JuliaCon 2026

We aim to illustrate the initialization features of Dyad by trimming the Nonlinear F-16 model dynamics using NLSQ for desired altitude and cruise speed. We will then use the analysis features of Dyad by designing an LQR for longitudinal stabilization under trim and demonstrate a dashboard that enables real time tuning and response behavior visualization.

The plant model is written in Dyad, a new declarative acausal modeling language. The F-16 model encodes full six-degree-of-freedom rigid-body dynamics: translational and rotational equations of motion with coupled aerodynamic force and moment coefficients, ISA atmosphere density, and Euler angle kinematics. Dyad's RealInput/RealOutput connectors and analysis_point annotations expose the model's control and measurement interfaces for downstream analysis without modifying the physics..

Controller design uses DyadControlSystems' LQGAnalysis, which automatically linearizes the closed-loop Dyad model at the trim operating point and solves the dual Riccati equations. The 12-measurement, 5-control, 8-controlled-output problem yields a 12-state observer-based feedback controller. An interactive GLMakie GUI with a plugin architecture (Gang of Four, Nyquist, step response, pole-zero map) allows real-time tuning of LQR weights and Kalman filter covariances. A GLMakie animation engine renders the 3D trajectory alongside user-selected state and control variable time histories.

The key contribution is demonstrating that Dyad's declarative syntax unifies what are traditionally separate modeling, analysis, and design stages into a single reproducible project. The same .dyad files that define the physics also declare the trim analysis, the LQG synthesis problem, and the simulation scenarios. Julia's composability: ModelingToolkit for symbolic-numeric transformations, DyadControlSystems for control theory and GLMakie for visualization eliminates the toolchain fragmentation typical of aerospace control workflows.