Control device, control system, and control method

Abstract

Provided is a control device comprising a control unit which synchronizes operations of a plurality of actuators that operate in different control periods. The control unit generates, as an actuator track for each of the actuators, a reference command value which is information indicating a positional command value for each predetermined reference period that is shared among the plurality of actuators. The control unit uses each reference command value to determine a transmission command value which is a positional command value for each control period of a respective actuator, and transmits the transmission command value to that actuator. When a control period of an actuator is different from the reference period, the control unit omits a reference command value which does not correspond to the control period, and uses a reference command value corresponding to the control period as the foregoing transmission command value.

Description

Control device, control system, and control method

[0001] The present disclosure relates to a control device, a control system, and a control method for controlling a plurality of actuators.

[0002] Control devices for controlling multiple actuators are known. For example, Japanese Patent Application Laid-Open Publication No. 2004-280195 describes a robot control device having an actuator, a detection means for detecting the actuator's state, such as its position and speed, a sub-controller for controlling the actuator based on the detection values ​​of the detection means, and a main controller for generating command values ​​for each actuator. The main controller is equipped with a control means for controlling the command value update period by changing the order in which command values ​​are sent to the sub-controller. This control device attempts to centrally allocate network resources by changing the command value update period according to the speed and accuracy required of the actuator, thereby ensuring high speed and accuracy for a minimum number of axes even in a system with multiple actuators.

[0003] In a robot having a robot arm and a hand, the control periods of the multiple actuators included therein may differ. In such a case, a technology is required that can suppress the deviation in the operation timing of the multiple actuators and contribute to the coordinated operation of the multiple actuators.

[0004] The present disclosure has been made to solve at least part of the above-mentioned problems, and can be realized, for example, in the following aspects.

[0005] According to a first aspect of the present disclosure, there is provided a control device for controlling a plurality of actuators that operate at different control periods. The control device includes a control unit that synchronizes the operation of the plurality of actuators. The control unit generates, for each actuator included in the plurality of actuators, a reference command value that is information on a position command value for each reference period as an actuator trajectory that is a trajectory of the actuator. The reference period is a period commonly used by the plurality of actuators. The control unit uses the reference command value for each actuator to determine a transmission command value that is a position command value for the actuator for each control period, and transmits the determined transmission command value to the actuator. When the control period of the actuator is different from the reference period, the control unit omits the reference command value that does not correspond to the control period, and sets the reference command value that corresponds to the control period as the transmission command value.

[0006] According to a second aspect of the present disclosure, there is provided a control system including a plurality of actuators operating at different control periods and a control device that controls the operation of the plurality of actuators. The control device includes a control unit that synchronizes the operation of the plurality of actuators. The control unit generates, for each actuator included in the plurality of actuators, a reference command value that is information on a position command value for each predetermined reference period that is used commonly by the plurality of actuators as an actuator trajectory that is a trajectory of the actuator. The control unit determines, for each actuator, a transmission command value that is a position command value for each control period of the actuator using the reference command value. The control unit transmits the determined transmission command value to the actuator. When the control period of the actuator is different from the reference period, the control unit omits the reference command value that does not correspond to the control period and sets the reference command value that corresponds to the control period as the transmission command value.

[0007] According to a third aspect of the present disclosure, there is provided a control method for synchronizing the operation of multiple actuators that operate at different control periods. The control method includes a process of generating, for each actuator included in the multiple actuators, a reference command value that is information on a position command value for each predetermined reference period that is used commonly by the multiple actuators as an actuator trajectory that is a trajectory of the actuator. The control method also includes a process of determining, for each actuator, a transmission command value that is a position command value for each control period of the actuator using the reference command value. The control method also includes a process of transmitting, for each actuator, the determined transmission command value to the actuator. In the process of determining the transmission command value, if the control period of the actuator is different from the reference period, the reference command value that does not correspond to the control period is omitted, and the reference command value that corresponds to the control period is used as the transmission command value.

[0008] FIG. 1 is a schematic diagram of a control hand system. FIG. 2 is a block diagram showing the configuration of a control system. FIG. 3 is a flowchart of a synchronization control process. FIG. 4 is a flowchart of a trajectory generation process. FIG. 5 is a flowchart of a transmission command value determination process. FIG. 6 is an image diagram of a transmission command value Cs generated in step S240. FIG. 7 is an image diagram of a transmission command value Cs generated in step S250. FIG. 8 is a flowchart of a transmission command value determination process in a second embodiment which is an image diagram of a transmission command value Cs generated in step S280. FIG. 9 is a flowchart of a transmission command value determination process in a third embodiment. FIG. 10 is a flowchart of a transmission command value determination process in a third embodiment. FIG. 11 is an image diagram of an emergency command value Ce generated in step S304. FIG. 12 is a block diagram showing the configuration of a control system in another embodiment which is a diagram showing the relationship between time and progress amount.

[0009] <First embodiment> <System configuration> Fig. 1 is a diagram showing an example of a control system 10 according to the first embodiment. The control system 10 is a system for cooperatively operating a plurality of actuators that operate at different control cycles. An "actuator" is a machine or mechanical element that converts an electrical signal output by a computer into physical movement.

[0010] The control system 10 of this embodiment includes a robot 20 having a robot arm 30 and a hand 40, an amplifier device 50 that transmits and receives electrical signals to the hand 40, an input device 60, and a control device 100. In Fig. 1, the configurations of the robot arm 30 and the hand 40 are simplified. As shown in Fig. 1, a container 201 and a container 202 are installed in the working area of ​​the robot 20. The control system 10 is configured to perform a so-called pick-and-place operation in which the robot 20 grasps a workpiece W in the container 201 and moves it to the container 202.

[0011] The robot arm 30 includes a plurality of first actuators 32 and a plurality of links L. Two adjacent first actuators 32 are connected by a link L. The first actuators 32 are also called joints or movable axes. The first actuators 32 include known components for operating the robot arm 30, such as a servo motor (hereinafter referred to as a first motor 33, see FIG. 2 ), an encoder, a reducer, etc. The first actuators 32 are driven by output from the control device 100. The robot arm 30 of this embodiment is a vertical articulated robot with six degrees of freedom.

