maegant / rabbit_opt_example

rabbit_opt_example

This repository is intended to provide a tutorial on how to set up a (P)HZD gait generation environment for the rabbit bipedal robot.

Tutorial

1. The most recent version of FROST requires MATLAB2022b. To avoid this you can pull the specific FROST commit shown in step 3. The repository also requires Ubuntu > 18.04 (I tested with 20.04).
2. Install FROST following the installation instructions provided here
3. This tutorial assumes that the FROST repository is set to the master branch with the following commit

   git clone https://github.com/ayonga/frost-dev.git
   cd frost-dev
   git checkout master
   git reset --hard 5e17cf8d9d2f2c239c3589d0a8bdb8ea49f09d53
   

• Note that you may need to add the following line to your .bashrc in order to successfully use the later FROST commits

  LD_LIBRARY_PATH=/usr/local/Wolfram/Mathematica/12.0/SystemFiles/Links/WSTP/DeveloperKit/Linux-x86-64/CompilerAdditions:$LD_LIBRARY_PATH
  

4. Edit the frost_path variable in main_opt (line 23) to point to your frost-dev cloned repo
5. The first time you run the main_opt script, you will need to compile the .mex files required to run the gait generation problem. To set the compile flags to true, change lines 39 and 48 of main_opt to:

   compileMex = [1,1];
   do_compile = [1,1,1];
   

   After compiling the mex files, you can set these lines to false (0). Note that you will need to recompile the .mex files if you change the gait generation problem setup.
6. Run the entire main_opt.m script to generate and simulate a gait

Options

Within startup_walker.m you can select from 2 different behaviors, and 2 different phaseTypes. Note that if you change any of these options, you will need to recompile the mex files.

Behaviors

1. The first behavior is a point-foot behavior that uses the five_link_walker.urdf model of the RABBIT biped. To select this behavior set behaviorName = 'planar_PF';
2. The second behavior is a flat-foot behavior that uses the seven_link_walker.urdf. This model is the RABBIT biped with feet (via the addition of ankle joints). To select this behavior set behaviorName = 'planar_FF';

Phase Types

1. The first phase type is time. This uses time as the phasing variable for the virtual constraints. Thus, it does not require a relative-degree 1 output -- instead the outputs are simply the 6 joint positions. Time-based is selected by setting PhaseType = 'TimeBased';
2. The second phase type is state (specifically the linearized forward hip position). If state-based is used with the seven link walker, then a relative degree 1 is added to the selected outputs (specifically forward hip velocity). State-based is selected by setting PhaseType = 'StateBased';