Towards Online Estimation of Human Joint Muscular Torque with a Lower Limb Exoskeleton Robot

Abstract

Exoskeleton robots demonstrate promise in their application in assisting or enhancing human physical capacity. Joint muscular torques (JMT) reflect human effort, which can be applied on an exoskeleton robot to realize an active power-assist function. The estimation of human JMT with a wearable exoskeleton is challenging. This paper proposed a novel human lower limb JMT estimation method based on the inverse dynamics of the human body. The method has two main parts: the inverse dynamic approach (IDA) and the sensing system. We solve the inverse dynamics of each human leg separately to shorten the serial chain and reduce computational complexity, and divide the JMT into the mass-induced one and the foot-contact-force (FCF)-induced one to avoid switching the dynamic equation due to different contact states of the feet. An exoskeleton embedded sensing system is designed to obtain the user’s motion data and FCF required by the IDA by mapping motion information from the exoskeleton to the human body. Compared with the popular electromyography (EMG) and wearable sensor based solutions, electrodes, sensors, and complex wiring on the human body are eliminated to improve wearing convenience. A comparison experiment shows that this method produces close output to a motion analysis system with different subjects in different motion.

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“…Actually, a number of studies inspired by the research in human neuroscience and biomechanics have sought to transfer the sEMG-based human limb stiffness regulation skills to the robots and achieved encouraging results [14,15]. By utilizing the sEMG signals collected from the human limb for representing the activation level of the human muscles, the human arm joint or endeffector stiffness can be estimated and in real-time extracted during the task execution [16][17][18][19].…”

Dynamic Parameter Identification of a Lower Extremity Exoskeleton Using RLS-PSO

“…Through the four-linkage mechanism, ABCD, the linear motion of the CD is converted to the rotation of B. The stretching and swinging of the CD cause In the sagittal plane, the right leg of the APAL exoskeleton was simplified into a two-linkage model [37], as shown in Figure 2.…”

“…Equation (1) In the sagittal plane, the right leg of the APAL exoskeleton was simplified into a two-linkage model [37], as shown in Figure 2.…”

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