Design and control of hybrid actuation lower limb exoskeleton

Abstract

In this article, two types of actuators are applied for a lower limb exoskeleton. They are DC motors with the harmonic drive and the pneumatic artificial muscles. This combination takes advantages of both the harmonic drive and the pneumatic artificial muscle. It provides both high accuracy position control and high ratio of strength and weight. The shortcomings of the two actuators are overcome by the hybrid actuation, for example, low control accuracy and modeling difficult of pneumatic artificial muscle, compactness, and structural flexibility of DC motors. The design and modeling processes are discussed to show the proposed exoskeleton can increase the strength of human lower limbs. Experiments and analysis of the exoskeleton are given to evaluate the effectiveness of the design and modeling.

Investigating the Effect of a Mechanism Combined with a Speed-Increasing Gear and a Pneumatic Artificial Muscle

“…This is because when a load was added to the bar (i.e., to the output shaft of the gearbox), the torque transmitted to the input shaft in the gear of G05P1-2 was twice the torque of the gear of G10P1-2. Therefore, the PAMs of G05P1-2 were pulled by double the force and stretched longer compared with G10P1-2, as shown in Equation (2). The longer stretch made the input and output shaft rotate more.…”

“…The change of length with respect to the unloaded natural length of each PAM piece, that is to say, lc, was measured under each weight, and the measurements were repeated 10 times. The resulting relational expression is shown in Equation (2). The correlation coefficient for approximation of the relationship between the Ft and lc in Figure 3d was −0.9971.…”

“…The PAM traction force Ft and contraction length lc were calculated by substituting the PADS rotational angle θPADS (in degrees) in Figure 1b into Equation (3) below and using Equation (2). Here, r is the radius of the pulley as shown in Figure 1a.…”

“…Elements and actuators that are used in the devices have a profound effect on the compliance and lightness of the whole device. These include springs, pneumatic artificial muscles (PAMs) [1][2][3][4][5][6][7][8][9][10][11], magnetorheological (MR) dampers [12][13][14], shape memory alloys (SMAs) [15][16][17], soft pneumatic actuators (SPAs) [18], and dielectric elastomer actuators (DEAs) [19]. Research and development of these components and devices that employ them are widely conducted.…”

The use of a cascaded Kinect and electromyography gesture decoding algorithm in an initial robot-aided hand neurorehabilitation

“…Intensive and long rehabilitation training process should be carried out with the help of clinical professionals and operational therapists (OTs) for the final recovery of delicate and subtle movements of hand and finger. 3,4 Clinicians involved must pay full attention to identify correct hand gestures while manually aiding as needed with awareness, verbal guidance, and assistance during the whole training process. This training process is effective when it conducts repetitively.…”