JPH035157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control method that can perform high-speed control with high precision by direct drive without using a reduction mechanism when an actuator is driven at an extremely low speed.

The general method for controlling the speed of an actuator is to detect the speed of the moving part by some method, feed back this speed signal, detect the deviation from the speed input signal, and perform speed control based on this deviation. being done. However, in this method, when the speed becomes extremely low, the detection level of the speed signal becomes extremely low, and the S/N ratio of the signal deteriorates significantly. For this reason, the loop gain cannot be increased much, and the torque generated by the actuator becomes extremely small, making highly accurate speed control in the low speed region almost impossible. Therefore, when performing low speed control, conventional control methods using speed feedback have limitations. On the other hand, as a way to deal with this, there is a method of controlling low speed through a reduction mechanism such as a gear, but wear and noise of the reduction mechanism becomes a problem, and speed control is limited to only low speed areas. There were other drawbacks.

In view of the above-mentioned circumstances, the present invention provides a speed control method that can perform high-precision speed control in a low speed region without using a speed reduction mechanism or the like. is converted into a position command signal, and the speed of the actuator is controlled based on the deviation (positional deviation) of these signals.

Embodiments of the present invention will be described below with reference to the drawings, but first the basic principle of the invention will be described.

FIG. 1 is a control block diagram for explaining the principle of the present invention, in which 1 is an actuator;
Reference numeral 2 denotes a position detector to which the movable part of the actuator 1 is attached, and which applies an output voltage V ₀ as shown in FIG. 2 to the output displacement θo of the movable part. 3 is a differential amplifier that detects the deviation between the input voltage (position command signal) Vi and the voltage V ₀ corresponding to the output displacement θ ₀ , and the output signal of this differential amplifier 3 is used for compensation to improve transient characteristics. The signal is supplied to a power amplifier 5 via a circuit 4, and the actuator 1 is driven by the output signal of the power amplifier 5. The control circuit described above constitutes a closed loop and operates so that the deviation between the voltages Vi and V ₀ is always zero. Therefore, when input voltage Vi is applied, the movable part moves to the corresponding position θi
and is fixed in that position.

As shown in FIG.
Then, the input voltage Vi is changed from −Vm to Vm (or
Vm to −Vm) at a constant rate, the output displacement θ ₀ also changes from −θm to θm (or θm
(from -θm) at a constant speed, and it can be seen that speed control can be performed without feeding back a speed signal. That is, if the slope of the input voltage Vi is made to correspond to the commanded speed, the voltage V ₀ changes to follow the voltage Vi, so the speed of the actuator movable part can be made to match the commanded speed. However, if the linear area of the position detector 2 is finite as described above, the control circuit shown in FIG. 1 can only operate from -θm to θm. Therefore, in the present invention, in order to make the operating range infinite, the position detector is configured to generate triangular wave-shaped multi-phase position signals with different phases, and the linear range of each position signal is switched and used, effectively The straight line area is expanded to an infinite range.

