PNNL engineers chose MATLAB® and Simulink® to evaluate alternative control strategies. Computer simulation allowed them to consider many operational parameters, such as the position, velocity, and acceleration of every point at each time step in the simulation. That data was then used in analysis routines to calculate optimal control equations.
PNNL engineers used DADS (Dynamic Analysis and Design System) 3D mechanical system simulation software from Computer Aided Design Software, Inc., to model the mechanics. This software, which interfaces with MATLAB and Simulink, allowed engineers to quickly model, simulate, and animate the basic test bed system. The model included open- and closed-loop control systems and realistic hydraulic valve and actuator properties. It also incorporated finite element results that accurately modeled the flexible link.
The tools had met the biggest simulation challenge—accurately reflecting physical reality. Once linearized, the model was used to develop the constant-coefficient differential equations that drive the controller design models (CDMs), the mathematical models that compute the actuator responses needed to dampen vibrations. The step functions developed from the simulation output were applied to the azimuth angle of the SRM, and the LRM tip response signals were measured.
PNNL engineers analyzed those responses to produce optimized linear transfer functions based on the step response of the robotic system. The analysis was performed under a variety of loading conditions to obtain a family of transfer functions.