The goal of the effort sensing subsystem is to take the measurements necessary to determine the effort input by the user. The system must be able to distinguish between user applied forces and system applied forces to ensure the mathematical model has the information to determine the output force that needs to be applied based on those different inputs. This ensures the effort sensing system can provide accurately calculated output to communicate the input to the other subsystems. The specifications below relate to the timeliness and accuracy of these measurements. For all sensor sampling rate constraints, further development is required to determine appropriate sampling rates. The specific metrics for sampling rates are unknown, but these rates should be maximized.
Table 6: Effort Sensing Team Specification and Metrics
| # | Metric/Specification | Minimum Value | Maximum Value | Unit | Maximize /Minimize/ Target/Constraint | Constrained Max/Min |
| ES1 | Sampling period of 9DOF measurement system | 0 | 10 | ms | Minimize | |
| ES2 | Sampling period of strain gauge measurement system | 0 | 10 | ms | Minimize | |
| ES3 | Error in measurement of force needed to overcome gravity on a slope | 0 | 10 | N | Minimize | |
| ES4 | Error in strain measurement | 0 | +/- 0.05 | kg | Minimize |
- The sampling rate of the 9 degree of freedom, or 9DOF, measurement system must be fast enough to ensure data is collected quickly enough for the system to provide an output for the angle and orientation of the chair in space. This ensures the 9DOF measurement system can provide timely output to communicate the input to the other subsystems.
- The sampling rate of the strain gauge measurement system must be fast enough to ensure data is collected quickly enough for the system to provide an output for the force of the wheel add-on on the chair. This ensures the strain gauge measurement system can provide timely output to communicate the input to the other subsystems.
- The error in the measurement of the force needed to overcome gravity on a slope should be minimized so that the chair can adapt appropriately to inclines. However, the value doesn’t need to be incredibly precise so long as it is reasonably close and the system will still function effectively enough.
- The error in the strain measurement of the wheelchair must be minimized to ensure the strain gauge measurement system’s force calculation is accurate and can be used with confidence in determining the horizontal component of the propulsive force. This is a critical measurement for both the mathematical model and to provide information for the propulsive subsystem.