An embodiment of the present invention will be described below. FIG. 3 is a control block diagram showing the configuration of this embodiment, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In this figure, 2' is a position detector which outputs four layers of triangular wave-like position detection signals having the same period and different phases. In this case, the phase of each phase is
They are shifted by 90 degrees. 6a to 6d are position signal detection circuits that amplify the position detection signals from the position detector 2' and obtain position signals Sa to Sd whose phases are shifted by 90 degrees as shown in Fig. 4A to D. . 7
A to 7d are pulse conversion circuits that slice the position signals Sa to Sd at predetermined reference levels +Vs (see A to D in Figure 4) and convert them into pulse signals Pa to Pd (Ho to H in Figure 4). . Here, the relationship between the position signals Sa to Sd and the pulse signals Pa to Pd will be explained. First, in this embodiment, the straight line portion (-
Instead of θm<θ ₀ <θm), thick line portions (straight line portions) of the position signals Sa to Sd shown in FIGS. 4A to 4D are appropriately switched and used (details will be described later).
Then, as shown in the figure, the pulse signal Pa becomes “H”.
The level period corresponds to the bold line part of the position signal Sb,
The “H” level period of the pulse signal Sb is the position signal Sc
Similarly, the pulse signals Pc and Pd correspond to the thick line part.
The “H” level periods correspond to the bold line portions of the position signals Sd and Sa, respectively. In this embodiment, the pulse signals Pc to Pd are used to generate the position signals Sa to Sd.
I am trying to switch between the two. Here, the reference level +Vs can be set so that the duty ratio of each of the pulse signals Pa to Pd is 1/4 as shown in the figure, but in reality, the level difference between each position signal Sa to Sd , it is virtually impossible to completely reduce the duty ratio to 1/4 due to level fluctuations.
However, as shown in Figure 5 A to D, the pulse signal
If the duty ratio of Pa to Pd is smaller than 1/4,
In the minute section indicated by the broken line in the same figure, there is no "H" level signal at all, so it is not possible to select a position signal. On the other hand, Figure 6 I~
As shown in d, if the duty ratio of the pulse signals Pa to Pd is larger than 1/4, it is sufficient to select either one in the portion where the “H” level overlaps (however, in the overlapping portion, the position signals Sa to The linearity of Sd must be guaranteed), but in reality, the reference level +
Set Vs. Next, 8 is a logic circuit that controls ON/OFF of each switch element 13a to 13d in the analog switch 13 based on the pulse signals Pa to Pd.
FIG. 7 shows the ON-OFF states of 3a to 13d.
Note that this figure corresponds to the case where the pulse signals Pa to Pd are in the state shown in FIG. 6. FIG. 8 is a circuit diagram showing a specific circuit example of the logic circuit 8. As shown in FIG. Moreover, as is clear from FIG. 3, when any of the switch elements 13a to 13d is ON,
Any one of the position signals Sa to Sd corresponding to each switch element is supplied to the inverting input terminal of the differential amplifier 3. Next, 9 is a trigger pulse circuit that detects the change point of the output of the logic circuit 8 and outputs the trigger pulse Tp shown in FIG. This is a sample and hold circuit that holds the level of Tp using the trigger pulse Tp as a sampling point. Therefore, the sample and hold circuit 10 holds the value of the position signal immediately after switching. 11 is a differential amplifier, and the output signal of an integrating circuit 12 consisting of an operational amplifier OP ₁ , a resistor R ₁ and a capacitor C ₁ ;
The difference with the output signal of the sample and hold circuit 10 is amplified and supplied to the differential amplifier 3. Reference numeral 14 denotes an analog switch which is turned on by the trigger pulse Tp, and constitutes a reset circuit for the integrating circuit 12 together with a resistor _R2 . Therefore, when the trigger pulse Tp is output, that is, the position signal Sa
Immediately after the switching of ~Sd, the integrating circuit 12 is reset and its output signal becomes 0.

Next, the operation of this embodiment with the above-described configuration will be explained.

