An Admittance-Controlled Force-Scaling Dexterous Assistive Robotic System

Play has a vital role in a child's development; it can affect everything from social and language to cognitive and perceptual skills. However, if a child has a physical disability, the fundamental limitations of their disability may prevent them from participating in all forms of play. Construction and block play is an example of play that may be dicult for children who have reduced upper body strength and are, therefore, unable to manipulate heavier objects in space. In this paper, we propose a novel 6 degree-of-freedom admittance-controlled, force-scaling robot that will allow for children to lift heavier objects than they would normally be able to, while still retaining the full range of motion of their upper-body. This assistive system is designed to retain the user's haptic perception, allowing the user to still partially feel the weight of the objects that they are manipulating. Two user studies are done to evaluate the usability of the system. First, in order to ensure that the force scaling of the system does not negatively affect a user's haptic perception, ten able-bodied individuals were asked to order a series of buckets with identical appearances but different masses from lightest to heaviest with three different force scaling factors. It was shown that the force amplification ability of the system does not significantly detract from user's ability to discriminate masses. Second, in order to evaluate the precision and the usefulness of the force scaling of the system, users were asked to perform a challenging peg-in-hole insertion task. Results indicate that the system has a positive effect on the ability of a user to perform the task when the assistance is necessary. However, increasing amounts of assistance do not have any significant effect past those required for participants to complete the task without issues. The effect of a modular reacher bar that can augment the workspace of users is investigated through a similar peg-in-hole insertion task. For the trials with the modular reacher bar attached, it is shown that the system's force amplification has a very positive effect in assisting users in completing the task. It should be noted that although the target population for this paper is children with disabilities, there can also be uses for this system as a general assistive technology for adults with upper-body weakness in their daily lives.