JPS646909B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is capable of only detecting the amount of axis movement;
Regarding load fluctuations, it does not have a detection function or a teaching function, and moreover, it is related to a simple structure industrial robot that has an axis that is required to start and stop at any position within the movable range. Fluctuation,
The present invention relates to a control method that enables smooth movement and reliable positioning using an on/off method without being affected by fluctuation factors such as changes in the moment of gravity.

In industrial robots such as handling devices that transfer workpieces between work tables and processing machines, it is necessary to not only detect the position of the tip of the hand during the workpiece transfer process, but also to detect the weight and gravity of the load on the hand axis and the gravitational moment. It is important to know how to apply this to ensure smooth movement and accurate positioning.

In particular, in the case of a shaft whose axis moves up and down in a vertical plane, the gravitational moment is different when moving from the vertical direction and when moving from the horizontal direction, and the latter movement is clearly larger. This difference becomes very large when the distance is long.

In addition, the load on the shaft will naturally vary depending on the size and material of the workpiece, and if these variables are ignored, even if precise control is performed, the load on the shaft will change overshoot or short of the target. There is a tendency for the operation to become uncertain due to unreachable values.

In this respect, the above problems can be solved by using feedback control that has the function of detecting these various variable factors and performs corrective actions, but this requires a very complex control system. The operation is cumbersome, and there is an inevitable disadvantage of high cost.Furthermore, even when the target point is reached, the servomechanism must remain in operation, making the hydraulic drive system more complicated. structure, and therefore is considered unsuitable as a general-purpose product.

Apart from such expensive devices, robots with a simple structure that operate on and off are able to control the load by continuously changing the on and off switching using a time constant (for example, by CR). Some systems have been designed to achieve smooth movement by controlling the flow rate and pressure of the hydraulic line depending on the extent of It is unavoidable that the workpiece will not reach the target, and therefore it is necessary to rely on means such as installing a sturdy stopper mechanism and using this to position the workpiece. , there was an unsightly rebound effect, and the problem was far from being a fundamental solution.

The present invention was devised in response to these conventional problems, and is based on an industrial robot with a simple structure that uses a hydraulic drive system and an on/off system. By setting and memorizing the conditions for changes in moment in advance, during actual operation, it is only necessary to teach the start and stop positions, and smooth movement comparable to feedback control methods can be achieved. It is an object of the invention to ensure reliable positioning.

In particular, the present invention is connected to a hydraulic actuator in which speed control is performed by a current proportional flow rate control valve, speed control is performed by directional control by an electromagnetic switching valve, and directional control is performed by an electromagnetic switching valve, and
In industrial robots with a simple structure that are required to start and stop at any position within the movable range for an axis whose only amount of movement can be detected, the axis moving at a predetermined speed can be stopped by a stop command. The minimum movement displacement corresponding to the amount of movement during which the shaft is moved while decelerating until it comes to a stop is stored in the memory as reference displacement information, and the movable area of the axis is divided into an appropriate number n in advance at each end of the sub-area. Store the position value in memory as area information corresponding to each sub-area,
Furthermore, a memory address is provided corresponding to each of the n ² divisions of the matrix created by forming the sub-areas in rows and columns, and any start position and stop position are preset by combining the sub-areas to which they belong. Each movement pattern information that has been determined,
The movement pattern information is stored in each of the memory addresses corresponding to each section obtained from the matrix, and the movement pattern information includes the opening degree of the current proportional flow control valve, the opening/closing timing of the electromagnetic switching valve, and the hydraulic line The trigger setting position, which is a pressure command and a trigger setting position that is a deceleration width approximate to the minimum movement displacement with respect to the stop position, can be read out sequentially, and the desired starting position and When issuing a start command after commanding a stop position, first,
The absolute value of the difference between the start position and the stop position is compared with the minimum movement displacement, and if the absolute value is smaller, a separately set minimum speed movement is performed regardless of the movement pattern information. According to the pattern information, the shaft is operated at the lowest speed under a constant flow rate and constant pressure, and stopped at a predetermined stop position, while when the absolute value is larger, the start position and the stop position belong to each other. Each sub-area is determined and the movement pattern information of the memory address corresponding to the set of sub-areas is read out. Until the trigger setting position is reached, the initial opening degree of the current proportional flow control valve and the opening timing of the electromagnetic switching valve are determined. as well as by specifying the initial pressure in the hydraulic line.
performing position control on the shaft at a predetermined high speed;
From the time when the trigger setting position is reached, the current proportional flow rate control valve is sequentially throttled in steps with a minimal time width, thereby controlling the time by step-like deceleration operation on the shaft, and reaching the stop position. By the way, the control method is characterized by closing the electromagnetic switching valve and stopping the shaft,
Overrun and recoil can be prevented by performing high-speed position control up to the trigger setting position near the target point, and time control while applying deceleration in steps from the trigger setting position to the target point. In this way, we were able to achieve our intended purpose.

