The Settling Time Component of Robot Cycle Time

The problem

Robot cycle time is the sum of motion time, process time, and overhead — I/O handshakes, vision acquisition, and settling. Of these, settling time is the least visible and the least optimized.

Settling time is the interval between the end of commanded motion and the moment the TCP enters and remains within its specified tolerance band. During this interval, the arm is physically at the target position (the controller reports "in position"), but residual vibration causes the TCP to oscillate outside the required accuracy window. The process cannot begin until the oscillation decays below threshold.

For point-to-point applications with precision requirements — pick and place, dispensing, welding starts, inspection — settling time can represent 10–40% of total cycle time, depending on speed, payload, and the arm's structural dynamics. This component is often invisible in cycle time analysis because it's buried inside "motion complete" to "process start" timing, or absorbed into programmer-added dwell commands.

Why trajectory optimization alone doesn't solve it

Trajectory optimization — smoothing paths, tuning acceleration profiles, optimizing via-point placement — reduces motion time. But the vibration that causes settling time is excited by the deceleration phase of the motion, not the trajectory shape during transit. A perfectly optimized trajectory that ends in a fast deceleration to zero velocity still excites the arm's flexible modes.

The conventional mitigation is to reduce the deceleration rate, which reduces vibration but extends the motion itself. This trades motion time for settling time — a lateral move in total cycle time.

Vibration compensation as a cycle time lever

Feedforward vibration compensation addresses the excitation directly. By modifying the command trajectory to avoid exciting the arm's identified flexible modes, the arm arrives at the target position with less residual oscillation. Settling time decreases because there is less vibration to settle.

The net cycle time improvement is the settling time reduction minus any command-shaping delay introduced by the compensation. In practice, the settling time saved typically exceeds the shaping delay, producing a net throughput improvement without increasing robot speed or reducing accuracy.

Performance

• Greater than 80% vibration reduction across deployments

• Up to 2x throughput improvement by eliminating settling time overhead

• Net cycle time improvement when settling is a significant fraction of total cycle time

• No change to robot speed, acceleration limits, or payload — the motion envelope stays the same

Quantified example

2 seconds of endpoint dwell per cycle × 1,000 daily cycles × 260 operating days = 144 robot-hours of annual production capacity recovered per arm. This is additive — it does not require the robot to move faster, only to settle faster.