Whole-body vibration is an important problem facing operators of off-road vehicles. Research has shown that operators exposed to low-frequency whole-body vibration can experience temporary and even permanent injuries. One solution to this problem is to develop an active seat capable of canceling the vibrations felt by the operator. Several passive, semi-active, active, and fully active seats have been designed and built to address this problem. Furthermore, controllers have been developed to optimize the seat performance. Vibration cancellation seating systems seem to be a promising and practical way to reduce the effects of whole-body vibration. To extend developments in this area, a Hyper-Active seat has been designed and built at the Georgia Institute of Technology. The seat utilizes a 3 Revolute-Prismatic-Revolute (RPR) parallel manipulator design which allows for the independent control of the vertical, horizontal and pitch angle directions. The seat is powered using three hydraulic actuators which are controlled using MATLAB's Simulink, xPC Target, and Real-Time Workshop. Controllers were developed to control the position of the seat, as well as cancel unwanted vibration. To test the performance of the Hyper-Active seat, the system identification of the seat was undertaken using open-loop forcing functions. The seat was evaluated in each degree of freedom to understand the potential of the seat to cancel harmful vibration. In addition to reducing harmful vibrations, the seat can double as a safety seat to reduce injuries during a frontal collision. If the front edge of the seat bottom can be raised very quickly, then the forward motion of the passenger can be reduced during a crash. An optimal method for performing this motion is developed.

A comprehensive comparison between an air-inflated seat cushion designed for truck seats and a commonly used foam cushion is provided, using a single-axis test rig designed for dynamic seat testing. Different types of tests are conducted in order to evaluate various aspects of each type of cushion; in terms of their response to narrow-band (single frequency) dynamics, broadband input of the type that is commonly used in the trucking industry for testing seats (ISO2), and a step input for assessing the damping characteristics of each cushion. The tests were conducted over a twelve-hour period -- in four-hour intervals -- measuring the changes that occur at the seat cushion over time and assessing how these changes can affect the metrics that are used for evaluating the cushions. The tests indicated a greater stiffening of the foam cushion over time, as compared with the air-inflated cushion that showed almost no change in stiffness when exposed to a static weight for twelve hours. Furthermore, pressure measurements at the seat showed higher-pressure concentrations for the foam cushion at the bony prominence of the seat profile -- namely, the ischial tuberosities -- as compared to the air-inflated cushion. A series of tests aimed at evaluating the damping properties of each cushion showed both cushions to have nearly identical damping properties. Other methods used for evaluating the dynamic properties of the two seat cushions included those recommended by studies in the past, as well as new techniques that were developed specifically for this study. The new techniques, named Seat Pressure Distribution (SPD%) and Area Pcrms (aPcrms) for the purpose of this study, are formulated such that they can best highlight the dynamic differences between different types of seat cushions, and their effect on driver comfort. The results show that the air-inflated seat cushion can provide significant improvements in pressure distribution between the seat cushion and the driver, therefore providing a more comfortable ride and causing less fatigue. / Master of Science

This research focuses on the dynamic seat comfort in aircrafts specifically during takeoff, landing and cruise through turbulence flight conditions. The experiments are performed using a multi axis shaker table in the Automotive Centre of Excellence (ACE) at the University of Ontario Institute of Technology subjected to sample takeoff, landing and cruise vibration recordings obtained onboard of an actual flight. The input vibrations introduced to the aircraft seats during actual flight conditions and during the experiments in the ACE are compared and it is concluded that the given flight conditions were successfully replicated for the interest of this thesis. The experiments are conducted with two different aircraft seats, economy class and business class. Furthermore, to investigate the importance of seat cushion characteristics in addition to economy and business class seat cushions, three laboratory made cushions were included in the investigation as well. Moreover, the effect of passenger weight is also discussed by conducting the experiments with 1 and 2 identical dummies. It is concluded that static seat properties play a significant role in the comfort perception level as well as flight conditions. Among the three flight condition, landing appeared to be the most uncomfortable case comparing to takeoff and cruise. In addition to experimental work, a numerical study to simulate the flight conditions is undertaken with the initial work of CAD modelling. The simulated responses of the seat is partially matching with experimental results due to unknown parameters of the cushion and the connections of the aircraft seat that cannot be created in the CAD model due to unknown manufacturing processes.

Thesis (M.A.)--Capital Bible Seminary, 1988. / Includes bibliographical references (leaves 65-72).

This thesis work is focused on the design of a mechanism for the passenger’s seat of a Volvo S80. This mechanism will facilitate the problems arised when somebody with limited mobility, either permanent or temporal, is entering or exiting the vehicle. The main aim is to obtain an affordable device that enhances the life of those with reduced mobility, but paying special attention to those who do not receive any kind of economical help from the government. The idea is to be able to move the seat to the outside of the car so that one can seat with no special effort. Then, the mechanism, manually, performs the movements to bring it back to the inside. The concept of being manual is to avoid electronic devices that will surely increase the cost. In this project, a possible design solution has been developed. A model was created with Autodesk Inventor 2012. The three basic positions of the mechanism were studied to determine the structural behavior of the product. For these studies, a load compensating the weight of a human was applied and the stresses and the deformation were analyzed by Finite Element Methods and the study was concluded when the safety factor was over 2.