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

Although not shown, the industrial robot according to the method of the present invention has a conventionally well-known structure capable of multidimensional movement having multiple axes, and is hydraulically driven. 1) does not operate simultaneously with other shafts, but operates independently, and the shaft 1 has a reservoir line 5 equipped with a current proportional flow control valve 6 and a pressure compensation valve 7, and a pump. A hydraulic actuator 3 is connected to a hydraulic circuit consisting of a pump line 4 connected to a pump (not shown) through a piloted pressure reducing valve 9, an electromagnetic switching valve 8, and a check valve 12. It is possible to move upward and downward, and a hand 2 for grasping a workpiece is attached to the tip.

The hydraulic actuator 3 is a single rod cylinder 3
a, 3b, and a rotating chain sprocket 1 in which the rods of each cylinder are provided at the base of the shaft 1.
The cylinder chambers on the rod side are respectively connected to the four-port three-position electromagnetic switching valve 8, and the cylinder chambers on the anti-rod side are connected to each other. When a push-pull type actuator is formed and the flow of pressure oil is switched by the electromagnetic switching valve 8, the hydraulic action area is kept constant regardless of the flow direction, and the same stroke movement is achieved under constant pressure. It's getting old.

On the other hand, the pressure reducing valve 9 with a pilot is connected to the pump line 4.
This is a pressure adjustment control valve installed in a pipe connecting the electromagnetic switching valve 8 and the pressure control valve 8, and has a current proportional pressure control valve 10 in its reservoir line. Thus, the hydraulic pressure applied to the hydraulic actuator 3 can be controlled.

Thus, the shaft 1 is controlled in speed by the current proportional flow rate control valve 6 and in direction by the electromagnetic switching valve 8, as well as by the amount of movement (in this case, the rotation angle).
can be detected accurately using encoder counts, etc., and is required to start and stop at any position within the movable range. It also has a system to detect load fluctuations and a function to teach them as parameters. When the electromagnetic switching valve 8 is operated from the neutral position by excitation of the solenoid _8s1 , the pressure set by the pilot pressure reducing valve 9 and the flow rate (speed) set by the current proportional flow control valve 6 are , the shaft 1 is rotated in the downward direction (clockwise in FIG. 1), and conversely, the shaft 1 is rotated in the upward direction (also counterclockwise) by the excitation of the solenoid _8s2 . It will be done.

Note that the hydraulic circuit connecting the hydraulic actuator 3 and the electromagnetic switching valve 8 is usually formed of a hose with a well-known reinforced core, and naturally the diameter of the hose changes due to pressure fluctuations of the circulating oil. It is unavoidable that there will be a slight change in magnitude, and this will have a slight influence on the control of axis 1.

Next, we will develop a method for controlling a robot having the structure described above.This control method is based on the instruction of the start position and stop position and the start command, which will be described later, and then the calculations and commands of the microcomputer. Therefore, this is done automatically, and the memory section of this microcomputer stores reference displacement information, area information _m , and movement pattern information Pn.
are written, and each of these pieces of information can be read out at any time as needed.

Each of the above information will be explained below.

(b) Reference displacement information, when the axis 1 is moving at a predetermined speed close to the maximum speed, the minimum displacement corresponding to the amount of movement required to stop the shaft 1 while decelerating in response to a stop command until it comes to a complete stop. Movement displacement H, axis 1
The value changes depending on the rotational position and load, but for example, it is sufficient to take the value on the safe side of each numerical value obtained experimentally, and the displacement information obtained in this way is stored in a dedicated memory. It is something to do.

