Jason Keith Moore

1. All means of infant transport cause vibration, which is transferred to the sitting or lying child. Unlike early-century perambulator design considerations (Behrend 1931), vibration is seemingly ...

The objective of this study was to comprehensively evaluate vibrations with dummies representing infants aged 0, 3, and 9 months lying or sitting in five strollers and two cargo bicycles with dedicated baby seats on six common road surfaces using the ISO standard for whole-body vibration. Strollers induced on average 0.4 m s−2 on tarmac and up to 5.0 m s−2 on cobblestones at a mean walking speed of 5.3 km h−1 . Cargo bicycles induced on average 0.6 m s−2 on tarmac and up to 10.7 m s−2 at 25 km h−1 on paver bricks. The standard suggests the highest accelerations for strollers and cargo bicycles are extremely uncomfortable and continuous exposure should be limited to less than 10 min. Vintage strollers have reduced vibrations compared to modern strollers, indicating benefits of compliant suspensions. We recommend that designers systematically consider vibration, users avoid prolonged exposure to surfaces rougher than tarmac, and researchers pursue scientifically founded test procedures and standards for infant vibration.

This project was designed to understand the causes and mechanisms of bicycle disc brake noise and use that information to formulate and evaluate possible mitigation techniques. Brake noise was generated by a real bicycle running on a treadmill and recorded by microphone and laser vibrometer. Six independent variables, brake force, rotor thickness, front fork stiffness, weather conditions, spoke tension, and friction coefficient, were varied according to a one-quarter fractional factorial design. A finite element model of the rotor, pads, and calliper was also formulated and analysed. The results of these two methods, particularly the disc mode shapes and frequencies, suggest that doublet mode splitting and reconverging plays a role in noise generation and that changing the rotor mass or breaking its symmetry could interfere with such noise generation. Finally, of these mitigations, breaking disc symmetry proved the most fruitful, with noise magnitude reductions from 72% to 99%, depending on frequency.

We evaluated the impact of Model Predictive Control (MPC) robotic-assisted compared to unassisted training, and the effect of alternating between MPC-assisted and unassisted training sequences on motor learning of a complex bicycle steering task. This task involved participants steering and collecting virtual stars displayed on a screen riding a steer-by-wire bicycle on a treadmill. Ten participants were split into two groups, alternating between MPC-assisted and unassisted training. Tasks’ motor skills were quantified by the distance to stars and its standard deviation (SD), while motor performance was determined by mean absolute and SD of steering rate across three evaluation time points: Baseline, Mid-Training, and Post-Training. The repeated-measures ANOVA indicated a significant improvement in task skill (SD of distance from stars) and steering performance (mean absolute and SD of steering rate) and an interaction effect of Group x Time Point on mean absolute and SD of steering rate. The group who initially trained without MPC exhibited a notable decrease in average and variation of steering rate, implying an advantage in starting training unassisted. Our findings suggest that the strategy of starting the training unassisted could stimulate an internal focus (concentrating on one’s own body movements) and intrinsic skill perception, which forms a basis for later integrating MPC assistance to further refining the gained motor skills. Such a sequential training approach may be beneficial in motor skill acquisition of complex dynamics tasks. MPC assistance could be advantageous for individuals with diminished internal model and skill perception, such as those with balance impairments, potentially allowing them to rely less on their impaired sensorimotor abilities.

The ollie is the base aerial human–board maneuver, foundational to most modern skateboarding tricks. We formulate and solve an optimal control problem of a two-dimensional simplified human model and a rigid body skateboard with the objective of maximizing the height of the ollie. Our solution simultaneously discovers realistic human-applied force trajectories and optimal board geometry. We accomplish this with a direct collocation formulation using a null seed initial guess by carefully modeling the discontinuous aspects of board–ground impact and foot–board friction. This leads to efficient and robust solutions that are 10 times more computationally efficient than prior work on similar problems. The solutions show that ollie height can increase 3% by decreasing the wheelbase and that a smaller board with a back-foot-dominated force strategy can give 12% higher ollies. Our model can be used to inform jump strategy and the effects of changes to the essential board geometry.

We previously presented a narrow-track tilting tricycle with a variable stability mechanism integrated between the swing arms that support a pair of rear wheels, in the so-called “delta” configuration, and with recumbent seating. We now examine adopting that variable stability mechanism to work on a tricycle with a split-parallelogram linkage between a pair of front wheels, in the so-called “tadpole” configuration, and with upright seating. It was fairly straightforward to allow for tilting by replacing the front wheel and fork with a split parallelogram comprising two paired A-arms and kingpins, controlling the motion of the two halves with a bell crank and two tie rods, and then varying the handling of the vehicle by moving the connection point of the tie rods on the bell crank, just as we did with the swing arms of the previous vehicle. We have also separated the two tasks of positioning the tie rod ends on the bell crank and enforcing symmetry of the tie rods. The former does not require much force and can be easily implemented with Bowden cables, but the latter does require large forces and is better implemented with a local rigid-bar linkage. Implementing decent Ackermann steering geometry, allowing for both large tilt and steer angles, and decoupling tilting from steering, however, proved to be quite a challenge, at least while we attempted to implement it with bar linkages. Fortunately, we discovered a 2006 paper by Prof Drstvenšek et al. describing a Bowden cable and cam system that looked promising. Finally, the resulting vehicle handles very nicely. When in “full bicycle” mode, it handles quite similar to the original bicycle that we had converted into the tricycle. When in “rigid tricycle” mode, it keeps the rider upright when stationary or when riding at a walking pace. In between these two extremes, it handles even better than the original bicycle in a slalom course and when slowly following a straight line.