Series Elastic Actuator: Design, Analysis and Comparison

Abstract

In general, actuators are built to be as stiff as possible to increase the bandwidth. When a robot works in a structured environment, its automation is easier than in a nonstructured environment in which case its modeling is quite difficult and presents a high computational effort. To overcome this difficulty, series elastic actuator SE" has been applied in compliant robotic grasping. Unlike rigid actuators, a SE" contains an elastic element in series with the mechanical energy source. Such an elastic element gives SE"s tolerance to impact loads, low mechanical output impedance, passive mechanical energy storage, and increased peak power output. The spring has to be able to support the loads, but it cannot be too stiff otherwise, system impedance will be high. This chapter describes a comparison between two types of SE", an electric series elastic actuator ESE" and a hydraulic series elastic actuator HSE" , for four-legged dynamic robot application. The parameters employed in the comparison are bandwidth, output impedance, time response, power density, and dynamic range. The results indicate that HSE" is a better actuator than ESE" for a weight carrying four-legged dynamic robot because of its higher power density and dynamic ratio with desirable output impedance, time response, and bandwidth.

Polymer Optical Fiber Sensors in Healthcare Applications: A Comprehensive Review

“…If a wearable robot is concerned, one of its main components is the actuator, which is responsible for delivering the mechanical power for moving the user’s joint or assisting the movement. As an important actuator technology, series elastic actuators (SEAs) are a core technology in wearable and assistive robotics due to their compliance and relative simplicity on the design and control [156]. The actuator comprises of an electric motor in series with a spring (or elastic element), which is in contact with the human joint, making it suitable for the development of compliant active orthosis [49].…”

Design, Modelling and Control of Novel Series-Elastic Actuators for Industrial Robots

“…As previously mentioned, a large number of SEA designs have already been developed over the last decades; they have been surveyed in [17][18][19] in great detail. Linear SEA is one of the classic designs and its elastic component is either composed by a single spring [9] or a set of springs connected in series [20].…”

“…Traditionally, the spring elements of the SEAs are modelled with the Hooke's law in a linearized form as presented for instance in [19]. The linear model fits the single spring system accurately, however, it cannot address the nonlinear effects that can be observed from more complex spring sets [22] or novel rubber elastic elements [24].…”

“…Table 3. Coefficients used to compute the torque estimates depicted in Figure 15 according to Equations (17)- (19).…”

Untethered quadrupedal hopping and bounding on a trampoline

“…A position-controlled robot may be able to jump by mounting elastic elements, subsequently reducing energy loss during touchdown impact. Among different methods, serial elastic actuation [16][17][18] has been widely used. A serial elastic actuator contains an elastic element in series and a mechanical energy source.…”