JPH0685139B2 - Lead angle compensation method in position control - Google Patents

Description

The present invention relates to a lead angle compensation system in position control.

[Conventional technology]

When controlling various machines, when the machine position is detected by a cam switch, limit switch, etc. attached to the machine and various controls are performed based on this position detection output, this position detection output timing and it There are time delays between when control is applied to the machine and due to various factors. Due to such a time delay, the position at which the switch or the like operates is apparently deviated, which causes a hindrance to accurate control. Therefore, in order to eliminate such inconvenience, it has been conventionally performed to perform compensation by apparently shifting the operating position of the limit switch or the like, the position detection data, or the positioning target set value by an amount commensurate with the time delay or operation delay. This is generally called lead angle compensation.

The simplest example of the lead angle compensation is to attach the limit switch or the like at a position displaced from the desired position by the amount of lead angle compensation. However, the amount of time delay as described above is not uniform, and varies in particular depending on the speed of the machine, so the amount of advance angle compensation also varies depending on the speed, and the switch mounting position is changed each time. The problem arises of having to do it.

Therefore, instead of actually using limit switches, etc., a position detector that can continuously detect the position of the machine is provided, and the target position detection is performed by comparing the position detector data with the target position set value. Getting the output done is done. In that case, the conventional lead angle compensation is performed by detecting the speed of the machine, obtaining the lead angle compensation amount according to the speed, and correcting the position detection data or the target position data according to the lead angle compensation amount. It is being appreciated. This is illustrated in FIG. 5, and in the lead angle amount calculation circuit 1, according to the machine speed v obtained by the speed detector 2 and the lead angle compensation parameter a set according to the operating condition of the machine. The lead angle amount θ _A is obtained, and this is added to the position data X detected by the position detector 3 to apparently advance the current position data of the machine by the lead angle amount θ _A to perform lead angle compensation. In this case, the arithmetic circuit 1 is configured to calculate the advance angle amount θ _A by executing the operation of a predetermined function f (v) in real time, or to store the advance angle amount θ _A corresponding to each speed in advance. Either of the configurations may be used in which the above memory is used to read it according to the speed v.

[Problems to be solved by the invention]

In the conventional method as described above, a speed detector is required, and the cost is increased accordingly, and the calculation time of the function f (v) for obtaining the advance angle amount is calculated in real time. Therefore, there is a problem that a time delay occurs due to this, and when a speed is calculated by calculating position detection data, a time delay occurs by the calculation time.

The present invention seeks to provide a lead angle compensation method that solves the various problems described above.

[Means for solving problems]

A lead angle compensation method in position control according to the present invention includes position detection means for detecting current position data of a moving object, position setting means for setting target position data in position control, the target position data and the current position. Comparing means for comparing the position data and outputting a control signal when they coincide with each other, storage means for sequentially storing the current position data detected by the position detecting means in time series, and a predetermined advance angle compensation parameter. A time setting means for setting the time data of the above, and a take-out means for taking out the position data at a time point before the time corresponding to the time data set by the time setting means from the storage means and outputting it as the previous position data, A calculation means for calculating the difference value between the previous position data and the current position data, and the difference value from this calculation means is used as the advance angle compensation amount. The present invention further includes position data correction means for correcting at least one of the current position data and the target position data based on the lead angle compensation amount and supplying the corrected data to the comparison means. It is what

[Operation and effect of the invention]

An example of the locus of the position data detected by the position detecting means over time is as shown in FIG. 1, which is sequentially stored in the storage means in time series. Assuming that the time Δt corresponds to the time data set as the lead angle compensation parameter, the take-out means takes out the previous position data X (−Δt) at the time point Δt before the present time point from the storage means. The difference value ΔX between the retrieved previous position data X (−Δt) and the current position data is used by the position data correction means as the advance angle compensation amount.

In the position data correction means, for example, Δ
By adding X and advancing the apparent current position data by the advance angle compensation amount ΔX, the apparent current position data with the advanced angle compensation is used as the position of the object after Δt time has elapsed from the present time. There is. That is, the position after the lapse of Δt time can be predicted by adding the difference value ΔX of the position before the lapse of Δt time to the current position data.

Further, by subtracting ΔX from the target position data and advancing the apparent target position data by the advance angle compensation amount ΔX, the current position data is set as the position of the object after Δt time has elapsed from the current time. That is, by subtracting the difference value ΔX of the position before the Δt time has elapsed from the target position data, the position after the Δt time has elapsed can be indirectly predicted.

Furthermore, add ΔX / 2 to the current position data to advance the apparent current position data by the amount of advance angle compensation amount ΔX / 2.
Further, even if ΔX / 2 is subtracted from the target position data and the apparent target position data is advanced by the advance angle compensation amount ΔX / 2, the position after Δt time can be similarly predicted.

Therefore, according to the present invention, no speed detecting means is required, and the function f (v) for obtaining the advance angle compensation amount is obtained.
Since the calculation of is also completely unnecessary, it is possible to solve the problem that the cost is high and the problem that a time delay occurs due to the calculation. Further, since the lead angle compensation parameter can be finely set on a time unit basis, it is possible to perform lead angle compensation that immediately corresponds to various delay conditions of the mechanical system.