The characteristics of an automotive passenger seat in response to vibrational excitations are examined and an active vibration isolation system incorporating smart materials is designed, built, and tested. Human sensitivity to vibration is discussed. Characteristics of road roughness are discussed and used to implement a representative test input to a passenger seat system. extsc{Matlab} is used to model the car seat and vehicle system with four degrees of freedom to determine actuator requirements. Selection and implementation of a low--profile, prestressed piezoceramic device into an active seat suspension system is described, and experimental results of the actuator assembly performance are presented. Vibration isolation is realized in an experimental setup representing one quarter of a seat and passenger's total mass, using one actuator assembly (representing one corner of the seat suspension). For an input power spectrum representative of a passenger vehicle environment, the smart material actuator assembly, as applied to a quarter seat experimental setup, is proven to be capable of isolating vibration with an isolation frequency of 2Hz and no resonant peak, versus 6Hz and a resonant peak of 2g/g for an actual passenger seat tested. / Master of Science

Car accidents happens daily, and it is very important to protect all involved in a carno matter the age. Persons that are old enough and can take care of themselves, usescar seat belts to be protected in traffic. A child, however, must be placed andfastened in a safety seat by a parent or another caregiver, to be fully protected. Children that are correctly secured in safety seats have a 2.7 times bigger chance tosurvive a car crash without serious injuries compared to unstrained children (Berget al., 2000; WHO,2004). Regardless tests and safety seats that are available ontoday’s market, there are still issues that needs to be eliminated. Daily users of thisproduct are a good starting point since these people want a safe seat for their childthat can be easy to install and affordable; and they can best tell what issues theyencounter. Based on several scientific articles in a combination with interviews andobservations, issues with the safety seats could be confirmed. The primary issue isthe seat belt that is attached to the safety seat. Children can develop a habit ofwriggling out of the belt in safety seats. There are belt collectors available on themarket which holds the shoulder belts in place. In this way, it is harder for thechildren to slide out of the belt and helps to keep the belt properly positioned(BeSafe, 2018). Instead of having this as an accessory, it has been considered in thebelt that have been developed. Another issue is that the belt is complicated tofastened since two straps has to be simultaneously clicked in the belt buckle. If thisis done incorrectly, the belt cannot be fastened, and it takes time to try it again. Tomake this easier, two straps and the strap between the child's leg will be fastenedseparately in a seat buckle each. In this way, parents and other caregivers will beable to fasten the belt easy and properly. They will also be sure that the child issafely fastened and will minimize injury during an accident or another situation.

M.Ing. (Transportation Engineering) / Please refer to full text to view abstract

For many years seat cushions have been investigated for their ability to reduce seating discomfort. The objective of this thesis is to examine air-inflated seat cushions to determine how seating comfort (determined by pressure change rate) is affected by changing various parameters of the cushion. To this end, a mathematical model was built using MatLab and SimuLINK to accurately represent the cushion and its response. Different aspects of the cushion, such as seating area, outlet size, cell height, and material elasticity are varied to determine how they each affect seating comfort. For each parameter three different weights are tested to see how the trends observed per parameter are affected by a person's weight. The results of this study indicate that by changing the base radius, the cell height, the outlet diameter, and the material elasticity of each cell, it is possible to improve seating comfort, as determined by pressure change rate. The study confirms that comfort levels increase with increasing seated area. The study also shows that although increasing the weight of a person decreases the comfort performance of the cushion, not all the trends observed when the cushion parameters are varied remain the same as the person's weight is changed. The trends observed when the cell height and outlet diameter are varied are not affected by the subject weight but all the other trends changed as the subject weight was changed. / Master of Science

Introduction: Several authors have demonstrated that, while cycling at a constant power output, EMG activity from the gastrocnemius increases systematically with increases in pedaling cadence, but that soleus EMG remains unchanged (Marsh & Martin 1995; Sanderson et al. 2006). The reason for this differential effect of cadence on the muscles of the triceps surae is unclear. Whatever factor(s) are responsible, it is assumed that, as they vary, the differential electromyographic response will vary accordingly. Decreasing the seat height has been shown to alter the kinematic characteristics of cycling (Too, 1990). The first objective of this study was to examine the effect of a decrease in seat height on the kinematics and muscle activation of the lower limb. The second objective was to investigate the effect of seat height on the relationship between cadence and triceps surae activation and, in doing so, to reveal possible factors mediating the response to changes in cadence. Methods: Participants pedaled a cycle ergometer at 200 Watts for five minutes at each of five cadences (50, 65, 80, 95, 110 rpm) and at each of two seat heights (100% and 90% trochanteric height). Kinematics of the lower limb were calculated from digitized video records of reflective markers placed on the skin over seven bony landmarks. EMG data were collected from eight lower-limb muscles. Results: The most notable findings were 1) that activation of the gastrocnemii was less in the low-seat condition and, contrary to what the findings of past research would suggest, was not associated with changes in muscle length; 2) that the medial and lateral gastrocnemii responded differently to changes in cadence at each seat height, suggesting that the functional roles of these muscles in cycling differ; 3) that several factors, including muscle length, muscle velocity, ankle angle and the direction of muscle action, were not responsible for the differential effect of cadence on activation of the soleus and gastrocnemius. Future research should investigate afferent feedback from proprioceptors in the knee joint and knee extensor muscles as possible factors mediating the effect.