SoloStand

The purpose of this scope of work is to highlight the progress and development of SoloStand sponsored by Derek Herrera, chief technical officer and founder of SpinalSingularity. SoloStand is an attachment to a wheelchair that will benefit paraplegics that use wheelchairs. A portable and customizable attachment to a wheelchair will allow the user to do everyday tasks without transferring into a separate standing wheelchair and travel more easily. This document outlines everything that has been done in fulfillment of our senior project requirements

Reduced Order Modelling of Hydraulic Valves

There is a need for accurate models of small and highly dynamic one-way valves such as those found in engine oil systems. Such reduced order models can then be included in larger oil system models that are too complex to model at high resolution. Two one-way valves are introduced and analysed using a fluid structure interaction simulation. The behaviour of the valves is examined, and the resultsgenerated are then used to develop two reduced order methodologies. The first is physics based. It combines physical phenomena and steady state simulation results to build up an accurate valve model. This model provides good results but is limited by the applicability of steady state simulations to dynamic behaviour, which is itself dependent on valve geometry and fluid properties. The second approach is based on a type of continuous-time recurrent neural network. This allows training on fluid structure interaction simulations with no need for physical insight. The network is trained directly on the dynamic behaviour and accurately reproduces it. Training methods are discussed. A multiple particle swarm methodology and in situ training technique is presented. The neural network-based model is applied to a more complex valve. Network architecture and size are investigated. A comparison is done over a range of time step sizes. Finally, an example workflow is given presenting the steps to train a neural network and use the resulting reduced order model within a larger oil system model

Design, Analysis, and Optimization of a FSAE Racecar

Each year SAE hosts the Formula SAE Colligate Design Competition for engineering students from around the world. The competition is judged based on the engineering, performance, and cost of a Formula style race car designed to be produced in a small 3000 unit production run. Our MQP analyzed an uncompleted FSAE car and designed and redesigned the different systems of the car. Another aspect of our project was studying the different systems of the car and determining how they can best be optimized to produce an increase in performance. A data acquisition system was also designed to record data from different systems to be used to help optimize the car. The data system was designed to be easily transferred between cars for use by future FSAE teams at WPI

Friction-induced Vibration in Lead Screw Systems

Lead screw drives are used in various motion delivery systems ranging from manufacturing to high precision medical devices. Lead screws come in many different shapes and sizes; they may be big enough to move a 140 tons theatre stage or small enough to be used in a 10ml liquid dispensing micro-pump. Disproportionate to the popularity of lead screws and their wide range of applications, very little attention has been paid to their dynamical behavior. Only a few works can be found in the literature that touch on the subject of lead screw dynamics and the instabilities caused by friction. The current work aims to fill this gap by presenting a comprehensive study of lead screw dynamics focusing on the friction-induced instability in such systems. In this thesis, a number of mathematical models are developed for lead screw drive systems. Starting from the basic kinematic model of lead screw and nut, dynamic models are developed with varying number of degrees of freedom to reflect different components of a real lead screw drive from the rotary driver (motor) to the translating payload. In these models, velocity-dependent friction between meshing lead screw and nut threads constitute the main source nonlinearity. A practical case study is presented where friction-induced vibration in a lead screw drive is the cause of excessive audible noise. Using a complete dynamical model of this drive, a two-stage system parameter identification and fine-tuning method is developed to estimate parameters of the velocity-dependent coefficient of friction. In this approach the coupling stiffness and damping in the lead screw supports are also estimated. The numerical simulation results using the identified parameters show the applicability of the developed method in reproducing the actual systems behavior when compared with the measurements. The verified mathematical model is then used to study the role of various system parameters on the stability of the system and the amplitude of vibrations. These studies lead to possible design modifications that solve the system’s excessive noise problem. Friction can cause instability in a dynamical system through different mechanisms. In this work, the three mechanisms relevant to the lead screw systems are considered. These mechanisms are: 1. negative damping; 2. kinematic constraint, and; 3. mode coupling. The negative damping instability, which is caused by the negative gradient of friction with respect to sliding velocity, is studied thorough linear eigenvalue analysis of a 1-DOF lead screw drive model. The first order averaging method is applied to this model to gain deeper insight into the role of velocity-dependent coefficient of friction and to analyze the stability of possible periodic solutions. This analysis also is extended to a 2-DOF model. It is also shown that higher order averaging methods can be used to predict the amplitude of vibrations with improved accuracy. Unlike the negative damping instability mechanism, kinematic constraint and mode coupling instability mechanisms can affect a system even when the coefficient of friction is constant. Parametric conditions for these instability mechanisms are found through linear eigenvalue analysis. It is shown that kinematic constraint and mode coupling instability mechanisms can only occur in self-locking lead screws. The experimental case study presented in this work demonstrates the need for active vibration control when eliminating vibration by design fails or when it is not feasible. Using the sliding mode control method, two speed regulators are developed for 1-DOF and 2-DOF lead screw drive system models where torque generated by the motor is the controlled input. In these robust controllers, no knowledge of the actual value of any of the system parameters is required and only the upper and lower bounds of parameters are assumed to be available. Simulation results show the applicability and performance of these controllers. The current work provides a detailed treatment of the dynamics of lead screw drives and the topic of friction-induced vibration in such systems. The reported findings regarding the three instability mechanisms and the friction parameters identification approach can improve the design process of lead screw drives. Furthermore, the developed robust vibration controllers can be used to extend the applicability of lead screws to cases where persistent vibrations caused by negative damping cannot be eliminated by design modifications due to constraints

