JPS6260220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a device in which a movable part is a load and the tip of the load is controlled to move between two arbitrary points. The present invention relates to a control method that allows the transmission part to operate smoothly even if there is a bump, and also enables highly accurate control.

As is well known, in mechanical devices, bumps occur to varying degrees.

This is due to the mechanical causes of movement of each part (for example, the involute tooth shape of the gear, the thread shape of the feed screw rod, etc.) and the machining accuracy, but due to the existence of this backlash, the following This is a major problem.

1. Since the positioning accuracy cannot be lower than the backlash width, it has not been possible to realize a device with higher positioning accuracy.

2. Since backlash is a factor that degrades stability in closed loop control, the loop gain can only be kept very small, resulting in poor response and hunting.

3. Collisions always occur in the backlash section when starting or stopping, which significantly shortens the life of the power transmission section.

Traditionally, these problems have been dealt with by taking special anti-backlash measures into the power transmission section. In addition to taking such measures, the servo mechanism forms a feedback loop consisting only of the actuator to deal with the backlashes that are outside the closed loop. A widely used method is to perform correction as a static state by adding up the position command value only when the operating direction changes.

However, although such a method can avoid the above 2), it is not a solution to the problems 1) and 3).

In addition, as a control method for a control system having a backlash, especially a device that drives a moving body on the load side through a gear device, a second drive system that is driven through the same type of gear device without a backlash is installed. Japanese Patent Publication No. 10646/1983 discloses a control method in which the difference in drive amount between the two drive systems is detected without contact, and the difference is fed back to the servo motor control circuit to eliminate backlash.

However, with this control method, although it is possible to automatically correct the target value for changes in the target value in the positive and negative directions, collisions between the drive unit and the load unit may occur before reaching the target point. This control method has the problem of 3) above because it does not take this into consideration.

Therefore, the present invention provides a device for detecting the position x and velocity x of each of the moving bodies A and B in a linear control system moving device in which there is a bump between the moving body A on the driving side and the moving body B on the load side. The presence or absence of a gap is detected from the detected value of the detection device, and when a gap due to backlash exists, gap control is performed to make the moving body A on the driving side relative to the acceleration side or deceleration side of the moving body B on the load side. Zero velocity (e =
0) In other words, when making contact without shock and moving from an arbitrary initial state to the target point, it is determined from that initial state whether acceleration or deceleration is necessary, and accordingly, after the gap control described above, linear control is used to move to the target point. The acceleration ←→ deceleration switch is performed earlier by the time T ₀ necessary for gear shift control than the point at which the acceleration ←→ deceleration switch is required when there is no backlash during the shift, and the target point is reached without collision due to backlash. This is a control method that causes the transition to.

Incidentally, the gap control referred to here means that (e, e)=(L/2,0) or (e, e)= for the gap e and the gap speed, that is, the relative speed e between the load part and the moving part. It is defined as controlling the position and speed of the drive unit so that (-L/2,0).

Normally, when building a control system, the most commonly used method is the linear feedback method.

A mobile machine that uses the linear feedback method applies a manipulated variable to the actuator that is proportional to the difference between the command value and the feedback amount to move the actuator from an arbitrary initial state to a target point.

The present invention utilizes the system configured as such a normal linear control system as much as possible, and furthermore,
The object of the present invention is to provide a control system that eliminates collisions due to backlash and allows positioning to be performed regardless of the gap width.

In other words, in a linear control system, the present invention provides conditions for clearly separating the conditions for gap control and load control from information on the deviation between the command value of the target position and the load position, and the speed, and provides a method for configuring the control system. The purpose of

For convenience of explanation, we will first consider a mobile machine with a linear control system in which there is no backlash in the power transmission section.

A normal second-order linear control system is represented by a block diagram as shown in FIG.

In the figure, x _Lr is the load unit target position command signal, K ₂₁ ,
K ₂₂ is each gain of proportional controllers 1 and 2, U(t) is the operating amount applied to the drive motor, J _LM is the sum of the load inertia moment J _L and the motor inertia moment J _M , and S is the differential calculation The child x _L represents the load position, and the response of this system is given by the following equation.

