Closed-loop stepping motor system closed-loop stepping motor is widely used in various industries due to its compact size, low price and stable operation.
Although stepping motors have been widely used, the realization of full closed-loop control by stepping motor motion control is still a major problem in industrial control industry.
The problem is mainly reflected in the uncertainty and out-of-step phenomenon of the origin.
At present, high-speed photoelectric switch is used as the origin of stepping system, and this error is in millimeter level, so it is unacceptable in the field of precise control.
In addition, in order to improve the operation accuracy, the stepping motor system is driven by multiple subdivisions, some of which are greater than 16. If it is used in the reciprocating motion process, the error is staggering. Can no longer adapt to the processing field.
Therefore, a full closed-loop control system for stepping motor is proposed to meet the needs of the current motion control field.
1. Hardware connection the hardware connection is equipped with an encoder. According to the subdivision requirements, different levels of resolution encoders are used for real-time feedback.
2. The Origin control identifies and calculates the origin of coordinates according to the Z signal of the encoder, which is the same as the numerical control system, and the accuracy can reach 2/encoder resolution ×4.
3. Out-of-step control adjusts the output pulse in real time according to the feedback data of the encoder, and adopts corresponding measures according to the out-of-step adjustment degree.
4. Circuit principle description the Circuit adopts ultra-large scale circuit FPGA, and the input and output can reach the corresponding frequency of megabytes, and the power supply 3.
3 V, using 2596 switching power supply, convert 24V to 3. 3 V, convenient and practical.
The input pulse and the feedback pulse are calculated after 4 times frequency orthogonal decoding, and the output pulse quantity and frequency are corrected in time.
5. Application Description this circuit has two modes, return to Origin mode and operation mode.
When the Origin enable switch is set, it enters the Origin mode, otherwise, it enters the operation mode.
In the Origin mode, the output pulse is synchronized with the frequency of the input pulse. When the Origin switch is touched, the output pulse frequency is reduced, and the coordinate origin is identified and calculated according to the Z signal of the encoder. After returning to the origin, output the signal.
This signal and its data are always maintained under the condition of continuous power supply.
In the operation mode, the pulse is output at the frequency synchronized with the input pulse, and the feedback data is calculated at the same time. If errors occur, correct them in time.
In addition, when the inertia is running, if the acceleration and deceleration settings are unreasonable, it may be corrected in time. 6. Technical indicators (1)Input and output corresponding frequency: ≤1 M; (2)Pulse synchronization time error: ≤10 ms; (
The main delay is in reverse correction, regardless of reverse correction, ≤10us)(3)Electrical accuracy of relocation: ≥2/encoder resolution ×4/motor resolution ×Subdivision)(4)Electrical accuracy of relocation origin ≥2/encoder resolution ×4/motor resolution ×Subdivision)(5)Adapt to PNP, NPN interface (6)Adapt to step pulse control (7)Adapt to various coding interfaces.
Once the above problems are solved by stepping motor motion control, full closed-loop control can be realized under the condition of increasing the cost by hundreds of yuan, which is not inferior to stepping motor system.
In particular, its low price, simple control and long service life may be superior to stepping systems in some occasions.
TAG closed loop stepper motor