CN107561340A - A kind of wide temperature drift of AC servo driver electric current is moved from correcting detection method - Google Patents

Abstract

It is moved from correcting detection method the present invention relates to a kind of wide temperature drift of AC servo driver electric current, belongs to AC servo detection field, for lifts the current detection accuracy of AC servo driver in wide temperature range.The present invention realizes current detecting using microcontroller (MCU), current sensor and multi-channel a/d converter.The phase current sensor output connection identical modulate circuit of two-way, wherein modulate circuit is directly accessed A/D converter passage A0 all the way, A/D converter passage A1 is accessed after another way series connection low-pass filter circuit.In addition, in the input channel of A/D converter, passage D0 collections reference voltage source information is used for offset correction all the way for design.Microprocessor control A/D converter synchronized sampling input signal, and sampled data is handled, effective current information is extracted, can realize that electric current accurately detects in wide temperature range.

Description

A kind of wide temperature drift of AC servo driver electric current is moved from correcting detection method

Technical field

The invention belongs to AC servo detection field.

Background technology

AC servo driver is the important component of Modern Motion Control System, is widely used in Radar IF simulation, work The fields such as industry robot, numerical control machining center.At present, AC servo driver is generally using the electric current based on vector controlled, speed Degree, position Three-loop control algorithm.For electric current loop as innermost ring, it exports the torque size of direct regulation motor.Therefore, electric current The quality of ring has large effect to the dynamic response and control accuracy of motor.Want to obtain good closed-loop current control Performance, first have to realize the accurate detection of AC permanent magnet synchronous motor three-phase current.AC servo applied to each occasion drives Dynamic device operating mode differs greatly, and need to be worked within the scope of wider temperature, and electromagnetic interference is than more serious, it is necessary to reduces as far as possible dry Disturb, temperature drift, the factor such as drift to detecting the influence of electric current, improve the precision of detection.

At present, common AC servo driver does not have wide temperature range sensor drift amount self-correcting positive work on the market Energy.For the above situation, the present invention devises a kind of strong and weak electric isolution, and can eliminate temperature drift, the self-correcting of drift automatically Positive current detection method, its temperature characterisitic independent of device, can realize the accurate of electric current within the scope of wider temperature Detection.

The content of the invention

AC servo driver current detecting block diagram is as shown in figure 1, due to there is three-phase current to need to detect, so devising Three tunnel current detecting passages.Current sensor uses Hall sensor, can realize isolation detection, reduces forceful electric power and light current is done Disturb.A/D converter is sent into after the conditioned processing of circuit of output signal of current sensor, A/D converter possesses multi pass acquisition work( Can, carry is on microcontroller (MCU) data/address bus.Microcontroller according to each passage of sequential timing acquiring of design data In memory space corresponding to deposit, and self-correcting and filtering process are carried out to data.

The present invention devises a kind of self-correcting current detection scheme, suitable for -25 to eliminate temperature drift, the influence of drift DEG C accurately detect to the electric current in the range of 60 DEG C, accuracy of detection can be improved 10%.Fig. 2 is situated between by taking the collection of a phase current as an example The implementation for the program that continues：Design two-way modulate circuit for current Hall sensor, two-way modulate circuit it is identical and PCB tries one's best symmetry arrangement when being laid out.The output of modulate circuit is directly entered the A0 acquisition channels of A/D converter, another way all the way The A1 acquisition channels for entering A/D converter after low-pass filter circuit are exported, A/D converter need to keep A0, A1 synchronized sampling. The packet of A0 passages collection is containing effective current information and current sensor, the drift information of modulate circuit；In A1 passages Low pass filter will only include drift information after effective current Information Filtration.It can be carried after the data of two passage collections are subtracted each other Take out effective current information.To reduce the error of A/D conversions, the reference voltage source of a Low Drift Temperature and real-time is accessed in D0 passages Sampling, for obtaining transformed error and result of calculation being modified, further improves conversion accuracy.

The selection for connecting the low pass filter cutoff frequency of A1 passages is an important link, is directly affected effectively The extraction of information.When carrying out low-pass filter circuit design, cut-off frequency ω_cIt can choose as follows：

Wherein n_LFor the minimum speed (unit of motor operation：Rev/min), p is the number of pole-pairs of motor.

Brief description of the drawings

Fig. 1 is the general frame of the present invention.

Fig. 2 is the schematic diagram of self-correcting current detection scheme.

Fig. 3 is current regulating examples of circuits figure.

Fig. 4 is the flow chart of current acquisition.

