUDIT.md, and this tool's green is not a substitute for one.
File banner (developer view)#
The top comment of the block's .cpp — the maths, the realization and the export strategy, addressed to whoever changes it. It must not contradict the description above (P7.5).
Aerodynamic Forces and Moments -- coefficients to body-axis forces and moments F = qbar*S * [CX; CY; CZ] M = qbar*S * [b*Cl; cbar*Cm; b*Cn] + F x (CG - CP)
Aerospace Blockset's aerolibadyn/Aerodynamic Forces and Moments, read out of the masked subsystem: the coefficient vector is split 3 + 3; the first three go through a coefAdjust Gain of [1 1 1] (Body axes) and are scaled by qbar*S; the last three are scaled by qbar*S*[b; cbar; b]; and a 3x3 Cross Product with A = the forces and B = CG - CP adds the moment transfer from the centre of pressure to the centre of gravity.
MEASURED AGAINST R2026a: with coefficients [0.3 -0.2 0.5 0.04 -0.07 0.02], qbar = 1234.5, CG = [0.4 -0.1 0.2], CP = [0.9 0.05 -0.15], S = 2.5, b = 3.1, cbar = 0.7, the block answers F = [925.875 -617.25 1543.125] and M = [398.12625 -1246.845 -256.15875], and the two expressions above reproduce both by hand -- which is what pins the ORDER of the cross product (F x d, not d x F: the other order negates the whole transfer term).
⚠ ALL-BODY ONLY. Any of the mask's three axis settings at Stability or Wind gives the Simulink block a FIFTH input (the body velocity, for alpha and beta) -- measured, 4 -> 5 ports on every such combination -- and the bridge has no way to say that a parameter moves a port. The three settings are pinned to Body as fixed parameters instead, so an import using another arrangement is reported rather than brought in with the wrong port list.
Sample results#
No sample run is committed for this block. Samples come from the headless harness (DOCS_PLAN.md P8.1) into docs/generated/samples/; until one exists this block's behaviour is witnessed by the parity and export-verification suites, not by a plot here.