Design and development of a durable series elastic actuator with an optimized spring topology

2021 ◽  
pp. 095440622110203
Author(s):  
Mehmet C Yildirim ◽  
Polat Sendur ◽  
Ahmet Talha Kansizoglu ◽  
Umut Uras ◽  
Onur Bilgin ◽  
...  
Keyword(s):  
Real Life ◽  
Integrated Design ◽  
Torque Control ◽  
Test Machine ◽  
Design Development ◽  
Test Procedures ◽  
Testing Procedures ◽  
Series Elastic Actuator ◽  
Series Elastic

This paper aims to present the integrated design, development, and testing procedures for a state-of-the-art torsion-based series elastic actuator that could be reliably employed for long-term use in force-controlled robot applications. The main objective in designing the actuator was to meet weight and dimensional requirements whilst improving the long-term durability, ensuring high torque output, and containing its total weight. A four-fold design approach was implemented: (i) following recursive design-and-test procedures, an optimal torsional spring topology was unveiled with the help of SIMP (Solid Isotropic Material with Penalization) topology optimization method, (ii) the proposed spring was manufactured and multiple specimens were experimentally tested via a torsional test machine to validate linearity, loading rate response, and mechanical limits, (iii) the actuator’s thermal response was experimentally scrutinized to ensure that the generated heat was dissipated for long-term use, and (iv) the fatigue life of the spring was computed with the help of real-life experiment data. Having concluded the development and verification procedures, two different versions of the actuator were built, and preliminary torque control experiments were conducted. In conclusion, favorable torque tracking with a bandwidth of 19 Hz was achieved while peak-to-peak torque input was 20 Nm.

Adaptive sliding mode observer–based integral sliding mode model-free torque control for elastomer series elastic actuator–based manipulator

2021 ◽  
pp. 095965182110647
Author(s):  
Yangchun Wei ◽  
Haoping Wang ◽  
Yang Tian
Keyword(s):  
Sliding Mode ◽  
Sliding Mode Observer ◽  
Torque Control ◽  
Terminal Sliding Mode ◽  
Series Elastic Actuator ◽  
Model Free ◽  
Output Torque ◽  
Nonsingular Terminal Sliding Mode ◽  
Model Free Control ◽  
Series Elastic

In this brief, an adaptive nonsingular terminal sliding mode observer–based adaptive integral terminal sliding mode model-free control is proposed for the trajectory tracking control of the output torque of elastomer series elastic actuator–based manipulator. Considering the tip load and its external disturbance, an elastomer series elastic actuator–based manipulator model is established. In order to realize the output torque tracking control of elastomer series elastic actuator–based manipulator, by using the characteristics of elastomer series elastic actuator, the output torque control is transformed into position control. Based on the idea of model-free control, an ultra-local model is applied to approximate the dynamic of the manipulator, and all the model information is considered as an unknown lumped disturbance. The adaptive nonsingular terminal sliding mode observer is designed to estimate the lumped disturbance, and the absolute value of the tracking error is introduced into the sliding surface to make the selection of parameters more flexible. Then, on the basis of adaptive nonsingular terminal sliding mode observer, the adaptive integral terminal sliding mode model-free control is proposed under model-free control framework. The design and analysis of both observer and controller do not rely on accurate model information. Finally, the performance of the proposed method is verified by simulation results.

Gait Phase-Based Control for a Rotary Series Elastic Actuator Assisting the Knee Joint

2011 ◽  
Vol 5 (3) ◽  
Author(s):  
Joonbum Bae ◽  
Kyoungchul Kong ◽  
Masayoshi Tomizuka
Keyword(s):  
Boundary Layer ◽  
Knee Joint ◽  
Sliding Mode ◽  
Human Robot Interaction ◽  
Torque Control ◽  
Modeling Uncertainty ◽  
Series Elastic Actuator ◽  
Chattering Phenomenon ◽  
Assistive Systems ◽  
Series Elastic

Actuators for physical human-robot interaction (pHRI) such as rehabilitation or assistive systems should generate the desired torque precisely. However, the resistive and inertia loads inherent in the actuators (e.g., friction, damping, and inertia) set challenges in the control of actuators in a force/torque mode. The resistive factors include nonlinear effects and should be considered in the controller design to generate the desired force accurately. Moreover, the uncertainties in the plant dynamics make the precise torque control difficult. In this paper, nonlinear control algorithms are exploited for a rotary series elastic actuator to generate the desired torque precisely in the presence of nonlinear resistive factors and modeling uncertainty. The sliding mode control smoothed by a boundary layer is applied to enhance the robustness for the modeling uncertainty without chattering phenomenon. In this paper, the rotary series elastic actuator (RSEA) is installed on the knee joint of an orthosis, and the thickness of the boundary layer is changed by gait phases in order to minimize the torque error without the chattering phenomenon. The performance of the proposed controller is verified by experiments with actual walking motions.

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