JPS6029292A - Control system of arm for robot - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is directed to a robot arm for manually driving a robot's arm during motion teaching. Regarding the arm control system of the kit, in particular, if an external force of a magnitude below a certain level is applied to the arm, the arm will maintain the previous arm position, but if an external force of a magnitude above a certain level is applied. This invention relates to a robot arm control system in which the arm is driven at a predetermined speed.

[Background of the invention]

Until now, the driving method for electric industrial robots has been to manually drive the arm while making use of the serve, memorize the posture values at representative points on the drive path, and then repeatedly reproduce the movement. Usually, many things are done. When adopting such a method, the robot's arm is directly pulled or pushed manually, but the arm may also be driven via a handle to make it easier to drive the arm. It has a tail. A handle f equipped with a force detector using a strain dart or the like to detect the magnitude of force applied from the outside.

When the arm of the pot is attached to a fixed position and the arm is driven in any direction by manually operating the handle, the tip of the arm is moved by the driving force of the power source according to the magnitude of the output of the force detector. The position can be changed.

FIG. 1 schematically shows an example of a robot constructed in this manner. According to this, the rotary cylinder 2 is placed on the support stand 1.
The power source 3, the arms 4, 5, etc. are connected in a predetermined combination, and the handle 6 mentioned above is added near the tip of the arm 5. In this case, the four power sources 3 are for driving the arms 4 and 5 as well as the wrists (not shown), and a power source for driving the rotating body 2 is also installed inside the rotating body 2. It has become so.

By the way, a force detector (not shown) is embedded in the handle 6 to detect the magnitude and direction of an external force acting on the handle 6. The purpose is to control the power source 3 to drive the tip of the arm 5 at a speed corresponding to the size of the arm. How the driving speed of each of the power sources 3 is controlled in relation to the driving direction and driving speed of the tip of the arm 5 is determined by a fixed function relationship, but generally this control is performed by a computer such as a microprocessor. is the actual situation.

FIG. 2 shows the configuration of a control system for converting the force acting on the handle by manual operation into a speed corresponding to the magnitude of the force. As shown in the figure, an external force f is converted into an electric signal V by a converter 7 as a force detector, and is inputted to a controller (including a power source?) 9 via a subtractor 8, while a velocity v (1 is input to the subtracter 8 as the speed control feedback signal VD via the speed detector 10.

The operation of the feedback control system constructed in this way is already well known, and by means of the feedback control system constructed in this way, the force f is changed to the velocity V.
However, in such a case it is the presence of drift in the converter 7 that is problematic. force f
In principle, there should be a proportional relationship between the electrical signal V and the electrical signal V, and it is ideal that the converter 7 has the characteristics ai as shown in Fig. 3, but a certain amount of drift will occur. . Characteristics (a) and (c) in Fig. 3 are for the case where a drift occurs, but as can be seen from these characteristics (e), even if the magnitude of the force f is zero, if the electric signal vld is zero, then Therefore, even if no force is applied to the handle d, the arm 5 will be driven and will not be able to stand completely still.

[Purpose of the invention]

The object of the present invention is that when the force acting on the handle is below a certain level, the arm can come to a complete standstill, and when the force is above a certain level, the arm is driven approximately in proportion to the force. It is to provide a robot arm control method to obtain.

[Summary of the invention]

For this purpose, the present invention detects the magnitude of an external force acting on the robot's arm in the same way as in the conventional case, but if the magnitude of the detection signal is within a certain range, the detection signal In addition to invalidating the arm position, the previous arm position is maintained. That is, the robot's arm will not be driven due to the presence of drift, and the robot's arm will not be driven even if the external force is minute.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 4 to 6.

FIG. 4 shows the configuration of an example of a control system according to the present invention, and the same components as those shown in FIG. 2 are given the same reference numerals.

According to this, the substantial difference from that shown in FIG. 2 is that the electrical signal vl(v) obtained from the converter 7 is
1, the comparator 12 determines whether the size is within a certain range. However, dead band element 1
1 is not necessarily required as will be described later. When the comparator 12 determines that the output v2 of the dead zone element 11 is within a certain range, the output v2 of the dead zone element 11
is invalidated, and the output B is used to switch the changeover switch 13 from the converter 7 side to the position control loop side; otherwise, it is assumed to be valid and switched to the converter 7 side. It is something.

