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C++ Motor Driver for Mini Cheetah-type Actuators from T-Motor/CubeMars

This driver was developed at the Underactuated Lab in Robotics Innovation Center at DFKI GmbH, Bremen.

It assumes the use of a CAN to USB adapter (such as PEAK System's PCAN-USB or ESD's CAN-USB/2) connected to a linux (tested on Ubuntu) computer. The SocketCAN interface is used which is supported natively in the Linux Kernel. For more information on SocketCAN in Linux, see here.

The communication send-reply frequencies are set up using the Serial Port of the motor and until now, this C++ driver was tested to achieve over 2KHz with single motor connected.

Dependencies

It has no external library dependencies as it only depends on the socket library provided by Linux and communicates via SocketCAN with the motor. Currently, a CAN-USB adapter is used (from either PEAK or ESD GmbH) which shows up as a SocketCAN interface on a Linux computer. CMake build system is used for compilation/installation.

Documentation

Pre-requisites:

  • Setting up the CAN interface:

    • Run this command and make sure that can0 (or any other can interface depending on the system)shows up as an interface after connecting the USB cable to your laptop: ip link show

    • Configure the can0 interface to have a 1 Mbaud communication frequency: sudo ip link set can0 type can bitrate 1000000

    • To bring up the can0 interface, run: sudo ip link set up can0

  • To change motor parameters such as CAN ID or to calibrate the encoder, a serial connection is used. The serial terminal used on linux for this purpose is screen. Example usage:

sudo apt-get install screen
screen /dev/ttyUSB0 921600

Build Instructions

mkdir build
cd build
cmake ..
make
sudo make install

Testing with a real motor and Usgae

See MotorDriverTest.cpp which is the provided test script.

Add the following header to your project code:

#include "mini_cheetah_motor_driver/MotorDriver.hpp"

For the available functions, see include/motor_driver/MotorDriver.hpp.

TODO: Adapt MotorDriverTrajTest.cpp to the new driver interface.

Using in other projects (ROS2 drivers, etc..)

This driver was tested and used in ROS2 for certain projects.

TODO: Create a generic ROS2 node for the actuators.

In the project's CMakeLists.txt add the following lines after compiling and installing the library on the computer:

link_directories(/usr/local/lib)
find_library(mini_cheetah_motor_driver REQUIRED)
target_link_libraries(${YOUR_TARGET} mini_cheetah_motor_driver ${OTHER_LIBS})

And add the following header to your project code:

#include "mini_cheetah_motor_driver/MotorDriver.hpp"

Supported Motor Configurations:

  • AK80-6 (From Cubemars, Firmware versions V1, V1.1, and V2): motor_driver::MotorType::AK80_6_V1, motor_driver::MotorType::AK80_6_V1p1 and motor_driver::MotorType::AK80_6_V2
  • AK80-9 (From Cubemars, Firmware version V1.1 and V2): motor_driver::MotorType::AK80_9_V1p1 and motor_driver::MotorType::AK80_9_V2
  • AK70-10 (From Cubemars, Firmware version V1.1): motor_driver::MotorType::AK70_10_V1p1
  • AK10-9 (From Cubemars, Firmware version V1.1): motor_driver::MotorType::AK10_9_V1p1. (TODO: The temperature and error codes are received but not yet decoded for the new firmware for this motor.)
# Working parameters for AK80-6 V1.0 firmware
AK80_6_V1_PARAMS = {
                "P_MIN" : -95.5,
                "P_MAX" : 95.5,
                "V_MIN" : -45.0,
                "V_MAX" : 45.0,
                "KP_MIN" : 0.0,
                "KP_MAX" : 500,
                "KD_MIN" : 0.0,
                "KD_MAX" : 5.0,
                "T_MIN" : -18.0,
                "T_MAX" : 18.0,
                "AXIS_DIRECTION" : -1
                }

# Working parameters for AK80-6 V1.1 firmware
AK80_6_V1p1_PARAMS = {
                "P_MIN" : -12.5,
                "P_MAX" : 12.5,
                "V_MIN" : -22.5,
                "V_MAX" : 22.5,
                "KP_MIN" : 0.0,
                "KP_MAX" : 500,
                "KD_MIN" : 0.0,
                "KD_MAX" : 5.0,
                "T_MIN" : -12.0,
                "T_MAX" : 12.0,
                "AXIS_DIRECTION" : -1
                }

# Working parameters for AK80-6 V2.0 firmware
AK80_6_V2_PARAMS = {
                "P_MIN" : -12.5,
                "P_MAX" : 12.5,
                "V_MIN" : -38.2,
                "V_MAX" : 38.2,
                "KP_MIN" : 0.0,
                "KP_MAX" : 500.0,
                "KD_MIN" : 0.0,
                "KD_MAX" : 5.0,
                "T_MIN" : -12.0,
                "T_MAX" : 12.0,
                "AXIS_DIRECTION" : 1
                }

# Working parameters for AK80-9 V1.1 firmware
AK80_9_V1p1_PARAMS = {
                "P_MIN" : -12.5,
                "P_MAX" : 12.5,
                "V_MIN" : -22.5,
                "V_MAX" : 22.5,
                "KP_MIN" : 0.0,
                "KP_MAX" : 500,
                "KD_MIN" : 0.0,
                "KD_MAX" : 5.0,
                "T_MIN" : -18.0,
                "T_MAX" : 18.0,
                "AXIS_DIRECTION" : 1
                }

# Working parameters for AK80-9 V2.0 firmware
AK80_9_V2_PARAMS = {
                    "P_MIN" : -12.5,
                    "P_MAX" : 12.5,
                    "V_MIN" : -25.64,
                    "V_MAX" : 25.64,
                    "KP_MIN" : 0.0,
                    "KP_MAX" : 500.0,
                    "KD_MIN" : 0.0,
                    "KD_MAX" : 5.0,
                    "T_MIN" : -18.0,
                    "T_MAX" : 18.0,
                    "AXIS_DIRECTION" : 1
                    }

// Working parameters for AK70-10 V1.1 firmware
AK70_10_V1p1_params = {
                      "P_MIN" :  -12.5,
                      "P_MAX" :  12.5,
                      "V_MIN" :  -50,
                      "V_MAX" :  50,
                      "KP_MIN" :  0,
                      "KP_MAX" :  500,
                      "KD_MIN" :  0,
                      "KD_MAX" :  5,
                      "T_MIN" :  -24.0,
                      "T_MAX" :  24.0,
                      "AXIS_DIRECTION" :  1
                    }

# Working parameters for AK10-9 V1.1 firmware
AK10_9_V1p1_PARAMS = {
                "P_MIN" : -12.5,
                "P_MAX" : 12.5,
                "V_MIN" : -50.0,
                "V_MAX" : 50.0,
                "KP_MIN" : 0.0,
                "KP_MAX" : 500,
                "KD_MIN" : 0.0,
                "KD_MAX" : 5.0,
                "T_MIN" : -65.0,
                "T_MAX" : 65.0,
                "AXIS_DIRECTION" : -1
                }

To add a new constants configuration use the change_motor_constants function or create an issue with the constants and motor information on the GitHub page to be added to the driver.

Known Issues

Issue Fixed: When having 2 motors on the CAN bus with either PCAN CAN-USB or ESD CAN-USB/2, sometimes the motors experience an initial short kick/impulse at when they are enabled again after being disabled. This was fixed in commit 7a00b4d.

As this is experimental software, there might be other unknown issues.