When the time Δt set as the lead angle compensation parameter by the time setting means becomes excessive, the difference value Δ between the previous position data X (−Δt) and the current position data before the time Δt has elapsed.
It is possible that X does not correspond exactly to the current speed. That is, the possibility that the speed changes during the time Δt increases. Therefore, the position data taken out from the storage means should be as close to the present time as possible.

Therefore, in the preferred embodiment of the present invention, in case the set time Δt is relatively large, the time Δt set as the lead angle compensation parameter by the take-out means is prepared.
The position data at a point in time preceding by a time Δt / N corresponding to 1 / N times the previous position data X (-
Δt / N), and the position data correction means substantially multiplies the difference value between the previous position data X (−Δt / N) and the current position data by N to obtain the advance angle compensation amount. Based on the above, at least one of the current position data and the target position data is corrected, and the corrected one is supplied to the comparison means. This situation is shown in FIG.

As a result, even when the time Δt set as the lead angle compensation parameter is relatively large, the data that reflects the current speed as much as possible can be used as the lead angle compensation amount. Further, the storage means for storing one data does not have to store such old position data, so that the storage capacity can be saved.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 3, the position detector 10 detects the position of the controlled object and outputs digital position data D _X.
When the object is a rotating body such as a motor, a rotary type position detector is used, and when the target is a linear moving body such as a cylinder, a linear type position detector is used. The memory circuit 11 sequentially stores the detected position data D _X according to the write clock CK, and is composed of, for example, a shift register or a RAM (random access memory). The lead angle setter 12 sets desired time data as a lead angle compensation parameter. The time set here is referred to as an advance angle setting time Δt. The logic circuit 13 determines the ratio N according to a predetermined standard according to the magnitude of the advance angle setting time Δt, And the data indicating N are output. Note that such a logic circuit 13 can be included in the advance angle setting device 12.

The take-out circuit 14 receives the time data Δt given from the logic circuit 13 or Depending on the The position data D _X (-Δt) at the previous time point is retrieved from the memory circuit. This take-out circuit 14 is, for example, a storage circuit 11
Is a shift register for selecting the output of the arbitrary stage, and is a read circuit for reading the stored data by designating an arbitrary address when the memory circuit 11 is a RAM.

The subtracter 15 subtracts the previous position data D _X (-Δt) extracted by the extraction circuit 14 from the current position data D _X , and the difference ΔX = D _X −D _X (−Δt). ). The difference ΔX thus obtained is the latest time interval Δt or Corresponding to the movement amount of the target object during the period, and the moving amount, that is, the difference ΔX is larger as the moving speed is higher. The multiplier 16 uses the data N supplied from the logic circuit 13 as a multiple and performs an operation for multiplying the difference ΔX by N. N times the difference data N.ΔX or ΔX (when N = 1) is added to the current position data D _X in the adder 17 and data indicating the predicted position after the advance angle setting time Δt. D _X (+ △ t) = D _X + N ・ △
X is required. In this way, the lead angle compensation of the position data is performed.

The target position setter 18 sets data indicating a target position for stop control or other appropriate operation control. The comparator 19 compares the set target position data S _X with the lead angle compensated position data D _X (+ Δt),
When both match, a control signal for stop control or other appropriate operation control is output. This control signal is
It is used as a signal equivalent to the output signal of the limit switch or cam switch that is known in normal position control. In this way, the position control is performed in the state where the lead angle is compensated. In this specification, position control includes not only stop control but also appropriate operation control at any specific position.

For example, if there is a time delay of Δt in the target positioning control system and the lead angle compensation is not performed, the actual position
The control is executed after Δt time from the time when D _X reaches the target position S _X , and at that time, the current position has passed the target position. However, if the lead angle compensation is performed as in the above-described embodiment, the lead angle compensated apparent current position data D before the current position reaches the target position is obtained.
_X (+ △ t) and target position data S _X match, and then △
True current value when control is executed after t time D _X Target position
It should just reach S _X. Therefore, accurate position control is performed.

The subtracter 15 for directly obtaining the difference ΔX and the multiplier 16 for directly multiplying the difference ΔX by N are not essential.
The difference ΔX may be substantially obtained, or the difference ΔX substantially multiplied by N may be obtained. For example, the lead angle compensated position data D _X (+ Δt) is, after all, D _X (+ Δt) = D _X + N (D _X −D _X (−Δt)) = (N + 1) D _X −N Since it is D _X (−Δt), when N = 1, the calculation of 2D _X −D _X (−Δt) is directly performed to omit the calculation of the difference ΔX, and D _X ( + △ t) can be determined, N is 2 or more even D _X when (N + 1) multiplied multiplier and D _X (- performs △ t) before the multiplication multiplying N, subtracting the product between By doing so, the difference ΔX can be obtained. Of course, such a detour complicates the arithmetic circuit (especially the multiplier) and is not preferable, but in practice, the difference ΔX is obtained and N is calculated.
Since it is equivalent to doubling, it is included in the scope of the present invention.