(b) Area information m _i , displacement X of axis 1 (in this example, the arm)
takes a value of e ₀ ≦X≦e ₁ , and e and X can be expressed, for example, by encoder counts. e ₀ and e ₁ correspond to the mechanical ends, and the movable area M of axis 1 is expressed as M = [e ₀ , e ₁ ], and this is divided into an appropriate number (n) of sub-areas. Divided into m ₁ ~ m _i ~ _{m o} , m ₁ = [e ₀ , X ₁ ), m ₂ = [X ₁ , X ₂ ),...m _i
= [X _i-1 , X _i ), ...m _o = [X _o-1 , e ₁ ] Each sub-region has the values (e ₀ ), (X ₁ ),
(X ₂ ), ... (X _o-1 ), (e ₁ ) are stored in memory as data.

In the example shown in Fig. 2, the rotation range from axis 1's origin A, that is, the state in which the hand unit is aligned with the work position on the work table, to the state in which it is aligned with the chuck C of the lathe, is the movable range M. The rotation angle is approximately 120°, and the encoder count is 785.
becomes. This movable region M is divided into a sub-region "0" of 20° (count number 130) clockwise from the origin A, a sub-region "" of the next 20° to 30° (230), a sub-region "" of 37° to 57° (370) sub-region "" (within this region the vertical state is included), sub-region "" from 57° to 80° (530), sub-region "" from 81° to 87° (570), and sub-region "" from 87° to 120°. (785) is divided into 5 sub-areas of ``'', and sub-area ``0'' is ``0'',
129'', subarea ``'' is ``130, 229'', subarea ``'' is ``230, 369'', subarea ``'' is ``370, 529'', subarea ``'' is ``530, 569'',
The sub-area "" may be stored in the memory as digital information of "570, 785".

(c) Movement pattern information Pn, the displacement values of the start position _S1 and the stop position _S2 are expressed by the count value of the encoder attached to the axis (arm) 1 or the digital value input by the operator using the keyboard. However, both positions S ₁ ,
Determine which of the sub-regions "0" to "" each _S2 belongs to, and store each movement pattern information Pn predetermined by the combination of the two corresponding sub-regions in a predetermined memory address. It is something.

This information storage means is characterized by being carried out as follows.

The sub-regions "0" to "" are arranged in a matrix X as shown in FIG.
Create _a memory address corresponding to each of the ₆ ² = 36 sections on this matrix When the movement pattern information _P1 is stored in the memory address determined by the corresponding section (the section indicated by the rectangular frame in Fig. 3), the movement pattern information is predetermined for each memory address.
It stores each Pn.

In this case, the movement pattern information Pn is
The opening degree of the current proportional flow rate control valve 6, the opening/closing timing of the electromagnetic switching valve 8, the pressure command of the hydraulic line, that is, the opening degree of the current proportional pressure control valve 10, and the stop position S ₂
, the trigger setting position T is an element, which is a position in front of the user by a deceleration width h which is approximate to the minimum movement displacement H (this differs depending on the type of movement pattern information Pn), In response to a read command, each element is sequentially read out in a predetermined order.

Examples of this movement pattern information are shown in Figures 3 and 2.
As shown in the figure, the starting position _S1 belongs to the sub-region "," and the stopping position _S2 belongs to the chuck C.
When teaching that the final position for centering the hand belongs to the sub-area ``'', as is clear from the matrix
Po is read out and becomes command information for the hydraulic actuator 3.

The motion pattern information Po at this time is obtained by first subtracting a predetermined value as the deceleration width h (count number 85) from the stop position (count number 785) and storing 785-85=700. After giving an opening command equivalent to, for example, 3.2V to the solenoid of the control valve 6, an opening command equivalent to the maximum pressure is given to the solenoid of the pressure control valve 10.

and axis 1 is the trigger set point T i.e. 700
When the count number reaches 2.8V50mm seconds, 2.45V100mm
Sequentially give opening commands of 2.15V 100mm seconds, 1.85V 150mm seconds, and finally give a 1.45V opening command.
A command is given to hold this position until the target position reaches 785 counts.

