scholarly journals A Sliding Mode Force and Position Controller Synthesis for Series Elastic Actuators

Robotica ◽  
2019 ◽  
Vol 38 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Emre Sariyildiz ◽  
Rahim Mutlu ◽  
Haoyong Yu
Keyword(s):  
Force Control ◽  
Dynamic Models ◽  
Position Control ◽  
Sliding Mode ◽  
Dynamic Environment ◽  
Industrial Robots ◽  
Motion Controller ◽  
Mismatched Disturbances ◽  
Series Elastic Actuators ◽  
Series Elastic

SummaryThis paper deals with the robust force and position control problems of series elastic actuators (SEAs). It is shown that an SEA’s force control problem can be described by a second-order dynamic model which suffers from only matched disturbances. However, the position control dynamics of an SEA is of fourth order and includes matched and mismatched disturbances. In other words, an SEA’s position control is more complicated than its force control, particularly when disturbances are considered. A novel robust motion controller is proposed for SEAs by using disturbance observer (DOb) and sliding mode control. When the proposed robust motion controller is implemented, an SEA can precisely track desired trajectories and safely contact with an unknown and dynamic environment. The proposed motion controller does not require precise dynamic models of environments and SEAs. Therefore, it can be applied to many different advanced robotic systems such as compliant humanoids, industrial robots and exoskeletons. The validity of the proposed motion controller is experimentally verified.

Experimental Validation of Unlumped Model and its Design Implications for Rotary Series Elastic Actuators

2017 ◽  
Author(s):  
Jeong H. Yoon ◽  
Daniel Sun ◽  
Vidur Sanandan ◽  
Dennis Hong
Keyword(s):  
Force Control ◽  
Experimental System ◽  
Open Loop ◽  
Design Guidelines ◽  
Trial And Error ◽  
Dynamic Simulations ◽  
Actuator Dynamics ◽  
Selection For ◽  
Series Elastic Actuators ◽  
Series Elastic

Series Elastic Actuators (SEA) have been in development for multiple decades. In spite of this, few design guidelines exist and stiffness selection for the compliant element still remains a trial-and-error process. In this paper, we experimentally validated the unlumped model first proposed by Orekhov for Rotary SEA (RSEA) and outlined a design methodology for selecting the spring stiffness based on the open loop force control bandwidth of unlumped model for series elastic actuators. We modified the unlumped model to apply to Rotary SEAs. Through experimental system identification, we demonstrated that our new unlumped model for RSEA is a valid model of actuator dynamics. Additionally, we recommended design guidelines for RSEA to achieve desired force control bandwidth based on the pure torque source assumption. An example of the design process was given and actuator performance was verified through dynamic simulations in ADAMS.

Force Control of Robot Fingers using Series Elastic Actuators

2012 ◽  
Vol 18 (10) ◽  
pp. 964-969 ◽  
Author(s):  
Seung-Yup Lee ◽  
Byeong-Sang Kim ◽  
Jae-Bok Song ◽  
Soo-Won Chae
Keyword(s):  
Force Control ◽  
Series Elastic Actuators ◽  
Series Elastic

Optimal Design of a Micro Series Elastic Actuator

2010 ◽  
Author(s):  
Ozan Tokatli ◽  
Volkan Patoglu
Keyword(s):  
Optimal Design ◽  
Force Control ◽  
Pareto Front ◽  
Position Control ◽  
Compliant Mechanism ◽  
Tracking Error ◽  
Movement Direction ◽  
Design Criteria ◽  
Coupling Element ◽  
Series Elastic

We propose using series elastic actuation (SEA) in micro mechanical devices to achieve precise control of the interaction forces. Using μSEA for force control removes the need for high-precision force sensors/actuators and allows for accurate force control through simple position control of the deflection of a compliant coupling element. Since the performance of a μSEA is highly dependent on the design of this compliant coupling element, we employ a design optimization framework to design this element. In particular, we propose a compliant, under-actuated half-pantograph mechanism as a feasible kinematic structure for this coupling element. Then, we consider multiple design objectives to optimize the performance of this compliant mechanism through dimensional synthesis, formulating an optimization problem to study the trade-offs between these design criteria. We optimize the directional manipulability of the mechanism, simultaneously with its task space stiffness, using a Pareto-front based framework. We select an optimal design by studying solutions on the Pareto-front curve and considering the linearity of the stiffness along the actuation direction as a secondary design criteria. The optimized mechanism possesses high manipulability and low stiffness along the movement direction of the actuator; hence, achieves a large stroke with high force resolution. At the same time, the mechanism has low manipulability and high stiffness along the direction perpendicular to the actuator motion, ensuring good disturbance rejection characteristics. We model the behavior of this compliant mechanism and utilize this model to synthesize a controller for μSEA to study its dynamic response. Simulated closed loop performance of the μSEA with optimized coupling element indicates that force references can be tracked without significant overshoot and with low tracking error (about 1.1%) even for periodic reference signals.

scholarly journals A Novel Sliding Mode Control Framework for Electrohydrostatic Position Actuation System

2018 ◽  
Vol 2018 ◽  
pp. 1-22 ◽  
Author(s):  
Rongrong Yang ◽  
Yongling Fu ◽  
Ling Zhang ◽  
Haitao Qi ◽  
Xu Han ◽  
...  
Keyword(s):  
Sliding Mode Control ◽  
Position Control ◽  
Sliding Mode ◽  
Reduced Order Model ◽  
Design Solution ◽  
Order Model ◽  
Reduced Order ◽  
Mode Control ◽  
Actuation System ◽  
Mismatched Disturbances

A novel sliding mode control (SMC) design framework is devoted to providing a favorable SMC design solution for the position tracking control of electrohydrostatic actuation system (EHSAS). This framework is composed of three submodules as follows: a reduced-order model of EHSAS, a disturbance sliding mode observer (DSMO), and a new adaptive reaching law (NARL). First, a reduced-order model is obtained by analyzing the flow rate continuation equation of EHSAS to avoid the use of a state observer. Second, DSMO is proposed to estimate and compensate mismatched disturbances existing in the reduced-order model. In addition, a NARL is developed to tackle the inherent chattering problem of SMC. Extensive simulations are conducted compared with the wide adoption of three-loop PID method on the cosimulation platform of EHSAS, which is built by combining AMESim with MATLAB/Simulink, to verify the feasibility and superiority of the proposed scheme. Results demonstrate that the chattering can be effectively attenuated, and the mismatched disturbance can be satisfyingly compensated. Moreover, the transient performance, steady-state accuracy, and robustness of position control are all improved.

Sign in / Sign up

Export Citation Format

Share Document