Patent Application
20210181730
The present application is based on, and claims priority from JP Application Serial Number 2019-223949, filed Dec. 11, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety.
The present disclosure relates to a robot system and a control device for a robot.
JP-A-2007-26028 discloses a microcomputer abnormality detection device having a timer clock generation unit, a free-running counter, a second timer clock generation unit, a second free-running counter, a comparison unit, and a determination unit. Of these units, the timer clock generation unit and the second timer clock generation unit generate a timer clock and a second timer clock, based on a system clock. The free-running counter counts, based on the timer clock. The second free-running counter counts, based on the second timer clock. The comparison unit compares the values of the free-running counter and the second free-running counter. The determination unit determines that the free-running counter has an abnormality when the values of the two free-running counters compared by the comparison unit do not coincide with each other.
JP-A-2007-26028 also discloses that the free-running counter is formed of a counter circuit with a predetermined number of bits and that, when a carry occurs, the free-running counter is reset to zero and subsequently performs count-up again.
A case where an abnormality occurs, for example, in the second free-running counter, of the free-running counter and the second free-running counter described in JP-A-2007-26028, is now considered. In this case, it is assumed that, due to the abnormality that has occurred, the second free-running counter happens to stop counting for the same period as the period of resetting the second free-running counter and subsequently restarts counting. In such a case, even when the value of the free-running counter and the value of the second free-running counter after the restart are compared with each other, the determination unit cannot detect the abnormality in the second free-running counter, which has stopped counting. When such an abnormality detection device is applied to a robot system, the correct position of a robot arm cannot be detected. Therefore, there is a problem in that the operation accuracy of the robot arm drops.
A robot system according to an application example of the present disclosure includes: a robot arm; a drive unit driving the robot arm; an encoder detecting a position of the robot arm; a drive control unit transmitting and receiving a first communication packet and a second communication packet in this order to and from the encoder and controlling an operation of the drive unit, based on a content of the first communication packet and the second communication packet; a storage unit storing the first communication packet and the second communication packet; a first timer unit having a time making a cycle of a finite time period, the first timer unit causing the storage unit to store a first time, which is the time when the first communication packet is stored into the storage unit, and a second time, which is the time when the second communication packet is stored into the storage unit; and a second timer unit measuring an elapsed time of a state of no communication after the first communication packet is detected.
A preferred embodiment of a robot system and a control device for a robot according to the present disclosure will now be described in detail with reference to the accompanying drawings.
First, the robot system according to the embodiment is described.
A robot system 1 shown in
The robot 2 shown in
The base 21 is fixed to an installation target part such as a floor, wall, ceiling, or movable trolley.
The robot arm 22 has an arm 221 coupled to the base 21 in such a way as to be able to swivel about a first axis J1, an arm 222 coupled to the arm 221 in such a way as to be able to swivel about a second axis J2, an arm 223 coupled to the arm 222 in such a way as to be able to swivel about a third axis J3, an arm 224 coupled to the arm 223 in such a way as to be able to swivel about a fourth axis J4, an arm 225 coupled to the arm 224 in such a way as to be able to swivel about a fifth axis J5, and an arm 226 coupled to the arm 225 in such a way as to be able to swivel about a sixth axis J6. An end effector 26 corresponding to work to be executed by the robot 2 is attached to the arm 226.
The robot 2 is not limited to the configuration in this embodiment. For example, the number of arms of the robot arm 22 may be one to five, or seven or more. The type of the robot 2 may be a SCARA robot or a dual-arm robot having two robot arms 22.
The robot 2 has a first drive unit 251, a second drive unit 252, a third drive unit 253, a fourth drive unit 254, a fifth drive unit 255, and a sixth drive unit 256, as shown in
The control device 5 controls the operation of each of the first drive unit 251, the second drive unit 252, the third drive unit 253, the fourth drive unit 254, the fifth drive unit 255, and the sixth drive unit 256 so that the arms 221 to 226 turn into a target position.
