SmartBathroom Data Visualization Tool to Inform OT Clinical Reasoning

Traditionally, Occupational Therapy assessment of an older adult’s toilet transfer performance has been based on qualitative observation and client self-report. The purpose of this study was to evaluate the effectiveness of supplementing traditional clinical reasoning with quantitative transfer performance data about body and foot position, balance, hand placement and grasping forces on grab bars. Specifically, we conducted an online survey of occupational therapy practitioners and educators to assess the usefulness and usability of 2D and 3D graphic visualizations representing foot and hand position and forces exerted on the floor, toilet seat and grab bars. These data were captured by sensors located throughout GA Tech’s SmartBathroom laboratory during a study of transfer performance. Findings are being used to identify the most useful sensor data and the most effective ways to convey that data to improve training of occupational therapy students.

Kinematics modeling and grasping experiment of pneumatic four-finger flexible robotic hand

To solve the complex structure, poor flexibility, and heavyweight of the rigid robotic hand, a pneumatic four-finger flexible robotic hand is developed in this paper. The robotic hand is about 1.3 times as large as that of a human hand and each finger is composed of a single multi-drive bending joint. The kinematic model of the robotic hand is established by using homogeneous coordinate transformation matrix. Through the simulation experiment of the robotic hand structure, the trajectory, and workspace of the robotic hand are established. According to the experimental results of grasping performance of the robotic hand, the grasping forces of different geometric positions along the finger axis are obtained. The results show that the robotic hand can realize a variety of grasping modes, has flexible action and strong adaptive ability; it can grasp, hold, and pinch, as well as stably grasp objects such as cylinder, box, and sphere. In pinch grasp mode, the robotic hand can grip objects as thin as 1 mm and the diameter of the grasped object varies from 28 mm to 160 mm; the maximum mass that the robotic hand can grasp an object with a diameter of 90 mm under 0.35 MPa is 1386 g.

Development and comprehensive evaluation of a new spring-steel-driven glove for grasping assistance during activities of daily living

Millions of people suffer from a decline in grip strength and hand function due to conditions such as chronic disease, injuries, and aging. Hand function decline results in difficulties with performing activities of daily living, where grasping, lifting, and releasing objects are essential. There is an increasing demand for assistive gloves to enhance users’ hand function and improve their independence. This paper presents the design of a new bidirectional lightweight assistive glove and demonstrates its capabilities through comprehensive experiments using human subjects. The developed glove can provide adequate power augmentation for grasping and releasing objects due to its simple yet effective design using spring steel strips and linear actuators. The glove directly transfers assistive forces to users’ fingertips without any complex intermediate mechanism, and its low weight of 196 g promotes its usability. The rigorous experiment design provided a thorough assessment of the developed glove by accounting for both parameters of size and weight of objects and by including subjects with different hand sizes. To quantify the glove’s performance, the subjects’ muscle activity, their finger and thumb joints’ trajectories, and their grasping forces while using the glove were investigated. The glove could generate the necessary grasping forces to assist with lifting common-household objects. The subjects’ muscle activity significantly decreased when using the glove for object manipulation. The trajectories of the index finger and thumb joints when using the glove were dependent on the size of objects similar to natural unassisted grasping. The obtained results demonstrate the glove’s ability for grip power augmentation of individuals with declining hand strength.

Design Human-Robot Collaborative Lifting Task Using Optimization

In this paper, an optimization-based dynamic modeling method is used for human-robot lifting motion prediction. The three-dimensional (3D) human arm model has 13 degrees of freedom (DOFs) and the 3D robotic arm (Sawyer robotic arm) has 10 DOFs. The human arm and robotic arm are built in Denavit-Hartenberg (DH) representation. In addition, the 3D box is modeled as a floating-base rigid body with 6 global DOFs. The interactions between human arm and box, and robot and box are modeled as a set of grasping forces which are treated as unknowns (design variables) in the optimization formulation. The inverse dynamic optimization is used to simulate the lifting motion where the summation of joint torque squares of human arm is minimized subjected to physical and task constraints. The design variables are control points of cubic B-splines of joint angle profiles of the human arm, robotic arm, and box, and the box grasping forces at each time point. A numerical example is simulated for huma-robot lifting with a 10 Kg box. The human and robotic arms’ joint angle, joint torque, and grasping force profiles are reported. These optimal outputs can be used as references to control the human-robot collaborative lifting task.

