Does the motor system need intermittent control?

Explanation of motor control is dominated by continuous neurophysiological pathways (e.g. trans-cortical, spinal) and the continuous control paradigm. Using new theoretical development, methodology and evidence, we propose intermittent control, which incorporates a serial ballistic process within the main feedback loop, provides a more general and more accurate paradigm necessary to explain attributes highly advantageous for competitive survival and performance

COMPARISON OF A MODIFIED HYBRID III ATD TO A HUMAN TEST PILOT DURING POWER WHEELCHAIR DRIVING

It is estimated that there are 85,000 serious wheelchair accidents annually, of which 80% are attributable to tips and falls. Despite the increasing trend in wheelchair accidents every year, there is little literature on the cause and prevention of these accidents. Test dummies provide an ethical and practical alternative to subjects when assessing the risks and prevention mechanisms of tips and falls in controlled studies. However, design criteria for anthropomorphic test devices (ATDs) were based on the response and tolerance data acquired from cadaver studies and human volunteers. Such cadavers are typically of advanced age, and have anthropometrics reflecting a healthy, unimpaired population. For that reason, use of ATDs in relatively low speed wheelchair studies may under estimate the risk of injury.The purpose of this study was to develop and validate a low speed, low impact test dummy for use in the study of the prevention of tips and falls from wheelchairs. A kinematic analysis comparing the trunk bending of a Hybrid III test dummy (HTD) to that of a wheelchair user during various braking trials served for validation. In addition, a dynamic model was used to determine underlying causes of the motion. Statistical differences were not found (p>.05) in the peak trunk angular range of motion, velocity, and acceleration measures of a modified HTD over a range of wheelchair speeds and decelerations. This is promising evidence that the test dummy is a suitable surrogate for a wheelchair user in low speed dynamic studies. However, the HTD underestimated the motion of a wheelchair test pilot during the fast speed and power-off braking condition.A dynamic model consisting of a cart with an inverted pendulum was used to provide additional insight into the differences in motion. Although the model produced consistent values for damping and stiffness coefficients, evidence indicates that the functional form of the model may be incorrect. The model likely estimated properties for a wheelchair/rider system rather than only the rider. Further analysis showed an impingement occurring between the pelvis and thighs of the HTD. Removing the impingement will further increase the similarities between the HTD and test pilot

HUMAN STRATEGIES IN THE CONTROL OF TIME CRITICAL UNSTABLE SYSTEMS

The purpose of this study is to investigate the human manual control strategy when balancing an inverted pendulum under time critical constraints. The strategy was assessed through the quantification and evaluation of human response while performing tasks that require fast reaction from the human operator. The results show that as the task becomes more difficult due to increased time delay or shortened pendulum length, the human operator adopts a more discrete-type strategy. Additionally, dissimilarities between control of a short pendulum and a delayed pendulum are identified and discussed. Finally, the discrete-control mechanism is interpreted by relating the observed human responses to human-performance models. These results can be applied to systems requiring human interaction, such as teleoperation, which could be designed to maximize human response

Safe Manual Control of Unstable Systems

This thesis deals with manual control of unstable systems, subject to control signal constraints. Allocation of control authority is critical in this situation. The manual control, or reference following, must not be performed at the risk of loosing stability. The conflicting objective is to achieve acceptable reference following performance. Design of control systems under such circumstances is critical, and has several important applications. One example is modern flight control systems for unstable fighter aircrafts. Experiments have been an important part of this work. An inverted pendulum of the Furuta type, has been used for experimental verification of the controller designs. This plant is unstable, but reasonably easy to analyze and perform experiments with. Theoretical as well as practical results are presented in this report. Controllers for the linearized pendulum model have been designed and simulated. Some of the designs were also implemented and evaluated on the real Furuta pendulum. The translation of the controllers from a simulation environment to the real plant proved quite difficult. Some modifications of the controllers had to be made, in order to achieve the desired results on the real Furuta pendulum. Compensation for friction also had to be done