The robot 2 has an encoder 24 provided at a rotary shaft of the motor or the speed reducer of each drive unit and detecting an angle of rotation of the rotary shaft. Thus, the encoder 24 acquires position information of the robot arm 22. The position information refers to information representing the angle of rotation of each rotary shaft. The encoder 24 also has the function of transmitting the acquired position information to the control device 5 with respect to each rotary shaft.
Specifically, the encoder 24 includes a first encoder 241, a second encoder 242, a third encoder 243, a fourth encoder 244, a fifth encoder 245, and a sixth encoder 246.
The motor or the speed reducer of the first drive unit 251 is provided with the first encoder 241 detecting the angle of rotation of the rotary shaft thereof. The motor or the speed reducer of the second drive unit 252 is provided with the second encoder 242 detecting the angle of rotation of the rotary shaft thereof. The motor or the speed reducer of the third drive unit 253 is provided with the third encoder 243 detecting the angle of rotation of the rotary shaft thereof. The motor or the speed reducer of the fourth drive unit 254 is provided with the fourth encoder 244 detecting the angle of rotation of the rotary shaft thereof. The motor or the speed reducer of the fifth drive unit 255 is provided with the fifth encoder 245 detecting the angle of rotation of the rotary shaft thereof. The motor or the speed reducer of the sixth drive unit 256 is provided with the sixth encoder 246 detecting the angle of rotation of the rotary shaft thereof. Each rotary shaft may be provided with a plurality of encoders.
Each motor may be, for example, an AC server motor, a DC servo motor or the like. Each speed reducer may be, for example, a planetary-gear speed reducer, a strain wave gear device or the like.
Each motor is electrically coupled to the control device 5 via a motor driver, not illustrated. The encoder 24, too, is electrically coupled to the control device 5.
The robot system 1 may have various sensors such as an image pickup sensor like a camera, a force sensor, a pressure sensor, and a proximity sensor, in addition to the above components.
The control device 5 is communicatively coupled to the robot 2. The control device 5 and the robot 2 may be wire-connected or wirelessly connected.
The control device 5 shown in
The drive control unit 51 is communicatively coupled to each of the first drive unit 251, the second drive unit 252, the third drive unit 253, the fourth drive unit 254, the fifth drive unit 255, and the sixth drive unit 256. The drive control unit 51 is also communicatively coupled to each of the first encoder 241, the second encoder 242, the third encoder 243, the fourth encoder 244, the fifth encoder 245, and the sixth encoder 246.
The communication between the drive control unit 51 and each of the drive units 251 to 256 and the communication between the drive control unit 51 and each encoder 24 are, for example, serial communication using a communication packet.
The drive control unit 51 has the function of controlling the operation of each of the drive units 251 to 256 and thus controlling the driving of the robot 2. The hardware configuration of the drive control unit 51 is not particularly limited. The drive control unit 51 has, for example, a configuration having a processor such as a CPU (central processing unit) or MPU (micro processing unit), various memories including a volatile memory such as a RAM (random-access memory) and a non-volatile memory such as a ROM (read-only memory), and an external interface or the like.
The processor reads out and executes various programs or the like stored in the memory. Thus, the drive control unit 51 can execute processing such as drive control, various computations, and various determinations about the robot 2. Specifically, the drive control unit 51 controls the operation of each drive unit and the end effector 26, based on position information acquired from the encoder 24. Thus, the drive control unit 51 can cause the robot 2 to execute target work. The drive control unit 51 limits the driving of the robot 2 when the communication monitoring unit 52, described later, has detected a communication abnormality. The communication monitoring unit 52 may have the function of directly limiting the driving of the robot 2. Alternatively, both the drive control unit 51 and the communication monitoring unit 52 may have this function.
The drive control unit 51 may also have another component in addition to these configurations. The program or the like stored in the memory may be provided from outside via a network.
Meanwhile, the communication monitoring unit 52 is coupled to a communication line branching out from between the drive control unit 51 and the encoder 24. Therefore, a communication packet transmitted and received between the drive control unit 51 and the encoder 24 is also distributed to the communication monitoring unit 52.
