How does the guidance system of the Horizontal Directional Machine work?

1. Detector measurement
Sensor principle: There are generally magnetic field sensors and accelerometers in the detector. The accelerometer obtains the detector's inclination and tool angle by measuring the earth's gravity field, and the magnetic field sensor mainly measures the earth's magnetic field and calculates the detector's azimuth by combining the gravity field. For example, the detector consists of three accelerometers Gx, Gy, Gz and three magnetic induction sensors Hx, Hy, Hz. The axis direction of the detector guide tube is the x-axis and the world coordinate system is the reference coordinate system for measurement.
Parameter feedback: The detector connects the measured inclination, azimuth, tool angle and other data through the signal line running through the drill pipe and the slip ring on the main shaft of the drilling rig, and then introduces it into the control terminal in the control room. The computer control software will further digitize and graph these data, and calculate the guide hole trajectory data, such as horizontal length, depth, left and right deviation, etc.
2. Signal transmission and reception
Transmitting signal: During guided drilling, the signal transmitter installed near the drill bit will transmit a signal, which contains information such as the position and angle of the drill bit. For example, a transmitter using the principle of electromagnetic induction will emit electromagnetic waves of a specific frequency.
Receiving signal: The receiver on the surface is responsible for receiving the signal sent by the transmitter. The receiver can determine the strength, direction and other parameters of the signal, and then calculate the approximate position and posture of the drill bit underground. Some systems will also arrange ground beacon systems on the ground on both sides of the entry and exit of the soil to help more accurately determine information such as the azimuth of the drill bit and the crossing center line.
3. Guidance control
Manual operation: The driller adjusts the propulsion and rotation of the drill rod according to the parameter information displayed on the control terminal and the pre-designed drilling trajectory by operating the control handle or button of the drilling rig, so as to change the drilling direction of the drill bit and make the drill bit move along the predetermined trajectory.
Automatic control: Some advanced guidance systems have automatic control functions. The system can automatically calculate the parameters that need to be adjusted according to the preset trajectory and the real-time measured drill position data, and control the actuator of the drill to make corresponding adjustments, reduce manual intervention, and improve the accuracy and efficiency of drilling.
4. Auxiliary guidance technology
Laser guidance: By installing a laser transmitter on the drill rig, a reflective target or receiver is set in the drilling area. The laser beam is directed to the reflective target, and the reflected laser signal is received by the receiver. According to the reflection angle and distance of the laser, the deviation of the drill from the predetermined trajectory is calculated, and adjustments are made.
Gyroscope guidance: The orientation and stability of the gyroscope are used to measure the attitude and direction changes of the drill. The gyroscope can provide high-precision angle and direction information, and is not interfered by external magnetic fields and other factors. It plays an important role in long-distance, high-precision directional drilling.