Robot control
Operational-space control
Definition
Operational-space control formulates a robot’s motion and force behavior in task coordinates, such as the position and orientation of its hand, while accounting for the robot’s dynamics. Secondary joint objectives can be coordinated with the primary task.
Also known as: Operational space control, OSC
Updated
Expressing the task at the hand
A manipulation task may specify where the hand should move and how it should respond to contact, rather than an independent target for every joint. Operational-space control uses the hand's task coordinates together with the robot's dynamics to calculate the required actuation.
MIT's manipulation notes derive an effective task-space inertia from the joint-space inertia and Jacobian. Desired task forces map to joint torques through the Jacobian transpose. This goes beyond solving inverse kinematics for a pose because it concerns dynamic behavior and forces.
Preserving room for secondary objectives
A redundant arm can often change its elbow position while holding its hand still. A secondary posture objective can act through a dynamically consistent null-space projection so that it does not interfere with the primary task under the model assumptions.
Conditions for using the model
Task-space inertia expressions require an appropriate rank condition; near a kinematic singularity, some task directions lose authority. Model errors, joint limits, and additional contacts also matter. Whole-body control extends related ideas to several tasks and constraints, including the feet and floating base of a humanoid.
Sources
Related terms
Robot Jacobian
A robot Jacobian is a configuration-dependent matrix that maps joint velocities to a chosen task velocity, often an end-effector twist. It describes the local relationship between joint motion and task motion.
Null space
The null space of a matrix is the set of vectors it maps to zero. For a robot task Jacobian, it contains joint velocities that produce no instantaneous motion in the specified task coordinates.
Whole-body control
Whole-body control coordinates a robot’s joints and contacts to satisfy several motion and force objectives together. In humanoids, it commonly combines balance, foot motion, hand tasks, and posture subject to physical constraints.
Impedance control
Impedance control shapes the dynamic relationship between a robot’s motion and the forces it exchanges with its environment. A common goal is for the robot to respond like a chosen mass, spring, and damper at a joint or end effector.