The communication monitoring unit 52 has the function of monitoring the communication between the drive control unit 51 and the encoder 24. The hardware configuration of the communication monitoring unit 52 is not particularly limited. The communication monitoring unit 52 has, for example, a configuration having a processor such as an FPGA (field-programmable gate array) or ASIC (application-specific integrated circuit), various memories including a volatile memory such as a RAM and a non-volatile memory such as a ROM, and an external interface or the like. Also, various memories can be built in the FPGA or the like.
The communication monitoring unit 52 shown in
The first monitoring unit 521 has a communication packet storage unit 5212, a status determination unit 5213, a count value generation unit 5214, a count value computation unit 5216, and a count value determination unit 5218.
The communication packet storage unit 5212 stores a communication packet distributed thereto. The communication packet storage unit 5212 is, for example, a memory having the function of FIFO (first-in, first-out).
The data stored in the communication packet storage unit 5212 is divided into addresses having a predetermined bit width, as shown in
In the communication packet storage unit 5212, the entirety of one communication packet is stored. Therefore, address numbers are suitably set according to the packet length of the communication packet. At the address 0, for example, the first synchronous frame of the communication packet is stored. At the address 1, for example, a count value generated by the count value generation unit 5214, described later, is stored. At the address 2 onward, for example, a received data portion of the communication packet is stored.
The status determination unit 5213 reads a status signal of the communication packet stored in the communication packet storage unit 5212 and determines whether the status signal satisfies a predetermined condition or not.
The count value generation unit 5214 is a free-running counter formed of a counter circuit with a predetermined number of bits. The count value generation unit 5214 in this embodiment generates, for example, a 31-bit-wide count value that increases at a frequency of 96 MHz. When the count value increases and overflows, the count value generation unit 5214 is reset to zero and then restarts count-up. When the communication packet transmitted and received between the drive control unit 51 and the encoder 24 is distributed to and stored into the communication packet storage unit 5212, the communication packet storage unit 5212 stores a count value corresponding to this timing along with the communication packet. Therefore, the count value generation unit 5214 functions as a first timer unit having a count value that is a time making a cycle of a finite time period. The frequency of generation of the count value and the bit width thereof are not particularly limited. The count value generation unit 5214 may also generate a count value that decreases.
The count value computation unit 5216 calculates the difference between a count value corresponding to the communication packet stored in the communication packet storage unit 5212 and a count value corresponding to a communication packet stored immediately before that communication packet.
The count value determination unit 5218 compares the difference between the count values calculated by the count value computation unit 5216 with a preset expected value. The count value determination unit 5218 then determines whether the difference between the count values is equal to the expected value or not. The communication monitoring unit 52 outputs the result of the determination by the count value determination unit 5218 to the drive control unit 51.
The second monitoring unit 522 has a no-communication time measuring unit 5222 and a no-communication time determination unit 5224. The first monitoring unit 521 and the second monitoring unit 522 are communicatively coupled together.
The no-communication time measuring unit 5222 detects a distributed communication packet and measures an elapsed time from the detection timing. The no-communication time measuring unit 5222 functions as a second timer unit measuring an elapsed time from the detection of a communication packet. Thus, the no-communication time measuring unit 5222 can measure a no-communication time between communication packets or a no-communication time after the last communication packet is detected.
The elapsed time may be a time period measured after a communication packet is detected, or a time period corresponding to that time period, for example, a computed value resulting from performing a predetermined computation on the measured time period. Also, the start point of measuring a time period may be the timing when a communication packet is detected, the timing when a communication packet is stored, or any other timing.
The no-communication time determination unit 5224 compares the no-communication time measured by the no-communication time measuring unit 5222 with a predetermined value. The no-communication time determination unit 5224 then determines whether the no-communication time is equal to or less than the predetermined value, or not. When the no-communication time exceeds the predetermined value, the no-communication time determination unit 5224 outputs information to that effect to the drive control unit 51.
