Motion Control for an Intelligent Walking Support Machine

Walking is a vital exercise for health promotion and fundamental ability necessary for everyday life. Up to now, many robots for walking support or walking rehabilitation of the elderly and the disabled are reported. In this paper, a new omni-directional walking support machine is developed. The machine can realize walking support by following the user's control intention which is detected according to the user's manipulation. However, the motion of the machine is affected by the nonlinear frictions, center-of-gravity (COG) shifts and loads changes caused by users. It is necessary to improve the machine's motion performance to follow the user intention and support the user. Therefore, this paper describes a motion control method based on digital acceleration control to deal with the problem of nonlinear frictions, COG shifts and loads changes. Simulations are executed and the results demonstrate the feasibility and effectiveness of the proposed digital acceleration control method

Improving the Motion Performance for an Intelligent Walking Support Machine by RLS Algorithm

To make the old people and handicapped people move easily by themselves, an omni-directional walking support machine (WSM) has been developed. In our previous study, to improve the motion performance of the WSM, a digital acceleration control method has been developed to deal with the nonlinear friction. However, the design of the digital acceleration controller requires to know the exact plant parameters of the WSM which are variable due to center of gravity (COG) shift and load changes. The change of the plant parameters affects the motion performance of the digital acceleration control system. Therefore, in this paper, a discrete-time system identification method using recursive least squares (RLS) algorithm is proposed to online identify the WSM’s plant parameters for the digital acceleration controller. Simulations are executed and compared with the digital acceleration controller without using RLS algorithm, and the results demonstrate the feasibility and effectiveness of the proposed control method

Bipartite containment of heterogeneous multi-agent systems under denial-of-service attacks: a historical information-based control scheme

A distributed control scheme based on historical information is designed to solve the problem of stable control of multi-agent systems under denial of service (DoS) attacks in this article. It achieves the control objective of bipartite output containment control, that is, the output states of the followers smoothly enter the target area. The control scheme updates the states of followers through historical information in the control protocol when agents are subjected to DoS attacks. A distributed state observer with a storage module is designed to efficiently estimate the state of followers and store the observed information as history information. The historical information of control protocol calls is not necessarily the real state information in the existence of DoS attacks. Consequently, a closed-loop feedback state compensator is designed. Then, the state compensator is converted from the time domain to the frequency domain for stability analysis using the Nyquist criterion. It is obtained that an upper bound on the amount of historical information can achieve the bipartite output trajectories containment of the controlled system. The output trajectories of the followers converge into two dynamic convex hulls, one of which is surrounded by multiple leaders, and the other is a convex hull with opposite signs of the leaders. Finally, a numerical simulation is used to verify the proposed control scheme, and the operability of the scheme is further demonstrated in a physical experiment

Optimal inventory strategies in supply chains under a value-at-risk constraint

published_or_final_versionIndustrial and Manufacturing Systems EngineeringDoctoralDoctor of Philosoph