Variable impedance control of finger exoskeleton for hand rehabilitation following stroke

Purpose The purpose of this paper is to propose a variable impedance control method of finger exoskeleton for hand rehabilitation using the contact forces between the finger and the exoskeleton, making the output trajectory of finger exoskeleton comply with the natural flexion-extension (NFE) trajectory accurately and adaptively. Design/methodology/approach This paper presents a variable impedance control method based on fuzzy neural network (FNN). The impedance control system sets the contact forces and joint angles collected by sensors as input. Then it uses the offline-trained FNN system to acquire the impedance parameters in real time, thus realizing tracking the NFE trajectory. K-means clustering method is applied to construct FNN, which can obtain the number of fuzzy rules automatically. Findings The results of simulations and experiments both show that the finger exoskeleton has an accurate output trajectory and an adaptive performance on three subjects with different physiological parameters. The variable impedance control system can drive the finger exoskeleton to comply with the NFE trajectory accurately and adaptively using the continuously changing contact forces. Originality/value The finger is regarded as a part of the control system to get the contact forces between finger and exoskeleton, and the impedance parameters can be updated in real time to make the output trajectory comply with the NFE trajectory accurately and adaptively during the rehabilitation.

A Trajectory Shaping Approach for Suppressing the Fundamental Vibratory Mode in Strain Wave Gearing Mechanisms

While strain wave gearing mechanisms, such as harmonic drives, have many practical benefits when properly utilized, they also create challenging problems for control engineers. Namely, these flexible gear reduction mechanisms can create output vibrations which cannot be directly measured or controlled by the actuator. In this paper, an input shaping approach will be proposed to pre-compensate the desired output trajectory to account for the transmission dynamics such that the system’s actual output will follow the original desired trajectory. Several system parameters need to be empirically identified prior to using the proposed procedure. This identification process will also be outlined. Both simulation and experimental results on a 6 degree of freedom industrial robot will be provided to demonstrate the effectiveness of the proposed approach.

Time Delay System Tracking Control Based on ADP Iterative Algorithm

Tracking control is to select a control strategy, so that the actual output of the system to be able to track the desired output trajectory, and makes minimal prescribed performance index function. Actually adjustment problem is also a special tracking problem, namely zero output trajectory tracking problem. Adaptive dynamic programming for solving delay systems tracking control aspects of the article is very small. The proposed delay systems tracking control features include two aspects: First, the research object containing the delay nonlinear discrete affine system, the second is the research method is adaptive dynamic programming iterative algorithm.

Simulation Study on a Controllable Mechanism Type Novel Planar 3-DOF Mechanical Excavator

This paper introduces a simulation study on the executive mechanism of a recent invented controllable mechanism type novel planar 3-DOF mechanical excavator using simulation analysis software MSC.ADAMS. A virtual prototype model is established first, based on which the forward kinematics simulation is carried out employing the DIM functions to achieve an output trajectory similar to the excavating process of a flexible hydraulic excavator. Subsequently, an inverse kinematics simulation is performed accomplishing a given V type output trajectory. Angular displacements, velocities and accelerations of the three input variables are obtained. Results of the simulation study may provide some useful references for further researches such as dimensional synthesis, dynamics and design of the controller of the new type of mechanical excavator.