MIT Mini Cheetah - quadrupedal robot

Anelito · October 3, 2022, 8:38pm

Hi everyone,
I’d like to repurpose a mini cheetah clone (more info here) sold on Aliexpress to using ArduPilot.

At it’s core, the robot consists of:

Aluminium chassis
12x motors with encoders and drivers
A 24V 5000 mAh battery
A 9 DoF IMU
An UpBoard Z8350
The SPIne (a custom PCB featuring two STM32 to create two independent CAN networks) and a ZigBee for the RC command
A power supply and distribution board

The companion computer (UP board) runs ROS and takes care of basic motion tasks by pushing CAN messages to the SPIne, that dispatches them to the motors.

Since ArduPilot supports CAN and battery monitoring, I was wondering if the SPIne could be replaced with a PixHawk. Doing so it would enable the whole ArduPilot software suite and it could be possible to start tinkering with the robot, although the companion computer would be giving directions mainly.

Update
Diving deeper into the Mini Cheetah docs it seems the choice of having two STMs is due to the limited CAN bandwidth a single microprocessor can support.

ppoirier · October 4, 2022, 1:00pm

Hello,

That is quite an interesting challenge, it reminds me of the Hexapod Robot integration.
https://ardupilot.org/rover/docs/walking-robots.html

Here are some additionnal links:

I think @khancyr could add some comments here

iampete · October 4, 2022, 1:03pm

Example of Mini Cheetah motor driver in scripting:

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/CAN_MiniCheetah_drive.lua

-- Control MiniCheetah motor driver over CAN
-- https://os.mbed.com/users/benkatz/code/HKC_MiniCheetah/docs/tip/CAN__com_8cpp_source.html

-- Load CAN driver with a buffer size of 20
local driver = CAN:get_device(20)

local target_ID = uint32_t(1)

local pos_max = 12.5
local vel_max = 65
local Kp_min = 0
local Kp_max = 500
local Kd_min = 0
local kd_max = 5
local torque_max = 18

local position_des = 0
local position_inc = 0.01

-- convert decimal to int within given range and width

This file has been truncated. show original

ppoirier · October 4, 2022, 1:30pm

@iampete what CAN_D1_PROTOCOL are you setting to talk to the Motor Controller ?

ok looking at code

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/CAN_read.lua#L3


      
          -- This script is an example of reading from the CAN bus
          
          
-- Load CAN driver1. The first will attach to a protocol of 10, the 2nd to a protocol of 12
          -- this allows the script to distinguish packets on two CAN interfaces
          local driver1 = CAN:get_device(5)
          local driver2 = CAN:get_device2(5)
          
          
if not driver1 and not driver2 then
             gcs:send_text(0,"No scripting CAN interfaces found")
             return
          end
          
          
function show_frame(dnum, frame)

Anelito · October 4, 2022, 2:10pm

More than that, if they used two STM uC because of CAN bandwidth, we need to check if the Pixhawk is able to support the two networks alone

ppoirier · October 4, 2022, 3:19pm

There are 2 CAN interfaces on high end FC like the Cube Orange

Anelito · October 4, 2022, 5:10pm

what is their bandwidth?

ppoirier · October 4, 2022, 5:23pm

You mean CAN Baudrate ?
1 Mbps, just like Ben Katz motor drive controller

MAVProxyUser · February 27, 2023, 5:10pm

Stop by and see us over at the Slack Group “TheDogPound - Animal control for stray robot dogs” and help foster this same discussion. Slack

You may have noted the CubePilot team just got a dog. Part of the reason is I’ve been trying to talk them into supporting a replacement for the Unitree go1 brain, which is in essence a Cheetah SPIne.
https://twitter.com/CubePilot/status/1622147303162392577