UMich-BipedLab / Cassie_Model

Repo containing the urdf and frost based models of Cassie

Cassie Model

This repository can be used to generate a model of the Cassie-series robot using FROST.

Requirements

• MATLAB 2016b or later
• MATLAB supported compiler for generating MEX files
• Mathematica 11
• FROST

Generating Cassie's kinematics and dynamics

1. Open the model_gen.m script in MATLAB.
2. Modify FROST_PATH to reflect your FROST installation directory.
3. Generate the Cassie FROST model by runnning the first block of code, ending at line
   cassie = Cassie('urdf/cassie.urdf').
4. Run the rest of the script to generate and export various kinematic and dynamics functions.

Cassie coordinate system

Base DOFs

• q(1) - x
• q(2) - y
• q(3) - z
• q(4) - yaw
• q(5) - pitch
• q(6) - roll

Left side joints

• q(7) - hip abduction
• q(8) - hip rotation
• q(9) - hip flexion
• q(10) - knee joint
• q(11) - knee spring (constrained to 0)
• q(12) - ankle joint (constrained to q12 = deg2rad(13) - q10)
• q(13) - toe joint

Right side joints

• q(14) - hip abduction
• q(15) - hip rotation
• q(16) - hip flexion
• q(17) - knee joint
• q(18) - knee spring (constrained to 0)
• q(19) - ankle joint (constrained to q19 = deg2rad(13) - q17)
• q(20) - toe joint