A magnetorheological knee prosthesis is presented that automatically adapts knee damping to the gait of the amputee using only local sensing of knee force, torque, and position. To assess the clinical effects of the user‐adaptive knee prosthesis, kinematic gait data were collected on four unilateral trans‐femoral amputees. Using the user‐adaptive knee and a conventional, non‐adaptive knee, gait kinematics were evaluated on both affected and unaffected sides. Results were compared to the kinematics of 12 age, weight and height matched normals. We find that the user‐adaptive knee successfully controls early stance damping, enabling amputee to undergo biologically‐realistic, early stance knee flexion. These results indicate that a user‐adaptive control scheme and local mechanical sensing are all that is required for amputees to walk with an increased level of biological realism compared to mechanically passive prosthetic systems.

User‐adaptive control of a magnetorheological prosthetic knee

https://engweb.swan.ac.uk/~adhikaris/fulltext/journal/ft12.pdf

Identification of damping: Part 1, viscous damping

http://engweb.swan.ac.uk/~adhikaris/fulltext/journal/ft23.pdf

Damping modelling using generalized proportional damping

The goal of this study was to design a robot system for assisting in the rehabilitation of patients with neuromuscular disorders by performing various facilitation movements. The robot should be able to guide patient's wrist to move along planned linear or circular trajectories. A hybrid position/force controller incorporating fuzzy logic was developed to constrain the movement in the desired direction and to maintain a constant force along the moving direction. The controller was stable in the application range of movements and forces. Offline analyses of data were used to quantitatively assess the progress of rehabilitation. The results show that the robot could guide the upper limbs of subjects in linear and circular movements under predefined external force levels and apply a desired force along the tangential direction of the movements.

A rehabilitation robot with force-position hybrid fuzzy controller: hybrid fuzzy control of rehabilitation robot

Damping models for structural vibration

A frequency-domain method for estimating the mass, stiffness and damping matrices of the model of a structure is presented. The developed method is based on our previous work on the extraction of normal modes from the complex modes of a structure. A transformation matrix is obtained from the relationship between the complex and the normal frequency response functions ofa structure. The transformation matrix is employed to calculate the damping matrix of the system. The mass and the stiffness matrices are identified from the normal frequency response functions by using the least squares method. Two simulated systems are employed to illustrate the applicability of the proposed method. The results indicate that the damping matrix can be identified accurately by the proposed method. The reason for the good results is that the damping matrix is identified independently from the mass and the stiffness matrices. In addition, the robustness of the new approach to uniformly distributed measurement noise is also addressed.

Estimation of Mass, Stiffness and Damping Matrices from Frequency Response Functions

Extraction of normal modes for highly coupled incomplete systems with general damping

A fuzzy controller is employed to control an electrohydraulic four-bar above-knee prosthesis for the swing phase in level walking. A two-dimensional (sagittal plane)mechanical model of the above-knee amputee is developed and the amputee prosthesis system is simulated for the swing phase. The man-machine system has two fuzzy controllers : a knee fuzzy controller which adjusts the knee damping moment so the prosthetic knee angle trajectory will track that of the patient's sound knee in the previous swing and a hip fuzzy controller utilized to model the way that an amputee will manipulate the prosthesis. From an optimal design procedure, a set of fuzzy controllers is found and an optimal relationship between variations of initial stump velocity and initial artificial shank velocity for the amputee is found. The results showed that the amputee swing gait can be controlled to a near normal one and walking with varied speed is possible.

Fuzzy Control of Electrohydraulic Above Knee Prostheses

Comparison of fuzzy logic and self-tuning adaptive control of single-link flexible arm

A frequency-domain technique to extract the normal mode shapes from the contaminated FRF measurements for highly coupled structures is developed. The relation between the complex FRFs and the normal mode shapes is derived. It is found that the normal mode shape cannot be extracted exactly from the complex mode shape. However, an exact relation between the normal mode shape and the complex FRF does exist. In the present method, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. Hence, the effects of measurement noise can be reduced. A numerical example is employed to illustrate the applicability of the technique. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled structure.

Y. G. Tsuei

Papers

Estimation of Mass, Stiffness and Damping Matrices from Frequency Response Functions

Extraction of normal modes for highly coupled incomplete systems with general damping

Fuzzy Control of Electrohydraulic Above Knee Prostheses

Comparison of fuzzy logic and self-tuning adaptive control of single-link flexible arm

Extraction of Normal Modes from Contaminated Measurement With Noise for Highly Coupled Structures