Which three control methods are commonly used in electric spindle operation
In machine tool processing, the frequency conversion speed regulation method is generally used for the electric spindle. At present, there are three control methods: general variable frequency drive and control, vector control drive and direct torque control.
General frequency conversion is scalar drive and control. Its drive control characteristic is constant torque drive. The output power is proportional to the speed. Generally, the dynamic function of frequency conversion control is not aspirational, the control function is not good at low speeds, the output power is not stable, and it does not have C-axis function. However, it is cheap and has a simple structure. It is generally used for grinding machines and general high-speed milling machines.
The vector control technology is modeled on the control of a DC motor. It is oriented to the rotor magnetic field and uses vector switching to complete the drive and control. It has outstanding dynamic functions. The vector control drive has a large torque value when it is just started. In addition, the electric spindle itself has a simple structure and small inertia, so the starting acceleration is large, and it can reach the allowable limit speed instantly after the start. This type of driver has two types: open-loop and closed-loop. The latter can complete the azimuth and speed response, not only has better dynamic function, but also can complete the C-axis function; while the former has slightly worse dynamic function and does not have C-axis function , But the price is cheaper.
Direct torque control is another new type of high-performance AC speed regulation technology developed after vector control technology. Its novel control idea and simple and clear architecture make it more suitable for high-speed electric spindle drive and more satisfied with high-speed electric spindle. The requirements of high speed, wide speed regulation scale, high-speed instantaneous exact stop dynamic and static characteristics have become a hot technology in the field of AC drive.