[0012] The hand 40 is attached to the arm tip 31 of the robot arm 30. The arm tip 31 also serves as a mounting portion configured to detachably mount the hand 40. The hand 40 is also referred to as a robot hand, an end effector, or a tool. The hand 40 includes multiple second actuators 42 as movable axes of the hand 40. Note that only one second actuator 42 is illustrated in FIG. 1 . The second actuator 42 includes known components for operating the hand 40, such as a servo motor (hereinafter referred to as the second motor 43, see FIG. 2 ), an encoder, and a reducer. The hand 40 is driven by output from an amplifier device 50 that receives commands from the control device 100. The hand 40 can grasp a workpiece W, which is the object of the operation, and can also release the grasped workpiece W. As a result, the robot 20 can grasp and move the workpiece W. Note that the hand 40 at the arm tip 31 can be changed depending on the application. This allows the user to control the robot 20 to perform desired operations.

[0013] In this embodiment, the multiple first actuators 32 in the robot arm 30 have the same characteristics. Similarly, the multiple second actuators 42 in the hand 40 have the same characteristics. The characteristics of the first actuators 32 are different from the characteristics of the second actuators 42. The characteristics of the first actuators 32 and the second actuators 42 are also referred to as the first characteristics and the second characteristics, respectively. The first characteristics and the second characteristics each include limit information regarding the upper limit of the speed, the upper limit of the acceleration, and the upper limit of the deceleration. The limits in the first characteristics and the second characteristics are determined in advance by the motor specifications, such as the current characteristics and torque characteristics, of the first motor 33 and the second motor 43. The limits may be determined in advance using the configuration, singular postures, movable ranges, etc. of the robot arm 30 and the hand 40 in addition to the motor specifications.

[0014] In this embodiment, the multiple first actuators 32 are driven by the control device 100 at a predetermined control cycle. In other words, the multiple first actuators 32 each operate at the same control cycle. Therefore, the entire robot arm 30 can be considered as a single actuator. The control cycle of the robot arm 30 is basically a first cycle T1f that is initially set in the control device 100. The control cycle of the robot arm 30 can vary from the first cycle T1f depending on the status of the control device 100, etc.

[0015] The amplifier device 50 drives the second actuators 42 of the hand 40 in accordance with command values ​​transmitted from the control device 100. The amplifier device 50 is also called a servo amplifier or a servo control unit. The amplifier device 50 controls the multiple second actuators 42 at a predetermined control period. In other words, the multiple second actuators 42 each operate at the same control period. Therefore, the entire hand 40 can be considered as a single actuator. The control period of the amplifier device 50 is basically an initially set second period T2f. The control period of the amplifier device 50 can vary from the second period T2f depending on the status of the amplifier device 50, etc. The second period T2f is different from the first period T1f of the robot arm 30.

[0016] The input device 60 is configured to allow a user to input various instructions to the control system 10. The instructions include an instruction to start the synchronous control process, which will be described later, and an instruction to urgently stop the synchronous control process. As the input device 60, various input terminals such as a touch panel or buttons can be used.

[0017] The control device 100 is a robot controller that comprehensively controls the movement of the robot 20. The control device 100 generates a trajectory for moving the tip 41 of the hand 40 from a start position to a target position, and causes the robot 20 to reproduce (play back) the generated trajectory. The control device 100 also executes synchronization control processing to suppress synchronization deviation, which is a deviation in the operation timing of the multiple actuators 32, 42. The control device 100 will be described in detail below.

[0018] As shown in FIG. 2 , the control device 100 includes a CPU (Central Processing Unit) 110, which is a processor, a memory 120, and an interface circuit 130. The control device 100 is communicatively connected to the robot arm 30, the amplifier device 50, the input device 60, and peripheral devices (not shown) via the interface circuit 130. These communications can be performed using wireless or wired communication methods known in the art. The control device 100 is also configured to output power to the robot arm 30 via the interface circuit 130. As described above, the robot arm 30 includes multiple first actuators 32, and the hand 40 includes multiple second actuators 42. However, FIG. 2 illustrates only one first actuator 32 and one first motor 33, and one second actuator 42 and one second motor 43.

[0019] The memory 120 includes a volatile memory and a non-volatile memory. Programs P1 and P2 and various information are stored in the memory 120. In this embodiment, the memory 120 stores a first characteristic, a second characteristic, a first period T1f, a second period T2f, and a reference period Tr (described later).

[0020] The CPU 110 functions as a first control unit 111 by deploying and executing the program P1 stored in the memory 120. The first control unit 111 executes a synchronization control process for the multiple actuators 32, 42 included in the robot 20 to suppress synchronization deviation and cause the actuators 32, 42 to operate in coordination. Synchronization deviation includes deviations in the timing of the start, stop, acceleration start, deceleration start, and other operations of the multiple actuators. As will be described in detail below, in the synchronization control process, the first control unit 111 generates position command values ​​for each actuator to synchronously control the multiple actuators 32, 42. The first control unit 111 executes at least a portion of the functions of a "control unit" in the present disclosure.

[0021] The second control unit 112 controls the robot arm 30 using the command values ​​generated by the first control unit 111. In this embodiment, the second control unit 112 controls the robot arm 30 by supplying an output to the first actuators 32 of the robot arm 30 via the interface circuit 130. The second control unit 112 is also called a servo control unit of the robot arm 30. The second control unit 112 basically drives the multiple first actuators 32 at an initially set first period T1f.

[0022] 3 is a flowchart of the synchronization control process executed by the control device 100. The synchronization control process is started, for example, when a start instruction is input to the control device 100 via the input device 60.

[0023] In step S100, the first control unit 111 executes a trajectory generation process. In step S100, the first control unit 111 acquires the first and second characteristics stored in the memory 120 and generates a trajectory that takes into account the limitations (characteristics) of each actuator. Specifically, the first control unit 111 generates a trajectory that can be reproduced even by the actuator with the strictest limitations. For example, the first control unit 111 applies the upper limit values ​​of the actuator with the smallest upper limit values ​​for acceleration, deceleration, and speed to the other actuators to generate an actuator trajectory.

