soft robot with motion control

Myself and a team of 3 other students developed a system to provide surgeons control over a pneumatically actuated soft robot with 2 rotational d.o.f. through a hand-mounted motion controller. The soft robot mimics the motion of the surgeon’s wrist by tracking the relative angle between inertial measurement units (IMU) mounted on a soft sleeve on the hand and wrist. The soft robot is a scaled up version of a soft endoscopic or catheter robot for minimally invasive surgery.

The system is built on an Arduino microcontroller with bang-bang control. As the relative angle of the hand changes beyond a specified threshold, a solenoid valve opens, the air pump turns on, and the corresponding chamber inflates creating a bending angle matching that of the hand. Closed loop feedback is made possible by pressure sensors on the pneumatic lines where internal pressure is mapped to bending angle of the robot. A calibration was obtained, mapping pressure to a bending angle obtained via an IMU. For the control, flexion and extension in the wrist are linked to pitch while abduction and adduction are linked to yaw, providing an intuitive human-robot interface.

The soft robot was fabricated by pouring EcoFlex 00-30 silicone elastomer as 4 PneuNet actuators in parallel which are designed to create bending due to expansion in only the most compliant regions (where pressure vessel walls are thinnest). The system was tested to have a range of motion of 80 degrees in the pitch, and 50 degrees in the yaw rotational directions, which would prove useful for a surgical robot.

Functionality of the device was evaluated by measuring the amount of time it took untrained test subjects to move the robot to a desired configuration. The objective was to move the robot such that a laser pointer was fixed on a goal location. Two subjects completed the tasks. After five minutes of training, the subjects’ time to reach the goal decreased by half. Additionally a NASA TLX surveying of each subject indicated a low work load completing the task.