| γ-Rays |
The detector recognize coal or rock interface using radioactive source. |
The law of ray attenuation is difficult to determine, so it is difficult to recognize coal or rock. |
| radar |
The degree of rock is detected by the speed, phase, propagation time and wave frequency of electro- magnetic wave. |
When the coal thickness exceeds a certain threshold, the signal attenuation is serious, even the signal can not be collected. |
| vibration |
Extract the coal and rock feature information of the vibration signals with signal processing techniques. |
Owing to large noise disturbance, it may not be enough to derive a desired level of recognition. |
| infrared radiation |
Identify coal or rock by the thermal distribution spectrum of shearer pick under different hardness. |
Affected by environment, temperature and other factors, the detection accuracy is low. |
| cutting stress |
By analysising the characteristics of shearer' cutting stress to identify coal or rock. |
The method can’t suite to top coal caving. |
| acoustic |
Extract the coal and rock feature information of the acoustic signals with signal processing techniques. |
Affected by large noise disturbance, the detection accuracy is low. |
| digital image |
Using image sensors, digital image processing technology and image analysis system are used to obtain the information of coal or rock. |
Largely effected by dust, light and other environmental factors, the detection accuracy is low. |