[0024] 4 is a specific flowchart of the trajectory generation process. In step S110, the first control unit 111 first generates a trajectory of the hand 40 for moving the tip 41 of the hand 40 from the start position to the target position while avoiding collision with obstacles. The trajectory describes the position and posture of the hand 40 in space using time as a parameter. Information on the initial position, the target position, and the position of the obstacle may be registered in advance in the memory 120, or may be acquired by the first control unit 111 via an imaging device (not shown).

[0025] Next, in step S120, the first control unit 111 generates actuator trajectories, which are trajectories (drive modes, operation modes) of each actuator for reproducing the position and posture of the hand 40 on the generated trajectory. The actuator trajectories may differ for each actuator. In step S120, the first control unit 111 generates a position command value for each reference period Tr for each actuator. The reference period Tr is a control period commonly used by the multiple actuators 32, 42 included in the robot 20. The reference period Tr is determined in advance through experiments or simulations and is stored in the memory 120. The position command value for each reference period Tr is also referred to as a "reference command value Cr." The reference command value Cr is a position command value that forms the basis of the transmission command value Cs that is ultimately transmitted to each actuator. The actuator trajectory is information on the position command value for each reference period Tr.

[0026] After generating the actuator trajectories, the first control unit 111 advances the synchronization control process to step S200 in Fig. 3. In step S200, the first control unit 111 determines a transmission command value Cs for each actuator using the reference command value Cr, and transmits the determined transmission command value Cs to each actuator.

[0027] 5 is a flowchart of the transmission command value determination process, which is executed for each actuator.

[0028] In step S210, the first control unit 111 acquires the control period Ta of the target actuator. In this embodiment, the first control unit 111 refers to the memory 120 and acquires the first period T1f or the second period T2f depending on the target actuator.

[0029] In step S220, the first control unit 111 determines whether the control period Ta of the target actuator is greater (longer) than the reference period Tr used to generate the actuator trajectory. If the control period Ta is greater than the reference period Tr (YES in step S220), the first control unit 111 proceeds to step S240, where it deletes the reference command value Cr for each reference period Tr in the actuator trajectory so as to correspond to the control period Ta, and generates (determines) a position command value (transmission command value Cs) to be transmitted to the target actuator. In other words, the first control unit 111 deletes the reference command values ​​Cr generated in step S120 of FIG. 4 that do not correspond to the control period Ta, and sets the reference command value Cr corresponding to the control period Ta as the transmission command value Cs. The processing of step S240 also serves as a process of reducing the reference command value in the actuator trajectory.

[0030] FIG. 6 is an image diagram of the transmission command value Cs generated in step S240. In FIG. 6, a portion of the actuator trajectory from the start position S to the target position G is schematically represented by a solid line P. The solid line P also shows a reference command value Cr and a transmission command value Cs. The reference command value Cr and the transmission command value Cs are position command values ​​having time data, and the notation (t, t+1, t+2, ...) in parentheses following the command values ​​Cr and Cs indicates the time data included in the command values ​​Cr and Cs. This also applies to the following figures. In the example shown in FIG. 6, the control period Ta of the actuator is twice the reference period Tr; for example, the control period Ta is 2 msec (millseconds) and the reference period Tr is 1 msec. Because the control period Ta is longer than the reference period Tr (FIG. 5, step S220, YES), the first control unit 111 omits the reference command values ​​Cr that do not match the control period Ta and sets the reference command value Cr corresponding to the control period Ta as the transmission command value Cs (FIG. 5, step S240). In the example shown in FIG. 6, among the reference command values ​​Cr(t), Cr(t+1), Cr(t+2), Cr(t+3), and Cr(t+4), the reference command values ​​Cr(t), Cr(t+2), and Cr(t+4) do not match the control period Ta, while the reference command values ​​Cr(t+1) and Cr(t+3) match the control period Ta. Therefore, the first control unit 111 skips the reference command values ​​Cr(t), Cr(t+2), and Cr(t+4) and determines the reference command values ​​Cr(t+1) and Cr(t+3) as the transmission command values ​​Cs.

[0031] 5, if the result of step S220 is negative, i.e., if the control period Ta is equal to or less than the reference period Tr, the first control unit 111 proceeds to step S230 and determines whether the control period Ta is shorter than the reference period Tr. If the result of step S230 is negative, the first control unit 111 determines whether the control period Ta is shorter than the reference period Tr. If the result of step S230 is negative, the first control unit 111 proceeds to step S260 and applies the reference command value Cr to the transmission command value Cs.

[0032] On the other hand, if the reference period Tr is smaller than the control period Ta (step S230, YES), the first control unit 111 proceeds to step S250, where it interpolates between two consecutive reference command values ​​Cr in the actuator trajectory so as to correspond to the control period Ta, thereby generating a transmission command value Cs. In this embodiment, the interpolation is linear. In other embodiments, the interpolation may be quadratic or cubic. This also applies to the interpolation mentioned in the following embodiments. The processing of step S250 is also an interpolation processing in which, in the actuator trajectory, a position command value at a time corresponding to the control period Ta is interpolated using a reference command value Cr having time data immediately before the control period Ta and a reference command value having time data immediately after the control period Ta.

[0033] FIG. 7 is an illustration of the transmission command value Cs generated in step S250. Similar to FIG. 6 , FIG. 7 shows a portion of the actuator trajectory (solid line P) from the start position S to the target position G, the reference command value Cr, and the transmission command value Cs. In the example shown in FIG. 7 , the control period Ta of the actuator is half the reference period Tr. For example, the control period Ta is 0.5 msec, and the reference period Tr is 1 msec. Because the control period Ta is shorter than the reference period Tr ( FIG. 5 , step S230, YES), the first control unit 111 uses consecutive reference command values ​​among the reference command values ​​Cr for each reference period Tr to interpolate a position command value between two consecutive reference command values, thereby generating the transmission command value Cs (step S250). In the example shown in FIG. 7 , for example, two consecutive reference command values ​​Cr(t) and Cr(t+1) among the reference command values ​​Cr(t), Cr(t+1), Cr(t+2), Cr(t+3), and Cr(t+4) are used to generate a command value (transmission command value) Cs(t+0.5) between the two reference command values ​​Cr(t) and Cr(t+1). The command value Cs(t+0.5) is also an interpolated command value. In this way, the first control unit 111 interpolates the position command value Cs at a time when the reference command value Cr is not generated and corresponds to the control period Ta using the consecutive reference command values ​​Cr and Cr, thereby generating the transmission command values ​​Cs(t), Cs(t+0.5), and Cs(t+1).

