Safety system for robot.

BACKGROUND OF THE INVENTION

Field of the Invention

0001The present invention relates to a safety system for preventing any accident which may occur during operation of a robot.

Description of the Prior Art

0002Nowadays, industrial robots can well simulate the motion of human hands and, hence, have acquired a stable position as excellent workers in place of human labourers, particularly in the fields of automation which could never be achieved by conventional mechine technology, as well as in the simple and monotonous works and works under severe condition which could not be sustained by human labourers. In facts, many robots are actually used in various production lines.

0003Most of industrial robots are adapted to operate in accordance with a predetermined sequence or to play back a motion following up the content of teaching. Once the playing back operation is started by, for example, the setting of the object to be worked (referred to as "work", hereinunder), the operation of the manipulator is successively performed until a series of steps in accordance with the content of teaching is completed.

0004The industrial robots, therefore, suffered from a possibility of accident due to contact between the movable part or tool on the robot and a person or any obstacle which may accidentally come into the area of reach of the robot during the playback operation or automatic operation of the robot. The accident may be caused also by a wrong contact between the tool and the work when the work is set in a wrong manner.

0005In order to avoid the accidents, hitherto, such safety measures have been taken as to demarcate a danger zone to keep persons away from the area of reach of the robot by, for example, setting up a fence.

0006These conventional safety measures, however, require additional spaces for safety zone and impairs the efficiency of various necessary works such as setting of the work, inspection and maintenance of the robot. In addition, these conventional measures are quite invalid in avoiding the danger when a person has accidentally stepped into the danger zone or when an obstacle is hapened to be put in the same.

SUMMARY OF THE INVENTION

0007Accordingly, an object of the invention is t_d provide a safety system for industrial robots capable of eliminate occurrence of accident in all events without requiring the additional space for safety and without necessitating setting up of fence, thereby to overcome the above-described problems of the prior art.

0008To this end, according to the invention, there is provided a safety system for industrial robots, having a photoelectric detecting means having a field of vision containing the area of reach of the robot. In operation data concerning the sight in the field of vision is obtained through the photoelectric means for each of predetermined motions of the robot and is compared with a predetermined data corresponding to the sight obtained when there is no obstacle. When a difference of a level exceeding a predetermined level is found between the data obtained through the photoelectric detecting means and the predetermined data, the movement of the robot to the next position of operation is prohibited.

0009Thus, in the safety system of the invention, the the confirmation of safety, as well as the judgement as to whether to allow the manipulator to move to the next step, is made in each of the steps of playing back or automatic operation of the robot. It is, therefore, not necessary to demarcate wide danger zone nor to set up a fence. Accordingly, the invention provides a highly reliable safety system for industrial robots, capable of performing a sure and delicate operation to ensure the safety, thereby to overcome the problems of the prior art.

0010These and other objects, features and advantages of the invention will become clear from the following description of the prior art taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0011<ul id="ul0001" list-style="none"><li>Fig. 1 is a block diagram of an embodiment of the safety system for a robot in accordance with the present invention;</li><li>Fig. 2 is a perspective view showing an example of mounting of a TV camera on a robot;</li><li>Fig. 3 is a flow chart of operation of the embodiment as shown in Figs. 1 and 2; and</li><li>Fig. 4 is a block diagram showing a different embodiment of the invention.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENT

0012Fig. 1 shows the control system of a playback type robot, including a safety device in accordance with an embodiment of the invention. The control system includes a teaching device 1, automatic switch device 2 for playback control, an operation mode change-over switch 3, an operation controller (computer) 4, a comparator 5, an actuator 6 for driving manipulator, a position detector 7, a memory device 8, a TV camera 9 and an input device 10 for inputting answer-back signal from peripheral equipments.

0013As the teaching device 1 is operated, the operation mode is swtched to the teaching mode by the switching device 3. In consequence, the operation controller 4 produces an operation signal in accordance with a controlk signal delivered by the teaching device in each step, and operates an actuator 6 through a cmparator 5.

