Feedback Linearizing Controller for a Flexible Single-Link Arm under Gravity and Joint Friction

Total knee arthroplasty is on the rise worldwide. Despite its success, revision surgeries are also increasing. According to the American Joint Replacement Registry 2020, 3.3% of revision surgeries are due to wear, and 24.2% are due to mechanical loosening. The combination of shear stresses and wear particles occurring at the bone/implant interface can lead to local osteolysis. Although the shear stresses are partially driven by joint friction, relatively little is known about the evolution of the coefficient of friction (CoF) during a gait cycle in total knee replacement. Here we describe the CoF during a gait cycle and investigate its association with kinematics (slide–roll-ratio), applied load, and relative velocity. The artificial knee was simulated by cobalt–chromium condyle on a flat ultra-high-molecular-weight polyethylene (UHMWPE) tibial plateau, lubricated by either water or proteinaceous solution. We found that the CoF is not a constant but fluctuates between the values close to 0 and 0.15. Cross-correlation suggested that this is primarily an effect of the slide–roll ratio and the contact pressure. There was no difference in the CoF between water and proteinaceous solution. Knowledge about the CoF behavior during a gait cycle will help to increase the accuracy of future computational models of total knee replacement.

Download Full-text

Output Feedback Stabilization of Flexible Joint Single Link Robotic Manipulator Using Extended Order High-Gain Observer

2020 IEEE 23rd International Multitopic Conference (INMIC) ◽

10.1109/inmic50486.2020.9318123 ◽

2020 ◽

Author(s):

Hameed Ullah ◽

Abid Raza ◽

Fahad Mumtaz Malik ◽

Muhammad Ibrahim ◽

Naveed Mazhar ◽

...

Keyword(s):

Output Feedback ◽

Robotic Manipulator ◽

High Gain ◽

Feedback Stabilization ◽

Flexible Joint ◽

Output Feedback Stabilization ◽

High Gain Observer ◽

Single Link

Download Full-text

The Study of Dynamic Modeling and Multivariable Feedback Control for Flexible Manipulators with Friction Effect and Terminal Load

Sensors ◽

10.3390/s21041522 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1522

Author(s):

Fuli Zhang ◽

Zhaohui Yuan

Keyword(s):

Dynamic Model ◽

Vibration Suppression ◽

Control Method ◽

Coupling Effect ◽

Flexible Manipulator ◽

Flexible Beam ◽

Robot Dynamics ◽

Joint Friction ◽

Balance Principle ◽

Multivariable Feedback

The flexible manipulato is widely used in the aerospace industry and various other special fields. Control accuracy is affected by the flexibility, joint friction, and terminal load. Therefore, this paper establishes a robot dynamics model under the coupling effect of flexibility, friction, and terminal load, and analyzes and studies its control. First of all, taking the structure of the central rigid body, the flexible beam, and load as the research object, the dynamic model of a flexible manipulator with terminal load is established by using the hypothesis mode and the Lagrange method. Based on the balance principle of the force and moment, the friction under the influence of flexibility and load is recalculated, and the dynamic model of the manipulator is further improved. Secondly, the coupled dynamic system is decomposed and the controller is designed by the multivariable feedback controller. Finally, using MATLAB as the simulation platform, the feasibility of dynamic simulation is verified through simulation comparison. The results show that the vibration amplitude can be reduced with the increase of friction coefficient. As the load increases, the vibration can increase further. The trajectory tracking and vibration suppression of the manipulator are effective under the control method of multi-feedback moment calculation. The research is of great significance to the control of flexible robots under the influence of multiple factors.

Download Full-text