Multi-link endoscopic manipulator robot actuated by shape memory alloys spring actuators controlled by a sliding mode

Area of Science:

• Robotics
• Control Systems
• Biomedical Engineering

Background:

• Minimally invasive surgery demands advanced robotic tools.
• Snake-like endoscopic manipulator robots (SLEMRs) offer enhanced dexterity.
• Precise control of SMA actuators is crucial for SLEMR functionality.

Purpose of the Study:

• To design and evaluate a prototype SLEMR with SMA actuators.
• To develop and validate a robust automatic controller using first-order sliding mode theory.
• To achieve accurate trajectory tracking for SLEMR joints and its tip.

Main Methods:

• Constructed a SLEMR with sequential links and two-DOF joints using SMA actuators in an agonist-antagonist configuration.
• Developed an elongation-temperature model for SMA actuators to determine velocity bounds.
• Implemented a first-order sliding mode controller for robust trajectory tracking, outputting PWM signals to regulate SMA temperature.

Main Results:

• The controller successfully achieved simultaneous trajectory tracking for all SLEMR joints.
• The SLEMR tip accurately followed reference positions.
• Experimental validation showed tracking errors less than 1.0 mm within 0.5 seconds.

Conclusions:

• The designed SLEMR and sliding mode controller effectively enabled precise robotic endoscope manipulation.
• The system demonstrated robustness against uncertainties and external perturbations.
• This technology holds promise for advancing minimally invasive surgical procedures.