J _LM・X¨ _{L +} K ₂₂ ^・ _{X〓 L} + _{K 21}・K ₂₂ ^・X _L =K ₂₁・_{K 22}・X _Lr ...(1) ...(2) However, ωn is the natural frequency ωn ² =K ₂₁・K ₂₂ /J _LM ζ is the damping coefficient ζ=K ₂₂ /2ωn The command signal X _Lr is applied to the quadratic linear control system expressed by this equation (2). When ζ>1, X _L and X _L change as shown in FIG. 2.

In this figure, from an arbitrary initial state (X _L , X〓 _L )=
(0,0), that is, the change when controlling with the origin as the target point.

In such a linear _{control system, a change in (XL ,} The load can be moved to the target position without any trouble.

In other words, in a linear control system, if a target position command signal is given, the control device can know the acceleration/deceleration switching point and control the movement to the target position without changing the manipulated variable.

However, in a linear control system where the gap due to backlash is between moving body A on the driving side and moving body B on the load side, as shown in Fig. 3, basically when accelerating the load, It is necessary to bring the drive side A into contact with the end (right end in Figure 3), and when decelerating, it is necessary to bring the drive side into contact with the deceleration end (left end in Figure 3) to control the gap to zero.

Therefore, in the case of linear control, the presence or absence of a gap during acceleration is detected, and if there is a gap, control is first performed to set the gap to 0, and then in linear control to move to the target point, the acceleration is automatically performed. If you clearly know the change point at which the deceleration changes, and perform gap control to bring the driving side moving body A into contact with the deceleration end of the load side moving body B a little before this change point, the load side The moving body A can be accurately stopped at the target position.

FIG. 4 is a block diagram of a control device for performing backlash control of a power transmission mechanism having backlash, and 5 is a block diagram of a control device in which a load portion 7 is connected via a feed screw rod 6.
8 is a position and speed detector for the drive section; 9 is a position and speed detection device for the load section 7; 1
0 is a calculation unit 11 that performs calculations and logical judgments on how to perform appropriate control based on the detection signals of the detectors 8 and 9;
1 is an actuator control section that sends out a command signal based on the calculation result of the calculation section 10, and 12 is a minor loop.

Note that the buck crash control referred to here refers to the entirety of the present invention, and even if there is bump crash between the drive section and the load section, the load section can be operated smoothly and with high accuracy. Defined as control.

The presence or absence of the gap mentioned above and the change point are determined by the calculation unit 1.
Detected by 0.

The inflection points are the inflection points C ₁ , C ₂ , ...C ₄ in Figure 2.
It is. In other words, this is the point corresponding to X _L =0. When these inflection points C ₁ , C ₂ . . . are connected, a straight line is formed, which will be referred to as an inflection point straight line f ₂ .

When finding the inflection point of the linear control system expressed by equation (2), if X _Lr is used as a step input, the following equation can be used.

X¨ _L +2ζω _o X〓 _L +ω _o ² X _L = 0 …(3) The solution to _equation (3) is (X _L ,
Let P = (X ₀ , ⁰ ) _{( see} Figure ₅ ^{) .
t} …(4) X〓 _L = _{αβX 0} / α ⁻ βe
_〓 ^t … ⁽ 5 ₎ (5) Find the _formula Indicates a positive value.

Therefore, when moving from point P in Figure 5 to the origin (target position ₎ , the manipulated variable U(t) changes in the form of X ¨ _L in Figure 6 c as (X _L , It will be given to you.

_One point C in X ¨ _L in Figure 6c satisfies equation (6) (X
_L , _X〓L ), and at this time the load changes from acceleration to deceleration.

Therefore, in order to eliminate collisions caused by backlash upon reaching the target position, it is necessary to bring the drive section into contact with the deceleration end (here, the left end) of the load section before reaching the _C1 point. In other words, gap control must be performed.

Otherwise, when the movable body A on the drive side reaches the target position, the movable body A on the load side will overrun by the gap width due to inertia.

