IntermediateTopic 57 of 102Manufacturing, Robotics & Systems
Inverse kinematics
Find joint angles for a desired end-effector pose.
In depth
IK finds joint values for a desired pose: may have zero, one, multiple or infinite solutions (elbow up/down). Analytical solutions exist for common geometries (spherical wrist); otherwise numerical methods (Jacobian pseudo-inverse, damped least squares). Check joint limits and collisions.
Key points
- Closed-form vs numerical
- Multiple configurations
- Singularities
ExampleA 2-link arm reaching a point has two solutions: elbow-up and elbow-down.
What is Inverse kinematics?
Find joint angles for a desired end-effector pose.
Why is it important to understand inverse kinematics?
Inverse kinematics finds the joint angles needed to reach a target, which is the calculation behind almost every robot motion command.
Why is inverse kinematics harder than forward?
Several solutions may exist or none, and it may be nonlinear, so the solver must choose the correct branch and handle limits.
What are common solution methods?
Analytic solutions for simple arms, and numerical methods such as the Jacobian transpose or pseudo-inverse for general arms.
How is Inverse kinematics used in practice?
Typical applications include moving a robot tool to a specified point on a part, solving the joint angles for a pick and place cycle and planning a welding path with many target poses.
What should I learn before Inverse kinematics?
Study "Forward kinematics" first (topic 56 of 102 in Manufacturing, Robotics & Systems). It covers the groundwork this topic builds on.
What are the key points of Inverse kinematics?
Closed-form vs numerical. Multiple configurations. Singularities.
Can you give an example of Inverse kinematics?
A 2-link arm reaching a point has two solutions: elbow-up and elbow-down.
What comes after Inverse kinematics?
The next topic is "Jacobian and singularities", which builds directly on this one.
How difficult is Inverse kinematics?
It is classed as Intermediate in Manufacturing, Robotics & Systems (topic 57 of 102). It is an intermediate topic. Work through the beginner topics in Manufacturing, Robotics & Systems first.