Multiplexed Single-Pump Actuation of Soft Robotic Systems for Patient-Conforming Radiotherapy Devices
Abstract
Purpose
Enhancing dosimetric accuracy, for example by reducing air gaps in bolus or through robust, reproducible, patient-specific immobilization, is a potential application of soft robotics in radiation therapy. This work sought to develop an inexpensive control system for fluid-actuated soft robotic therapeutic applications. This system aims to provide control over multiple fluid lines with a single pump, potentially expanding the functionality and versatility of soft robotics in clinical settings.
Methods
A multiplexer-style control system was designed and prototyped, enabling the control of up to 25 distinct fluid lines from a single 100cc pump. This system was tested using compressed air to actuate a robot structured as a 4x6 array of 3.4 cm3 cubes. Each cube essentially became addressable for open-loop, volume-controlled filling, allowing control of the planar surface below the cubes. Motions of arching, twisting, and bending were explored through various actuation sequences.
Results
The system successfully managed 25 independent fluid lines (24 fill plus 1 for outlet). Cubes filled on the order of seconds for simple actuations and minutes for multi-channel shapes. Complex surfaces such as arch or twist were achieved, demonstrating the system’s ability to handle independent lines, whether to generate programmed surfaces or respond to specific commands. Relative volume filling accuracy was primarily limited by the resolution of the linear potentiometer used for geared motor feedback on the pump.
Conclusion
We demonstrated the ability to prototype a low-cost, multiplexed control system capable of actuating 25 fluid channels in soft robotic devices using a single pump. The design enables complex deformations needed for patient conforming surfaces in radiation therapy yet keeps hardware complexity and cost at a minimum. Future work will focus on integration into clinically relevant soft robotic boluses and immobilization prototypes.