Modeling and Control of a Cable-Driven Rotary Series Elastic Actuator for an Upper Limb Rehabilitation Robot

Abstract

This paper focuses on the design, modeling, and control of a novel remote actuation, including a compact rotary series elastic actuator (SEA) and Bowden cable. This kind of remote actuation is used for an upper limb rehabilitation robot (ULRR) with four powered degrees of freedom (DOFs). The SEA mainly consists of a DC motor with planetary gearheads, inner/outer sleeves, and eight linearly translational springs. The key innovations include (1) an encoder for direct spring displacement measurement, which can be used to calculate the output torque of SEA equivalently, (2) the embedded springs can absorb the negative impact of backlash on SEA control performance, (3) and the Bowden cable enables long-distance actuation and reduces the bulky structure on the robotic joint. In modeling of this actuation, the SEA's stiffness coefficient, the dynamics of the SEA, and the force transmission of the Bowden cable are considered for computing the inputs on each powered joint of the robot. Then, both torque and impedance controllers consisting of proportional-derivative (PD) feedback, disturbance observer (DOB), and feedforward compensation terms are developed. Simulation and experimental results verify the performance of these controllers. The preliminary results show that this new kind of actuation can not only implement stable and friendly actuation over a long distance but also be customized to meet the requirements of other robotic system design.

Design of a Cable-Driven Actuator for Pronation and Supination of the Forearm to Integrate an Active Arm Orthosis

“…The power transmission efficiency (𝜂 𝑟 ) of the gearbox coupled to the motor should also be considered. The force transmission efficiency can be modeled similarly as for a cable sliding on a stationary pulley by Equation (3) [18,19], where μ is the Coulomb friction coefficient between the cable and the sheath and ф is the bending angle of the sheath.…”

Autonomous Exercise Generator for Upper Extremity Rehabilitation: A Fuzzy-Logic-Based Approach

“…In contrast with end-effector robots, exoskeleton robots can be used in a more compact working environment. Exoskeleton robots have had similar success where multiple developments have shown great potential [22][23][24][25][26][27][28] and technological advancement only facilitates the improvement in the performance of these robots [29][30][31][32][33][34][35]. These robotic systems can easily give consistent training and monitor performance with great accuracy and reliability, and hence can provide crucial components for rehabilitation independently such as intensive movement therapy, just-right challenge, task-specific movement, and feedback on performance.…”

A Novel 3-RRR Spherical Parallel Instrument for Daily Living Emulation (SPINDLE) for Functional Rehabilitation of Patients with Stroke

“…25,26 Another new direction of wrist devices focuses on the compactness of the devices to develop lightweight systems stressing on the practical use of the devices. [27][28][29][30] Researchers tried to make the system more compact by implementing a compact series elastic actuator for variable stiffness control or employing smart mechanism for a fully portable 5-DoF wrist-elbow rehabilitation device. 29,30 Most of the developed devices are exoskeleton type, which require aligning the human and robot joint axes before training the patient.…”

“…[27][28][29][30] Researchers tried to make the system more compact by implementing a compact series elastic actuator for variable stiffness control or employing smart mechanism for a fully portable 5-DoF wrist-elbow rehabilitation device. 29,30 Most of the developed devices are exoskeleton type, which require aligning the human and robot joint axes before training the patient. These devices have the advantage of training the individual distal joints, but the training task is different from how humans use their upper limbs to interact with the environment.…”