Coriolis and centrifugal forces are the velocity-dependent effects that make a robot's joints tug on each other as they move — the coupling term in the equations of motion that fast, precise robots must account for.
When a robot's joints are moving, they create extra forces that push on the other joints — centrifugal (flinging outward) and Coriolis (from combined motions). At low speed you can ignore them; at high speed they matter a lot.
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Coriolis and centrifugal forces in a robot arm depend on…
An arm that tracks a target beautifully at slow speed can wander off when it moves fast. A big reason is a set of forces that only appear while things are moving: the Coriolis and centrifugal terms.
What they are
These are velocity-dependent forces inside a multi-joint robot:
Centrifugal — the outward effect of a joint rotating (like the pull you feel on a merry-go-round). It grows with the square of a joint's speed.
Coriolis — an effect that arises when two joints move at once, coupling their motions in a way that isn't obvious from either alone.
Crucially, both are zero when the robot is still and grow as it speeds up — which is exactly why they're easy to ignore in slow motion and impossible to ignore in fast motion.
Motion creates coupling forces
The faster the joints move, the more they disturb one another. These forces are the C(θ,θ̇)θ̇ term in the equations of motion.
Where they live in the math
In the manipulator equations of motion, M(θ)θ̈ + C(θ,θ̇)θ̇ + g(θ) = τ, they are the C(θ,θ̇)θ̇ term. A slow robot can drop it and rely on feedback to mop up the small error. A fast, high-performance robot must model it: computed-torque control explicitly cancels the Coriolis/centrifugal term (along with gravity and inertia) so each joint tracks cleanly regardless of speed.
Intuition
Think of a spinning ice skater extending an arm — the arm feels forces purely because of the rotation, not because anyone pushed it. In a robot, one joint's rotation creates similar apparent forces on the links beyond it. They are "fictitious" in the sense of arising from motion in a rotating frame, but their effect on the real motors is very real.
Why it matters
Coriolis and centrifugal forces are the reason robot dynamics can't be reduced to "just gravity and inertia" for fast machines. Accounting for them is what separates a controller that works at demo speed from one that works at production speed.
