Multiobjective Optimization for Stiffness and Position Control in a Soft Robot Arm Module

Abstract

The central concept of this letter is to develop an assistive manipulator that can automate the bathing task for elderly citizens. We propose to exploit principles of soft robotic technologies to design and control a compliant system to ensure safe human-robot interaction, a primary requirement for the task. The overall system is intended to be modular with a proximal segment that provides structural integrity to overcome gravitational challenges and a distal segment to perform the main bathing activities. The focus of this letter is on the design and control of the latter module. The design comprises of alternating tendons and pneumatics in a radial arrangement, which enables elongation, contraction, and omnidirectional bending. Additionally, a synergetic coactivation of cables and tendons in a given configuration allows for stiffness modulation, which is necessary to facilitate washing and scrubbing. The novelty of the work is twofold: 1) Three base cases of antagonistic actuation are identified that enable stiffness variation. Each category is then experimentally characterized by the application of an external force that imposes a linear displacement at the tip in both axial and lateral directions. 2) The development of a novel algorithm based on cooperative multiagent reinforcement learning that simultaneously optimizes stiffness and position. The results highlight the effectiveness of the design and control to contribute toward the development of the assistive device

Design of Paired Pouch Motors for Robotic Applications

“…A wide range of robotic continuum manipulators have been developed ranging from tendon‐driven manipulators installed on moving vehicles and others that behave as an octopus arm, pneumatically and vacuum‐driven continuum manipulators, vacuum‐driven continuum manipulators composed of stackable modules, fluidic elastomer manipulators, continuum actuators combining tendons and PAM actuators for combined position and stiffness control, and sPAMs‐driven continuum actuators . Other types of robotic arms have used jointed motions using either inflatable joints with a series of single degree‐of‐freedom (DOF) joints or PAMs to produce multi‐DOF joints capable of 3D positioning .…”

Collaborative robot zero moment control for direct teaching based on self-measured gravity and friction

“…The constant matrix I c can be obtained experimentally, as described in the following section. equation (8) yields the amount of current I g needed to achieve gravitational moment compensation.…”

“…7 The foundation of zero moment control technology based on position control is the transformation of the magnitude and direction of external forces into corresponding position commands. 8,9 The servo drive works in the position mode and provides the direct teaching function by tracking the location instruction. There are two ways to obtain the main moment information: one method utilizes sensors, with a six-dimensional moment sensor 5 at the end of each linkage or torque sensors at all joints to realize detection of an external force, and the second technique is to adopt the method of estimation.…”

Model-Based Pose Control of Inflatable Eversion Robot With Variable Stiffness

“…However, stiffness variation which occurs due to the increase in internal pressure once the robot achieves its maximum length is not considered in this work. Recent work explores position and stiffness control of a soft robot with antagonistic pneumatic-tendon actuators [22]. Kinematic control for an inflatable manipulator which considers the change in structural stiffness has also been reported recently [23].…”