Walking Robots

ArduPilot Rover 4.1 (and higher) includes basic support for four legged walking robots. More details can be found in this GSoC 2020 blog post

Warning

This page is still a work-in-progress

Hardware Required

Hardware Setup

Frontal view

../_images/Walking_robot-front.JPG
  • It is critically important that the Ardupilot knows the orientation of each leg when the servos are centered. The code assumes that, when all the servos are centered, the coxa faces directly away from the body, the femur is level with the ground, and the tibia is at an angle of 90 degrees relative to the femur.

Images can be used for reference.

Leg orientation

../_images/Walking_robot-leg.JPG

Top view

../_images/Walking_robot-top_view.JPG ../_images/Walking_robot-Anatomy.jpg

Connect the AutoPilot’s pwm outputs to each servo as listed below:

Output Servo
1 front right coxa (hip) servo
2 front right femur(thigh) servo
3 front right tibia(shin) servo
4 front left coxa(hip) servo
5 front left femur(thigh) servo
6 front left tibia(shin) servo
7 back left coxa(hip) servo
8 back left femur(thigh) servo
9 back left tibia(shin) servo
10 back right coxa(hip) servo
11 back right femur(thigh) servo
12 back right tibia(shin) servo

Configuration and Setup

1) Connections, Firmware and Calibration

  1. Refer to autopilot system assembly instructions for making connections between the autopilot board and each of these components:

    • Power Module
    • Servos
    • RC Receiver
    • GPS(optional)
    • Telemetry(optional)

Use a ground station to load Rover-4.1 (or higher) to the autopilot #. Install GCS (Mission Planner recommended) and upload rover firmware, if ArduPilot firmware already is installed, or Loading Firmware onto boards without existing ArduPilot firmware (first time only) #. Perform all the hardware calibration steps for:

2) Loading lua script to ardupilot

  • Connect with a ground station and set SCR_ENABLE = 1 to enable Lua scripting and reboot the autopilot
  • Download quadruped.lua from the ArduPilot Github repo to your PC
  • Load the quadruped.lua script to the autopilot using MAVFTP or by directly copying to the SD Card’s APM/scripts directory (see video)

3) Additional Parameter Configuration

  • set RCx_OPTION parameters
  • set any unused channels to access these features

Supported Features

RCx_OPTION value Feature Description
201 Roll
202 Pitch
203 Walking Height

4) Arming

  • Set a transmitter switch for arming. Ensure the channel used for the switch has been calibrated. To configure a channel for arming, for example channel 7, then set the parameter:

    • RC7_OPTION =41 (Sets function of channel 7 as arming/disarming)
  • Connect the battery. Connect the autopilot board to GCS via USB or telemetry.

  • Keep the robot on its belly and then arm it. If arming is not successful check the error message on the GCS and identify the problem from the rover arming page .

  • After the autopilot board arms, the robot should stand up on it’s own

Simulation with SITL and pyBullet

The following steps will get you running with the quadruped example.

pip3 install pybullet
  • cd to the ardupilot/Rover directory
  • create a “scripts” directory and copy quadruped.lua into it
  • Open a terminal to /ardupilot/Rover directory and start ArduPilot SITL
simvehicle.py --map --console -D -f JSON
  • Enable scripting and then restart SITL
param set SCR_ENABLE 1
  • Set channels for roll, pitch and height
    Example:
param set RCx_OPTION 202
  • Open another termial to launch pyBullet
cd ardupilot/libraries/SITL/examples/JSON/pybullet
python3 walking_robot.py