Multi-Sensor Fusion for State Estimation and Control of Cable-Driven Soft Robots

Cable-driven soft robots exhibit complex deformations, making state estimation challenging. Hence, this paper develops a multi-sensor fusion approach using a gradient descent strategy to estimate the weighting coefficients. These coefficients combine measurements from proprioceptive sensors, such as resistive flex sensors, to determine the bending angle. Additionally, the fusion strategy adopted provides robust state estimates, overcoming mismatches between the flex sensors and soft robot dimensions. Furthermore, a nonlinear differentiator is introduced to filter the differentiated sensor signals to address noise and irrational values generated by the Analog-to-Digital Converter. A rational polynomial equation is also introduced to compensate for temperature drift exhibited by the resistive flex sensors, which affect the accuracy of state estimation and control. The processed multi-sensor data is then utilized in an improved PD controller for closed-loop control of the soft robot. The controller incorporates the nonlinear differentiator and drift compensation, enhancing tracking performance. Experimental results validate the effectiveness of the integrated approach, demonstrating improved tracking accuracy and robustness compared to traditional PD controllers.