Goal of Test: The goal of this test is to determine if the propulsion force measurement using the strain gauge measurement apparatus is within the percent error stated in the specification report. Similarly, this will also ensure the horizontal bending force applied is being properly isolated by the measurement system. This test will test for Specification ES2 [Specifications Report].
Procedure:
- Place the wheelchair including the strain gauge measurement system attachment in a clear testing area on flat ground.
- Ensure propulsive add-on has been removed from the rod. If not, remove the subsystem so just the strain gauges and the left and right rod attachments are connected to the wheelchair.
- Turn on the strain gauge measurement system.
- Connect the spring using the spring mating attachment to the rod.
- Position the spring at a known angle using the angle measurement device. Take a picture of the spring with the measurement angle device for documentation.
- Use a ruler to measure and record the initial length of the spring.
- Calibrate the strain gauge measurement system.
- Pull the spring to apply a force. Record the strain gauge measurement taken by the subsystem. Take a picture of the final length of the spring that it’s been pulled to. The following Figure 2a and 2b depict how the spring attachment and spring should be positioned and pulled to apply the force.
- Return the spring to the starting position by releasing the tension from pulling.
- Repeat steps 5-8 for 10 different angle and force combinations.
- Using the known information about spring constant, initial and final lengths of the spring, the angle at which the spring was applied, and the pictures from each of tests, find the horizontal component of the force applied by the spring and compare it to the measurement of the strain gauge subsystem by calculating percent error.
Figure 2. Diagram representing the spring attachment, force application, and important parameters to record during testing.
Required Equipment:
- Spring (with a known k constant)
- Spring mating attachment
- Specifically to attach to the propulsion rod to apply a known force to the rod
- Strain gauge measurement subsystem
- Angle measurement device
- Ruler
- Camera
Safety:
Overall, this test does not have extreme safety concerns. That being said, the wheelchair will still be powered during this test which adds risk. To further mitigate this risk all testing speeds will not exceed zero and an emergency shut off will be available to cut the test off short should the wheelchair experience issues.
Conducted by: Drew Freeland, Nick Moosic
Data of Test: 5/11/2021