Embodiment

So that a rated output power is 5.5kW AC servo driver as an example, its output-current rating 19A, peak value Electric current 53A.To realize current detecting, sensor selects the LA-25-P of LEM companies, and measurement range is -55A~55A, meet volume Journey needs, and can realize the isolation detection of electric current, improves antijamming capability.The conduction of the sensor is compared for 1000：1, i.e., it is defeated Go out -55mA~+55mA current signal.

The performance of A/D converter has considerable influence to the precision of current detecting, selects to consider to differentiate during A/D converter The indexs such as rate, sampling rate, interface mode.It is the needs for meeting the design simultaneously, A/D converter need to possess Multi-path synchronous sampling Function.The detection of 0.01A electric currents is realized in hope in the range of -55A~+55A in design：

Therefore the A/D converter of 14 bit resolutions is needed to meet required precision.A/D converter to gather three-phase current with And reference power supply information all the way, as a result of self-correcting current acquisition scheme, and two acquisition channels are needed per phase current, therefore A/D converter needs seven sampling channels altogether.A/D type selectings are carried out according to above-mentioned requirements, have selected the ADS8545 of TI companies can expire Sufficient design requirement.The chip supports input voltage range -5V~+5V.

Hall current sensor output -55mA~+55mA current signal, and A/D converter reception -5V~+5V electricity Signal is pressed, so to design modulate circuit carries out I/V conversions, modulate circuit design example is as shown in Figure 3.Hall current sensor Output first pass around 120 Ω 1% precision resistance and be converted into -6.6V~+6.6V voltage signal, then put by computing Big device carries out amplitude conditioning.The transmission relation of modulate circuit is：

So the amplitude of input a/d converter signal is -4.95V~+4.95V, meets converter requirement.

Large time constant filter circuit design is carried out, if motor minimum operation rotating speed is 1rpm, motor number of pole-pairs is 4, is pressed It is ω that formula (1), which can calculate low-pass cut-off frequencies,_cFor 4.2Hz, low pass filter uses single order RC filter circuits, resistance resistance It is 33 μ F, cut-off frequency 4.02Hz to be worth for 1.2k Ω, capacitor's capacity.

Reference voltage source selects the REF5025 of TI companies, and the voltage reference exports 2.5V voltage, and temperature drift is 8ppm/ DEG C, Precision is 0.1%.The chip can provide stable voltage base in the range of -10 DEG C~+60 DEG C of the design work temperature of driver It is accurate.A/D converter is acquired to the voltage reference, and theoretical transformation value is 4096, is subtracted each other with actual converted result with theoretical value, Obtain offset error δ.

Current acquisition flow is as shown in Figure 4.The maximum slew rate of A/D converter is 600kSPS, i.e., each while right The channel sample of A0, A1 two, conversion time only expend about 2 μ s, and the controlling cycle of electric current loop is set as 100 μ s, can within this cycle To make full use of the switching rate of A/D converter to carry out over-sampling, sampling precision is improved.Because microcontroller also needs in electric current loop Other complex calculations are carried out, so the result of collection is stored in A0, A1 repeated sampling 20 times within an electric current loop cycle In two arrays, each array is handled after repeated sampling, rejects outlier first, medium filtering is then carried out and obtainsWithAfter completing aforesaid operations, result of calculation is subjected to linear operation extraction electric current effective informationAgain The information of collection D0 passage reference voltage sources tries to achieve offset error δ, according to δ pairs of offset errorIt is modified and just can obtain aA is the effective current information that drift value is free of in this current loop control cycle.Finally can be as needed, profit With the electric current a in this cycle and electric current a in upper cycle_lastLPF is carried out, obtains final results of weak current.

Claims (2)

1. a kind of wide temperature drift of AC servo driver electric current is moved from correcting detection method, it is characterised in that：Using microcontroller, electricity Flow sensor and multi-channel a/d converter detect phase current, the output connection two-way identical conditioning of each current sensor Circuit, all the way modulate circuit be directly connected to the A0 passages of A/D converter, connect after another way modulate circuit series connection low-pass filter circuit Connect the A1 passages of A/D converter；Design basis voltage source circuit is simultaneously gathered using another passage D0 of A/D converter；Micro-control Device processed calculates the exact value of phase current according to the sampled result of tri- passages of A0, A1 and D0.

2. the wide temperature drift of AC servo driver electric current according to claim 1 is moved from correcting detection method, it is characterised in that： The microcontroller calculates the exact value of phase current with the following method：The multiple synchronized sampling of microprocessor control A/D converter Two passages of A0, A1, by sampled result storage into two arrays, elimination of burst noise is carried out to array data and median filter process obtains ArriveWithResult of calculation is subjected to linear operation extraction electric current effective informationWhereinFinally using gathering base δ pairs of the error deviation amount that reference voltage source obtainsCurrent acquisition result a can be obtained by being modified, wherein