Analysis of inverse simulation algorithms with an application to planetary rover guidance and control

Rover exploration is a contributing factor to driving the relevant research forward on guidance, navigation, and control (GNC). Yet, there is a need for incorporating the dynamic model into the controller for increased accuracy. Methods that use the model are limited by issues such as linearity, systems affine in the control, number of inputs and outputs. Inverse Simulation is a more general approach that uses a mathematical model and a numerical scheme to calculate the control inputs necessary to produce a desired response defined using the output variables. This thesis develops the Inverse Simulation algorithm for a general state space model and utilises a numerical Newton-Raphson scheme to converge to the inputs using two approaches: The Differentiation method converges based on the state and output equations. The Integration method converges based on whether the output matches the desired and is suitable for grey or black-box models. The thesis offers extensive insights into the requirements and application of Inverse Simulation and the performance parameters. Attention is given to how the inputs and outputs affect the Jacobian formulation and ensure an efficient solution. The linear case and the relationship with feedback linearisation are examined. Examples are given using simple mechanical systems and an example is also given as to how Inverse Simulation can be used for determining system input disturbances. Inverse Simulation is applied for the first time for guidance and control of a fourwheeled, differentially driven rover. The desired output is the time history of the desired trajectory and is used to produce the required control inputs. The control inputs are nominal and are applied to the rover without additional correction. Using insights from the system’s physics and actuation, the Differentiation and Integration schemes are developed based on the general method presented in this thesis. The novel Differentiation scheme employs a non-square Jacobian. The method provides very accurate position and orientation control of the rover while considering the limitations of the model used. Finally, the application of Inverse Simulation to the rover is supported by a review of current designs that resulted in a rover taxonomy

Passive Actuation of a Planetary Rover to Assist Sandy Slope Traverse

This thesis introduces the design of a novel locomotive methodology. The problem being addressed is the traverse of unmanned locomotion over sandy inclined traverses. This is a special terramechanical issue regarding terrain or regolith that is non-cohesive in nature. The method uses a planetary exploration rover, Solar Rover 2 as its base. The proposed solution methodology includes a passively-actuated leg affixed to the rover to assist in slope traversal. Proposed physical implementations are designed and virtual representations are created, studied, and simulated in SolidWorks. This solution is justified through the use of a simulation designed in MATLAB

Modeling, analysis, and measurement of passenger vehicle stability

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 114-118).Vehicle rollover represents a significant percentage of single-vehicle accidents and accounts for over 9,000 fatalities and over 200,000 non-fatal injuries each year. Previous automotive research has studied ways for detecting and mitigating rollover on flat ground at high speed, and robotics research has studied the rollover stability of robots on rough terrain at low speed. Accident statistics show, however, that over 80% of rollovers occur when a vehicle departs the roadway and encounters sloped and rough terrain at high speed. This thesis investigates the stability limits imposed by off-road terrain conditions and techniques for measuring vehicle stability in the presence of off-road terrain factors. An analysis of the effects of terrain slope, roughness, and deformability on vehicle rollover stability in road departure scenarios is presented. A simple model that captures the first-order effects of each of these terrain features is presented and used to compare the relative danger posed by each factor. A new stability measure is developed that is valid in off-road conditions, which include sloped, rough, and deformable terrain. The measure is based on the distribution of wheel-terrain contact forces and is measurable with practical sensors.(cont.) The measure is compared to existing stability measures and is able to detect wheel lift-off with greater accuracy in off-road conditions. The measure is experimentally validated with wheel lift-off detection as well. An uncertainty analysis of the measure is presented that assesses the relative importance of each sensor and parameter in the measure.by Steven C. Peters.S.M

Advances in Mechanical Systems Dynamics 2020

The fundamentals of mechanical system dynamics were established before the beginning of the industrial era. The 18th century was a very important time for science and was characterized by the development of classical mechanics. This development progressed in the 19th century, and new, important applications related to industrialization were found and studied. The development of computers in the 20th century revolutionized mechanical system dynamics owing to the development of numerical simulation. We are now in the presence of the fourth industrial revolution. Mechanical systems are increasingly integrated with electrical, fluidic, and electronic systems, and the industrial environment has become characterized by the cyber-physical systems of industry 4.0. Within this framework, the status-of-the-art has become represented by integrated mechanical systems and supported by accurate dynamic models able to predict their dynamic behavior. Therefore, mechanical systems dynamics will play a central role in forthcoming years. This Special Issue aims to disseminate the latest research findings and ideas in the field of mechanical systems dynamics, with particular emphasis on novel trends and applications