[0034] After determining (generating) transmission command values ​​Cs for all actuators, the first control unit 111 transmits the determined transmission command values ​​Cs to each actuator. In this embodiment, the first control unit 111 transmits the transmission command values ​​Cs to the first actuator 32 via the second control unit 112. The second control unit 112 converts a digital signal indicating the transmission command value Cs determined by the first control unit 111 into a current value and outputs it to the first actuator 32. The first control unit 111 transmits the transmission command value Cs to the second actuator 42 via the amplifier device 50. The first control unit 111 transmits a digital signal indicating the transmission command value Cs for the second actuator 42 to the amplifier device 50, and the amplifier device 50 converts the digital signal into a current value and outputs it to the second actuator 42. In this manner, the synchronization control process is performed.

[0035] According to the first embodiment described above, the first control unit 111 acquires first and second characteristics, including limitations on the actuator's speed, acceleration, deceleration, etc., and generates an actuator trajectory that can be reproduced even by an actuator with the strictest limitations. Each actuator trajectory is based on a reference command value Cr, which is a position command value for each reference period Tr. The reference period Tr is common to all actuators. The first control unit 111 uses the reference command value Cr to determine a transmission command value Cs, which is a position command value for each control period Ta of the actuator. Therefore, according to this embodiment, the control period Ta of the actuator can be maintained compared to a configuration in which the transmission command value for each actuator is generated based on the longest control period Ta among the control periods Ta of the multiple actuators. This prevents a loss of actuator operation accuracy. As a result, for example, it is possible to synchronize the operation of all multiple actuators while causing an actuator with a short control period Ta to perform an operation in a constricted section, such as inside the container 202 in FIG. 1 . Furthermore, since multiple actuators can be synchronously controlled regardless of the control period Ta, the degree of freedom of the actuators applied to the robot 20 is improved.

[0036] Furthermore, when the control period Ta of an actuator is longer than the reference period Tr, the first control unit 111 omits the reference command value Cr that does not correspond to the control period Ta and sets the reference command value Cr that corresponds to the control period Ta as the transmission command value Cs. Furthermore, when the control period Ta is shorter (shorter) than the reference period Tr, the first control unit 111 uses two consecutive reference command values ​​Cr to interpolate a position command value between the two reference command values ​​Cr so as to correspond to the control period Ta, thereby generating the transmission command value Cs. In this way, the same reference period Tr is used for the multiple actuators 32, 42 with different control periods Ta, and the transmission command value Cs is generated based on the reference command value Cr for each reference period Tr, thereby suppressing synchronization errors between the actuators.

[0037] Second Embodiment In the transmission command value determination process ( FIG. 5 ) described in the first embodiment, the first control unit 111 acquires the initially set first period T1f and second period T2f as the control period Ta of the actuators in step S200. This control period Ta may vary. Variation in the control period Ta may occur due to variations in signal transmission and reception in the control device 100, etc. Even in such a case, the control device 100 can synchronize the operation of each actuator in accordance with the variation in the control period Ta. In the second embodiment, a synchronization control process when variation in the control period Ta occurs will be described.

[0038] FIG. 8 is a flowchart showing the transmission command value determination process when the control period fluctuates. While executing steps S210 to S260 in the transmission command value determination process shown in FIG. 5 to transmit the transmission command value Cs, the first control unit 111 further determines whether there is a fluctuation in the control period Ta of the target actuator (step S270 in FIG. 8). In this embodiment, the first control unit 111 sequentially acquires a first signal corresponding to the reception of the transmission command value Cs in the actuators 32, 42 from the actuators 32, 42 or devices associated with the actuators 32, 42. The first signal is, for example, a signal that requests the first control unit 111 to transmit the next transmission command value Cs after the second control unit 112 (servo control unit) has output a signal corresponding to the transmission command value Cs to the first actuator 32. The first signal is, for example, a signal that the amplifier device 50, which outputs to the second actuator 42, sends to the first control unit 111 to transmit the next transmission command value Cs after outputting to the second actuator 42. The first control unit 111 determines whether or not there is a fluctuation in the control period Ta of the target actuator from the acquisition interval of the first signal. If there is no fluctuation in the control period Ta (step S270, NO), the first control unit 111 continues to transmit the transmission command value Cs determined in steps S240 to S260 of FIG. 5 to the actuators 32, 42.

[0039] If there is a variation in the control period Ta (FIG. 8, step S270, YES), the first control unit 111 proceeds to step S280 and generates a transmission command value Cs corresponding to the variation in the control period Ta. In this embodiment, the first control unit 111 stores the previous transmission time of the transmission command value Cs in the memory 120. The first control unit 111 calculates the scheduled transmission time from the previous transmission time and the acquisition interval of the first signal. The scheduled transmission time is the time at which the transmission command value Cs is transmitted to the actuator next after the previous transmission time. The first control unit 111 interpolates the transmission command value Csn at the scheduled transmission time using the ratio of the reference command value Cr having time data before the scheduled transmission time to the reference command value having time data after the scheduled transmission time.

