JPS58197519A - Control system of servo system using friction transmission mechanism - Google Patents

Abstract

PURPOSE:To prevent the slipping of a friction transmission mechamism by controlling a load position in a nonslip state and setting the relative speed between a load side and a driving side to zero in a slip state. CONSTITUTION:The difference between a linear position X and KTtheta (product of rotation positin theta and transfer coefficient KT) is calculated by a subtracter 21 and supplied to an absolute value circuit 22, and the difference between the output of the circuit 22 and a comparison reference value epsilonmax is obtained by a comparator 23 and passed through a gate 24 synchronizing with a clock to obtain a slip detection value. Logic 1 corresponds to the slip state and logic 0 corresponds to the nonslip state. The AND result between the slip detection value and a state (showing the nonslip state by logic 1 and the slip state by logic 0) is inputted to the R (reset) of an RS flip-flop 28 which outputs a state. Therefore, the RS flip-flop 28 is reset only when the state is 1 and the slip detection value is 1, and the state changes from 1 to 0.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a servo system that controls the position of a moving body in a mechanism configured to drive the moving body on a track such as a rail by friction transmission.

First, the friction transmission mechanism will be explained based on FIG. The two rollers are cylinders with the same diameter, and when they are rotated in opposite directions at the same angular velocity, the rollers (21, +31 and their supports move linearly along the rail (11). This principle can be applied to electric trains and The basic principle of converting zero rotational force into linear driving force, which is the same as moving a car by rotating its wheels, is the frictional force between rollers and rails.To highlight the interesting points, in the case of trains and cars. The driving force is related to the gravitational force acting on the wheels and the rail or the ground, and in the friction transmission mechanism, the force that forcibly tightens the rail with rollers is related.

FIG. 2 shows an example of a method of rotating two rollers in opposite directions at the same angular velocity using one drive motor (4). In the figure, (5) to (9) are gears, respectively.

Next, the characteristics of the friction transmission mechanism will be explained with reference to FIGS. 3 and 4. Let the diameter of the roller be x, the tightening force be F, and the roller has an angular velocity of 6 (=dθ/di).

Assuming that it rotates with torque T, in the linear direction v −
D 6 / 2 ・・・・・・ (1 formula) Fo=DT
/2... Generates the speed and driving force of (2 formula).

When the coefficient of friction between the roller and the rail is μ, the FD is limited by the value FO=μF (Equation 3).

If the roller attempts to generate a torque that exceeds the Fo film/(D/2), the driving force will be limited to the FD and at the same time a speed difference will occur between the roller and the rail, resulting in a state of slipping on the contact surface. When such a slipping condition occurs, it becomes impossible to control the linear speed and driving force of the roller by manipulating the rotational speed and torque of the roller.
The most serious problem in controlling a servo system using a friction transmission mechanism is the sudden change in characteristics between a state where there is no slip and a state where there is slip on the contact surface.

An inconvenient phenomenon that occurs when a servo system using a friction transmission mechanism is operated by a conventional control method will be explained based on FIG. 9.

[In the case of the configuration shown in FIG. 9(a)] This is a system that performs speed control and position control by feeding back the speed and position of the moving body, respectively.

A speed command 6y proportional to the difference between the 0 position command r and the load position X, assuming that the load locks for some reason while positioning the load at a certain position.
-kp (r x) is generated, but since the load is locked, the speed command 6. and feed puncture speed kT
A speed deviation occurs between the This speed deviation becomes a motor rotation command by the PI controller of the speed control system, which is proportional to the speed deviation in P operation and proportional to the integral value of the speed deviation in I operation. A motor torque is generated in the direction of zero, and the motor speed gradually increases until it reaches the maximum value of the motor speed. In this state, the friction transmission mechanism is biased towards the motor! The integral value of
The line "1--g" occurs until it is reset, resulting in an undesirable response.

[In the case of the configuration of the ninth open mountain] This is a system that feeds back the motor rotation speed for speed control and the position of the moving body for position control.

In this system, when the load locks, a speed command 6r =kp (r-x) proportional to the positional deviation is generated to the motor,
In steady state, the friction transmitting part will slide at a sliding speed equal to this speed. Although the sliding speed depends on the positional deviation when the load is locked, steady slipping occurs, which is undesirable because it causes serious wear on the sliding surface.

