Fast Kinematics

This is a cuda enabled library for calculating forward kinematics and Jacobian of a kinematics chain. It can be used with numpy arrays or pytorch tensors. Compared to pytorch_kinematics, this is about 1000 times faster at Jacobian calculation with 4096 parallel 7dof robot arms.

Installation

From PyPi

pip install fast_kinematics

From Source

1. Get the docker image

   docker pull lexseal/fast_kinematics:latest
   

2. Run the docker image

   docker run -it lexseal/fast_kinematics:latest
   

3. Update the repo

   cd /workspace/fast_kinematics && git pull
   

4. Run build.sh to build all wheels. The built wheels will showup in the wheelhouse dir

   ./build.sh
   

5. Take the wheel out of the docker container. From your host machine, run

   docker cp <container_id>:/workspace/fast_kinematics/wheelhouse .
   

Usage

[!WARNING] Please use dtype np.float32 or torch.float32 for the joint configuration. The library is optimized for float32 and will not work with float64.

[!NOTE] You might need to import torch before using this library as torch will load the shared libraries. Your mileage may vary.

Minimal numpy example:

import numpy as np
from fast_kinematics import FastKinematics

N = 1024  # number of parallel calculations

# need the urdf file, number of parallel calculations and end effector link
model = FastKinematics("kuka_iiwa.urdf", N, "lbr_iiwa_link_7")

# this robot has 7 joints, so the joint configuration has size (N*7,) (1d array)
# the first 7 values are for the first robot... Note we need to use float32!
joint_config = np.random.rand(N*7).astype(np.float32)

# get the forward kinematics size (N*7,) (1d array)
# the first 7 values are the first robot's pose [x,y,z,qw,qx,qy,qz]
ee_pose = model.forward_kinematics(joint_config)

# get the jacobian size (N*6*7,) (1d array) The 7 here is the number of joints
jac = model.jacobian_mixed_frame(joint_config)
# we can reshape the jacobian to (N,7,6) and then transpose to (N,6,7)
jac = jac.reshape(-1, 6, 7).transpose(0, 2, 1)

Minimal pytorch example:

import torch
from fast_kinematics import FastKinematics

N = 1024
model = FastKinematics("kuka_iiwa.urdf", N, "lbr_iiwa_link_7")

joint_config = torch.rand(N*7, dtype=torch.float32, device="cuda")

ee_pose = model.forward_kinematics_pytorch(joint_config)
ee_pose = ee_pose.view(-1,7,6).permute(0,2,1)

There is also a jupyter notebook in the tests folder that contains usage as well as some benchmarks against pytorch_kinematics.

APIs

The docs are embedded in the library itself, you can either print out the doc string or use the code suggestions in your IDE to see the API documentation. Alternatively, please see pybind11/pybind_fast_kinematics.cpp for the API documentation.