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Tutorial
First Tutorial
This page is a tutorial to help you in beginning to use the HuMAnS toolbox. The main idea is also to explain what is done and how, giving you a complete understanding of the software architecture. This way it should be easier for you to see how to make your own applications. Lines of code will be given, and when you want to know what a script or a function does, click on its name to be directed to a page dedicated to it. At first, the descriptions might not be very detailed, but new tutorials should be added later to make them more precise. When a function is explained, the full source code of the function will probably not be given. You might find useful therefore to have a text editor ready to read at will the corresponding source file.
Maybe a few words about the general architecture of the software before starting, even if this is already detailed in the User Documentation. A necessary module for all uses of the toolbox is the Kernel module/directory: of interest to this Tutorial, it contains the Simulation function and calls to functions updating the state of the contacts and of the actuators. The mechanical model is defined in the LagrangianModel/*Name* module/directory. The ActuationModel/*Name* module/directory concerns everything about the actuation: a model of the actuators and of the control laws which can be applied. The LagrangianDynamics/*Name* module/directory handles the way the dynamics will be computed, dealing with contact forces and all other forces acting on the system.
First application
What is needed
- It is assumed that you installed the HuMAnS toolbox and that it works correctly (be sure that the different scripts described in the README file work).
- To have an idea of the problems that can be solved by this toolbox, a first glance at the User Documentation is strongly advised if you haven't done so yet, at least sections 1.1 and 2.1 to know in general what kind of problems are modeled and how they are solved.
- It is assumed that you know how to use Scilab properly.
- A VRML viewer compatible with the H-Anim format can be useful, but is not mandatory.
Objectives
We are going to detail here a very simple application: we are going to
define a simple trajectory and apply it to an existing model (the human
biomechanical model called Human36, because of its 36 axes of rotation).
The trajectory will be defined later. Here we go:
Open a new Scilab script ('Tutorial.sci' for example), read and copy the
lines given in the next section. Another file will have to be modified:
please pay attention to the comments, which will give you directions to
follow.
Let's do some coding
// You always need to execute the KickStart first,// then load the modules that will be used in your application
exec(KickStart.sci);
execstr(LoadModule('LagrangianModel/Human36'));
execstr(LoadModule('LagrangianDynamics/Complete'));
execstr(LoadModule('ActuationModel/NoDynamics'));
execstr(LoadModule('ActuationModel/NoDynamics/ComputedTorqueControl'));
execstr(LoadModule('Kernel'));
// Definition of the period (in seconds) with which the Spy function will
// be called (to check the evolution of the simulation)
SpyPeriod = 1e-1;
// Choice of the trajectory that will be used.
// The function Trajectory has to be modified in this case,
// following the guidelines given here. In a few words,
// a new trajectory name is defined so as not to lose the other existing
// trajectories defined in the rest of the function Trajectory
TrajectoryName = 'ArmMovement';
[q, qdot] = Trajectory(0);
// As its name says, this function realizes the simulation.
// This function is also detailed in chapter 5 of the User Documentation.
printf('\nStarting Simulation...\n');
[T, Q, QDOT, Z, ACTUATIONSTATE, CONTACTSTATE] = Simulation(0, 1, 1e-2, q, qdot);
// Now the simulation is finished and the rest of the program
// is devoted to the "analysis" of its results.
// Contact forces are computed here.
printf('\nComputing Contact Forces...\n');
LAMBDA = ComputeContactForces(T, Q, QDOT, Z, ACTUATIONSTATE, CONTACTSTATE);
// Here the joint positions and the contact forces are plotted with regular
// Scilab functions
xset('window', 1);
xname('Q (HuMAnS)');
plot2d(T', Q');
xset('window', 2);
xname('LAMBDA (HuMAnS)');
plot2d(T', LAMBDA');
// This is to generate a VRML 3D animation of the simulation
printf('Creation of a VRML file...\n);
CreateVRML(1e-2, Q, HAnimJointsNames, 'Human36', 'High', 'Tutorial.wrl', LAMBDA, HAnimContactSolidsNames, HAnimContactSolidsRGB);
// This is to generate the plain Scilab stick figure 3D animation of the simulation
Visu(Q(:, 1:10:$), LAMBDA(:, 1:10:$));
Running the script
Now execute this script in Scilab and watch the result. If you get an error message saying that 'position variable is undefined', it probably means that you haven't read that. Otherwise you should see a 3D stick figure moving the right arm up and down. If a VRML viewer is installed on your computer, you can watch a much nicer animation in the 'Tutorial.wrl' file. This application is very simple because we did not use any specific model of actuators and there is no change in the contact state, furthermore the joint trajectory given here presents no change in the actuation state either.