[0040] FIG. 9 is an illustration of the transmission command value Cs generated in step S270. FIG. 9 shows a portion of the actuator trajectory (solid line P) from the start position S to the target position G, the reference command value Cr, the transmission command value Cs, and the transmission interval D of the transmission command value Cs. The transmission interval D is calculated, for example, using the previous transmission time and the acquisition interval of the first signal. The transmission interval D is also the interval from the previous transmission time to the scheduled transmission time. In the example shown in FIG. 9, the reference command values ​​Cr(t-1), Cr(t), Cr(t+1), Cr(t+2), and Cr(t+3) are generated with a reference period Tr of 1.0 msec ( FIG. 3 , step S100; FIG. 4 , step S120). After the transmission command values ​​Cs(t-1) and Cs(t) are transmitted to the actuator (steps S210 to S260), the control period Ta fluctuates (step S270, YES). Therefore, the first control unit 111 calculates the next scheduled transmission time (t+1.5) using, for example, the previous transmission time (t) and the acquisition interval of the first signal (step S280). For example, the first control unit 111 identifies, on the actuator trajectory, a reference command value Cr(t+1) having time data immediately before the scheduled transmission time (t+1.5) and a reference command value Cr(t+2) having time data immediately after the scheduled transmission time (t+1.5), and linearly interpolates the transmission command value Csn(Cs(t+1.5)) at the scheduled transmission time (t+1.5) based on these command values. Similarly, the first control unit 111 calculates the next scheduled transmission time (t+2.8) using the transmission time of the transmission command value Cs(t+1.5), which is the previous transmission time, and the first signal acquired for the transmission of the transmission command value Cs(t+1.5). The first control unit 111 identifies a reference command value Cr(t+2) having time data immediately before the scheduled transmission time (t+2.8) and a reference command value Cr(t+3) having time data immediately after the scheduled transmission time (t+2.8), and performs linear interpolation of the transmission command value Csn(Cs(t+2.8)) at the scheduled transmission time (t+2.8) based on these command values.

[0041] 8, after the first control unit 111 transmits the interpolated transmission command value Csn to the actuator in step S280, it determines in step S290 whether the actuator has reached the target position G of the actuator trajectory. If the actuator has not reached the target position G (step S290, NO), the process returns to step S270 and the fluctuation of the control period Ta is monitored. If the actuator has reached the target position (step S290, YES), the process ends.

[0042] According to this embodiment, when the control period Ta of the actuator fluctuates, the first control unit 111 uses the reference command value Cr to generate a position command value (transmission command value Cs) that matches the fluctuated control period, so that even if the control period Ta fluctuates due to some factor, synchronization loss of the multiple actuators 32, 42 can be suppressed.

[0043] Furthermore, since the first control unit 111 is configured to sequentially acquire the first signal corresponding to the reception of the transmission command value Cs at the actuators 32, 42, the fluctuation of the control period Ta can be determined using the acquisition interval of the first signal.

[0044] Third Embodiment The control device 100 of the first and second embodiments is further configured to stop the actuators while synchronously operating them when a stop instruction is given during execution of the synchronous operation process. The stop instruction is an instruction to bring all the actuators to an emergency stop regardless of whether the hand 40 has reached the target position G. The synchronous operation process when a stop instruction is given will be described below.

[0045] 10 and 11 are flowcharts illustrating the synchronization control process when a stop command is issued. If the first control unit 111 receives a stop command, for example, via the input device 60, during the synchronization control process (step S300, YES), the first control unit 111 refers to the memory 120 and calculates the operation stop time td using the characteristics of each actuator 32 (step S302). The operation stop time td is the stop time of the actuator that takes the longest time to stop, assuming that each actuator operates at its maximum deceleration after the stop command is issued. The time td may be determined by the actuator with the smallest maximum deceleration. The first control unit 111 calculates the stop time from the time the stop command is issued, assuming that the actuators 32, 42 stop at their respective maximum decelerations, using the maximum decelerations included in the characteristics of each actuator. The first control unit 111 determines the time at which the longest stop time has elapsed since the reference time when the stop command was issued, as the operation stop time td of all actuators, i.e., the entire robot 20.

[0046] Next, in step S304, the first control unit 111 generates an emergency command value Ce for each actuator using the operation stop time td and the reference command value Cr. The emergency command value Ce is a position command value for maintaining the actuator trajectory generated in step S100 (FIGS. 3 and 4) and stopping the actuator at time td. In step S304, the first control unit 111 monotonically decreases the progress amount so that the progress amount becomes zero at time td. The progress amount is the amount of movement between each position command value relative to the amount of movement during the period from time t0 when the stop command is issued to operation stop time td. The progress amount is the amount of progress of the actuator per unit time in the actuator trajectory, and is the amount of trajectory reproduction by the actuator. The degree of decrease in the progress amount is the same for all actuators. The monotonic decrease is a monotonic decrease in a broad sense. The emergency command value Ce is a position command value obtained when the reproduction speed of the actuator trajectory is decreased at a deceleration that can be achieved by all actuators.

[0047] FIG. 12 is an illustration of the emergency command value Ce generated in step S304. FIG. 12 shows a solid line P, a reference command value Cr, and an emergency command value Ce. In the example shown in FIG. 12, reference command values ​​Cr(t), Cr(t+1), Cr(t+2), Cr(t+3), and Cr(t+4) are generated with a reference period Tr of 1.0 msec (FIG. 3, step S100; FIG. 4, step S120). An emergency stop command is issued at time (t) (FIG. 9, step S300, YES). Therefore, the first control unit 111 references the memory 120 and determines the operation stop time td at the maximum deceleration using the maximum deceleration of each actuator (FIG. 9, step S302). In FIG. 12, the operation stop time td is time (t+8). The first control unit 111 generates the emergency command value Ce by reducing the amount of progress of the reference command value Cr on the actuator trajectory toward the stop time td ( FIG. 10 , step S304). In the example shown in FIG. 12 , the amount of progress gradually decreases from time (t+1) and reaches zero at time (t+8). The emergency command value Ce can be generated, for example, by applying the amount of progress at each time to the reference command value Cr on the actuator trajectory and performing interpolation.

[0048] After generating the emergency command value Ce, the first control unit 111 proceeds to step S310 in Fig. 11 to execute a process for determining a transmission command value when a stop instruction is issued. The transmission command value determination process shown in Fig. 11 differs from the transmission command value determination process shown in Fig. 5 in that the emergency command value Ce is used instead of the reference command value Cr, but is otherwise similar. The processes from step S310 to step S330 correspond to the processes from step S210 to step S360 in Fig. 5.