0014The position control object portion P of the robot R is actuated by an actuator 6, and the position of this portion P is detected by the position detector 7. The position detected by the position detector 7 is fed back to the comparator 5 so that the manipulator is brought to the predetermined command position. Meanwhile, the arithmetic operation cntroller 4 picks up, at each time of receipt of teaching completion signal from the teaching device 1 in each step, a signal from the position detector 7 and other various control signals necessary in the present step. These signals are stored in the predetermined memory area of the memory device 8. Simultaneously, the arithmetic operation controller 4 performs a control for writing in the memory device 8 so that different memory areas are appointed for different steps.

0015In consequence, the positions of the position control object portion P of the robot R in respective steps of movement of the robot and various control data associated therewith are stored in different memory areas, until the teaching device 4 completes the teaching in accordance with a predetermined sequence of operation.

0016After the completion of the teaching, the automatic switch device 2 produces a signal to operate the switching device 3 to switch the operation mode to the playback mode. Subsequently, a start signal is produced by the automatic switch device 2 so that the arithmetic operation control device 4 reads out the successive positions from corresponding memory areas in the memory device 8 starting from the first memory area. The actuator 6 is operated in response to the thus read out positions to successively control the position of the position control object portion P of the robot R to make the latter perform the necessary tasks.

0017The above-described operation of the playback type robot is well known.

0018As shown in Fig. 2, a TV camera 9 is mounted on a portion in the vicinity of the position control object portion P of the robot R or a part of a manipulator (not shown) provided on the position control object portion P so that the field of vision of the TV camera 9 covers a predetermined area including the movable part of the manipulator, particularly te wrist thereof. Thus, the TV camera can take up the image of the movement of the manipulator together with the background or peripheral scenery, during teaching of the robot and during playing back operation of the same.

0019On the other hand, the memory device 8 is constructed to store a predetermined number of frames of image signals (video signals) taken up by the TV camera 9.

0020The arithmetic operation controller 4 picks up the image signal from the TV camera in the form of independent frame in each of the above-mentioned steps or in selected ones of the above-mentioned steps, and stores the image signals in predetermined memory areas within the memory device 8. This operation is performed simultaneously with the writing of the position signal derived from the position detector 7 and various control signals in the present step.

0021Then, as the operation mode is switched to the playback mode, the arithmetic operation controller 4 pickes up the image signal in the form of independent frames from the TV camera 9 in each of the steps of the playback operation. The image signal thus picked up are then written in a buffer frame memory provided in one of the memory areas of the memory device 8. Then, the image signal of one frame written in the buffer memory and the image signal of one frame of the corresponding step in the teaching are read out in the form of independent of pitcutre elements or in the form of groups of picture elements. Thus, these two image signals are compared with each other for each of picture elements or for groups of picture elements.

0022The arithmetic operation controller 4 allows the robot to take the next step of operation only when there is no substantial difference between these two image signals. However, when there is a difference in excess of a predetermined level of difference between the two image signals, the arithmetic operation controller 4 operates to prohibit the robot to move to the next step and initiates an alarming operation as required.

0023The above-described operation of the safety system during the playback operation will be more fully understood from the following description taken with specific reference to Fig. 2 showing the flow chart of the operation.

0024As the playback operation is commenced, the position data is read out from the memory device 8 in a step Sl, and a judgement is made in the next step S2 as to whether the position for confirming the safety is reached. There are two types of safety confirmation. Namely, a first type in which the conformation is made in all of the positions or steps of operation of the robot manipulator and a second type in which the safety conformation is made only in selected steps of operation of manipulator. In the latter case, each control signal which is to be written in the memory device in each step of teaching contains a discrimination signal concerning the necessity of the safety confirmation, so that the pick up of the frame of image signal from the TV camera is omitted in the step which does not require the safety confirmation. Thus, in the playing back operation, the discrimination signal is examined in the step S2 of the flow chart to judge as to whether the present step of manipulator operation requires the safety confirmation. It will be understood that the step S2 of the flow chart can be dispended with if the safety system is intended for making safety cnfirmation in all of the steps of the manipulator operation. In such a case, the operation proceeds from the step Sl directly a step S6.

0025If the result of the checking in the step S2 of the flow chart is "NO", i.e. when the present step of the manipulator operation requires no confirmation of safety, steps S3 and S4 are taken in which, as in the case of ordinary playback operation, an operation is made to attain a coincidence between the actual position of the manipulator and the position data read out from the memory device 8. This operation is repeated until a checking result "YES" is obtained in a checking step S5, i.e. until the manipulator reaches the final position of the present step in the payback operation.

