README
¶
Kinematics
This repo contains the code for the Golang kinematics library, which implements forward and inverse kinematics for robotic arms. We provide default parameters for the AR2 / AR3 robotic arm from Annin Robotics, but other parameters can be used for other arms.
Package documentation can be found at pkg.go.dev or godoc.io
Documentation
¶
Overview ¶
Package kinematics calculates forward and inverse kinematics for robotic arm systems.
Forward kinematics takes joint angles and returns the end effector Pose. Inverse kinematics takes a Pose and returns joint angles that move the end effector to that Pose.
ForwardKinematics (joint angles -> Pose) InverseKinematics (Pose -> joint angles)
Each function also requires a Denavit-Hartenberg Parameter set for the arm of interest. This package provides defaults for the following arm systems:
AR2/AR3
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var MaxInverseKinematicIteration int = 50
MaxInverseKinematicIteration is the max number of times InverseKinematics should try new seeds before failing. 50 is used here because it is approximately the number of iterations that will take 1 second to compute.
Functions ¶
This section is empty.
Types ¶
type DhParameters ¶
type DhParameters struct {
ThetaOffsets [6]float64
AlphaValues [6]float64
AValues [6]float64
DValues [6]float64
}
DhParameters stand for "Denavit-Hartenberg Parameters". These parameters define a robotic arm for input into forward or reverse kinematics.
var AR3DhParameters DhParameters = DhParameters{ ThetaOffsets: [...]float64{0, 0, -math.Pi / 2, 0, 0, math.Pi}, AlphaValues: [...]float64{-(math.Pi / 2), 0, math.Pi / 2, -(math.Pi / 2), math.Pi / 2, 0}, AValues: [...]float64{64.2, 305, 0, 0, 0, 0}, DValues: [...]float64{169.77, 0, 0, -222.63, 0, -36.25}, }
Denavit-Hartenberg Parameters of AR3 provided by AR2 Version 2.0 software executable files from https://www.anninrobotics.com/downloads Those parameters are the same between the AR2 and AR3.
type JointAngles ¶ added in v1.0.1
JointAngles represents angles of the joints in radians.
func InverseKinematics ¶
func InverseKinematics(desiredEndEffector Pose, dhParameters DhParameters, thetasInit JointAngles) (JointAngles, error)
InverseKinematics calculates joint angles to achieve an end effector Pose given the desired Pose coordinates, the robotic DH parameters and a starting set of joint angles
Example ¶
package main
import (
"fmt"
"github.com/koeng101/kinematics"
)
func main() {
// Establish the original joint angles
thetasInit := kinematics.JointAngles{0, 0, 0, 0, 0, 0}
// Establish coordinates to go to
coordinates := kinematics.Pose{Position: kinematics.Position{X: -100, Y: 250, Z: 250}, Rotation: kinematics.Quaternion{W: 0.41903052745255764, X: 0.4007833787652043, Y: -0.021233218878182854, Z: 0.9086418268616911}}
// Run kinematics procedure
angles, _ := kinematics.InverseKinematics(coordinates, kinematics.AR3DhParameters, thetasInit)
// Math works slightly differently on arm and x86 machines when calculating
// inverse kinematics. We check 5 decimals deep, since it appears numbers can
// have slight variations between arm and x86 at 6 decimals.
fmt.Printf("%5f, %5f, %5f, %5f, %5f, %5f\n", angles.J1, angles.J2, angles.J3, angles.J4, angles.J5, angles.J6)
}
Output: 1.846274, 0.341672, -2.313720, -1.776501, 2.221810, 1.231879
type Pose ¶ added in v1.0.1
type Pose struct {
Position Position
Rotation Quaternion
}
Pose represents a position and rotation, where Position is the translational component, and Rot is the quaternion representing the rotation.
func ForwardKinematics ¶
func ForwardKinematics(thetas JointAngles, dhParameters DhParameters) Pose
ForwardKinematics calculates the end effector Pose coordinates given joint angles and robotic arm parameters.
Example ¶
package main
import (
"fmt"
"github.com/koeng101/kinematics"
)
func main() {
angles := kinematics.JointAngles{J1: 10, J2: 1, J3: 1, J4: 0, J5: 0, J6: 0}
coordinates := kinematics.ForwardKinematics(angles, kinematics.AR3DhParameters)
fmt.Println(coordinates)
// Output {{-101.74590611879692 -65.96805988175777 -322.27756822304093} {0.06040824945687102 -0.20421099379003957 0.2771553334491873 0.9369277637862541}}
}
Output:
Source Files