What is the difference between the pose of a robot and the configuration of a robot?

Question

Do "configuration" and "pose" means the same thing? If not what is the difference?

Answer 1

Do "configuration" and "pose" means the same thing?

No.

---

One of the most clear definitions of 'pose' that I've heard is in Peter Corke's Robotics, Vision and Control (RVC). It states that:

"The position and orientation of a coordinate frame is known as its pose and is shown graphically as a set of coordinate axes. The relative pose of a frame with respect to a reference coordinate frame is denoted by the symbol ξ".

The following figure is figure 2.2 in RVC:

The point P can be described by coordinate vectors relative to either frame {A} or {B}. The pose of {B} relative to {A} is $ ^{A} ξ _{B} $

---

The 'configuration' of a robot is a set of scalar parameters that specify the positions of all of the robot's points relative to some fixed coordinate system. This can be expressed as a vector of positions and orientations, for example:

q = ($x$, $y$, $\theta$)

or

q = (($x$, $y$, $z$, $\alpha$, $\beta$, $\gamma$))

The set of all possible configurations is the 'configuration space', or 'C-space'.

---

If we consider the two-link planar manipulator with 2 revolute joints (2R-arm), shown here (taken from fig 7.3 in RVC):

The configuration can be expressed in terms of just the two joint angles $\theta _{1}$ and $\theta _{2}$, while the configuration space is the set of all possible combinations of the joint angles $\theta _{1}$ and $\theta _{2}$.

Note that configurations are not necessarily unique. For this robot, there are two possible configurations that result in the same end-effector position, but the end effector will have a different orientation in each case.

---

A worked example using MATLAB can be found in the Analyzing a 2-joint planar robot arm lesson on Peter's QUT Robot academy. This includes a visual description of the 2R-arm shown above.