0026If an affirmative answer "YES" is obtained in the step S2, i.e. when the present step of manipulator operation requires a safety confirmation, the process proceeds from the step S2 to the step S6 mentioned before. In the step S6, the frame of image signal presently available through the TV camera 9 is written in the buffer frame memory. Then, the process proceeds to a next step S7 in which a preparation is made for the reading out of the frame of image signals which was stored in the corresponding step in the course of the teaching and the frame of image signals written in the buffer frame memory. Furthermore, in this step S8 of the flow chart, two frames of image signals are compared with each other for each of picture elements or for each of groups of picture elements, the result of which is evaluated in the next step S9 of the flow chart. When the answer derived through the step S9 is "NO", i.e. when there is a difference greater than a predetermined level of difference exists between two frames of image signals, the process proceeds to the next step S10 in which an instruction is given to temporarily stop the playback operation and to activate a suitable alarming device as required.

0027The difference between the sight within te field of vision of the TV camera as obtained in each step in the teaching process and the sight within the TV camera 9 as obtained in each step in the course of the playback operation is caused when a person has happened to come into the area of reach of the manipulator or when an obstacle is accidentally put into the same. The difference is caused also when the work to the processed by the robot is set in a wrong manner. The difference in te sight is then automatically detected and the movement of the manipulator to the nex step is stopped, so that the occurrence of the accident is avoided and prevented without fail.

0028When the playback operation is suspended by the safety device, a suitable alarming device is activated to inform the operator of the suspension of operation. Therefore, the operator can restart the playback operation by taking the necessary measure such as the removal of the obstacle.

0029Thus, in the described embodiment, it is possible to confirm the safety minutely and acurately because the safety conformation can be made for each of the steps of the manipulator operation during the playback operation, so that the safety system of the invention can enjoy a high reliability of operation for avoiding any denager.

0030Although in the described embodiment the confirmation of safety is made through comparing frames of iimage signals obtained through the TV camera 9, this is not exclusive and the safety conformation can be made by other means that the TV camera, as in the case of another embodiment shown in Fig. 4.

0031Namely, in the arrangement shown in Fig. 4, at least two photoelectric detectors 9a to 9d covering different detection areas are provided to output sight informations, and the safety conformation is made by conducting a comparison between the signals obtained during the teaching through these photoelectric detectors 9a to 9d and those obtained in the course of the playback operation. Symbols La to Ld designate light-emitting elements. In Fig. 4, the light beams emitted from the light-emitting elements La to Lc are received by the corresponding photoelectric detectors 9a to 9c but the light beam from the light-emitting element Ld is interrupted by the work W and cannot reach the corresponding photoelectric detectors 9d.

0032In this robot, the danger zone, i.e. the reach of the manipulator is changed in accordance with the movement of the manipulator. Therefore, by mounting a TV camera or photoelectric detectors on the movable part of the manipulator so that the detection of any obstacle in the danger zone is made regardless of the change in the danger zone in accordance with the motion of the manipulator. Thus, the safety confirmation is made for the danger zone peculiar to each step of operation of the manipulator. Therefore, the manipulator is not stopped solely for the reason such as an approach of a person to the robot manipulator but the operation of the manipulator is suspended only when any accident is expected in the next step of operation of the manipulator. It is, therefore, possible to attain a high reliability of operation of the industrial robot.

0033Although not mentioned specifically, an important factor in the operation of te safety system is the selection of the threshold level of judgement between accordance and discordance of two independent image signals. It is, therefore, desirable that the threshold level is adjustable so that the safety confirmation can be made with the optimum sensitivity.

0034It is also possible to compare the two kinds of the image signals in the form of binary codes to permit the judgement of the accordance or discordance by a pattern recognition technic.

0035The technic for the binary coding of the image signals is detailed in U.S.P.No. 4,136,957 and no further explanation seems to be needed in this connection.

0036Although the invention has been described through specific terms, the described embodiments are not exclusive and various changes and modificatons may be imparted thereto without departing from the scope of the invention which is limited solely by the appended claims.