Here, the dead band element 11 will be explained. The width of the dead band is set to be larger than the expected output fluctuation due to drift in the converter 7, and its input/output characteristics are as shown in FIG. As a result, the output v2 of the dead zone element 1 with respect to the force f is obtained as shown in FIG. That is, characteristic a' shows the output sound of the dead band element when no drift exists in the converter 7, and characteristics b' and c' show the output sound when drift exists. As can be seen from FIG. 6, even if there is a drift in the transducer 7, the output v2 of the dead band element 11 is set to zero if the force f does not act at all or if it does act, it is very small. , it is conceivable to input the output v2' of the dead zone element 11 as is to the subtracter 8. However, since the motion system that involves velocity is an analog system and an analog element is always used as a velocity feedback control system, even if the output vzk of the dead zone element 11 set to zero is directly input to the subtractor 8, the velocity vo will be In reality, it may not be completely zero.

In order to solve this problem, the comparator 12 described above is provided. The comparator 12 compares the output v2 of the dead zone element 11 with two built-in threshold values rvshJ and r-vahJ, and determines the absolute value IV21 of the output v2.
It is determined whether 1v21<V, ) or 1v21>Vsh k.

For example, the determination output 8 is output as a high-level state signal when l vz l > Vsh, and as a low-level state signal otherwise. The switching is controlled as described above. That is, when the output S is a high level state signal, it is input to the subtracter 8 as the switching output v3 via the output v2i changeover switch 13 of the dead band element l, but when it is a low level state signal, it is input to the subtracter 8. The output v6 is input to the subtracter 8 as the switching output v3 via the changeover switch 13, and the control system operates as a position control system. As shown in the figure, the position control loop includes an integral element 14 having a speed V6-position XQ conversion function, a position detector 15 that detects the position from the output XQ of the integral element 14, and a sample hold at the falling edge of the output 8 for the position detection signal v4'. a sample hold element 16, a subtracter 17 and a subtracter 1 that calculates the difference between the sampled and held position detection signal v5 and the position detection signal v4.
Position controller 1 that performs PID control on the output eX of 7
It consists of 8.

Therefore, when a large force is applied to the arm of the robot from the outside via the handle, the changeover switch 13
The arm can be driven in the direction of the force. When almost no force is applied, the changeover switch 13 is switched to the position control loop side, and position control is performed using the position detection signal v4 sampled and held in the sample hold element 16 at the time when no force is applied. It is done. With this position control, as long as the sword does not act, the robot's arm will be held in the position it was in when the sword ceased to act. Although a certain degree of positional deviation occurs during this position holding, arm drive due to drift is more effectively prevented than when the speed control system's zero speed control function is used alone.

Although the present invention is as described above, as described above, the dead zone element is not necessarily necessary, and it is also possible to provide the comparator with this function. However, when a dead zone element is provided, the threshold value in the comparator can be kept small, and the position holding function and speed control function can be performed smoothly.

〔Effect of the invention〕

As explained above, the present invention detects the magnitude of an external force acting on a robot's arm, determines the magnitude of the force, and determines that the magnitude of the force is within a certain range. In this case, the previous arm position is maintained. Therefore, in the case of the present invention, even if the influence of drift is constantly present in the detection of the force magnitude,
When almost no force is applied from the outside (there is an effect that the arm is held in the previous position).

[Brief explanation of drawings]

Figure 1 shows an example of a robot whose arm can be driven manually, and Figure 2 shows an example of a robot in which the arm of the robot can be driven manually. A diagram showing the configuration of a control system, FIG. 3 is a diagram for explaining the conversion characteristics of a converter as a force detector, and FIG. 4 is a diagram showing the configuration of an example of the control system according to the present invention. Figure 5 shows
FIG. 6 is a diagram showing the input/output characteristics of the dead zone element in this configuration, and is a diagram for explaining the output characteristic with respect to force of the dead zone element. 7...Transducer (force detector), 8.17...Subtractor,
9... Controller, 10... Speed detector, 12... Comparator, 13... Changeover switch, 14... Integral element,
15...Position detector, 16...Sample hold element, 18...Position controller. Representative Patent Attorney Tadashi Akimoto Figure 1 Figure 2 Figure 3 Figure 4 Figure 2 Gogo Figure 5

Claims (1)

[Claims] A handle equipped with a force detector is attached to a certain position of the arm in order to manually drive the arm, and the power source is activated by the output of the force detector according to the magnitude of the force acting on the handle. In a robot arm control method that allows the tip of the arm to be driven in the direction of the force at a speed that corresponds to the magnitude of the output of the force detector, when the magnitude of the output of the force detector is below a certain level. If it is determined that the force is not below a certain level, the arm is driven and controlled by the output of the force detector, and if it is determined that the force is below a certain level, the output of the force detector is disabled and A robot arm control method that is characterized by keeping the arm in the position before any force is applied.