Position Control for Soft Actuators, Next Steps toward Inherently Safe Interaction

Abstract

Soft robots present an avenue toward unprecedented societal acceptance, utility in populated environments, and direct interaction with humans. However, the compliance that makes them attractive also makes soft robots difficult to control. We present two low-cost approaches to control the motion of soft actuators in applications common in human-interaction tasks. First, we present a passive impedance approach, which employs restriction to pneumatic channels to regulate the inflation/deflation rate of a pneumatic actuator and eliminate the overshoot/oscillation seen in many underdamped silicone-based soft actuators. Second, we present a visual servoing feedback control approach. We present an elastomeric pneumatic finger as an example system on which both methods are evaluated and compared to an uncontrolled underdamped actuator. We perturb the actuator and demonstrate its ability to increase distal curvature around the obstacle and maintain the desired end position. In this approach, we use the continuum deformation characteristic of soft actuators as an advantage for control rather than a problem to be minimized. With their low cost and complexity, these techniques present great opportunity for soft robots to improve human–robot interaction.

A Review of End-Effector Research Based on Compliance Control

“…Finally, they demonstrated the feasibility of bending the actuator. Wehner et al [59]. controlled the flow of air in and out of the actuator by tuning the impedance limits to produce bending actuation.…”

Low Power Sensor Location Prediction Using Spatial Dimension Transformation and Pattern Recognition

“…Sensors owned by humans include smartphones [22] and beacons. If a sensor is installed on a robot, the robot's motion control [23] function can be used to predict its future positions. In general, there are various methods that can be used to determine the location of a specific object in space, but methods using a sensor mainly use a triangulation technique based on the estimation of the DTOA (differential time of arrival) [24].…”

A Dynamic Pole Motion Approach for Control of Nonlinear Hybrid Soft Legs: A Preliminary Study

“…Adaptive control schemes have been applied for nonlinear systems, such as inverse optimal controllers [33,34], and the scope of the adaptive controls has been extended to soft robotics [35,36]. Other closed-loop control approaches have also been studied, such as PD or PID controls [37][38][39] and FEM-based controls [40][41][42]. However, those approaches have not completely been solutions of nonlinearity soft robots exhibit owing to large deformations.…”