[0049] In this way, the transmission command value Cs when a stop command is issued is determined and transmitted to each actuator 32, 42, whereby each actuator 32, 42 reduces its progress without deviating from the actuator trajectory and stops at time td.

[0050] According to this embodiment, the first control unit 111 generates an emergency command value Ce for each actuator by monotonically decreasing the progress amount of the actuator so that the progress amount of the actuator becomes zero at the operation stop time td, and generates a transmission command value Cs using the emergency command value Ce. Furthermore, the degree of decrease in the progress amount is the same for all actuators 32, 42. Therefore, according to this embodiment, all actuators 32, 42 can be stopped at a deceleration that can be achieved by all actuators 32, 42. Furthermore, the actuators 32, 42 can be appropriately decelerated and stopped while suppressing synchronization loss between the actuators 32, 42.

[0051] FIG. 13 is a diagram illustrating the relationship between time and the progress amount. FIG. 13 illustrates an example of a decrease in the progress amount. The first control unit 111 may linearly decrease the progress amount from time t0 when the stop instruction is issued to operation stop time td, using the relationship of the dashed line L1. Alternatively, the first control unit 111 may (i) decrease the rate of decrease of the progress amount from time t0 when the stop instruction is issued to a first time ta immediately thereafter, (ii) increase the rate of decrease of the progress amount from the first time ta to a second time tb immediately before operation stop time td, and (iii) decrease the rate of decrease of the progress amount again from the second time tb to operation stop time td, as illustrated by the solid line curve L2. As shown by curve L2, by making the rate of decrease in the amount of progress from time t0 when the stop command is issued to the first time ta immediately thereafter, and from the second time tb immediately before the operation stop time td to the operation stop time td smaller than the rate of decrease in the amount of progress from the first time ta to the second time tb, the actuators are prevented from suddenly decelerating immediately after the stop command is issued or immediately before the stop time td, thereby making it possible to more smoothly stop the multiple actuators 32, 42.

[0052] Other Embodiments In the above embodiment, the control system 10 includes a single control device 100 that functions as the first control unit 111 that executes the synchronization control process and the second control unit 112 that controls the robot arm 30. The amplifier device 50 that controls the hand 40 is provided separately from the control device 100. However, the configuration of the control device that executes the synchronization control process and the control device that controls the drive of the actuators in the control system 10 is not limited to the above embodiment, and various configurations are applicable. For example, as shown in FIG. 14 , the control system 10a may include a control device 100a that has the functionality of the first control unit 111 and a separate second control device 140a that has the functionality of the second control unit 112. Alternatively, the robot arm 30 may have the functionality of the second control unit 112, and the hand 40 may have the functionality of the amplifier device 50.

[0053] The transmission command value determination process of the above embodiment can also be applied when the control period Ta is not an integer multiple of the reference period Tr. For example, the first control unit 111 may proceed to step S240 ( FIG. 6 ) even when the control period Ta is greater than 1 but is not an integer multiple of the reference period Tr, such as 1.5 or 3.2 times. In step S240, the first control unit 111 may (i) omit the reference command value Cr that does not correspond to the control period Ta and set the reference command value Cr that corresponds to the control period Ta as the transmission command value Cs. In addition, the first control unit 111 may (ii) interpolate the position command value at a time corresponding to the control period Ta, when the reference command value Cr has not been generated, using the reference command value Cr having time data before that time and the reference command value Cr having time data after that time, to set the transmission command value Cs.

[0054] The control device 100 (first control unit 111, second control unit 112) may increase the control period Ta of at least one of the multiple actuators 32, 42 when a predetermined condition is met, such as when the load on the control device 100 exceeds a predetermined threshold. Preferably, the at least one actuator is an actuator whose trajectory accuracy is lower than that of the other actuators. The first control unit 111 may execute the synchronization control process shown in FIG. 8 using the increased control period Ta. In this case, for example, the memory 120 may store, in advance, the relationship between the load threshold of the control device 100 and the control period Ta, as well as information on the actuators whose control period Ta is to be increased, which have been determined through experiments or simulations. The first control unit 111 may then make a positive determination in step S270 of FIG. 8 when the load reaches the threshold. The load on the control device 100 may be the computational load of the CPU 110 or the processing load of the interface circuit 130. This configuration allows the control device 100 to execute other processes required by the control device 100 while executing the synchronization control process.

[0055] In the above embodiment, the multiple first actuators 32 of the robot arm 30 are configured to operate at the same first period T1f, and the multiple second actuators 42 of the hand 40 are configured to operate at the same second period T2f. In contrast, for example, the multiple first actuators 32 of the robot arm 30 may be configured to operate at different control periods Ta, or the multiple second actuators 42 of the hand 40 may be configured to operate at different control periods Ta. The first control unit 111 can synchronously control the entire robot arm 30 by, for example, acquiring the control period Ta of the target actuator in the robot arm 30 and executing the transmission command value determination process. Furthermore, the multiple first actuators 32 may each have different characteristics.

[0056] In the above embodiment, the robot arm 30 and the hand 40 are shown as actuators included in the control system 10. However, the actuator may be any machine or mechanical element that converts electrical signals output by a computer into physical movement. For example, various actuators such as a belt conveyor or a moving device that moves the robot arm 30 can be applied.

