Project description

To come...

Setup

Kinematics implementation

C++ and C++ libraries are used to implement forward and inverse kinematics for the Yumi.

The Robotics Library is used to parse the robotic configuration from an .urdf file and compute the forward kinematics as well as the Jacobian.

For inverse kinematics the broccoli library of the Chair of Applied Mechanics at TUM is used to implement a gradient based projection method which takes two additional constraints - a norm for maximal joint values and a norm for the distance of any singularities - into account and projects them into the nullspace of the robot. Projecting these constraints into the nullspace helps to avoid maximal joint values and singularities without affecting the pose of the end effector.

Interface to robot

Communication to the IRB14000 is performed via an UDP interface using Google Protobuffres. It is aimed to use an existing Python client and calling C++ code for the kinematics from the Python program.

Force sensing

In order to keep the wire tensioned during the foam cutting application sensor data is needed to setup a feedback loop. Therefore a one dimensional load cell is going to be mounted to the end effector of Yumi. The signal of the full bridge that meassures the gauge of the cell is amplified by an HX711 AD-Converter and conntected to an Arduino Uno. The data is then going to be send to the controller that runs on the pc over a Serial Interface.

Hot Wire

The wire is going to be heated by appling a voltage that results in a current, depending on the resistance of the wire. The current is going to be controlled using a dc converter.

Installation instructions

C++

The project needs a few dependencies to be installed. These are broccoli, the robotics library as well as pybind11 in order to create bindings between Python and C++ code. To prevent any troubles while installing them in the next step make sure you have the following packages installed. Check or otherwise install them running sudo apt install cmake python3-dev python3-distutils in the command line.

Download eigen and put them into your /opt/ folder.

pybind11

There are several ways how to use pybind11. Number 1 was tested succesfully and is recommanded

1. Inlcude pybind11 as submodule Within the c++ folder run

git submodule add -b stable https://github.com/pybind/pybind11 deps/pybind11
git submodule update --init

2. Run the following commands to install pybind11 globally to your system

# Classic CMake
cd pybind11
mkdir build
cd build
cmake ..
make install

# CMake 3.15+
cd pybind11
cmake -S . -B build
cmake --build build -j 2  # Build on 2 cores
cmake --install build

Installation instruction for pybind11 can be also found here

broccoli

Broccoli can be directly installed to the system (tested and works) or included as an external project. To install broccoli directly to the system clone the respective repo using git. Then cd in cloned brocolli repo and run the following commands to install brocolli to your system

mkdir build
cd build
cmake ..
make install

Broccoli and installation instruction can be found here.

Robotics Library

To install the whole robotics library to your system run:

sudo apt-add-repository ppa:roblib/ppa
sudo apt-get update
sudo apt-get install librl librl-demos librl-examples
sudo apt-get install librl-dev
sudo apt-get install librl-extras librl-doc librl-dbg

Official installation instruction can be found here.

Python

Follow the steps to create a virtual environment and install the neccessary dependencies:

1. Create a directory for your virtual environment within the python folder
2. Create a virtual environment running python3 -m venv ./myvenv
3. Activate the virtual environment running source myvenv/bin/activate
4. Install the dependencies for the abb-egm-client:

• Install protoc from protobuf. There are prebuilt binaries available from GitHub if protoc is not available in your package manager.
• Find egm.proto in either %LOCALAPPDATA%\ABB\RobotWare\RobotWare_6.XXXXX\utility\Template\EGM\egm.proto or on the robot.

Run protoc to generate protobuf classes for python. Substitute $SRC_DIR for the location of egm.proto

protoc --python_out=abb_egm_pyclient $SRC_DIR/egm.proto

Install this package in your environment of choice.

cd abb_egm_pyclient
pip install -e .

5. Install all other dependencies with pip install -r requirements.txt

Troubles

Compiling the project with cmake runs without errors but when trying to import the python binding the following error appears: ImportError: /home/joschua/Coding/forceControl/master-project/c++/build/example.cpython-38-x86_64-linux-gnu.so: undefined symbol: _Z3gpmRN5Eigen6MatrixIdLi6ELi1ELi0ELi6ELi1EEES2_RNS0_IdLi7ELi1ELi0ELi7ELi1EEES4_S4_ddi The error can be demangled using an online demangler like https://demangler.com The python binding code (the generated *.so file) can be imported by running import example within an interactive python session. An official example can be found here