The point at which this gap control starts is (X _L , X〓
This can be determined from the measured value of _L ).

That is, the time point at which gap control is started is before the time T ₀ required for gap control from the point of change (inflection point).

This time T ₀ can be determined as follows.

_The response of the drive section is found by solving J _M X¨ _M +K ₁₂ X〓 _M +K ₁₂ K ₁₁
If it is set to 1, two real roots α' and β' can be found. As a practical settling time, T ₀ may be set to 3 to 5 times (1/B'). (However, 1/β'>1/α') Here, T ₀ =4/β' (8).

That is, the target value of gap control (L/2,
0), (-L/2, 0) can be settled within at least T ₀ time.

In other words, the change in ( _XL , _X〓L ) when no operation amount is applied to the load section on the ( _XL , _X〓L ) phase plane is _XL = _-kX〓L (9). However, k is determined experimentally. The gap control start line is used to determine the point at which gap control should be performed using this straight line and the inflection point line f ₂ obtained earlier.
Find f ₁ . (See Figure 7) The above can be summarized as follows.

Consider a case where there is a transition from a certain initial state to ( _XL , _X〓L )→(0,0). However, X _L <0.

First, measure X _L , X〓 _L , X _M , X〓 _M (e,
If e) is not (L/2,0), gap control is performed.

The target value of gap control at this time is (L/2,
0).

After gap control to (L/2,0) is achieved, linear control is performed as a unit of the drive section and load section.

During that time, while adding the operating amount to the drive unit, X _L , X〓 _L ,
Constantly measure X _M and X〓 _M.

And (X _L , X〓 _L ) is the gap control starting straight line f ₁
When the upper point is reached, perform gap control. The target value at this time is (-L/2,0). Hereinafter, f ₁ will be referred to as a first determination straight line, and f ₂ will be referred to as a second determination straight line.

After achieving gap control to ( _-L /2,0) _{, confirm that the state of (XL ,} All you have to do is do this. When X _L >0, the same effect can be achieved by substituting -L instead of L.

Since this load control is linear control, the manipulated variable is increased until X _L reaches the target value, and when the target value is reached, the manipulated variable becomes zero and remains stationary at the target position.

(e, e〓) is always measured even when the drive part and load part are integrally controlled, and gap control is performed immediately if the state of acceleration or deceleration deviates from the state.

If the measured value _of (X _{L ,}

Next, the embodiment shown in FIG. 8 will be explained.

This embodiment shows an embodiment in which the present invention is applied when a load 14 is driven by a motor M via a power transmission mechanism 13 with bumps, and 15 is a speed detector connected to the motor M.
TG ₁ and the detection signal of the position detector PG ₁ using a pulse generator and the speed detector TG ₂ connected to the load 14
, the detection signal of the position detector PG ₂ using a pulse generator, and the first and second judgment straight lines f ₁ and f ₂ set in advance or selected based on those detection signals, to the switching devices 16 and 17. A determination device consisting of a minicomputer or the like that sends out a switching signal; 18, an L/2 command value setting device for performing gap control on the acceleration side; 19, a L/2 command value setting device for performing gap control on the deceleration side; 20 is a gap width L setting device, 21 to 24 are proportional controllers, and 25 is a power amplifier.

A determination flowchart for obtaining switching signals for the switching devices 16 and 17 in the determination device 15 is shown in FIG.

Now, when the gap due to buck crush is on the acceleration side at the time of starting, first, the switching devices 16 and 17 are switched to the 16b and 17a sides by the judgment device 15, and the switching command value setter 18 is selected to control the acceleration of the motor M and reduce the gap to 0. Then, control is performed to switch the switching device 16 to 16a and move to the target position.

The operation control determining device 15 operates to compare the determination straight lines f ₁ and f ₂ with the measured values X _L and X _L to determine whether or not deceleration is required.

_When X _{L ,} Switching device 16 to 16
At step b, the switching device 17 is again switched to 17b and the command value setting device 19 is selected to perform gap control.