[0057] Additionally, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0058] The present disclosure is not limited to the above-described embodiments and can be realized in various forms without departing from the spirit thereof. For example, the present disclosure can also be realized in the following aspects. The technical features in the above embodiments corresponding to the technical features in each aspect described below can be appropriately replaced or combined to solve some or all of the problems of the present disclosure or to achieve some or all of the effects of the present disclosure. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0059] <1> According to a first aspect of the present disclosure, there is provided a control device for controlling multiple actuators operating at different control periods. The control device includes a control unit that synchronizes the operation of the multiple actuators. The control unit generates, for each actuator included in the multiple actuators, a reference command value that is information on a position command value for each reference period as an actuator trajectory that is a trajectory of the actuator. The reference period is a period commonly used by the multiple actuators. The control unit uses the reference command value for each actuator to determine a transmission command value that is a position command value for the actuator for each control period, and transmits the determined transmission command value to the actuator. When the control period of the actuator is different from the reference period, the control unit omits the reference command value that does not correspond to the control period, and sets the reference command value corresponding to the control period as the transmission command value. According to this aspect, the transmission command value of each actuator is based on the reference command value generated for each reference period commonly used by the multiple actuators. Therefore, synchronization deviation between multiple actuators with different control periods is suppressed. Furthermore, when the control period differs from the reference period, the control unit omits the reference command value that does not correspond to the control period and sets the reference command value that corresponds to the control period as the transmission command value. This allows for rational generation of transmission command values. Furthermore, compared to a configuration in which transmission command values ​​for each actuator are generated according to the largest (longest) control period among the control periods of the multiple actuators in order to synchronously control the multiple actuators, this configuration can prevent performance impairment of the actuators. Furthermore, it can improve the degree of freedom of the actuators used in the multiple actuators. In this embodiment, synchronous control is control that suppresses synchronization deviation. Synchronization deviation includes deviations in the timing of start and stop of the multiple actuators. Synchronization deviation may further include deviations in the timing of acceleration and deceleration of the multiple actuators.

[0060] <2> In the above aspect, the control unit may acquire actuator limitations, including velocity, acceleration, and deceleration, for each of the plurality of actuators when generating the actuator trajectories. The control unit may further generate the actuator trajectory that can be reproduced for the actuator with the strictest limitation. According to this aspect, the control unit generates actuator trajectories for all actuators taking into account limitations, including velocity, acceleration, and deceleration, thereby suppressing synchronization loss among a plurality of actuators with different limitations.

[0061] <3> In the above-described embodiment, when the control period of the actuator is shorter than the reference period, the control unit may generate the transmission command value by interpolating between two consecutive reference command values ​​in the actuator trajectory to correspond to the control period. According to this embodiment, for a plurality of actuators having different control periods, the transmission command value is generated using a reference command value for the same reference period, thereby suppressing synchronization loss among the actuators. Furthermore, when the control period is shorter than the reference period, the control unit generates the transmission command value by interpolating between two consecutive reference command values ​​to correspond to the control period, thereby enabling rational generation of the transmission command value. In this embodiment, interpolating between two consecutive reference command values ​​to correspond to the control period may mean that the control unit generates a position command value at a third time corresponding to the control period using the reference command value having time data before the third time and the reference command value having time data after the third time.

[0062] <4> In the above aspect, when the control period varies, the control unit may use the reference command value as the transmission command value to generate a position command value corresponding to the varied control period. According to this aspect, even when the control period varies due to some factor, it is possible to suppress synchronization loss among the multiple actuators.

[0063] <5> In the above aspect, the control unit may acquire, for each actuator included in the plurality of actuators, a first signal corresponding to reception of the transmission command value at the actuator when the transmission command value is transmitted to the actuator. The control unit may determine that the control period has fluctuated when an interval at which the first signal is acquired differs from the control period. According to this aspect, fluctuation in the control period can be easily determined using the interval at which the first signal is acquired.

[0064] <6> In the above aspect, the control device may include a memory unit that stores a previous transmission time when the control unit last transmitted the transmission command value to the actuator. The control unit may calculate a scheduled transmission time at which the transmission command value will be transmitted to the actuator after the previous transmission time, based on the previous transmission time stored in the memory unit and the acquisition interval of the first signal. The control unit may generate the transmission command value at the scheduled transmission time using the reference command value having time data before the scheduled transmission time and the reference command value having time data after the scheduled transmission time. According to this aspect, the control unit calculates the next scheduled transmission time from the previous transmission time and the acquisition interval of the first signal, and generates (interpolates) a position command value at the scheduled transmission time using reference command values ​​before and after the scheduled transmission time. Therefore, according to this aspect, synchronization loss among multiple actuators can be suppressed even if the control period dynamically changes.

[0065] <7> In the above aspect, the control unit may be configured to acquire a load on the control device through processing executed by the control device. When the load is equal to or greater than a predetermined threshold, the control unit may lengthen the control period for at least one of the plurality of actuators. According to this aspect, the control device can perform other processing required by the control device while suppressing synchronization loss among the plurality of actuators.

[0066] <8> In the above aspect, when the control unit receives a stop instruction for the multiple actuators, the control unit may calculate, for each of the multiple actuators, a stop time for the actuator that would occur if the actuator were stopped at the maximum deceleration after receiving the stop instruction, using the maximum deceleration of the actuator. The control unit may determine the longest stop time among the stop times for the multiple actuators as the operation stop time for stopping the operation of the multiple actuators. The control unit may generate, as a position command value from receiving the stop instruction to the operation stop time, an emergency command value by monotonically decreasing the progress amount of the actuator included in the reference command value so that the progress amount becomes zero at the operation stop time. The control unit may determine the transmission command value using the emergency command value. According to this aspect, the multiple actuators can be stopped at decelerations that can be achieved by all of the multiple actuators. Furthermore, the control unit generates, as a transmission command value, a position command value by monotonically decreasing the progress amount of the actuator so that the progress amount of the actuator becomes zero at the operation stop time. The degree of decrease in the amount of progress is the same for all actuators, so that the multiple actuators can be appropriately decelerated and stopped while suppressing misalignment of the multiple actuators.

[0067] <9> In the above aspect, the control unit may set a smaller degree of decrease in the progress amount from the stop instruction to a first time point and from a second time point that is after the first time point but before the operation stop time to the operation stop time than a smaller degree of decrease in the progress amount from the first time point to the second time point. This aspect prevents the actuators from suddenly decelerating immediately after the stop instruction or immediately before the operation stop time. This makes it possible to more smoothly stop the multiple actuators.

[0068] <10> According to a second aspect of the present disclosure, there is provided a control system including a plurality of actuators operating at different control periods and a control device that controls the operation of the plurality of actuators. The control device includes a control unit that synchronizes the operation of the plurality of actuators. The control unit generates, for each actuator included in the plurality of actuators, a reference command value that is information on a position command value for each predetermined reference period that is used commonly by the plurality of actuators as an actuator trajectory that is a trajectory of the actuator. The control unit uses the reference command value to determine a transmission command value that is a position command value for each control period of the actuator. The control unit transmits the determined transmission command value to the actuator. When the control period of the actuator is different from the reference period, the control unit omits the reference command value that does not correspond to the control period and sets the reference command value that corresponds to the control period as the transmission command value.