The operations of the control device 5 will now be described.
The communication monitoring unit 52 of the control device 5 is required to detect that a communication packet is normally transmitted and received, under various circumstances. Thus, the reliability of position information from the encoder 24 is secured and a reduction in the operation accuracy of the robot arm 22 can be restrained. That is, an inability to detect that the robot arm 22 is in an abnormal position, due to a drop in the reliability of position information caused by a communication disconnection, can be prevented. Thus, the robot system 1 with excellent safety can be achieved.
Operation examples of the control device 5 under various circumstances will now be described.
The communication packet 0 is a communication packet transmitted from the control device 5 to the encoder 24. The communication packet 0 is transmitted at a timing when 100 ps have passed since the start of communication. The “elapsed time” in the table is described for the sake of convenience and is not the time measured in the control device 5.
As the communication packet 0 is distributed to the communication monitoring unit 52, the communication packet 0 is stored into the communication packet storage unit 5212. Also, a count value generated by the count value generation unit 5214 and coinciding with the timing when the communication packet 0 is stored is stored into the communication packet storage unit 5212 along with the communication packet 0. Here, for example, a hexadecimal count value “00002580” is stored into the communication packet storage unit 5212.
The communication packet 1 (first communication packet) is a communication packet transmitted from the encoder 24 to the control device 5. The communication packet 1 is transmitted at a timing when 200 μs have passed since the start of communication.
As the communication packet 1 is distributed to the communication monitoring unit 52, the communication packet 1 is stored into the communication packet storage unit 5212. Also, a count value generated by the count value generation unit 5214 and coinciding with the timing when the communication packet 1 is stored is stored into the communication packet storage unit 5212 along with the communication packet 1. Here, for example, a hexadecimal count value “00004B00” is stored into the communication packet storage unit 5212.
The communication packet 2 (second communication packet) is a communication packet transmitted from the control device 5 to the encoder 24. The communication packet 2 is transmitted at a timing when 300 μs has have passed since the start of communication.
As the communication packet 2 is distributed to the communication monitoring unit 52, the communication packet 2 is stored into the communication packet storage unit 5212. Also, a count value generated by the count value generation unit 5214 and coinciding with the timing when the communication packet 2 is stored is stored into the communication packet storage unit 5212 along with the communication packet 2. Here, for example, a hexadecimal count value “00007080” is stored into the communication packet storage unit 5212.
The communication packet 3 is a communication packet transmitted from the encoder 24 to the control device 5. The communication packet 3 is transmitted at a timing when 400 μs have passed since the start of communication.
As the communication packet 3 is distributed to the communication monitoring unit 52, the communication packet 3 is stored into the communication packet storage unit 5212. Also, a count value generated by the count value generation unit 5214 and coinciding with the timing when the communication packet 3 is stored is stored into the communication packet storage unit 5212 along with the communication packet 3. Here, for example, a hexadecimal count value “00009600” is stored into the communication packet storage unit 5212.
Here, for example, the case where the communication monitoring shown in
In step S1 shown in
In step S2 shown in
In step S4 shown in
In step S5 shown in
In step S6 shown in
In step S7 shown in
In step S8 shown in
In step S9 shown in
In
In this specification, the “expected value” is equivalent to the interval of transmitting a communication packet and is a prescribed value. However, the interval of transmission may change depending on the communication environment. Considering this, a small range of variance may be provided for the expected value.
In the description of the second operation example, the difference from the first operation example is mainly described and the description of similar matters is omitted. The communication packet 0 and the communication packet 1 shown in
As the count value overflows, the hexadecimal count value is reset from 7FFFFFFF to 00000000. Therefore, calculating the difference between count values without considering the resetting of the count value in the foregoing step S8 results in an abnormal numerical value.
