Lab 7 - Pupper Control and Simulation

Mini-lecture - TBD

Slides: https://docs.google.com/presentation/d/1yjNz9ybcmJLKLkAnhHgILDR1hkjVbzhAphLXwZrO3mI/edit?usp=sharing |

Lab instructions

These instructions assume you are running mac or linux. If you have Windows 10 or lower, I recommend dual-booting linux. If you have Windows 11, try using the Windows Linux Subsystem

Step 1. Set up simulation environment

  1. git pull the latest puppersim repository, which is the same you used in Lab 5 https://github.com/jietan/puppersim/.

  2. Install additional dependencies pip3 install numpy transforms3d pyserial. Use pip if pip3 doesn’t work.

Step 2. Try out the simulator

  1. Follow the instructions in the Simulating the heuristic controller section of the puppersim repository.

  2. Check out these keyboard controls:

    • wasd: –> moves robot forward/back left/right.

    • arrow keys: –> turns robot left/right

    • q: –> activates robot

    • e: –> starts trotting

    • ijkl: –> tilts robot

  3. To activate the robot, press q. To start trotting, press e.

  4. Enjoy the simulator!

  5. To close the simulator, do not press use the usual close button in the top left of the simulator window. Instead do Ctrl-C in both terminal tabs/windows.

Expected result:

../_images/sim.png

Expected simulator window.

../_images/terminal.png

Expected output from python3 run_djipupper_sim.py.

Step 3. Experiment

  1. Try changing self.overlap_time (line 52) in StanfordQuadruped/djipupper/Config.py. This controls the amount of time in which all four legs are on the ground for the trot.

  2. Try changing self.swing_time (line 53) in StanfordQuadruped/djipupper/Config.py. This controls the amount of time in which just two legs are on the ground for the trot.

  3. Mess around with other things:

Other available parameters

Maximum commands:

  • max_x_velocity: Maximum forward velocity. Default: 0.6. Reasonable range: [0, 1.2]. Units: [meters/sec].

  • max_y_velocity: Maximum horizontal velocities. Default: 0.6. Reasonable range: [0, 1.2]. Units: [meters/sec].

  • max_yaw_rate: Maximum turning rate. Default: 2.5. Reasonable range: [0, 4]. Units: [rad/sec].

Foot placement parameters:

  • delta_x: When the robot is trotting in place, this is 1/2 the forward/back distance between the feet. Default: 0.1. Reasonable range: [0.05, 0.15]. Units: [meters].

  • delta_y: When the robot is trotting in place, this is 1/2 the left/right distance between the feet. Default: 0.1. Reasonable range: [0.05, 0.15]. Units: [meters].

  • x_shift: This is the amount that the robot walks in front of it’s center of mass vs behind. Default: 0.005. Reasonable range: [-0.03, 0.03]. Units: [meters].

  • default_z_ref: Default amount that the feet are beneath the CoM of the robot. Default: -0.14. Reasonable range: [-0.05, -0.18]. Units: [meters].

Trotting parameters:

  • overlap_time: 1/2 the duration of time in each trot cycle when all four feet are on the ground. Default: 0.05. Reasonable range: [0, 0.25]. Units: [seconds].

  • swing_time: 1/2 the duration of time in each trot cycle when two feet are on the ground and two are in the air. Default: 0.15. Reasonable range: [0, 0.25]. Units: [seconds].

Note: The total period of the trot gait is 2 * overlap_time + 2 * swing_time in seconds. So if you wanted a 1Hz gait, you could set overlap_time=0.25 and swing_time=0.25.