Design of a Compact Energy Storage with Rotary Series Elastic Actuator for Lumbar Support Exoskeleton

Abstract

Lumbar support exoskeletons with active and passive actuators are currently the cutting-edge technology for preventing back injuries in workers while lifting heavy objects. However, many challenges still exist in both types of exoskeletons, including rigid actuators, risks of human–robot interaction, high battery consumption, bulky design, and limited assistance. In this paper, the design of a compact, lightweight energy storage device combined with a rotary series elastic actuator (ES-RSEA) is proposed for use in a lumbar support exoskeleton to increase the level of assistance and exploit the human bioenergy during the two stages of the lifting task. The energy storage device takes the responsibility to store and release passive mechanical energy while RSEA provides excellent compliance and prevents injury from the human body’s undesired movement. The experimental tests on the spiral spring show excellent linear characteristics (above 99%) with an actual spring stiffness of 9.96 Nm/rad. The results demonstrate that ES-RSEA can provide maximum torque assistance in the ascent phase with 66.6 Nm while generating nearly 21 Nm of spring torque during descent without turning on the DC motor. Ultimately, the proposed design can maximize the energy storage of human energy, exploit the biomechanics of lifting tasks, and reduce the burden on human effort to perform lifting tasks.

Design and Characterization of a Low-Cost and Efficient Torsional Spring for ES-RSEA

“…The ES-RSEA actuator was designed for use in a lumbar support exoskeleton to provide torque assistance during the ascent and descent phases of lifting tasks [ 13 ]. The rotary series elastic actuator (RSEA) and the energy storage device (ES) work together to achieve this goal.…”

“…However, wearable robots would be more effective if they were more compact and lightweight than current SEA designs, which are bulky and heavy. To address this, a novel energy storage-rotary series elastic actuator (ES-RSEA) has been developed, as detailed in our previous publication [ 13 , 14 ], to assist with squat lifting tasks. The compact and modular design of the ES-RSEA leverages the biomechanics of the human squat strategy to utilize the kinetic energy of limbs for semi-squat lifting tasks.…”

Modeling and Dynamic performance of Energy Storage -Rotary Series Elastic Actuator for Lumbar Support Exoskeleton

“…The classic series elastic actuator (SEA) configuration consists of an output link, spring, transmission reducer, and motor drive, where the attached spring can sense the output torque from its deformation [11]. However, ES-RSEA was modified [12] based on this configuration by combining the spiral spring with an actuator layout. The spiral spring is meant to store and release the energy to provide additional energy to the lumbar support exoskeleton to assist the lifting task.…”

“…The proposed lumbar support exoskeleton consists of two actuators ES-RSEA located on each hip joint with a flexible wearable structure, as shown in Fig. 3 [12]. ES-RSEA is designed in compact and modular design, as Fig.…”

“…However, it is still great challenging to achieve a high overall performance of the actuators in the field of exoskeletons. Therefore, novel energy storage-rotary series elastic actuator (ES-RSEA) has been proposed and developed at the University of Malaya [10] to provide higher torque assistance and compliance with less power consumption in compact and modular design. The key role of ES-RSEA is to harness the kinetic energy through human movement during the lifting task and generate assistance torque without an external power source.…”