The present invention eliminates the drawbacks of such conventional control methods,
By detecting the slipping and non-slipping states of the moving body and controlling the load position in the non-slipping state, and controlling the relative speed between the load side and the drive side to be 0 in the slipping state, the slip in the friction transmission mechanism is reduced. The purpose is to eliminate the

The present invention will be explained below.

FIG. 5 is an explanatory diagram showing the configuration of a servo system according to the present invention, in which a friction transmission mechanism including a rail il+ and a roller (2) is used as a drive system, and a rotary servo motor is used as a drive motor (4). (to) is a rotational motion detector directly connected to the drive motor (4), which detects the rotational position (angle) θ or rotational speed 6. (11) is a linear motion detector of a moving body, which detects a linear position X and a linear velocity ■.

(B) Detection of the slip state of the transmission part Since the gist of the present invention is to perform different control depending on whether the transmission part is slipping or not, detection of the slip state is an essential requirement. It is.

When the transmission section is in a non-slip state, the movements on the drive side and the load side correspond approximately one to one. Assuming that the transmission coefficient between the positions on the drive side and the load side is 0, x-k θ+ε (Formula 4) holds in the non-slip state.

Here, 8 is the transmission error caused by the shape error of the transmission part, etc., and if the increment values ΔX and Δθ are used to the extent that they can usually be ignored, equation 4 becomes Δx=□Δθ0C'... (Equation 5 ) can also be written.

Furthermore, considering the speed, v=7Q+ε"...
(Equation 6) or Δv=□Δ6+ε... (
Equation 7) holds true.

A flowchart for detecting a slip state is shown in FIG. Here, the judgment of the slip state is ■1x-7θI≧ε film... (Formula 8) ■lΔ
x-kTΔθ1≧ε′ category... (Formula 9) ■lv- to 7c31≧ε” protection... (Formula 10) ■1Δv-
7Δ01≧ε film... It is determined that any of the following conditions (Equation 11) is satisfied.

To determine the non-slip state, ■1ΔX-□Δθ1≦in... (Formula 12)■
1v-kT 61≦ε-1 It is determined that any one of the following conditions (Equation 13) is satisfied.

(ε'film~ε-'mil'l+'- is a constant set in advance.) This slip state detection procedure (shown in the flowchart in Figure 6) is assumed to be executed at regular intervals. .

The feature of this detection procedure is that if any of the conditions for determining the slip state in Equations 8 to 11 above are satisfied even once, it is determined that the state is in a slip state, and the condition for determining the non-slip state in Equations 12 or 13 is met for a certain period of time or longer. It is determined that the non-slip state exists only when the condition is subsequently established (determined by a counter). Therefore, in cases where the non-slip state occurs instantaneously (when the V curve and the kT6 curve intersect at one point), as shown in Fig. 7 (18), Equation 13 holds true only once. 7th Kaizan) indicates a case where Equation 13 holds true twice or more.

The determinations of formulas 8 to 13 above are mere comparisons and can be realized by a comparator. The steps in the flowchart of FIG. 6 can be realized very easily with a microcomputer, and can also be easily realized with a logic circuit.

Depending on which judgment condition is used to detect the above-mentioned slip state, appropriate rotational motion detectors and linear motion detectors are required.

The procedure for detecting a slipping state will be explained based on the flowchart shown in FIG.

First, it is determined whether the previous detection was a slip state or a non-slip state. (Determination is made using formulas 8 to 13) If the previous state was a non-slip state, it is determined whether the current state is a slip state. If this judgment is a non-slip state, the counter value is set to 0.
Then, the non-slip state is set and the detection ends. When the slip state determination is a slip state, the slip state is set and the detection is terminated.

If the previous state was in a slipping state, it is determined whether or not the current state is in a non-slip state. When this determination is a slip state, the value of the counter is set to 0, and the slip state is set and detection is terminated.When the 0 determination is a non-slip state, the counter is incremented. As a result, if the counter value is equal to or larger than the set value, a non-slip state is set and the detection is terminated.

If the counter value is smaller than the set value, a slip condition is detected.

Next, this procedure will be explained based on the logic circuit shown in FIG.

Slip detection is performed using τθ between the linear position
Subtract the difference between (product with c) I! Calculate by (21) and give this to the absolute value circuit (22) and compare the output with the reference value a
Compare the difference with llD using comparator (23),
This is done by using a gate (24) synchronized with the clock as a slip detection value. A logic 1 corresponds to slip and a logic 0 corresponds to no slip.