Thus, the count value computation unit 5216 in this embodiment has a correction function to avoid such a situation. Specifically, the count value stored in the communication packet storage unit 5212 corresponding to the communication packet 2 (second communication packet) is a value increased from the reset value of 00000000, as shown in
As described above, the control device 5 in this embodiment has the count value generation unit 5214 generating a count value making a cycle of a finite time period. However, the control device 5 also has the correction function as described above and therefore can prevent the calculation of an abnormal value. Therefore, the occurrence of a problem due to using an abnormal value as it is, that is, the problem of erroneously recognizing that a communication disconnection has occurred even when no communication disconnection has occurred, can be prevented. Thus, unnecessary limitation on the driving of the robot 2 can be prevented.
In the description of the third operation example, the difference from the first operation example is mainly described and the description of similar matters is omitted. The communication packet 0 and the communication packet 1 shown in
In the third operation example, it is assumed that, after the communication packet 1 (first communication packet) is transmitted, a communication disconnection lasting 300 μs occurs in the communication line between the drive control unit 51 and the encoder 24 and the communication is subsequently restored.
First, in step S1, the no-communication time measuring unit 5222 measures a no-communication time. Then, in step S2, whether the measured no-communication time is equal to or less than a predetermined value, or not, is determined. The duration of the communication disconnection shown in
In step S6, a count value corresponding to the communication packet 2 (second communication packet) is read out. Then, in step S8, the difference between the count value corresponding to the communication packet 2 and the count value corresponding to the communication packet 1 is calculated. The count value continues increasing even during the communication disconnection. Therefore, the time calculated from the count value corresponds to the actual elapsed time without being influenced by the duration of the communication disconnection. Thus, for the communication packet 2 shown in
In step S9, whether the calculated difference between the count values is equal to the expected value or not is determined. Here, the time calculated from the difference between the count values and the time of the expected value are compared with each other to perform the determination. The communication packet 2 shown in
As described above, in the control device 5 in this embodiment, even when a short communication disconnection that cannot be detected by the second monitoring unit 522 occurs, the first monitoring unit 521 can detect this communication disconnection. Therefore, even when there is a time period during which the position information of the encoder 24 cannot be acquired due to a communication disconnection, this can be detected and the driving of the robot 2 can be limited. Thus, the safety of the robot system 1 can be increased.
In the description of the fourth operation example, the difference from the first operation example is mainly described and the description of similar matters is omitted. The communication packet 0 and the communication packet 1 shown in
In the fourth operation example, it is assumed that, after the communication packet 1 (first communication packet) is transmitted, a communication disconnection lasting 22369721.34 μs occurs in the communication line between the drive control unit 51 and the encoder 24 and the communication is subsequently restored.
First, in step S1, the no-communication time measuring unit 5222 measures a no-communication time. Then, in step S2, whether the measured no-communication time is equal to or less than a predetermined value, or not, is determined. The duration of the communication disconnection shown in
Meanwhile, the first monitoring unit 521 cannot detect this communication disconnection. The reason for this is described below.
In step S6, a count value corresponding to the communication packet 2 (second communication packet) is read out. Then, in step S8, the difference between the count value corresponding to the communication packet 2 and the count value corresponding to the communication packet 1 is calculated. The count value continues increasing even during the communication disconnection. Therefore, the time calculated from the count value corresponds to the actual elapsed time without being influenced by the duration of the communication disconnection. Thus, the duration of the communication disconnection can be calculated in the third operation example.
However, the count value corresponding to the communication packet 2 can make a round via an overflow and end up coinciding with the expected value, though with a very low probability. Specifically, when the count value has a 31-bit width and a communication disconnection lasting 22369721.34 μs occurs between the communication packet 1 and the communication packet 2, the count value corresponding to the communication packet 2 becomes 00007080. This value is the same as the count value corresponding to the communication packet 2 in the first operation example. In this case, when the difference is calculated using this count value and the time is calculated from this difference, no influence of the communication disconnection is included in the result of the calculation. That is, at the first monitoring unit 521, the time calculated from the difference between the count values is 100 μs, which is the same as in the first operation example. Therefore, the result of the determination is the same as when no communication disconnection has occurred. Thus, in
As described above, in the control device 5 in this embodiment, even when a relatively long communication disconnection with a predetermined length that cannot be detected by the first monitoring unit 521 occurs, the second monitoring unit 522 can detect this communication disconnection. That is, the monitoring function of the first monitoring unit 521 and the monitoring function of the second monitoring unit 522 are complementary with each other, as can be explained in the third operation example and the fourth operation example. Therefore, even when there is a time period during which the position information of the encoder 24 cannot be acquired due to a communication disconnection, this can be detected and the driving of the robot 2 can be limited. Thus, the safety of the robot system 1 can be increased.
