Adaptive Motion Estimation and Control of Intelligent Walkers

Intelligent walker;nonlinear control;observer;robust control;parameter estimation;state estimation;Mechanical Engineering

Zengin, Nursefa

University of Waterloo

关键词: Intelligent walker;    nonlinear control;    observer;    robust control;    parameter estimation;    state estimation;    Mechanical Engineering;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/9462/3/Zengin_Nursefa.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

One of the most critical factors in the quality of elderly lives is their ability to move. Asthe size of the ageing society grows, more elderly people suffer from walking impairments.Most of them prefer to stay at home due to the shortage of the nursing care staff, sincethey deal with the daily challenges alone. Robotics researchers have developed variousintelligent walking support systems to meet the needs of elderly and handicapped people.A particular problem in path tracking for such systems is maintaining the tracking performance,which is affected by the center of gravity (CG) shifts and load changes due tohuman-walker interactions. This thesis focuses on design of feedback controllers for safemotion of intelligent walker (i-walker) systems robust to CG shifts and load changes. Ourdesign follows a two level approach, one for kinematics, the other for dynamics. The highlevel kinematic controller is designed based on integrator backstepping to produce desiredvelocities required for trajectory tracking. The low level dynamic controller is composed ofa feedback linearization unit and a linear feedback controller to apply the control torquefor tracking the desired velocity produced by the high level kinematic controller. As dynamiccontrollers, proportional-derivative (PD) and sliding mode controllers (SMCs) aredesigned. In our initial design, we assume that all system states are available. However, inthe actual case, even if the wheel velocities can be measured with some sensor devices liketachometers, the measurements carry noise, which poses important problems in control algorithms.To obtain the estimates of the wheel velocities, avoiding the noise problems, thedesign of sliding mode observers and high gain observers is studied. The state feedbackPD and SMC schemes are later integrated with these observers to form implementableoutput feedback controllers. In practice, the human mass and the distance due to the CGshift depend on the user. To address this issue, the output feedback control designs arefurther made adaptive, integrating with a parameter identifier to estimate these variables.The parameter identifier design involves a linear parametric model of the i-walker systemdynamics and a least-square adaptive law based on this parametric model. Adaptive versionsof the above observers and control designs are done utilizing estimated parametersand states. The effectiveness and applicability of the proposed controllers are verified viavarious simulations in MATLAB/Simulink environment.