ANYmal PD control test


ANYmal test is to test computational efficiency in solving articulated dynamics. In this test, a 18 DOF quadrupedal robot ANYmal is feedback-controlled to stand on a flat ground.

The test focuses on:

  1. Computational cost
  2. Scalability

Test scenario

  1. direct joint torque control based on PD position control scheme
  2. flat ground
  3. quadruped robot ANYmal
  4. maintain one contact per feet: controlled by ERP and parameter tuning
  5. tested with 1 x 1, 2 x 2, 3 x 3, 4 x 4, 5 x 5, 7 x 7, 10 x 10 and 15 x 15 number of ANYmals for scalability check

Tested solver list



The results of the test are as following figures:

The plot above indicates RaiSim is remarkably fast for articulated system simulation with contacts by virtue of its efficient multibody dynamics implementation.

MuJoCo relatively performs well for articulated system simulation compared to Bullet, Dart, and ODE. However, as we mentioned above, it has consistent slip without no-slip iteration.

ODE is significantly slower than other engines for this simulation since it uses the maximal coordinate representation for multibody systems which is considerably expensive.

Note that we failed to test more than 5 x 5 robots on Bullet since the PD controller failed to make the robot stands on the plane due to inaccurate contact impulse solution.