Volume 15, Issue 6 (8-2015)                   Modares Mechanical Engineering 2015, 15(6): 257-268 | Back to browse issues page

XML Persian Abstract Print


Download citation:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:

Fathi M, Najafi F. Admittance Control Stability Analysis of a Lower Limb Rehabilitation Servo-Pneumatic System. Modares Mechanical Engineering 2015; 15 (6) :257-268
URL: http://mme.modares.ac.ir/article-15-9718-en.html
Abstract:   (5452 Views)
In this study, a vertically placed double-acting pneumatic cylinder controlled by two On/Off solenoid valves is applied for the purpose of the lower limb rehabilitation. Because of the different physical conditions and degrees of disability of patients and changes of the system dynamic parameters, admittance control strategy is used to compliantly interact between users and actuator. To analyze the stability, a linear model of the servo-pneumatic system is developed and its continuous transfer function is derived. Due to the exponential functions in the continuous transfer function of the system, the necessary transformations are used to achieve the discrete closed-loop transfer function of the system. In this way, the determination of the stable performance boundaries of the admittance control parameters related to changes in other dynamic parameters of the system is possible by root locus analysis of the discrete closed-loop system. These dynamics parameters include equivalent mass, damping and stiffness of the actuator and leg impedance and the proportional and differential gains of the inner loop position controller. Good correspondence is observed between the analytical and experimental stability limits of the system. Analytical results for appropriate choice of the admittance control and other dynamic parameters of the servo-pneumatic system are applicable to get smoothly and stable performance during the rehabilitation process.
Full-Text [PDF 1053 kb]   (8389 Downloads)    
Article Type: Research Article | Subject: Control
Received: 2015/01/18 | Accepted: 2015/04/7 | Published: 2015/04/29

Add your comments about this article : Your username or Email:
CAPTCHA

Rights and permissions
Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.