Soft Elbow Exoskeleton for Upper Limb Assistance Incorporating Dual Motor-Tendon Actuator

Abstract

Loss of muscle functions, such as the elbow, can affect the quality of life of a person. This research is aimed at developing an affordable two DOF soft elbow exoskeleton incorporating a dual motor-tendon actuator. The soft elbow exoskeleton can be used to assist two DOF motions of the upper limb, especially elbow and wrist movements. The exoskeleton is developed using fabric for the convenience purpose of the user. The dual motor-tendon actuator subsystem employs two DC motors coupled with lead-to-screw converting motion from angular into linear motion. The output is connected to the upper arm hook on the soft exoskeleton elbow. With this mechanism, the proposed actuator system is able to assist two DOF movements for flexion/extension and pronation/supination motion. Proportional-Integral (PI) control is implemented for controlling the motion. The optimized value of Kp and Ki are 200 and 20, respectively. Based on the test results, there is a slight steady-state error between the first and the second DC motor. When the exoskeleton is worn by a user, it gives more steady-state errors because of the load from the arm weight. The test results demonstrate that the proposed soft exoskeleton elbow can be worn easily and comfortably by a user to assist two DOF for elbow and wrist motion. The resulted range of motion (ROM) for elbow flexion–extension can be varied from 90° to 157°, whereas the maximum of ROM that can be achieved for pronation and supination movements are 19° and 18°, respectively.

Lower limb exoskeleton robot and its cooperative control: A review, trends, and challenges for future research

“…(E) Exoskeletons can deliver direct help for heavy hand tools by offloading their weight onto external support, such as a floor, via a series of linkages at hips, knees, and ankles, bypassing the wearer's body. (F) A powered exoskeleton's ability to communicate or combine different materials, such as batteries, sensors, actuators, and motors, is crucial (Ismail et al, 2019 ). (G) Powered exoskeletons can expand the human body by supplying and influencing energy to the arms and legs.…”

Sensors and Actuation Technologies in Exoskeletons: A Review

“…Sometimes, an alternative type of mechanical transmission used involves the use of different sensors than usual. For example, in the work by Ismail et al [ 138 ], an infrared sensor was used as limit switch within a mechanism based on a high precision lead screw, which moved a tendon cable able to transfer the movement from the actuator to the interface between human and exoskeleton.…”

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Soft Exoskeletons: Development, Requirements, and Challenges of the Last Decade

“…Figure 3 shows the components of the device. Ismail et al [7] made an exoskeleton with two degrees of freedom for the elbow. It allows a flexion/extension range of motion of 90 • to 157 • , while the maximum range of motion for pronation and supination are 19 • and 18 • , respectively.…”

“…Additionally, due to their characteristics, they are easier to transport and install, allowing the patient to use these devices alone and in multiple locations. Soft exoskeletons have been made to aid the movement of the fingers [3,4], wrist [5,6], elbow [7,8], shoulder [9,10], hip [11,12], knee [13,14], and ankle [15,16].…”