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How to adjust the velocity profile of a 3-axis robot to avoid vibration?

2025/07/04 By Topstar

3-axis robot 8-8

Designed for precision injection molding applications, 3-axis robots are designed explicitly for pick-and-place operations. If slight vibrations during part removal can affect quality, increase cycle time, and cause unplanned maintenance. Therefore, we integrate vibration suppression functions throughout the mechanical design and control firmware of the 3-axis robot, while also considering how to adjust the speed profile. First, sudden acceleration or deceleration in production can cause structural resonance in the arm and wrist. Second, improper adjustment of the motion segment can produce oscillations, which will reduce long-term reliability. By carefully designing the acceleration, constant speed, and deceleration phases, we can significantly reduce mechanical shocks.

Dynamics of a 3-axis robot integrated with injection molding

During the injection molding process, fast part ejection, pick-and-place movements, and different payloads generate dynamic loads. When accelerating a 2 kg molded part, the robot’s wrist and arm may be subjected to inertial forces of more than 15 kg·m/s²; in addition, the cantilever section of the arm is close to the resonant frequency of 3-5 Hz, and this minor disturbance can also be amplified into significant vibrations. Therefore, modal testing using accelerometers and shakers is performed during the design process to analyze each motion axis, identify resonance peaks, and quantify damping ratios. Based on this data, we defined the maximum allowed acceleration and jerk values ​​for each segment. By modeling these dynamics in simulation tools such as MATLAB Simulink or ROS Gazebo, we ensured that the velocity profile prevented resonance amplification, allowing the 3-axis robot to perform high-speed, high-precision removals without causing harmful vibrations or reducing part accuracy.

Designing S-curve velocity profiles for smooth motion

Building on the 3-axis robot’s vibration suppression capabilities, we implemented S-curve velocity profiles, allowing acceleration and deceleration to change smoothly rather than abruptly. First, we calculated the maximum acceleration below the payload-specific resonance threshold. Then, I adjusted the acceleration profile to keep the acceleration rate within ±5000 mm/s³ to prevent sudden torque peaks from causing the end effector to bounce. Next, I wrote the motion planner for the 3-axis robot controller to interpolate velocities using a quintic polynomial, achieving seamless transitions between motion phases.

Additionally, I verified on the physical hardware that the peak torque demand did not exceed the motor rating, ensuring both the drive and the mechanism remained within a safe operating range. This strict S-curve implementation keeps the net forces on this type of injection molding robot structure within a safe range, resulting in smoother part pick-and-place cycles and eliminating micro-oscillations that reduce the accuracy of injection molding robots.

Bringing stable torque and high-speed capabilities to the injection robot

Segmenting Complex Paths of 3-Axis Robot to Reduce Vibration

The motions in the injection molding robot sequence are not all simple point-to-point moves, and complex trajectories can exacerbate vibrations if they are not appropriately segmented. At the same time, if not segmented, combining linear and joint interpolation motions can cause abrupt changes in velocity vectors; therefore, I decompose each multi-axis path into small linear or spline segments, each with an individually adjusted S-curve profile. Operators adjust the segment length to ensure each sub-move lasts over 100 milliseconds, giving the controller enough time to handle acceleration and avoid differential coordinate jumps. Additionally, we incorporate midpoint dwell commands in narrow corners to prevent centrifugal forces from shaking the robot arm. This fine segmentation, combined with real-time feedback monitoring of encoder ripple, prevents cumulative vibration and ensures that each part of the path maintains high accuracy.

Adaptive Real-Time Feedback and Vibration Correction

To further suppress vibration, our 3-axis robot controller integrates an adaptive real-time feedback loop into the motion control firmware. Our accelerometer, mounted on the robot’s wrist, continuously feeds vibration data into the controller. In addition, the control algorithm dynamically adjusts upcoming motion segments to suppress detected vibrations. We fine-tune the motion controller’s gains to prioritize vibration signals, cutting acceleration commands by 20% when they exceed thresholds. We also implement notch filters for identified resonant frequencies to attenuate end-effector wobble. By continuously analyzing the robot’s dynamic response, we dynamically adjust the velocity profile to ensure that each cycle compensates for subtle changes in payload, temperature, or wear, thereby maintaining consistent, vibration-free removal performance.

Practical Tips for Field Implementation

When deploying a 3-axis robot, engineers must consider several practical factors to ensure long-term vibration-optimized performance. First, perform a dry-run calibration at each new installation site to account for ground stiffness and anchoring conditions. Next, adjust acceleration and jerk parameters in 10% increments and monitor position errors using a laser tracker during initial runs. In addition, diagnostic tools are available to visualize velocity profiles and identify any “peaks” that may cause vibration. Additionally, technicians regularly recalibrate and conduct resonance tests to preserve S-curve setting integrity. This ensures your injection molding robot delivers flawless, vibration-free cycles while sustaining peak throughput.

injection molding robots Modular design brings flexibility

Speed ​​Profile Optimization

Adjusting the velocity profile of a 3-axis robot is crucial for preventing vibration and achieving high-precision performance in injection molding applications. Identify dynamic resonances, design S-curve motion segments, segment complex paths, and implement adaptive feedback to ensure smooth operation under any conditions. This will optimize your injection molding robot integration, increase production efficiency, and minimize scrap.

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