The contents of the information stored in the microcomputer have been explained above. Next, a control method for operating the shaft 1 based on such information will be explained below.

When a start command is issued after the start position S ₁ and stop position S ₂ are specified, the microcomputer is programmed to calculate the absolute value S of the difference between the start position S ₁ and stop position S ₂ and the minimum displacement H. Have students perform comparative calculations.

If the result of this calculation is S≦H, the shaft 1 is operated with separately set minimum speed movement pattern information _PL , regardless of each movement pattern information Pm shown on the matrix X in FIG.

In this case, the movement pattern information P _L is for each control valve 6,
Only the operation timings 8 and 10 and commands for the solenoids of the flow control valve 6 and pressure control valve 10 are included as data, and thus it is possible to operate the lowest speed shaft 1 under a constant flow rate and constant pressure. In this case, the starting position S ₁ is close to the stopping position S ₂ , so the movement is performed slowly with almost no impact and no overrun occurs. On the other hand, if the calculation result is S>H, the sub-region m _i to which the start position S ₁ belongs and the sub-region m _j to which the stop position S ₂ belongs are determined, and the set of both sub-regions m _i and m _j is determined. Therefore, a section on the matrix X is selected, and movement pattern information P _i of a memory address corresponding to the section is selected.

The deceleration width h determined by this motion pattern information P _i is compared with the absolute value S, and if S<h, the lowest speed motion pattern information P _L is selected again and the information is Axis 1 is activated by the P _L command.

If S > h in the reaction, the initial valve opening degree and initial pressure entered in the movement pattern information P _i are maintained from the starting position S ₁ until the trigger setting position T is reached before the stopping position S ₂ . Data υo and Po are output to the controllers of the flow rate control 6 and pressure control valve 10 based on the corresponding flow rate and pressure commands. During this time, control is performed by position monitoring.

When the trigger setting position T is reached, the flow force and pressure are controlled according to time based on the data subsequently outputted from the information P _i .

In this case, the information P _i holds the command values regarding the opening degree and pressure for a time in mm seconds, as described above, but normally the information is decelerated in steps at intervals of 50 mm seconds to 100 mm seconds. Let it go and gradually slow down.

After the stepwise deceleration is completed, the opening degree and pressure are maintained at the minimum, and when it is confirmed that the shaft 1 has reached the stop position _S2 , the next trigger signal is issued to control the control valves 6 and 8. It opens and closes and sets the pressure of the pressure control valve 10. These command signals are included in the movement pattern.

Note that among the elements of information P _i , pressure may not change with changes in valve opening, but in this case, the previously set data will be latched as is unless it is written as data. You can also leave it as

The control after reaching the trigger setting position T described above is not a position monitoring but a time control, and the arrival at the stop position _S2 is detected by the encoder and the stop position is correctly stopped at the target position.

By the way, the opening/closing timing data of the control valve is mainly used for the purpose of buying time for switching the flow path and balancing the pressure applied to the actuator before increasing the flow rate and pressure, that is, at the start of the movement. This data consists of the control valve's solenoid number, on/off operation selection, and the time between them. On the other hand, the trigger setting position T is the stop position S ₁
It is determined by calculating S ₁ ±H from the value of and the minimum displacement H. The symbol ± at this time is determined depending on the direction of movement, and the minimum movement displacement H is naturally included in the movement pattern information P _i .

Figures 4A and 4B show how to apply the command voltage to the current proportional flow rate control valve 6 when S>H and S>H among the control modes (see Figure 4A), and the displacement of the shaft 1. For the flow control valve 6, when the shaft 1 reaches the trigger setting position T determined by the target value and deceleration width, the command current given to the solenoid is reduced in steps, On the other hand, when the encoder count matches the count of the target stop position _S2 , the electromagnetic switching valve 8 is closed and stopped.
However, when it is in the entry position, rather than in the middle position, it should be pressed under low pressure.

By carrying out the above-described control, it is possible to give the shaft 1 movement with almost no shock, overrun, or recoil.

The aspects of the method of the present invention are as described above, and the effects will be described next.

(b) Even if the axis 1 is affected by fluctuation factors such as load fluctuations, oil temperature fluctuations, and changes in gravity moment, if the structure is such that even the amount of movement can be detected, it can be set in advance by implementing the present invention. By moving the axis 1 according to the set movement pattern information, smooth movement and reliable positioning can be achieved.