First, since the logic circuit 8 selects one of the position detection signals Sa to Sd based on the pulse signals Pa to Pd, it is assumed that the position detection signal Sa is selected in the initial state, for example. In this state, when a voltage Ei (speed command signal) is applied to the input terminal of the integrating circuit 12, the output signal of the integrating circuit 12 increases (decreases) at a slope corresponding to the value of the voltage Ei. Therefore, the voltage Vi (position command signal)
also changes with the same slope as the output signal of the integrating circuit 12. In this case, the voltage V ₀ of the voltage Vi (position signal
Similar to the circuit shown in Figure 1, the voltage value of Sa) is
Since they are controlled to be always equal, the movable part of the actuator 1 has a speed corresponding to the slope of the voltage Vi, that is, the value of the voltage Ei. For example, when the value of voltage V ₀ becomes +Vs (point A in Figure 4, P ₁
), the logic circuit 8 switches the position signal to Sb (point P ₂ in FIG. 4). At this time, the trigger pulse Tp is outputted from the trigger pulse circuit 9 (see FIG. 4), so that the sample and hold circuit performs a sampling operation, and the integrating circuit 12 is reset. As a result, the value of the position signal Sb immediately after switching -Vs (the fourth
(see figure 2) is supplied, and the output voltage 0V of the integrating circuit 12 is supplied to the inverting input terminal. Therefore, the voltage Vi becomes -Vs, which matches the value -Vs of the voltage V ₀ at this time. Thereafter, as in the case described above, the output voltage of the integrating circuit 12 increases with a slope corresponding to the value of the voltage Ei, so the voltage Vi also increases with the same slope. That is, the movable part of the actuator 1 continues to rotate at a speed corresponding to the voltage Ei, as in the case described above. Then, as the voltage V ₀ changes from point P ₂ to point P ₃ along the thick line of the position signal Sb, as shown in FIG. Figure 4, point C (P ₄ ). Thereafter, operations similar to those described above are repeated, but the slope of voltage Vi always corresponds to voltage Ei, and the linear portions of position signals Sa to Sd are sequentially fed back by logic circuit 8. Because,
The movable part of the actuator 1 always has a speed corresponding to the voltage Ei. And the voltage in the above operation
As shown in FIG. 4, Vi becomes a sawtooth wave with a period equal to the switching period of the position signals Sa to Sd. Also, if the polarity of voltage Ei is reversed, actuator 1
The movable part of is displaced in the opposite direction, which can be easily understood from the above explanation.

In the above-described embodiment, the position detector 2' outputs four-phase position detection signals, but the number of phases varies depending on when the position signals of each phase are switched at a certain reference level. Since the condition is that the signal level after switching falls within the linear region of the position signal of the next phase, the number of phases may be sufficient to satisfy this condition. Furthermore, in order to ensure stability of operation, it is actually desirable that the linear regions of the position signals before and after switching sufficiently overlap.

As explained above, according to the present invention, speed control is performed by feedback of position signals without feeding back speed signals, so that highly accurate speed control can be performed even when the speed is extremely slow. . Further, normal speed feedback control can also be used, allowing a wide range of speed control to be performed.

[Brief explanation of the drawing]

FIG. 1 is a control block diagram explaining the principle of speed control according to the present invention, FIG. 2 is an output characteristic diagram of the position detector 2, and FIG. 3 is a control block diagram showing the configuration of an embodiment of the present invention. Figure 4 is a waveform diagram showing the waveforms of each part of the circuit shown in Figure 3, Figures 5 A to D, and Figure 6.
Figures A to D are diagrams showing the phase relationships of practical pulse signals Pa to Pd, respectively. Figure 7 is a diagram for explaining the switching operation of the logic circuit 8, and Figure 8 is a diagram showing a specific example of the logic circuit 8. FIG. 1... Actuator (movable part), 2'... Position detector (position detection means), 3... Differential amplifier, 4
... Compensation circuit, 5 ... Power amplifier, 6a, 6b,
6c, 6d...Position signal detection circuit (position detection means), 7a, 7b, 7c, 7d...Pulse conversion circuit (feedback selection means), 8...Logic circuit (feedback selection means), 9...Trigger pulse circuit , 10...sample hold circuit, 11...differential amplifier, 12...
Integrating circuit, 13...analog switch (feedback selection means), 14...analog switch.

Claims (1)

[Claims] 1. A position detection means that outputs a plurality of triangular wave position detection signals corresponding to the displacement of the movable part and having a predetermined phase difference between each phase, and selectively selecting each of the position detection signals. feedback selection means for feeding back only the linear characteristic portion of each of the position detection signals, and immediately after the feedback selection means performs the selection operation, the value becomes equal to the initial value of the selected position detection signal; After becoming equal to the initial value, a position command signal is created that changes with a slope corresponding to the level of the speed command signal, and further, the deviation between the position command signal and the currently selected position detection signal is zero. A speed control method characterized in that the movable part is driven to