Faculty Advisor or Committee Member

Taskin Padir, Advisor

Faculty Advisor or Committee Member

Raghvendra V. Cowlagi, Committee Member

Faculty Advisor or Committee Member

Sonia Chernova, Committee Member

Faculty Advisor or Committee Member

Marko B. Popovic, Committee Member

Identifier

etd-050117-140934

Abstract

For a wide range of people with limited upper- and lower-body mobility, interaction with robots remains a challenging problem. Due to various health conditions, they are often unable to use standard joystick interface, most of wheelchairs are equipped with. To accommodate this audience, a number of alternative human-machine interfaces have been designed, such as single switch, sip-and-puff, brain-computer interfaces. They are known as low throughput interfaces referring to the amount of information that an operator can pass into the machine. Using them to control a wheelchair poses a number of challenges. This thesis makes several contributions towards the design of robotic wheelchairs controlled via low throughput human-machine interfaces: (1) To improve wheelchair motion control, an adaptive controller with online parameter estimation is developed for a differentially driven wheelchair. (2) Steering control scheme is designed that provides a unified framework integrating different types of low throughput human-machine interfaces with an obstacle avoidance mechanism. (3) A novel approach to the design of control systems with low throughput human-machine interfaces has been proposed. Based on the approach, position control scheme for a holonomic robot that aims to probabilistically minimize time to destination is developed and tested in simulation. The scheme is adopted for a real differentially driven wheelchair. In contrast to other methods, the proposed scheme allows to use prior information about the user habits, but does not restrict navigation to a set of pre-defined points, and parallelizes the inference and motion reducing the navigation time. (4) To enable the real time operation of the position control, a high-performance algorithm for single-source any-angle path planning on a grid has been developed. By abandoning the graph model and introducing discrete geometric primitives to represent the propagating wave front, we were able to design a planning algorithm that uses only integer addition and bit shifting. Experiments revealed a significant performance advantage. Several modifications, including optimal and multithreaded implementations, are also presented.

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Robotics Engineering

Project Type

Dissertation

Date Accepted

2017-05-01

Accessibility

Unrestricted

Subjects

CWave, assistive drive, adaptive control, wheelchair, shared steering control, any-angle path planning, NoVeLTI, brain-computer interface, navigation, shared control, BCI, low throughput interface, shared position control

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