# Combining Load and Motor Encoders to Compensate Nonlinear Disturbances for High Precision Tracking Control of Gear-Driven Gimbal

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## Abstract

**:**

## 1. Introduction

## 2. Control Model of Gear-Driven Gimbal

## 3. Robustness Analysis of the Rate Loop

## 4. Disturbance Observer of the Gear-Drive Gimbal

## 5. Experimental Setup

_{r}= 0.01°sin0.5t, the improved DOB can keep the steady state error lower than 0.01 degree, when approximated to the encoder precision. Without the DOB, disturbances regarding the friction and backlash lead to dead zone, which can be seen obviously in Figure 9 if the reference angular position is θ

_{r}= 5°sin0.5t. The DOB based on the sensor-fusion makes the tracking error smaller than that without the DOB both in the low-velocity tracking and the high-velocity tracking.

## 6. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 2.**The classical control block diagram of gear-drive gimbal. ${C}_{p}(s)$: position controller; ${C}_{m}(s)$: speed loop controller; ${\omega}_{L}(s)$: load angular velocity; ${\omega}_{m}(s)$: motor angular velocity; ${\theta}_{L}(s)$: load angular position; ${\theta}_{r}(s)$: reference angular position; ${P}_{1}(s)$: torque constant of motor; ${P}_{2}(s)$: mechanical transfer function of motor; $N$: reduction ratio; ${P}_{3}(s)$: the transfer function of gear; ${P}_{4}(s)$: load transfer function; ${T}_{L}(s)$: disturbance forces in the load side; ${T}_{m}(s)$: disturbance forces in the motor side.

**Figure 9.**Tracking error under different reference angular positions. The left reference angular position is the sinusoidal trajectory of θ

_{r}= 0.01°sin0.5t, and the right is the sinusoidal trajectory of θ

_{r}= 5°sin0.5t.

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**MDPI and ACS Style**

Tang, T.; Chen, S.; Huang, X.; Yang, T.; Qi, B.
Combining Load and Motor Encoders to Compensate Nonlinear Disturbances for High Precision Tracking Control of Gear-Driven Gimbal. *Sensors* **2018**, *18*, 754.
https://doi.org/10.3390/s18030754

**AMA Style**

Tang T, Chen S, Huang X, Yang T, Qi B.
Combining Load and Motor Encoders to Compensate Nonlinear Disturbances for High Precision Tracking Control of Gear-Driven Gimbal. *Sensors*. 2018; 18(3):754.
https://doi.org/10.3390/s18030754

**Chicago/Turabian Style**

Tang, Tao, Sisi Chen, Xuanlin Huang, Tao Yang, and Bo Qi.
2018. "Combining Load and Motor Encoders to Compensate Nonlinear Disturbances for High Precision Tracking Control of Gear-Driven Gimbal" *Sensors* 18, no. 3: 754.
https://doi.org/10.3390/s18030754