Since the concept of a Personal Mobility Vehicle (PMV) that tilts inward while turning is relatively new, there is currently a lack of theoretical considerations regarding the suspension mechanism. Therefore, this study aims to explore the theoretical relationship between suspension geometry and the pitching posture during turning in a PMV with two front wheels and one rear wheel that tilts inward during turns. Our findings suggest that a combination of a front telescopic suspension and a rear full trailing arm (swing arm) suspension is suitable for minimizing both the squatting pitching of the vehicle body during turns and the disturbances caused by changes in tread and tire camber angles during wheel strokes in the upright driving position from a static force balance perspective. From a dynamic perspective, there is no significant concern about pitching occurring even in cases where there may be a delay in active tilt angle tracking (PID) control when using the combination of front telescopic suspension and rear full trailing arm suspension. However, it is essential to note that a large sprung roll moment of inertia can still induce the squatting pitching.
The suspension system of a vehicle is essentially conceived with two objectives: to provide comfort to the passengers and maintain tires in contact with the ground (roadholding). It is well known, however, that optimal comfort and roadholding cannot be achieved simultaneously since they require a different set of stiffness and damping. Simple models are used to comprehend the variables involved with which the response acceleration, tyre force and suspension displacements due to random roads had been derived, together with optimal suspensions. Nonetheless the required suspension travel and suspension sag have not been extensively discussed. In this article we derive expressions to determine the suspension travel and suspension sag (static compression) required to transit a random road. It was also analysed the case when the optimal suspensions are used, and the expressions where simplified. Lastly, a numerical example show that the derived equations provide reasonable values for a first approximation.
Motorcycles are systems with complex dynamic behaviour that can become unstable under certain driving conditions. Avoiding such instabilities from the design stage is not trivial since they depend on various interrelated parameters, one of which is aerodynamics. Aerodynamic forces in a vehicle can be essentially described by its longitudinal (drag) and vertical (lift) components acting in a point known as the centre of pressure (CoP). Additionally, several authors explain that drag influences stability through four mechanisms: dampening lateral motion and changing weight distribution, tire cornering stiffness, and rake geometry. On the other hand, the lift force, which has been used importantly in sports motorcycles in recent years, can also influence stability, however, its effect has not been described in the literature. Therefore the aim of this research is to analyse the influence of lift magnitude and CoP position on motorcycle stability in straight-running conditions. To this end, we develop a motorcycle stability model and perform an analysis on a motorcycle with several CoP and downforce values. We consider the CoP ahead, aligned, and behind the motorcycle centre of mass, together with multiple lift coefficients. Results showed that CoP towards the front end stabilises wobble mode, while rear CoP may cause instability on weave mode. The result contributes to the understanding of motorcycle aerodynamics providing new insights into how to use aerodynamics to enhance stability.
The development of computationally efficient and validated single-track vehicle-rider models has traditionally required handcrafted one-off models. Here we introduce BRiM, a software package that facilitates building these models in a modular fashion while retaining access to the mathematical elements for handcrafted modeling when desired. We demonstrate the flexibility of the software by constructing the Carvallo-Whipple bicycle model with different numerical parameters representing different bicycles, modifying it with a front fork suspension travel model, and extending it with moving rider arms driven by joint torques at the elbows. Using these models we solve a lane-change optimal control problem for six different model variations which solve in mere seconds on a modern laptop. Our tool enables flexible and rapid modeling of single-track vehicle-rider models that give precise results at high computational efficiency.
A leaf spring is a very simple type of mechanical spring which is commonly used for heavy duty suspension systems. In single-track vehicles, such as motorcycles or bicycles, the coil and air spring are most widespread as well as current state of the art. However, the application of a leaf spring is nothing new on these types of vehicles. Various design approaches can be admired in museums. A century ago, it was even more common than the coil spring, but history shows us that this spring system has gradually been replaced due to its inherent disadvantages. So why should we deal with it again now? Because we believe that the leaf spring is not yet old news and has the potential to improve current vehicles. In this document, we want to introduce an alternative leaf spring design and the associated benefits. One that at the core is old and simple in form but utilizes new approaches and technologies to meet the demands of modern motorcycle and improve riding behavior.
Cyclists have various route options to get to their destination. They can share lanes with vehicles, share lanes with pedestrians, or have their own lane. In Germany there are often marked lanes across intersections and stop lines in front of the crossing, guiding the cyclists their way. However, these markings are not always respected in the way they should be. This study is intended to examine the stopping behaviour of cyclists at a traffic light-controlled intersection. A distinction was made between cyclists riding alone (n = 1,411) and cyclists riding in groups (more than one cyclist; n = 475). The stopping area was divided into polygons to understand where most people stop before an intersection. Furthermore, it was examined where people continued to ride after stopping (path marked for cyclists or path marked for pedestrians) and this was compared with cyclists who did not stop. The aim of this study is to investigate cyclists’ stopping behaviour (e.g. stopping position) at intersections with consideration of the impact of groups, wrong-way riding and road usage. It is to be investigated whether cyclists alone behave differently than cyclists in groups and whether there are differences in the two groups for wrong way cyclists. Both - cyclists alone (69.38%) and cyclists in groups (84.57%) - crossed the intersection more frequently without stopping within the observation period. In all cases, cyclists stopped more often at the bicycle stopping line or used the special marked bicycle lane, thereby complying with the law. Most wrong way cyclists on the special marked bicycle lane were found for cyclists alone with stopping (10%, n = 27) and cyclists in groups with stopping (8%, n = 12). The speeds were also compared. The speeds between cyclists alone and cyclists in groups differ slightly, and the stopping behaviour is very similar if the special marked bicycle lane is used after the stop. The information can be used to improve models of cyclists’ behaviour, for example in microscopic simulations, in which cyclists only stop at clearly defined locations. Furthermore, the results of this study will provide further knowledge, which help developing autonomous driving functions correctly anticipating cycle behaviour at intersections.
