Dynamic Performance of Neck Protection Devices: Performance Analysis Based on a Simplified Multibody Model of the Human Neck

This work is focused on the evaluation of the dynamic performance of different neck protection devices. In order to evaluate the mechanical response of the safety devices, a multibody model of the human neck has been developed in Matlab™ SimMechanics™. The mechanical behavior of the neck is described in the paper and different injury indices are presented and compared. The information about anatomy and physiology of the cervical spine of the neck has been collected from the literature, with particular focus on the mechanism of damage of vertebrae, disks and soft tissues. The multibody model has been validated against experimental data available in the literature concerning impulsive loads representative of crash phenomena. By means of the presented model, some relevant injury indices are computed for an accident involving a motorcyclist. Since the focus has been set on mild injuries of the neck, the simulated crash should cause a high probability of injuries of the neck together with a low probability of damages of the head while wearing a standard helmet. The performance of neck safety devices that link the helmet with the thoracic-shield are evaluated and compared. For sake of clearness, three types of neck safety devices are considered referencing to US patents: an airbag jacket, a 3D cushion wrapping the motorcyclist’s neck, and a “spring and dampers” system. The airbag jacket has been modeled as a high stiffness and low deformation system by considering the airbag in its fully deployed configuration and by neglecting its dynamic performance during inflation phase. The other safety devices have been modeled as lumped parameters spring-damper systems. A sensitivity analysis on the injury indexes has been performed by changing the stiffness and the damping parameters of these safety systems. The injury indexes collected by simulating the different neck safety systems have been compared.

Vehicle Stability Control Through Predictive and Optimal Tire Saturation Management

This paper presents a predictive vehicle stability control (VSC) strategy that distributes the drive/braking torques to each wheel of the vehicle based on the optimal exploitation of the available traction capability for each tire. To this end, tire saturation levels are defined as the deficiency of a tire to generate a force that linearly increases with the relevant slip quantities. These saturation levels are then used to set up an optimization objective for a torque distribution problem within a novel cascade control structure that exploits the natural time scale separation of the slower lateral handling dynamics of the vehicle from the relatively faster rotational dynamics of the wheel/tire. The envisaged application of the proposed vehicle stability strategy is for vehicles with advanced and emerging pure electric, hybrid electric or hydraulic hybrid power trains featuring independent wheel drives. The developed predictive control strategy is evaluated for, a two-axle truck featuring such an independent drive system and subjected to a transient handling maneuver.

Nonlinear Control of Semi-Active MacPherson Suspension System

This paper presents the control design and analysis of a non-linear model of a MacPherson suspension system equipped with a magnetorheological (MR) damper. The model suspension considered incorporates the kinematics of the suspension linkages. An output feedback controller is developed using an ℒ2-gain analysis based on the concept of energy dissipation. The controller is effectively a smooth saturated PID. The performance of the closed-loop system is compared with a purely passive MacPherson suspension system and a semi-active damper, whose damping coefficient is tunned by a Skyhook-Acceleration Driven Damping (SH-ADD) method. Simulation results show that the developed controller outperforms the passive case at both the rattle space, tire hop frequencies and the SH-ADD at tire hop frequency while showing a close performance to the SH-ADD at the rattle space frequency. Time domain simulation results confirmed that the control strategy satisfies the dissipative constraint.

Development of 2 Stage CVT Shift Control Algorithm to Reduce Torque Variation During 1-2 Upshift of Planetary Gear

In this paper, a 2 stage continuously variable transmission (CVT) shift control algorithm is proposed for the 1–2 upshift of the planetary gear to achieve the shift quality. A fuzzy control algorithm is designed considering the relatively slower response characteristics of CVT. In order to evaluate the performance of the control algorithm, a 2 stage CVT vehicle simulator is developed including a dynamic model of the CVT powertrain. From the simulation results, it is found that CVT gear ratio changes faster in the inertia phase and remains constant after the inertia phase of the planetary gear shift, which provides the reduced torque variation by the proposed control algorithm.

Optimal Design of Lightweight Machines Using Flexible Multibody System Dynamics

In many machine and robotic applications energy efficiency is an increasingly crucial issue. In order to achieve energy efficiency lightweight structural designs are necessary. However, undesired elastic deformations might occur due to the light wight design. In order to achieve good system performance the actual dynamic loads must be taken into account in the design of the system’s components. In this paper optimization approaches for lightweight machine designs are employed to improve the tracking behavior the systems. Thereby, fully dynamical simulations of flexible multibody systems are coupled with both shape or topology optimization for the elastic members of the multibody system. It is shown, that by these approaches the end-effector trajectory tracking error of light wight manipulators can be decreased significantly.