In the description of the fifth operation example, the difference from the first operation example is mainly described and the description of similar matters is omitted. The communication packet 0 and the communication packet 1 shown in
In the fifth operation example, it is assumed that, after the communication packet 1 (first communication packet) is transmitted, a communication disconnection occurs in the communication line between the drive control unit 51 and the encoder 24 and the communication is not subsequently restored.
First, in step S1, the no-communication time measuring unit 5222 measures a no-communication time. Then, in step S2, whether the measured no-communication time is equal to or less than a predetermined value, or not, is determined. In the case of the communication disconnection shown in
In step S3, the second monitoring unit 522 outputs information that the no-communication time exceeds the predetermined value, to the drive control unit 51.
Meanwhile, the first monitoring unit 521 cannot detect this communication disconnection. The reason for this is described below.
If the communication is not restored, there is no communication packet following the communication packet 1. In this case, the count value of the next communication packet cannot be acquired. Therefore, there is no count value that is necessary for the first monitoring unit 521 to determine the presence or absence of a communication abnormality, and the first monitoring unit 521 cannot perform determination. Thus, the drive control unit 51 cannot be notified of any abnormality, posing a problem in that the driving of the robot 2 cannot be limited.
In contrast, in the control device 5 in this embodiment, even when a communication disconnection occurs and the communication is not subsequently restored, the second monitoring unit 522 can detect this. Therefore, even in the circumstance where the communication is not restored, this can be detected and the driving of the robot 2 can be limited. Thus, the safety of the robot system 1 can be increased.
As described above, the robot system 1 according to this embodiment has the robot arm 22, the drive units 251 to 256, the encoder 24, the drive control unit 51, the communication packet storage unit 5212, the count value generation unit 5214 as the first timer unit, and the no-communication time measuring unit 5222 as the second timer unit. Of these, the drive units 251 to 256 drive the robot arm 22. The encoder 24 detects the position of the robot arm 22. The drive control unit 51 transmits and receives the communication packet 1 (first communication packet) and the communication packet 2 (second communication packet) in this order to and from the encoder 24 and controls the operation of the drive units 251 to 256, based on the contents of the communication packet 1 and the communication packet 2. The communication packet storage unit 5212 stores the communication packet 1 and the communication packet 2.
The count value generation unit 5214 has a count value that is a time making a cycle of a finite time period, and causes the communication packet storage unit 5212 to store the count value (first time) when the communication packet 1 is stored into the communication packet storage unit 5212 and the count value (second time) when the communication packet 2 is stored into the communication packet storage unit 5212.
The no-communication time measuring unit 5222 measures the elapsed time of the state of no communication after the communication packet 1 is detected.
In such a robot system 1, a communication disconnection can be detected, using the count value generated by the count value generation unit 5214 and the no-communication time measured by the no-communication time measuring unit 5222. Since the monitoring of communication based on the count value and the monitoring of communication based on the no-communication time are complementary with each other, a communication disconnection can be detected under various circumstances. Thus, the robot system 1 in which an abnormality occurring in the communication from the encoder 24 can be detected more securely using the results of such monitoring of communication, when the operation of the robot arm 22 is controlled based on the position information from the encoder 24, can be achieved.