Segmentations in fins enable large morphing amplitudes combined with high flexural stiffness for fish-inspired robotic materials

Fish fins do not contain muscles, yet fish can change their shape with high precision and speed to produce large and complex hydrodynamic forces—a combination of high morphing efficiency and high flexural stiffness that is rare in modern morphing and robotic materials. These “flexo-morphing” capabilities are rare in modern morphing and robotic materials. The thin rays that stiffen the fins and transmit actuation include mineral segments, a prominent feature whose mechanics and function are not fully understood. Here, we use mechanical modeling and mechanical testing on 3D-printed ray models to show that the function of the segmentation is to provide combinations of high flexural stiffness and high morphing amplitude that are critical to the performance of the fins and would not be possible with rays made of a continuous material. Fish fin–inspired designs that combine very soft materials and very stiff segments can provide robotic materials with large morphing amplitudes and strong grasping forces.

Evaluation of Grip Force and Energy Efficiency of the “Federica” Hand

The actual grip force provided by a hand prosthesis is an important parameter to evaluate its efficiency. To this end, a split cylindrical handlebar embedding a single-axis load cell was designed, 3D printed and assembled. Various measurements were made to evaluate the performances of the “Federica” hand, a simple low-cost hand prosthesis. The handlebar was placed at different angular positions with respect to the hand palm, and the experimental data were processed to estimate the overall grip force. In addition, piezoresistive force sensors were applied on selected phalanxes of the prosthesis, in order to map the distribution of the grasping forces between them. The electrical current supplied to the single servomotor that actuates all the five fingers, was monitored to estimate the force exerted on the main actuator tendon, while tendon displacement was evaluated by a rotary potentiometer fixed to the servomotor shaft. The force transfer ratio of the whole system was about 12.85 %, and the mean dissipated energy for a complete cycle of closing-opening was 106.80 Nmm, resulting lower than that of many commercial prostheses. The mean grip force of the “Federica” hand was 8.80 N, that is enough to support the user in many actions of daily life, also considering the adaptive wrapping capability of the prosthesis. On average, the middle phalanges exerted the greatest grip force (2.65 N) on the handlebar, while the distal phalanges a force of 1.66 N.

A Novel Design for a Compliant Mechanism Based Variable Stiffness Grasper Through Structure Modulation

Robots utilize graspers for interacting with an environment. Conventional robot graspers are composed of rigid links and are dedicated to perform a particular task. However, such graspers have difficulty conforming to objects of varied shape and exerting varying grasping forces. Soft robotic graspers provide these features through different modalities. However, such modalities that vary the stiffness of soft robotic graspers face issues such as slow response time, requirement of external power packs for operation and low variation of stiffness. A variable stiffness compliant robotic grasper that is simple in design and operation would improve end effectors used in assistive robotics and prostheses where ability to vary stiffness would benefit in handling a wide array of objects. This research presents a novel method of achieving variable stiffness through structural transformations. Current designs utilizing structural transformations do not provide shape conformance while grasping objects. We propose a design for a soft robotic grasper utilizing the concept of stability of structures. This design is capable of adapting to the surface of an object being grasped and can rapidly vary its stiffness. The grasper behavior is modelled using Finite Element Analysis and validated experimentally. Our results demonstrate that structural transformation of flexible elements is a potential solution for achieving variable stiffness in a grasper.

Contact force analysis on two-fingered robot grasping

A procedure for inverse kinetic analysis on two hard fingers grasping a hard sphere is proposed in this study. Contact forces may be found for given linear and angular accelerations of a spherical body. Elastic force-displacement relations predicted by Hertz contact theory are used to remove the indeterminancy produced by rigid body modelling. Two types of inverse kinetic analysis may be dealt with. Firstly, as the fingers impose a given tightening displacement on the body, and carry it to move with known accelerations, corresponding grasping forces may be determined by a numerical procedure. In this procedure one contact force may be chosen as the principal unknown, and all other contact forces are expressed in terms of this force. The numerical procedure is hence very efficient since it deals with a problem with only one unknown. The solution procedure eliminates slipping thus only nonslip solutions, if they exist, are found. Secondly, when the body is moving with known accelerations, if the grasping direction of the two fingers is also known, then the minimum tightening displacement required for non-sliding grasping may be obtained in closed form. In short, the proposed technique deals with a grasping system that has accelerations, and in this study the authors show that indeterminancy may be used to reduce the complexity of the problem.