Robot Cycle Time Optimization: Beyond Trajectory Planning

The landscape

Robot cycle time has four components: motion time, settling time, process time, and overhead (I/O, vision, communication). Optimization efforts typically focus on motion time — shorter paths, faster acceleration, better via-point placement. But settling time, which often represents 10–40% of total cycle time in precision applications, is frequently overlooked because it's not explicitly visible in trajectory planning tools.

Optimization Approach	Component Addressed	Strengths	Trade-offs
Path and trajectory optimization	Motion time	Well-understood; broad tool support	Diminishing returns at high optimization; doesn't address settling
Speed and acceleration tuning	Motion time	Direct cycle time reduction	May increase vibration, worsening settling; accuracy trade-off
End-of-arm tool optimization	Process time	Reduces process-dependent delays	Application-specific; may require hardware changes
I/O and communication optimization	Overhead	Reduces handshake and synchronization delays	Often small absolute gains
Vibration compensation	Settling time	Reduces settling without reducing speed; additive to other methods	Requires per-arm calibration; supported platform needed

Why settling time matters

Settling time is the gap between "motion complete" (controller flag) and "process ready" (TCP within tolerance). It exists because robot arms are not perfectly rigid — deceleration excites structural vibration modes, and the TCP oscillates around the target until the vibration decays. Programmers compensate with dwell commands, fine zones, or speed reduction, each of which adds time.

Unlike motion time, settling time is not visible in trajectory planners or offline programming tools. It can only be measured in the physical system, which means it's typically addressed reactively (programmer adds dwell until quality is acceptable) rather than optimized systematically.

Vibration compensation as a settling time method

Feedforward vibration compensation modifies the command trajectory to avoid exciting the arm's structural vibration modes. The arm follows a slightly different command profile that produces the same endpoint position with less residual oscillation. The result is shorter settling time without reducing motion speed or tightening trajectory constraints.

Key characteristics:

Additive with other optimization methods: Motion time and settling time are independent; optimizing both compounds the cycle time improvement
Per-arm identification: The vibration model captures the specific dynamics of each arm, not a generic platform model
No speed reduction: The robot maintains its commanded speed and acceleration — the improvement comes from how it decelerates, not how fast it moves
Measurable: Settling time improvement can be directly measured with an accelerometer or high-speed position capture

Quantified impact

For a precision pick-and-place application with 10 stops per cycle, 200 ms of settling per stop, and 1,000 cycles per day:

Settling time per cycle: 2,000 ms (2 seconds)
With settling time eliminated: up to 2,000 ms recovered per cycle
Annual recovery at 260 operating days: up to 144 robot-hours per arm

For applications with more stops, longer settling, or multiple arms, the recovery scales proportionally.

What this means for your product

If your product or system includes robot cells where settling time is a significant fraction of cycle time — which it typically is in any application with precision stops — vibration compensation is a cycle time lever that works independently of trajectory optimization. It's most impactful in high-cycle-count applications where small per-cycle improvements accumulate to material throughput gains.