The robot system 1 also has the communication monitoring unit 52 monitoring the state of communication between the encoder 24 and the drive control unit 51, based on the difference between the count value (first time) when the communication packet 1 is stored into the communication packet storage unit 5212 and the count value (second time) when the communication packet 2 is stored into the communication packet storage unit 5212, and based on the elapsed time of the state of no communication after the communication packet 1 is detected.
In such a configuration, the communication monitoring unit 52 can be easily made independent of the drive control unit 51 and therefore the independence and reliability of the operation of the communication monitoring unit 52 can be increased. Thus, the robot system 1 having an enhanced monitoring ability and higher functional safety can be achieved.
The communication monitoring unit 52 also has the function of reporting an abnormality in the state of communication when the elapsed time of the state of no communication after the communication packet 1 is detected exceeds a predetermined value. By outputting that the elapsed time exceeds the predetermined value, the communication monitoring unit 52 can detect a communication disconnection of such a degree as to influence the drive control of the robot 2 and can notify the drive control unit 51 of the communication disconnection. Thus, the robot system 1 having higher functional safety as the operation of the drive control unit 51 reflects the occurrence of the communication disconnection can be achieved.
The communication monitoring unit 52 also has the function of reporting an abnormality in the state of communication when the difference between the count value (first time) when the communication packet 1 is stored into the communication packet storage unit 5212 and the count value (second time) when the communication packet 2 is stored into the communication packet storage unit 5212 is deviated from the expected value. By outputting that the difference is different from the expected value, the communication monitoring unit 52 can detect a communication disconnection and notify the drive control unit 51 of the communication disconnection. Thus, the robot system 1 having higher functional safety as the operation of the drive control unit 51 reflects the occurrence of the communication disconnection can be achieved.
The drive control unit 51 also limits the driving of the robot arm 22, based on the result of monitoring by the communication monitoring unit 52. Thus, even when an abnormality occurs in the communication between the drive control unit 51 and the encoder 24 and the accurate position of the robot arm 22 cannot be detected, a collision between the robot arm 22 and a person or an object can be prevented. Thus, the robot system 1 having higher functional safety can be achieved.
The control device 5 for the robot 2 having the robot arm 22, the drive units 251 to 256, and the encoder 24 according to this embodiment has the drive control unit 51, the communication packet storage unit 5212, the count value generation unit 5214 as the first timer unit, and the no-communication time measuring unit 5222 as the second timer unit. Of these, the drive units 251 to 256 drive the robot arm 22. The encoder 24 detects the position of the robot arm 22. The drive control unit 51 transmits and receives the communication packet 1 (first communication packet) and the communication packet 2 (second communication packet) in this order to and from the encoder 24 and controls the operation of the drive units 251 to 256, based on the contents of the communication packet 1 and the communication packet 2. The communication packet storage unit 5212 stores the communication packet 1 and the communication packet 2.
The count value generation unit 5214 has a count value that is a time making a cycle of a finite time period, and causes the communication packet storage unit 5212 to store the count value (first time) when the communication packet 1 is stored into the communication packet storage unit 5212 and the count value (second time) when the communication packet 2 is stored into the communication packet storage unit 5212.
The no-communication time measuring unit 5222 measures the elapsed time of the state of no communication after the communication packet 1 is detected.
In such a control device 5, a communication disconnection can be detected, using the count value generated by the count value generation unit 5214 and the no-communication time measured by the no-communication time measuring unit 5222. Since the monitoring of communication based on the count value and the monitoring of communication based on the no-communication time are complementary with each other, a communication disconnection can be detected under various circumstances. Thus, the control device 5 that can more securely detect an abnormality occurring in the communication from the encoder 24, using the results of such monitoring of communication, when the operation of the robot arm 22 is controlled based on the position information from the encoder 24, can be achieved.
The robot system and the control device for the robot according to the present disclosure have been described, based on the illustrated embodiment. However, the present disclosure is not limited to this embodiment. The configuration of each part can be replaced by any configuration having a similar function. Also, any other component may be added to the embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-223949 | Dec 2019 | JP | national |