Rolling Condition and Gyroscopic Moments in Curve Negotiations

In vehicle system dynamics, the effect of the gyroscopic moments can be significant during curve negotiations. The absolute angular velocity of the body can be expressed as the sum of two vectors; one vector is due to the curvature of the curve, while the second vector is due to the rate of changes of the angles that define the orientation of the body with respect to a coordinate system that follows the body motion. In this paper, the configuration of the body in the global coordinate system is defined using the trajectory coordinates in order to examine the effect of the gyroscopic moments in the case of curve negotiations. These coordinates consist of arc length, two relative translations and three relative angles. The relative translations and relative angles are defined with respect to a trajectory coordinate system that follows the motion of the body on the curve. It is shown that when the yaw and roll angles relative to the trajectory coordinate system are constrained and the motion is predominantly rolling, the effect of the gyroscopic moment on the motion becomes negligible, and in the case of pure rolling and zero yaw and roll angles, the generalized gyroscopic moment associated with the system degrees of freedom becomes identically zero. The analysis presented in this investigation sheds light on the danger of using derailment criteria that are not obtained using laws of motion, and therefore, such criteria should not be used in judging the stability of railroad vehicle systems. Furthermore, The analysis presented in this paper shows that the roll moment which can have a significant effect on the wheel/rail contact forces depends on the forward velocity in the case of curve negotiations. For this reason, roller rigs that do not allow for the wheelset forward velocity cannot capture these moment components, and therefore, cannot be used in the analysis of curve negotiations. A model of a suspended railroad wheelset is used in this investigation to study the gyroscopic effect during curve negotiations.

On the Effects of Driving Amplitude, Frequency and Magnetic Fields on the Feed Rate of a Vibratory Micro-Pin Feeder

The use of micro-pin feeder-bowls has been established as a way to singulate and orient micro-scale metallic pins of varying lengths. Increasing the rate and reliability with which pins can feed through the bowl is important when considering the use of such a feeder-bowl in an industrial setting. Previous experimental work, which was limited to a single driving frequency and small range of driving amplitudes of the feeder-bowl, showed low feed rates and long capture times for pins whose aspect ratio exceeded five-to-one. New experimental work has shown that by altering the driving amplitude and frequency of the feeder-bowl, pins with aspect ratios exceeding seven-to-one could be fed. Because the frequency response of feeder-bowls may be limited, other techniques for improving the feed rate for long pins were also sought. One such technique was the magnetizing of the pins to increase their response to a magnetic field which surrounded the feeder-bowl. In some circumstances, more than a 70% reduction in average capture time was observed. The improved capture performance for long pins will permit more freedom in the design of devices that can be assembled with the aid of vibratory micro-pin feeder-bowls. The research results will also be used to improve the accuracy of feeder bowl simulations.

Magnitude of Axle Tramp Response to Partially Detreaded Tire Imbalance in Highway-Speed Driving

Tire tread separations on light trucks and SUVs have resulted in numerous catastrophic highway accidents over the past two decades in the United States. These accidents frequently involve single-vehicle rollovers or deviations of the impaired vehicle into oncoming traffic, where high speed frontal collisions may ensue. On light trucks and SUVs equipped with a Hotchkiss rear suspension, one explanation for the loss of driver control during an in-process rear tire tread separation is solid axle tramp response to the imbalanced separating tire. This explanation has met with some controversy. The present study will demonstrate that the imbalance forces generated at highway speeds from a partially detreaded tire are sufficient to induce continuous cyclical axle tramp, and can even be sufficient to completely elevate rear-axle tires out of contact with the paved roadway. This imbalance-induced tramping action may be exacerbated during braking and the vehicle’s terminal yaw, when rear traction is crucial to avoiding a catastrophic accident. In addition to test data, several field examples of such events are presented. A key metric of solid axle response to an imbalanced, partially detreaded tire is shock absorber motion. In the present study, shock absorber displacement on the test vehicles, as measured during highway speed tread separation axle tramp events, is found to oscillate through a stroke generally less than one inch (2.5 cm) in length at a frequency in excess of 10 Hz. Peak instantaneous velocities of the shock absorber have been observed as high as 40 in/s (16 cm/s) or more during straight driving under axle tramp conditions. Confirming several previously published findings, the present study shows that increasing shock damping force at the higher operational velocities of the shock absorber reduces the magnitude of axle tramp and assists in keeping the rear axle tires in contact with the ground. Additionally, increasing the distance between the shock absorbers by moving them closer to the wheels provides the same advantage.

HIL Development of Control Algorithm for Vehicle Demand-Driven Production of H2 From an Al/Mg and H2O Reaction

This technical paper provides instruction by example on how to apply hardware-in-the-loop (HIL) simulation for accelerated development of a complex control algorithm. The instruction provided in this technical paper is directed to HIL test bench setup, software, simulated and real hardware, and test methods. As an example, the authors reference their collaborative development project of the last couple of years, now completed. The objective of that project was to develop a demand-driven hydrogen production system and integrate it with a hydrogen-fueled internal combustion engine-powered vehicle test platform. The instruction provided in this technical paper is supported by data from the referenced project example.

Using Model Uncertainty to Reduce Verification and Validation in Noise and Vibration Problems

Verifying and validating that a mechanical system meets the design requirements is often a costly iterative activity. This is particularity true, for example, with complex vehicle systems that must meet noise and vibration requirements to ensure vehicle occupant comfort. We show here how analysis of model uncertainty can speed verification testing by bounding and guiding hardware prototype redesign. Vibration and acoustic model uncertainty and residual errors are estimated, and then analysis derived to ensure that this uncertainty range is covered by a planned set of design changes. We further use these results to define a complexity metric based on uncertainty, and an adaptability metric based on the domain of available adjustment. We then propose a capability metric by comparing the range of uncertainty against the range of adaptability provided. We demonstrate the efficacy with an example from the elevator system design, rapidly meeting noise and vibration requirements with only one prototype iteration.