(b) By controlling on/off control valves such as the switching valve 8 and the flow rate control valve 6, reliable movement to the target position is possible, which greatly contributes to improving the reliability of industrial robots with a simple structure. be.

(c) If you write the movement pattern information Pn first, the actual operation will be from the start position S ₁ to the stop position.
It is extremely easy to handle, as all you need to do is command the _S2 and perform the start operation.

[Brief explanation of drawings]

FIG. 1 is an exploded view of the main parts of the hydraulic circuit of a robot according to the method of the present invention, FIG. 2 is a diagram showing the motion area divisions of the axis of the robot shown in FIG. 1, and FIG. 3 is a diagram showing motion pattern information according to the present invention. A chart showing an example of a matrix for explaining the storage mode, FIG. 4A is a command voltage transition diagram of the current proportional flow control valve of the robot shown in FIG. is also a displacement transition diagram of the shaft. 1... Axis, 3... Hydraulic actuator, 6...
Current proportional flow control valve, 8... Solenoid switching valve, h...
Deceleration width, H...Minimum movement displacement, m ₁ ~m _i ~m _o ...
Sub-area, M...Movable area, Pn...Movement pattern information, S...Absolute value, _S1 ...Start position, _S2 ...
Stop position, T...Trigger setting position, X...Matrix.

Claims (1)

[Claims] 1. With respect to the shaft 1, which is connected to the hydraulic actuator 3 whose speed is controlled by the current proportional flow rate control valve 6 and direction controlled by the electromagnetic switching valve 8, and whose movement amount can be detected, In an industrial robot that is required to start and stop at an arbitrary position and has a simple structure that does not have a system for detecting load fluctuations or a function for teaching them as parameters, the shaft 1 is moving at a predetermined speed. The minimum movement displacement H corresponding to the amount of movement required to decelerate and stop the shaft 1 in response to a stop command is stored in the memory as reference displacement information, and the movable region M of the shaft 1 is divided into an appropriate number n in advance. The obtained values at both end positions of the sub-regions m ₁ -m _i -m _o are stored in memory as area information corresponding to each sub-region, and further, the values of the sub-regions m ₁ -m _{i -m} o are stored in the memory as area information corresponding to each sub-region.
A memory address corresponding to each of the n ² divisions of the matrix X created by m _o in row units and column units is provided, and an arbitrary starting position S ₁ and arbitrary stopping position S ₂ can be set.
Each piece of movement pattern information Pn, which is predetermined by a combination of the sub-areas to which each sub-area belongs, is stored in each of the memory addresses corresponding to each section obtained from the matrix X. The information Pn includes the opening degree of the current proportional flow rate control valve 6, the opening/closing timing of the electromagnetic switching valve 8, and the deceleration width h that is approximate to the minimum movement displacement H with respect to the pressure command stop position _S2 of the hydraulic line. It is possible to sequentially read out the trigger setting position T as an element, and when a start command is issued after specifying the desired start position S ₁ and stop position S ₂ , the start position The absolute value S of the difference between _S1 and the stop position _S2 is compared with the minimum movement displacement H, and if the absolute value S is smaller, regardless of the movement pattern information Pn, _A constant flow rate,
The shaft 1 is operated at the lowest speed under a constant pressure and stopped at a predetermined stop position _S2 , while when the absolute value S is larger, the start position _S1 and the stop position _S2 are The motion pattern information Pi of the memory address corresponding to the set of sub-regions is determined by determining each sub-region to which each sub-region belongs, and the initial opening degree of the current proportional flow control valve 6, the electromagnetic By specifying the opening timing of the switching valve 8 and the initial pressure of the hydraulic line, the shaft 1 is controlled in position at a predetermined high speed, and from the time when the trigger setting position T is reached, the current proportional flow rate control valve 6 is controlled. is sequentially narrowed down in steps with a minimal time width, thereby controlling the time of the shaft 1 through a step-like deceleration operation,
A method for controlling an industrial robot, characterized in that when the stop position _S1 is reached, the electromagnetic switching valve 8 is closed to stop the shaft 1.