# Laboratory Assessment of Manual Wheelchair Propulsion
## 2 Experimental Testing Methods  
### Dynamometer  
A wheelchair dynamometer is a stationary testing device used to measure the propulsion parameters of manual wheelchairs. There are three primary methods for measuring these parameters [27]: mobile ergometers, based on an electromagnetic brake mounted in the wheelchair [28]; stationary ergometers in which the wheelchair is set on a treadmill [29]; and stationary roller ergometers [30]. [PERSON] et al. in 2020 [31] compared 50 wheelchair ergometers and highlighted the advantages and disadvantages of different ergometers used to test wheelchair propulsion under laboratory conditions. They noticed that each type of ergometer has advantages and limitations, and the choice of equipment should depend on specific research goals and requirements. The cited authors also emphasize the diversity and lack of consensus in this respect, which suggests the need for further research and standardization efforts to improve the usefulness of laboratory tests of wheelchair drives. However, it is highlighted that roller ergometers allow the use of a personal wheelchair, which can be significant in studying the interaction of a specific person's wheelchair with their wheelchair. Wheelchair treadmills are commonly used to investigate wheelchair propulsion performance. Unlike traditional treadmills designed for runners, wheelchair treadmills feature a platform to accommodate a wheelchair, enabling users to propel themselves against the treadmill belt while seated. These treadmills can be adjusted to simulate various terrains, including hills and flat surfaces [32]. Wheelchair treadmills offer an effective alternative to instrumented push-rims for measuring temporal and kinetic parameters. Research has demonstrated strong correlations between measurements obtained from treadmills and during driving [33]. As part of Poznan University of Technology's scientific activities in Poland, a stationary roller dynamometer was developed to measure wheelchair drive characteristics, such as torque, speed, and energy consumption as a function of time. Such a specialized test stand was patented, built, and validated [34]. This test stand records the rotational parameters of a wheelchair's driving wheels and can simulate inclined surfaces. Additionally, the stand has sensors to measure critical biomechanical parameters of propelling the wheelchair. Figure 2 illustrates the information flow within the dynamometer system. The stationary roller dynamometer shown in Figure 3 consists of a support frame (1) to which a weighing pan (3) is attached using strain gauges (2). The strain gauges measure the pressures under each wheel of the wheelchair, and based on this, the position of the center of mass (COM) of the human-wheelchair system is determined. Due to the sensitivity of strain gauge scales to longitudinal loads, three linear guides (4) are used to allow only vertical movement of the weighing scales relative to the support frame. The weighing pan is equipped with a wheelchair frame clamping system (5) and two (6) that ensure slip-free contact with the wheelchair's driving wheels, a critical factor in accurate testing. The wheelchair frame clamping element, shown in Figure 4, allows the wheelchair to tilt in the sagittal plane. Each traction roller system consists of two rubber-covered, truncated cone-shaped rollers that taper towards the center of the stand. A brushless DC electric motor (BLDC) is attached to the front of each system, making it an active roller. During the test, active rollers receive rotational energy from the wheelchair's driving wheels, which simulates rolling resistance. They can also drive the wheels, which simulate the wheelchair's descent down an incline. The rear roller of the traction roller system is a passive roller whose function is solely to support the wheelchair. Two encoders (8) convert the rotational motion parameters of the driving wheels into electrical signals, enabling independent measurement of the left and right wheels.