When the gap control is completed, the judgment device 15
Next, the switching device 16 is switched to 16a, and automatic control is performed to stop the load at the target position.

In addition, each gain K ₁₁ of the proportional controllers 21 and 22,
K ₁₂ , are K ₂₁ , K ₂₂ in equation (2) if J _LM of the control system is known.
From the relationship between and ωn, ωn=2πf ₀ is determined from the frequency f ₀ desired to be realized as a control system, and ζ is determined to be larger than 1.

The respective gains K ₂₁ and K ₂₂ of the proportional controllers 23 and 24 are J _M
If you know, it can be determined by calculation. The calculation formula is the same as formula (2).

Preferably, T ₀ is four times the slowest time constant of the drive system.

In practical use, when a large Coulomb friction force acts on a load section, if no operation amount is applied to the drive section when the load speed is below a certain load speed (X〓 _LC ), the load section will come to a standstill due to the friction force.

This means that the load speed will drop during the gap control period of T ₀ , and when performing gap control from the information of _{( XL} , .

FIG. 10 shows the trajectory when a frictional force is applied to f ₃ and f ₄ and X _L and X _L become stationary.

X〓 _LC can be known by actual measurement, and this X〓 _LC ,
−X〓 Shift f ₁ to the left and right so that it touches f ₃ and f ₄ at _LC . The ff thus obtained is used as a new gap control judgment curve.

At this time, determine |X〓 _L |X〓 _LC and do not apply any operation amount to the drive unit.

In other words, the switching device 16 is kept neutral.
By performing such control, positioning can be performed smoothly even when a large Coulomb friction force acts.

As described above, according to the present invention, even if there is a backlash, a collision does not occur at the backlash portion, and
Therefore, the life of the machine can be greatly extended, and there is also a manufacturing advantage in that there is no need to require unreasonable precision in machine assembly, and the control system is completely stable even if the backlash is in a closed loop. This is an industrially excellent invention, as it is guaranteed that the

When controlling a mobile machine with backlash using linear control, the present invention can greatly expand the scope of application of backlash control by clarifying the method of specifying the switching point between gap control and load control. It is of particular industrial value.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the linear control system, Figure 2 is a diagram showing the relationship between the position and speed of the load (driven part) in the linear control system, Figure 3 is a model diagram of the backlash section, and Figure 4 is a block diagram of a control device for a power transmission mechanism having backlash, FIG. 5 is an explanatory diagram of an inflection point straight line (second judgment straight line), and FIG. 6 is a diagram showing changes in load position, speed, and acceleration. 7th
The figure shows the relationship between the straight line according to equation (9) and the first and second judgment straight lines, Fig. 8 is a block diagram of an embodiment of the present invention, Fig. 9 is a judgment flowchart in the judgment device, and Fig. 10 is FIG. 6 is an explanatory diagram of first and second determination straight lines when a large Chloron friction force acts on the load portion. M... Drive motor, 13... Power transmission mechanism with backlash, TG ₁ , TG ₂ ... Speed detector, PG ₁ ,
PG ₂ ... Position detector, 14... Load, 15... Judgment device, 16, 17... Switching device, 18, 19... Gap control command value setting device, 20... Gap width setting device, 21-24... Proportional controller, 25...Power amplifier.

Claims (1)

[Claims] 1. In a linear control system moving device in which there is a backlash between a moving body A on the drive side and a moving body B on the load side, a device is provided to detect the position x and speed x of both moving bodies A and B, respectively. From the detection value of the detection device,
The presence or absence of back crash is detected, and if there is a gap due to back crash on the acceleration side, gap control is performed to reduce the relative velocity of moving body A on the drive side to zero (e
= 0), and when moving from an arbitrary initial state to the target point, it is determined whether acceleration or deceleration is necessary from that initial state, and accordingly, the target point is moved by linear control after the gap control described above. ←→
A method for controlling a mobile machine having a backlash characterized by linearly controlling up to a target point by performing acceleration←→deceleration switching earlier by the time _T0 required for gear shift control than the point at which deceleration switching is required.