Non-slip detection is performed by subtracting the difference between linear velocity V and 6 by 1
1 (31), and gives this to the absolute value circuit (32), and compares the difference between its output and the comparison reference value "min" using the comparator (33), and synchronizes with the clock)
This is done by setting the non-slip detection value to the non-slip detection value via (34). Here, logic 1 corresponds to no slip and logic O corresponds to slip.

Slip detection value and status (Logic 1 is non-slip state, logic O
(corresponding to the slip state) is input to R (reset) of the RS flip-flop (28) that outputs the state. Therefore, only when the state is 1 and the slip detection is 1, the RS free knob flow knob (28) is depressed and the state changes from 1 to 0. A clock is input to the counter (38) only when the non-slip detection value is 1, and the counter is counted and amplified. This counter is reset, that is, its contents become 0, when the state is 0 or the non-slip detection value is 0.

The comparator (3) compares the contents of the counter (38) with the set value.
9), and when the count value ≧ the set value, the comparator (39
) output becomes 1, and the output becomes 0 when the count value is the set value.

The AND of the output of the comparator (39) and the negation of the state is input to S (set) of the RS flip-flop (28) that outputs the state. Therefore, if the state is 0 and the comparator (39)
The RS flip-flop (28) is sent only when the output of is 1, and the state changes from 0 to 1. In the same figure, (2
5), (27), (36) are AND circuits, (2
6) , (35,) is knot 41&, (37)
□ is an OR circuit.

FIG. 10 is a block diagram of a servo system according to the control method of the present invention. This corresponds to the servo system of the conventional control method shown in FIG. 9(b).

According to the detection of the slip state in (a), if it is determined that there is no slip, switches 1-3 are in the connected state, resulting in the same configuration as the conventional vIA control type servo system shown in FIG. 9 fbl.

When it is determined that there is a slipping state, the switch 2-3 is in the connected state, and a speed control system is configured in which the motor follows the speed of the load so that the slipping speed in the friction transmission section is zero.

If it is inconvenient for the command to change suddenly when the switch is switched, a relaxation filter that acts only when the switch is switched is inserted after the switch output terminal 3.

As described above, the present invention provides a servo system that drives a movable body using frictional power transmission and controls the position of the movable body.
It detects whether or not the power transmission section is in a slipping state, and when the transmission section is not in a slipping state, the position of the moving object is controlled, and when the transmission section is in a slipping state, the relative speed between the drive side and the track side of the transmission section is zero. Since the speed is controlled so that the friction transmission mechanism quickly shifts to a non-slip state and wear does not occur in the friction transmission mechanism, it also causes undesirable transient response when excessive force is applied or the lock is released. Without a doubt,
By adopting the control method of the present invention, since it is possible to quickly shift to the response of a normal position control system, the friction transmission mechanism, which had the drawback of causing slip, can be used as a practical servo system transmission mechanism. This has the effect of being able to

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the basic principle of the friction transmission mechanism, Fig. 2 is a schematic diagram showing an example of a driving method using the friction transmission mechanism, and Fig. 3 is an explanatory diagram showing the conversion of motion between a rotational system and a linear system. Fourth
The figure is a graph explaining the static characteristics of driving force FD and torque TO, Figure 5 is an explanatory diagram showing the configuration of the servo system using the friction transmission mechanism, Figure 6 is a flowchart showing the slip detection procedure, and Figure 7 is a non-linear diagram. A graph showing a judgment pattern in slip state judgment, Fig. 8 is a block diagram showing a logic circuit for slip state judgment, Fig. 9 is a block diagram showing an example of a conventional control method, and Fig. 10 is a control according to the present invention. FIG. 2 is a block diagram illustrating an embodiment of the scheme. Patent Applicant Makoto Ishizaka, Director General of the Agency of Industrial Science and Technology - Figure 7 Figure 8 Figure 149 - F - Continuing Amendment (Nagi February 2, 1980) Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, Indication of the Case 1982 Patent Application No. No. 80272 No. 2, Title of the invention: Servo system control method using a friction transmission mechanism 3, Relationship with the person making the amendment Case Patent applicant 5, Specification subject to amendment 106-

Claims (1)

[Claims] 1. A servo system control system using a friction transmission mechanism that drives a moving body by transmitting power through friction and is characterized by each movement.