3 Performance Evaluation
For the threshold of acceleration 1, a person weighted 60 kg will receive a force of
770 N at the peak of the acceleration. The pressure applied by falling is the same as a
free fall egg from 5th floor. It can be seen that the threshold is reasonable, and under
this force, human body is indeed injured. And it is same as threshold 2 (Table 5).
The overall fall accuracy is relatively high, and the sensitivity and specificity are
relatively balanced; thus, the detection effect is excellent. According to the data
Table 3. XGBoost three-dimensional threshold training results
Single data angular velocity threshold
gyro > 13 3.6826 deg/s
Single data acceleration threshold 1
azz < 3,9453 m/s
2 or
azz > 13.3214 m/s
2
Single data pitch angle threshold
agz < 19.9387° or 29.37185° < agz < 38.3750°
Fig. 2. XGBoost training effect
Table 4. Maximum “window satisfaction rate” in different scenarios
Activities
Maximum “window
satisfaction rate” of
combined acceleration
(set)
Maximum “window
satisfaction rate” of XOY
plane angular velocity
(set)
Maximum
“window
satisfaction rate” of
pitch angle (set)
Running
205
3
40
Squatting
61
0
0
Walking
94
1
0
Upstairs and
downstairs
62
0
0
Lie down
0
1
300
Jumping
92
0
22
The improved
average
“satisfaction rate”
when falling
35
24
38
54
M. Xiao et al.