Measurement of wheelchair contact force with a low cost bench test

Characterization of the vehicle emissions in the Greater Taipei Area through vision-based traffic analysis system and its impacts on urban air quality

In recent years, many surveillance cameras have been installed in the Greater Taipei Area, Taiwan; traffic data obtained from these surveillance cameras could be useful for the development of roadway-based emissions inventories. In this study, web-based traffic information covering the Greater Taipei Area was obtained using a vision-based traffic analysis system. Web-based traffic data were normalized and applied to the Community Multiscale Air Quality (CMAQ) model to study the impact of vehicle emissions on air quality in the Greater Taipei Area. According to an analysis of the obtained traffic data, sedans were the most common vehicles in the Greater Taipei Area, followed by motorcycles. Moderate traffic conditions with an average speed of 30-50 km/h were most prominent during weekdays, whereas traffic flow with an average speed of 50-70 km/h was most common during weekends. The proportion of traffic flows in free-flow conditions (>70 km/h) was higher on weekends than on weekdays. Two peaks of traffic flow were observed during the morning and afternoon peak hours on weekdays. On the weekends, this morning peak was not observed, and the variation in vehicle numbers was lower than on weekdays. The simulation results suggested that the addition of real-time traffic data improved the CMAQ model's performance, especially for the carbon monoxide (CO) and fine particulate matter (PM_2.5) concentrations. According to sensitivity tests for total and vehicle emissions in the Greater Taipei Area, vehicle emissions contributed to >90% of CO, 80% of nitrogen oxides (NO_x), and approximately 50% of PM_2.5 in the downtown areas of Taipei. The vehicle emissions contribution was affected by both vehicle emissions and meteorological conditions. The connection between the surveillance camera data, vehicle emissions, and regional air quality models in this study can also be used to explore the impact of special events (e.g., long weekends and COVID-19 lockdowns) on air quality.

A high prevalence of manual wheelchair rear-wheel misalignment could be leading to increased risk of repetitive strain injuries

PURPOSE

To determine the prevalence and severity of manual wheelchair rear wheel misalignment in community-dwelling manual wheelchair users and estimate the associated increases in rolling resistance (RR) and risk of repetitive strain injuries (RSIs).

MATERIALS AND METHODS

Data were collected in an outpatient rehabilitation clinic, a university research laboratory, and at adaptive sporting events in the United States. Two hundred active, self-propelling manual wheelchair users were recruited. Angular misalignment (referred to as toe angle) while the wheelchair was loaded with the user, and the difference between the maximum and minimum toe angle (referred to as slop) with the wheelchair unloaded.

RESULTS

Average results for toe angle and slop (movement in the rear wheels) were 0.92 and 0.61 degrees, respectively. Using a lab-based testing method, we quantified the impact of increased RR forces due to misalignment in increased RR forces. Our results indicate that the average toe angle while under load and slop, without loading, measured in the community increase required propulsion force by 3.0 N. Combined toe angle and slop (i.e., the worst-case scenario) added increased propulsion force by 3.9 N.

CONCLUSIONS

We found that rear-wheel misalignment was prevalent and severe enough that it may increase the risk for RSIs and decrease participation. To mitigate this issue, future work should focus on reducing misalignment through improved maintenance interventions and increased manufacturing quality through more stringent standards.Implications for RehabilitationThe work reveals a previously unknown and significant contributor to RR that could have health implications for users who self-propel.Maintenance and repairs should be adjusted to help reduce the impact of misalignment.Our results suggests that WC designers should take additional care to designs wheels and frames to minimize misalignment.Service providers setting up wheelchairs should take additional care to make sure the wheels are aligned.Users should monitor misalignment and prioritize maintaining or having their chair repaired when misalignment occurs.

Scoping review of the rolling resistance testing methods and factors that impact manual wheelchairs

Introduction

Rolling resistance (RR) is a drag force acting on manual wheelchairs that is associated with increased propulsion force and is linked to secondary disabling conditions of the upper limbs. A scoping review was conducted to understand how RR of manual wheelchairs has been measured and to identify limitations of those test methods and the factors tested.

Methods

A total of 42 papers were identified and reviewed, and test methods were categorized based on the measurement style of RR, testing level, and if multiple parameters could be tested. Additionally, 34 articles were reviewed for what factors were tested.

Results

Seven different testing methods categories were identified: drag test, treadmill, motor draw, deceleration, physiological expenditure, ergometer/dynamometer, and robotic test rig. Relevant articles were categorized into testing factor categories: camber, toe, tire type, tire pressure, caster type, mass, mass distribution, and type of surface.

