Crate k

k: Kinematics library for rust-lang

k has below functionalities.

1. Forward kinematics
2. Inverse kinematics
3. URDF Loader

k uses nalgebra as math library.

See Document and examples/ for more details.

Requirements to build examples

sudo apt install g++ cmake xorg-dev libglu1-mesa-dev

IK example with GUI

cargo run --release --example interactive_ik

Push below keys to move the end of the manipulator.

• f: forward
• b: backward
• p: up
• n: down
• l: left
• r: right
• z: reset the manipulator state.

Create link tree from urdf and solve IK

use k::prelude::*;

fn main() {
    // Load urdf file
    let chain = k::Chain::<f32>::from_urdf_file("urdf/sample.urdf").unwrap();
    println!("chain: {chain}");

    // Set initial joint angles
    let angles = vec![0.2, 0.2, 0.0, -1.0, 0.0, 0.0, 0.2, 0.2, 0.0, -1.0, 0.0, 0.0];

    chain.set_joint_positions(&angles).unwrap();
    println!("initial angles={:?}", chain.joint_positions());

    let target_link = chain.find("l_wrist_pitch").unwrap();

    // Get the transform of the end of the manipulator (forward kinematics)
    chain.update_transforms();
    let mut target = target_link.world_transform().unwrap();

    println!("initial target pos = {}", target.translation);
    println!("move z: +0.1");
    target.translation.vector.z += 0.1;

    // Create IK solver with default settings
    let solver = k::JacobianIkSolver::default();

    // Create a set of joints from end joint
    let arm = k::SerialChain::from_end(target_link);
    // solve and move the manipulator angles
    solver.solve(&arm, &target).unwrap();
    println!("solved angles={:?}", chain.joint_positions());

    chain.update_transforms();
    let solved_pose = target_link.world_transform().unwrap();
    println!("solved target pos = {}", solved_pose.translation);
}

Structure of API

Top level interface is Chain struct. It contains Nodes and they have the relations between nodes (parent/children). Actual data (joint angle(position), transform between nodes) is stored in Joint object inside nodes.

You can get local/world transform of nodes. See below figure to understand what is the node’s local_transform() and world_transform().

OpenRR Community

Here is a discord server for OpenRR users and developers.

Re-exports

pub use crate::joint::Joint;

pub use crate::joint::JointType;

pub use crate::link::Link;

pub use crate::node::Node;

pub use crate::node::NodeBuilder;

pub use nalgebra::Isometry3;

pub use nalgebra::RealField as Real;

pub use nalgebra::RealField;

pub use nalgebra::Translation3;

pub use nalgebra::UnitQuaternion;

pub use nalgebra::Vector3;

pub use simba::scalar::SubsetOf;

pub use simba::scalar::SupersetOf;

pub use nalgebra;

pub use simba;

Modules

iterator

Iterators to iterate descendants and ancestors

joint

Joint related structs

link

link can be used to show the shape of the robot, or collision checking libraries.

node

graph structure for kinematic chain

prelude

Load basic traits of k

urdf

Load URDF format and create k::Chain

Macros

connect

set parents easily

Structs

Chain

Kinematic Chain using Node

Constraints

A bundle of flags determining which coordinates are constrained for a target

JacobianIkSolver

Inverse Kinematics Solver using Jacobian matrix

SerialChain

Kinematic chain without any branch.

Enums

Error

The reason of joint error

Traits

InverseKinematicsSolver

IK solver

Functions

center_of_mass

Calculate the center of mass of the chain

create_reference_positions_nullspace_function

Utility function to create nullspace function using reference joint positions. This is just an example to use nullspace.

jacobian

Calculate Jacobian of the serial chain (manipulator).