Test and modeling results are reported on a bicycle crankset with limited elasticity. Like record-breaking running shoes, the crank set has spring action which mitigates the effect of the dead zone during the pedal stroke. Fiber composite leaf springs are inserted inside the hollow carbon crank arms. The crank arms are not directly attached to the crank axle. Instead, sleeve bearings allow the crank arms to rotate by up to about five degrees relative to the crank axle. The rotation is counteracted by the springs and is proportional to applied torque at the pedals. The novel crank set and a conventional crank set with forged aluminum crank arms were both tested on a stationary bike. The ratio of effective speed to input power is used as a measure of cycling efficiency. Depending on the difference in torque during the downstroke and in the dead zone, this ratio is typically a few percent higher for the novel crankset than for a conventional crankset. Multiple tests show efficiency improvements in the range of 1 to 4% at power levels of 200 W and cadence of 71 rpm with average of around 2%. Details of a test with 2.3 % improvement are presented. This would translate, for example, into a one minute advantage in a 45 minute time trial. In an attempt to understand the test results computer modeling of bicycle speed and crank arm angular velocity vs. time was performed for non-elastic and and elastic crank arms. It is difficult to explain the test results with computer modeling unless it is assumed that conventional crank sets introduce energy losses in the drivetrain from twisting of the crank arms and flexing of the bicycle frame under load at the pedals and that these energy losses are reduced for the crank set with built-in elasticity.
An important performance determinant in wheelchair sports is the power exchanged between the athlete-wheelchair combination and the environment, in short, mechanical power. To monitor the mechanical power during wheelchair sports practice, inertial measurement units (IMUs) might be used. However, a well-founded and unambiguous theoretical framework that follows the dynamics of manual wheelchair propulsion is required to validly apply IMUs for mechanical power assessment in wheelchair sports. Such a framework does not yet exist. Therefore, this research has two goals. First, to present a theoretical framework that supports the use of IMUs to estimate power output via power balance equations. Second, to create a set of guidelines on how to use IMUs to monitor mechanical power during wheelchair propulsion supported by experimental data. After verifying the theoretical framework, an IMU model was defined. Subsequently, the validity of the IMU model and underlying assumptions was determined. Therefore, power was estimated from IMU data during wheelchair propulsion and was subsequently compared to gold standard optical motion capture data. Data was collected from eleven participants without wheelchair experience propelled an all-court sports wheelchair on a large treadmill. At the same time, kinematics were measured using two IMUs and an optical motion capture system. The results reveal that, with a proper drag or deceleration test, one IMU on the wheelchair frame and one IMU on the wheel axis, decent power estimations can be obtained in daily wheelchair (sports) practice. To conclude, the theoretical framework and the resulting IMU-based power is thus well suitable to estimate mechanical power during straight-line wheelchair propulsion in wheelchair court sports and daily wheelchair practice, and it is an important first step towards feasible power estimations in all wheelchair (sports) situations.
This study used the Technology Acceptance Model (TAM) to predict students' acceptance of Learning Management Systems (LMS) through Behavioural Intention in the English Department of Ibn Zohr University. A quantitative approach with a cross-sectional survey design was adopted. Convenience sampling as a non-probability sampling technique was used. Data were collected from 126 respondents through a questionnaire developed. The structural model developed was based on previous works into TAM and included Social Influence (SI), computer self-efficacy (CSE), Perceived Usefulness (PU), Perceived Ease of Use (PEU), Attitude (ATT), and Behavioural Intention (BI). The proposed model was tested and evaluated using the partial least squares structural equation modelling (PLS-SEM) data analysis technique. There were eight supported hypotheses. Albeit, there were six rejected hypotheses. SI had a significant strong effect on both PU and ATT. PEU had a significant strong effect on PU. CSE had a significant strong effect on both PEU and BI. PU had a significant strong effect on both ATT and BI. Nonetheless, SI had an insignificant effect on both BI and PEU. CSE had an insignificant negative effect on PU and an insignificant effect on ATT. PEU had an insignificant negative effect on BI and an insignificant effect on ATT. Of all the proposed variables, ATT had the greatest effect on BI. This study discovered that the resulting model was able to predict and explain BI amongst students at Ibn Zohr University. Furthermore, the model showed an ability to explain 66.2% of the variance in BI, 44.2% in PU, 59.9% in PEU, and 63.5% in ATT. These findings have important implications for developing and improving LMS that can be accepted by students. The findings of this study are pertinent to the higher education management administrations, LMS developers, researchers, and stakeholders for improving and promoting the use of Learning Management Systems amongst university students.