The coordinate measuring head system is a detection and aiming system for coordinate measuring machines, which is a highly sensitive sensor. The three coordinate probe generates an aiming signal through its own linear or angular displacement, and the displacement is also limited to a small range. If the displacement exceeds this range, the probe will be damaged. Therefore, the probe protection awareness is one of the tasks of the control system.

The control system has protective measures for the departure probe. When the probe moves, the CPU continuously tracks the three coordinate values of x, y, and z. If the measuring end comes into contact with the workpiece, the measuring head produces a sampling signal. In the interrupt service program, the CPU not only stores the instantaneous values of the x, y, and z coordinates alone and stores them in the sampling transform, but also stops the interpolation operation, causing the coordinate measuring machine to stop moving. The CPU resets the command position in the opposite direction to the original feed according to the preset backward speed and distance, controls the servo system to return the original feed path of the probe, and stops after moving the predetermined backward distance. Using this method can ensure that the measuring end only moves a small distance after contacting the workpiece, and immediately disengages from contact with the workpiece. The measuring end should be able to move only a small distance after contacting the workpiece, and immediately disengage from the workpiece. As long as the measuring end can contact the workpiece, it must be fed along a safe measurement path, and the new words will not collide with other parts of the workpiece if they follow the original path.

Of course, the setting of the setback distance should be reasonable. "She should be smaller than the inner dimension of the workpiece on the north side, otherwise, after the probe contacts one side of the inner dimension, it moves towards the other side according to the preset backward distance, and before it stops, it contacts that side again. This way, the probe will generate a gap on both sides of the inner dimension, causing the control system to fall into a dead cycle.". Therefore, when designing a CNC measurement program, the relevant dimensions of all measurement points should be carefully calculated first, and then the CNC control parameters should be initially set.

The analog probe side aiming displacement and limit displacement have been set during initialization, so when the measuring end reaches the aiming displacement, the control system immediately controls the servo feed system to slow down and stop the CMM. If the probe continues to feed and reaches the limit displacement, the control system immediately sends an emergency braking signal to automatically lock the system. For scanning measurement, it always controls the motion of the servo system along the tangent direction of the scanned curve. The displacement amount of the three-coordinate probe is preset. The three-coordinate control system calculates the position of the probe at each sampling period, so that the modulus of the probe displacement vector is always maintained at the set value.