## 4 Discussion  
The tests were carried out on three subjects with different levels of wheelchair propulsion skills and different techniques of propulsion using hand rims [21]. Therefore, it was first verified whether the measurements obtained for these subjects can be compared, using the Pearson correlation coefficient. The obtained values for the measured parameters showed a strong correlation between the number of drive cycles performed for individual patients. The correlation coefficient was more than 90% between individual patients, regardless of the value of the assistance amplification coefficient. Based on that, an assumption was made that difference in skills of the subjects does not exclude the possibility of comparing among them the basic parameters of motion kinematics of the wheelchair. Analyzing the speed waveforms during the uphill climb without the use of assistance modes (\(w=0\%\)), an average speed value \(M\)\(v\) equal to 1.73 km/h on the hill was noted. The obtained average speed result is consistent with the results of other researchers. The publication [22] showed that an unmodified track on an incline of approximately 3\({}^{\circ}\) reaches an average speed of 1.54 km/h. Additionally, when analyzing the measurements, a characteristic increase in the speed amplitude on the slope was observed compared to the movement of the wheelchair on the horizontal section. The average speed amplitude \(\Delta v\) on the hill was \(1.8\pm 0.14\) km/h. Due to low average uphill speed and large speed amplitude, the subjects needed an average of \(12\pm 1\) full propulsive cycles to reach the hill. The results obtained for the system without assistance are obvious, and result from a significant increase in the motion resistance, being the effect of the force of gravity, which is confirmed by the impact on the kinematics of wheelchair movement also by other researchers. The assistance modes were used to reduce the impact of rolling resistance forces on wheelchair motion kinematics. The optimal configuration of the assistance mode control program requires the selection of appropriate values of the assistance amplification coefficient. The selected value should noticeably improve kinematic parameters, reduce the user's effort and allow control over the wheelchair, guaranteeing safety of use. Analyzing the hill-climbing assistance mode (t3), it was observed that regardless of the value of the assistance amplification coefficient (w), the BLCD motors supporting the drive torque generated by the upper limb started start with a delay, which was shown on the speed waveforms between SC and SA. The delay was caused by the motor control program, which, in the first 300 ms after changing the angle, checks if the wheelchair is on the ramp or the angle change read by the gyroscope was temporary due to uneven terrain. For each tested subject, the delay in the start of the assistance relative to the time the wheelchair was on the slope was on average 2 sec. It is possible to reduce the time during which the control program detects the wheelchair inclination angle. However, that would make  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**w**} & \multirow{2}{*}{**value**} & \multicolumn{3}{c}{**t3**} & \multicolumn{3}{c}{**t4**} \\ \cline{3-8}  & & **Subject 1** & **Subject 2** & **Subject 3** & **Subject 1** & **Subject 2** & **Subject 3** \\ \hline \multirow{2}{*}{0\%} & effort & \  
the wheelchair more sensitive to accidental interference, and would cause automatic activation of the hill-climbing assistance mode, especially on uneven terrain that generates high vibration. Analyzing the speed of a wheelchair moving with the hill-climbing assistance mode turned on (t3), it was determined that between the points SC and SA, i.e., before starting the BLCD motors, the speed of the wheelchair was at a similar level as during the climb uphill without the assistance modes. However, after passing the SA points, a significant improvement in the kinematic parameters of the wheelchair was noted.