Driver – ECO-car system: design and computer simulation of dynamics

The 21st century certainly poses new challenges for the construction of means and systems of transport, particularly in the greater metropolitan areas. Issues related with public transport are generally well-known. Research studies are constructively oriented towards finding solutions to reduce energy consumption, minimize construction and maintenance costs, guarantee profitability, reduce emissions of air pollutants, and first and foremost, solutions which would be human-friendly and specifically tailored to meet the needs of the people. This paper presents the concept of a new electric ECO-car designed within the remit of the scientific and research programme at Warsaw University of Technology. The car is equipped to carry both able-bodied passengers and the disabled. The car uses an integrated drive and brake-by-wire system, as well as powered by lithium-ion batteries and a super capacitor system. During the design process special attention was also paid to ergonomic issues. Due to the theme of the conference, special attention will be paid to the dynamic properties of a complex system of driver-vehicle-road. It will show dynamic phenomena in the implementation of the so-called moose test

Advanced Low-Floor Vehicle (ALFV) Specification Research

This report details the results of research on market comparison, operational cost efficiencies, and prototype tests conducted on a novel design for an Advanced Low Floor Vehicle (ALFV), flex-route transit bus. Section I describes how the need for such a bus arises from a combination of diminishing transit funding from the federal government and demographic and transportation factors. Section II describes the unique features of this bus design that render it suitable for rural and urban operation, including improved transit passenger and wheelchair accessibility, reduced maintenance, structural design features, safety provisions, and the technical specifications of this design. Section III details the potential differences in capital and operational costs of procuring and operating this bus in a fleet. Potential cost reductions due to the long-life vehicle concept, maneuverability, operational savings (from APTA Bus Roadeo tests), and reserve fleet savings are explored. Section IV refers to the Federal Transit Administration (FTA) new model bus tests (“Altoona Testing”). However, at the this time, the Altoona Bus Test Report for these tests is not yet released by the bus manufacturer, Ride Solution, Inc., as is its right under the Bus Testing Regulation. The report must be released to the public before this bus can be purchased by a transit agency using FTA funds. In addition to the standard Altoona Bus Test, additional research was conducted to determine the turning ability, suspension travel, ramp travel index, field of view for the driver, compliance to Americans with Disabilities Act (ADA) requirements, and timed assessment of wheelchair securement. Section IV also presents the results of these tests. Section V presents results from a market comparison that included the buses in this mid-size category that were tested at Altoona and are expected to be available for FTA grantees to purchase. The specifications and performance of the ALFV bus are compared with these buses. Section VI presents a flex-route utilization plan, and Section VII provides the results from a survey of transit professionals about their interest in the features of this bus design. Section VIII gives Ride Solution’s experience in developing the concept for ALFV. Conclusions of this report are presented in Section IX, followed by the references and appendices