Conclusions

The variety of testing methods suggests the need for a standardized method that can be used for wheelchair wheel design and selection to reduce RR. It is important to use adjustments, such as a forward rear axle position to mitigate RR as well as using high-pressure pneumatic tires that are properly inflated.

Contrary to basic kinematic modelling, during tight turns, wheelchairs can slide sideways by non-negligible magnitudes: Collision risks may be increased

Small spaces make collision-free turns difficult for wheelchair users. Contrary to basic kinematic wheelchair modelling and not considered previously by engineers; when wheelchairs turn in small spaces, could lateral drift (sideways slipping) increase the risk of collisions with surrounding structures such as walls and doorways? An improved kinematic understanding can inform building design and therapeutic involvement with wheelchair use. Wheelchair lateral drift is investigated. Two experiments with assisted wheelchair use are reported. Weights represented wheelchair occupants. First, lateral drift was measured by motion capture (VICON): turns (n = 225) made by the experimenter, for six radii of curvature (0-613 mm) and four total-masses (81-142 kg). Second, lateral drift was measured by ruler: turns (n = 105) made by experienced wheelchair assistants (n = 22), for three radii of curvature (0, 306, and 800 mm), and self-selected maximum comfortable weights. Lateral drift away from centre of curvature occurred for all radii of curvature greater than 0 mm, and a maximum median lateral drift of 27 mm/rad occurred for 142 kg total mass with 459 mm radius of curvature. Lateral drift increased with mass (r² = 0.68 for 358 mm radius of curvature). During tight turns, lateral drift magnitude and direction is such that it can increase risks of collisions with surrounding structures.

Modeling manual wheelchair propulsion cost during straight and curvilinear trajectories

Minimizing the effort to propel a manual wheelchair is important to all users in order to optimize the efficiency of maneuvering throughout the day. Assessing the propulsion cost of wheelchairs as a mechanical system is a key aspect of understanding the influences of wheelchair design and configuration. The objective of this study was to model the relationships between inertial and energy-loss parameters to the mechanical propulsion cost across different wheelchair configurations during straight and curvilinear trajectories. Inertial parameters of an occupied wheelchair and energy loss parameters of drive wheels and casters were entered into regression models representing three different maneuvers. A wheelchair-propelling robot was used to measure propulsion cost. General linear models showed strong relationships (R² > 0.84) between the system-level costs of propulsion and the selected predictor variables representing sources of energy loss and inertial influences. System energy loss parameters were significant predictors in all three maneuvers. Yaw inertia was also a significant predictor during zero-radius turns. The results indicate that simple energy loss measurements can predict system-level performance, and inertial influences are mostly overshadowed by the increased resistive losses caused by added mass, though weight distribution can mitigate some of this added cost.

Measurement of rolling resistance and scrub torque of manual wheelchair drive wheels and casters

The effort needed to maneuver a manual wheelchair is a function of the occupied wheelchair's inertia and energy loss. The primary source of energy loss is due to the resistance of the drive wheels and casters on the ground. Specifically, manual wheelchairs have two major sources of frictional energy loss: rolling resistance and scrub torque. The objective of this study was to develop and validate component-level test methods to evaluate the energy loss properties of drive wheels and casters on different surfaces and with different applied loads. Rolling resistance is measured using a weighted coast-down cart and scrub torque is calculated by measuring the force required to rotate a plate that is loaded onto the tire's surface. Each test method was iterated and then applied to a cohort of drive wheels and casters. Both test methods demonstrated acceptable repeatability and the ability to distinguish energy loss parameters between common wheelchair components. The results show that caster and drive wheel energy losses can vary significantly across surfaces and with increased load on the casters. However, the findings also illuminate complex relationships between rolling resistance and scrub torque performance that embody a tradeoff in performance as applied to mobility during everyday life.

A lateral dynamics of a wheelchair: identification and analysis of tire parameters

In vehicle dynamics studies, the tire behaviour plays an important role in planar motion of the vehicle. Therefore, a correct representation of tire is a necessity. This paper describes a mathematical model for wheelchair tire based on the Magic Formula model. This model is widely used to represent forces and moments between the tire and the ground; however some experimental parameters must be determined. The purpose of this work is to identify the tire parameters for the wheelchair tire model, implementing them in a dynamic model of the wheelchair. For this, we developed an experimental test rig to measure the tires parameters for the lateral dynamics of a wheelchair. This dynamic model was made using a multi-body software and the wheelchair behaviour was analysed and discussed according to the tire parameters. The result of this work is one step further towards the understanding of wheelchair dynamics.