Closing the Sim2Real Gap: A Comparative Analysis of Kinco Actuator Joints in Isaac Sim
Introduction
One of the most persistent challenges in robotics development is the discrepancy between simulated environments and real-world hardware behavior—commonly known as the Sim2Real gap. To address this, each Kinco actuator joint is paired with a corresponding simulated joint that has been carefully tuned with parameters derived from real hardware testing. This article presents a comparative study between the Kinco simulated actuator joint and the default simulated joint available in Isaac Sim, demonstrating that the parameter-tuned Kinco model achieves significantly higher fidelity to real-world behavior.
Methodology
We conducted a series of standardized comparison tests between the Kinco simulated joint (Model A: Parameter Tuning Model) and the default simulated joint (Model B: Default Parameter Model) within the Isaac Sim environment.
The testing protocol included:
1. TN Curve Testing – Evaluation of torque-speed characteristics to verify dynamic response accuracy
2. Second-Hand Motion Testing – Assessment of fine motor control and low-speed precision
3. 175° Positioning Testing – Verification of large-angle positioning accuracy and repeatability
4. Constant-Speed Motion Testing – Evaluation of velocity stability under varying loads
Parameter Comparison
The following table summarizes the key parameter differences between the two models:
| Parameter (iFMH55H100.usd) | A · Parameter tuning model | B · Default parameter model |
|---|---|---|
| Max Force | 35 Nm | inf |
| Speed-Effort Gradient | 4.285714 (deg/s)/Nm | 0 |
| Velocity Dependent Resistance | 0 | 0 |
| Maximum Joint Velocity | 300 deg/s | 1e6 deg/s |
| Armature | 0.0808408 kg·m² | 0 |
| Static Friction Effort | 1.791 Nm | 0 |
| Dynamic Friction Effort | 1.791 Nm | 0 |
| Viscous Friction Coefficient | 0.0119 N·m·s/deg | 0 |
Torque – Speed Curve
The most notable distinction lies in the Max Force parameter. While the default model applies infinite force—an idealized assumption that fails to capture real actuator limitations—the Kinco tuned model correctly constrains torque to 35 Nm, reflecting the physical capabilities of the actual hardware. Similarly, the Speed-Effort Gradient of 4.285714 (deg/s)/Nm in the Kinco model introduces realistic velocity-dependent behavior that is entirely absent in the default model (gradient = 0).
Results
Across all four test categories, the Kinco simulated joint consistently outperformed the default model in terms of consistency with real hardware. The parameter-tuned model demonstrated:
• More accurate torque-speed trade-offs matching physical actuator behavior
• Improved low-speed motion fidelity
• Higher positioning accuracy at large angles
• More realistic velocity control under load
These improvements collectively resulted in a smaller Sim2Real gap compared to the default Isaac Sim joint model.
Demonstration Setup
The accompanying demonstration is organized into two visual sections:
• Left Side (A): The parameter tuning model, showing the sim-to-real workflow, the physical robot actuator, and a motion control demonstration
• Right Side (B): The default parameter model running the same test scenarios for direct comparison
Conclusion
The results conclusively show that the Kinco simulated joint—with its carefully tuned parameters—achieves superior consistency with real hardware compared to the default Isaac Sim model. By accurately modeling physical constraints such as finite maximum force and speed-effort gradients, the Kinco model provides a more reliable foundation for simulation-based development, reducing the risk of control policy failures when transitioning from simulation to real-world deployment. This work underscores the importance of parameter tuning in actuator modeling and its direct impact on closing the Sim2Real gap in robotic applications.