Nonlinear Observers for Human-in-the-loop Control Systems

The development of models for a human-in-the-loop with hardware is an area of ongoing research. The ability to simulate a human-in-the-loop with hardware provides a platform for better understanding the dynamics of human and machine cognition. A human-in-the-loop model provides information that can be used to design more efficient human interfaces and smarter autonomous assistant controllers. This can make a complex task such as flying an aircraft safer and more accessible. This thesis explores different possibilities for human operator models to be modeled in the loop with a vehicle. A human is modeled as a linear state feedback controller in the loop with the task of controlling a simple solid ball. The human arm is modeled controlling a joystick as the human is considered to control the ball with a joystick. Nonlinear sliding mode observers are developed to estimate the gains of a feedback control law and nonlinear sliding mode observers are developed to estimate the torques on the shoulder, elbow, and joystick joints. The nonlinear observers are simulated on a human-in-the-loop system to show the accuracy of the observers

Robust Intelligent Sensing and Control Multi Agent Analysis Platform for Research and Education

The aim of this thesis is the development and implementation of a controlled testing platform for the Robust Intelligent Sensing and Controls (RISC) Lab at Utah State University (USU). This will be an open source adaptable expandable robotics platform usable for both education and research. This differs from the many other platforms developed in that the entire platform software will be made open source. This open source software will encourage collaboration among other universities and enable researchers to essentially pick up where others have left off without the necessity of replicating months or even years of work. The expected results of this research will create a foundation for diverse robotics investigation at USU as well as enable attempts at novel methods of control, estimation and optimization. This will also contribute a complete software testbed setup to the already vibrant robotics open source research community. This thesis first outlines the platform setup and novel developments therein. The second stage provides an example of how this has been used in education, providing an example curriculum implementing modern control techniques. The third section provides some exploratory research in trajectory control and state estimation of the tip of an inverted pendulum atop a small unmanned aerial vehicle as well as bearing-only cooperative localization experimentation. Finally, a conclusion and future work is discussed

Master of Science

thesisIncreased demand for powered wheelchairs and their inherent mobility limitations have prompted the development of omnidirectional wheelchairs. These wheelchairs provide improved mobility in confined spaces, but can be more difficult to control and impact the ability of the user to embody the wheelchair. We hypothesize that control and embodiment of omnidirectional wheelchairs can be improved by providing intuitive control with three degree of freedom (3-DOF) haptic feedback that directly corresponds to the degrees of freedom of an omnidirectional wheelchair. This thesis introduces a novel 3-DOF Haptic Joystick designed for the purpose of controlling omnidirectional wheelchairs. When coupled with range finders, it is able to provide the user with feedback that improves the operator's awareness of the area surrounding the vehicle and assists the driver in obstacle avoidance. The haptic controller design and a stability analysis of the coupled wheelchair joystick systems are presented. Experimental results from the coupled systems validate the ability of the controller to influence the trajectory of the wheelchair and assist in obstacle avoidance

A reconfigurable wheelchair for mobility and rehabilitation:Design and development

This paper presents the design and development of a prototype of a reconfigurable wheelchair for rehabilitation and self-assistance to fit the size of a seven years old child (average 35 kg weight). Though the developed prototype is developed at this stage to fit a child, it can be resized, after considering variations in weight and size, to fit an older adult. The developed prototype has a mechanism that enables the user to transform from sit-to-stand (STS) posture and vice versa. With the help of the developed wheelchair, the user will also be able to adjust the posture of his upper body using an adjustable back support using two linear actuators. This configuration will allow the user to use the wheelchair as a mobility device as well as for rehabilitation purposes without the need of external support. The availability of STS and back adjustment mechanisms will allow the user to do regular exercising which will enhance blood circulation as sitting for long periods inflates lower limbs disability. The proposed configuration will help in enhancing the functional capabilities of end-users allowing for increased independence and ultimately quality of life