Further, the advance angle compensation can be achieved not only by advancing the position data D _X as shown in FIG. 3, but also by advancing the target position data S _X as shown in FIG. The parts omitted in FIG. 4 are the same as those in FIG. 3, and only the changed portions are shown. The subtractor 20 calculates the difference data N given by the multiplier 16 from the target position data S _X given by the setter 18.
-Subtracting ΔX or ΔX to apparently accelerate the target position. Target position data with lead angle compensation
S _X ′ = S _X −N · ΔX is input to the comparator 19 and compared with the data D _X indicating the true current position, and when both match, a control signal is generated. That is, the apparent target position S _X ′
There is set just before the position true N · △ X or from the target position S _X △ X, the true current position D _X is the front only N · △ X or △ X reaches the true target position S _X When the coincidence of the comparator 19 is established at the position and the control is executed after the time period Δt, the true current position D _X should just reach the true target position S _X.

In addition, lead angle compensation is performed using position data D _X and target position data S _X.
It can also be carried out by modifying both of them by an appropriate amount. For example, And add May be subtracted and the two may be compared.

Next, an example of the relationship between the value of N and the advance angle setting time Δt to which it is applied is shown.

If the number of storage positions (number of addresses or stages) in the memory circuit 11 is 199, and the cycle of the write clock CK is 0.1 ms, the memory circuit 11 stores position data of 199 samples up to 19.9 ms in units of 0.1 ms. Can be memorized. Therefore, when N is limited to 1 (in this case, the logic circuit 13 and the multiplier 16 in FIG. 3 are unnecessary), the settable advance angle setting time Δt is 0.1 ms to 19.9 ms, and 0.1 It can be set in ms increments.

By setting N = 2 in the range of advance angle setting time Δt = 20ms to 39.8ms, The previous position data may be retrieved from the storage circuit 11. In this case, Δt can be set in steps of 0.2 ms.

By setting N = 5 in the range of advance angle setting time Δt = 40ms to 99.5ms, The previous position data may be retrieved from the storage circuit 11. In this case, Δt can be set in steps of 0.5 ms.

By setting N = 10 in the range of lead angle setting time Δt = 100ms to 199ms, The previous position data may be retrieved from the storage circuit 11. In this case, Δt can be set in steps of 1 ms.

The above examples are listed in the table below.

As the position detector 10, any structure may be used as long as it can continuously detect the position of the object and digitally generate the position data. For example, it is possible to use an absolute encoder, an incremental encoder and a counter that counts its output pulses, a resolver and a unit that obtains digital position detection data based on its output signal, and the like. In particular, the Japanese Patent
57-70406, JP-A-58-106691, JP-A-59-79114
It is preferable to use an induction type (variable magnetic resistance type) rotary position detecting device or a linear position detecting device adopting a phase shift method as shown in Japanese Utility Model Publication No. 58-136718. In such a phase shift type position detection device, a digital count value indicating the phase shift of the secondary output AC signal is sampled for each 0 phase of the reference AC signal for exciting the primary coil, and this is sampled as position detection data D The sampling clock (that is, the clock pulse synchronized with the reference AC signal) is preferably used as the capture clock CK of the storage circuit 11 for outputting as _X.

Although the circuit of the embodiment of FIG. 3 is configured by hard-wired logic, the present invention is not limited to this, and the same function can be implemented by a software program using a microcomputer. Within the scope of the present invention.

[Brief description of drawings]

1 and 2 are graphs for explaining the principle of the present invention, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a block showing a modification of FIG. FIG. 5 is a block diagram showing an example of a conventional technique. 10 …… Position detector, 11 …… Memory circuit, 12 …… Advance angle setting device, 14 …… Retrieval circuit, 15,20 …… Subtractor, 16 …… Multiplier, 17 …… Adder, 18… … Target position setter, 19 …… Comparator.

Claims (2)

[Claims] 1. A position detecting means for detecting current position data of a moving object, a position setting means for setting target position data in position control, and a comparison of the target position data and the current position data. Comparison means for outputting a control signal at the time of coincidence, storage means for sequentially storing the current position data detected by the position detection means in time series, and time setting for setting predetermined time data as a lead angle compensation parameter Means, a take-out means for taking out the position data at a point in time before the time corresponding to the time data set by the time setting means from the storage means and outputting it as previous position data, the previous position data and the current position data And a difference value from this calculation means is used as a lead angle compensation amount, and based on this lead angle compensation amount, A lead angle compensation method in position control, comprising: position data correction means for correcting at least one of the current position data and the target position data and supplying the corrected data to the comparison means. 2. The fetching means fetches the position data at a time point before the time corresponding to 1 / N times the time corresponding to the time data set by the time setting means from the storage means and outputs the previous position data. The position data correction means sets a value obtained by multiplying the difference value from the calculation means by N as a lead angle compensation amount, and based on the lead angle compensation amount, at least one of the current position data and the target position data. The lead angle compensation method in position control according to claim 1, wherein the corrected value is supplied to the comparison means.