Improving Robotic Weld Quality Through Motion Compensation: Approaches and Trade-offs

The landscape

Weld defects in robotic welding frequently trace to the robot's motion quality — not to the welding process parameters. Two motion-level problems dominate: torch vibration at corners and start/stop points, and positional drift along the seam path. Several approaches address these issues:

Approach	Strengths	Trade-offs
Seam tracking (laser/vision)	Corrects for part variation in real time	Adds sensor cost, integration complexity; doesn't address vibration; latency in correction loop
Travel speed reduction	Reduces vibration amplitude and improves path following	Lower throughput; changes heat input profile, which can affect weld metallurgy
Path smoothing / corner blending	Reduces deceleration-induced vibration	May deviate from programmed path at corners; limited by OEM trajectory planner capabilities
Higher-rigidity robot platform	Mechanically reduces vibration	Capital cost; may still have kinematic accuracy limitations
Software-based vibration + accuracy compensation	Addresses both vibration and path accuracy at the control level	Requires per-arm calibration; supported command interface required

How motion compensation works for welding

Software-based compensation combines two techniques:

Vibration compensation (Shaper) reduces TCP oscillation by shaping trajectory commands to avoid exciting the arm's flexible modes. The torch arrives at corners and start points with less overshoot, improving bead consistency at direction changes.

Accuracy compensation (Joint Tracker / KineCal) corrects kinematic model errors and compensates for dynamic effects (thermal drift, payload compliance). The torch follows the programmed seam path more closely, reducing seam deviation — particularly in offline-programmed paths and multi-pass welds.

Key characteristics:

Addresses root cause, not symptom: Improves the robot's motion quality rather than adding compensating sensors
Compatible with seam tracking: Compensation improves the baseline motion; tracking corrects for part-level variation. The two are complementary.
No welding system changes: Operates at the robot control level — torch, wire feed, gas, and power supply are unaffected
Per-arm calibration: Each arm is individually characterized, capturing its specific vibration and accuracy characteristics
Feedforward architecture: Compensation is applied to commands before they reach the servo loop — no production sensors required

Demonstrated performance

Greater than 80% vibration reduction at TCP during testing
Up to 5.7x TCP accuracy improvement on collaborative robot platforms
Applicable to MIG/MAG, TIG, laser, and resistance welding processes
Real-time compensation at 250 Hz command rate
No permanent sensors or mechanical modifications to the robot or welding system
Cloud-based model identification; local runtime execution

Evaluation path

Start with one welding arm in a representative application. Calibrate the arm (accelerometer-based, under one hour), identify the vibration and accuracy models, and run comparative weld tests — same program, same parameters, with and without compensation. Evaluate bead consistency at corners and path deviation along seam lines using your standard inspection methods.

Current platform support: Standard Bots, UFACTORY, Trossen, and Denso.

What this means for your product

If weld quality limitations in your product trace to the robot's motion rather than the welding process — inconsistent corners, wandering seams, start-point defects — software-based motion compensation addresses the root cause. For product teams evaluating seam tracking or platform upgrades to improve weld quality, it's worth isolating the motion contribution first: compensation may resolve the issue at lower cost and complexity, or it may complement tracking by providing a cleaner baseline for the sensor to work from.