[0069] <11> In the above aspect, the plurality of actuators may include a robot arm and a robot hand attached to the robot arm. According to this aspect, it is possible to suppress misalignment between the robot arm and the robot hand.

[0070] <12> According to a third aspect of the present disclosure, there is provided a control method for synchronizing the operation of multiple actuators operating at different control periods. The control method includes a process of generating, for each actuator included in the multiple actuators, a reference command value that is information on a position command value for each predetermined reference period that is used commonly by the multiple actuators as an actuator trajectory that is a trajectory of the actuator. The control method includes a process of determining, for each actuator, a transmission command value that is a position command value for each control period of the actuator using the reference command value. The control method includes a process of transmitting, for each actuator, the determined transmission command value to the actuator. In the process of determining the transmission command value, if the control period of the actuator is different from the reference period, the reference command value that does not correspond to the control period is omitted, and the reference command value that corresponds to the control period is set as the transmission command value.

[0071] <13> According to a fourth aspect of the present disclosure, there is provided a program for synchronizing the operations of multiple actuators operating at different control periods. The program causes a computer to: generate, for each actuator included in the multiple actuators, a reference command value that is information on a position command value for each predetermined reference period used commonly by the multiple actuators as an actuator trajectory that is a trajectory of the actuator; determine a transmission command value that is a position command value for each control period of the actuator using the reference command value; and transmit the determined transmission command value to the actuator. The program further causes the computer to: if the control period of the actuator is different from the reference period, omit the reference command value that does not correspond to the control period, and set the reference command value that corresponds to the control period as the transmission command value.

[0072] The present disclosure may be realized in various forms other than those described above, such as a non-transitory storage medium on which a computer program for implementing at least one function of the control device 100, the first control unit 111, and the second control unit 112 is recorded.

[0073] 10, 10a: control system, 20: robot, 30: robot arm, 31: arm tip, 32: first actuator, 33: first motor, 40: hand, 41: tip, 42: second actuator, 43: second motor, 50: amplifier device, 60: input device, 100: control device, 100a: control device, 110: CPU, 111: first control unit, 112: second control unit, 120: memory, 130: interface circuit, 140a: second control device, 201: container, 202: container, L: link, P1: program, P2: program, Ce: emergency command value, Cr: reference command value, Cs: transmission command value, Csn: transmission command value at scheduled transmission time, S: start position, G: target position, P: actuator trajectory, D: transmission interval, T1f: first period, T2f: second period, Ta: control period, Tr: reference period, L1: straight line showing the relationship between progress amount and time, L2: curved line showing the relationship between progress amount and time, W: work, t0: stop command time, ta: first time, tb: second time, td: operation stop time

Claims

1. A control device for controlling a plurality of actuators operating in different control cycles, comprising a control unit for synchronizing the operations of the plurality of actuators, wherein the control unit, for each actuator included in the plurality of actuators, generates a reference command value, which is information on position command values for each predetermined reference cycle commonly used by the plurality of actuators, as an actuator trajectory of the actuator; determines a transmission command value, which is a position command value for each control cycle of the actuator, using the reference command value; transmits the determined transmission command value to the actuator; and when the control cycle of the actuator is different from the reference cycle, the control unit omits the reference command value not corresponding to the control cycle and uses the reference command value corresponding to the control cycle as the transmission command value.

2. The control device according to claim 1, wherein in generating the actuator trajectory, the control unit acquires restrictions of the actuator including speed, acceleration, and deceleration for each actuator included in the plurality of actuators, and generates an actuator trajectory reproducible in the actuator with the most stringent restrictions.

3. The control device according to claim 1, wherein when the control cycle of the actuator is shorter than the reference cycle, the control unit generates the transmission command value by interpolating between two consecutive reference command values corresponding to the control cycle in the actuator trajectory.

4. The control device according to claim 1, wherein when the control cycle varies, the control unit generates a position command value corresponding to the varied control cycle using the reference command value as the transmission command value.

5. The control device according to claim 4, wherein for each actuator included in the plurality of actuators, the control unit acquires a first signal corresponding to the reception of the transmission command value in the actuator when the transmission command value is transmitted to the actuator, and determines that the control cycle varies when the interval for acquiring the first signal is different from the control cycle.

6. The control device according to claim 5, further comprising a storage unit that stores the previous transmission time at which the control unit last transmitted the transmission command value to the actuator, wherein the control unit calculates a scheduled transmission time at which to transmit the transmission command value to the actuator next after the previous transmission time based on the previous transmission time stored in the storage unit and the acquisition interval of the first signal, and generates the transmission command value at the scheduled transmission time using the reference command value having time data before the scheduled transmission time and the reference command value having time data after the scheduled transmission time.

7. The control device according to claim 3, wherein the control unit is configured to acquire a load on the control device by a process executed by the control device, and when the load is equal to or greater than a predetermined threshold value, lengthen the control cycle for at least one of the plurality of actuators.

8. The control device according to claim 1, wherein when the control unit acquires a stop instruction for the plurality of actuators, for each actuator among the plurality of actuators, calculates a stop time of the actuator when the actuator stops at the maximum deceleration rate after acquiring the stop instruction using the maximum deceleration rate of the actuator, determines the longest stop time among the stop times of the plurality of actuators as an operation stop time for stopping the operation of the plurality of actuators, generates an emergency command value in which the progress amount of the actuator included in the reference command value is monotonically decreased so as to be zero at the operation stop time as a position command value from the time of acquiring the stop instruction to the operation stop time, and determines the transmission command value using the emergency command value.

9. The control device according to claim 8, wherein the control unit makes the degree of decrease in the progress amount from the time of acquiring the stop instruction to a first time and from a second time after the first time and before the operation stop time to the operation stop time smaller than the degree of decrease in the progress amount from the first time to the second time.

10. A control system comprising a plurality of actuators operating at different control periods and a control device for controlling the operation of the plurality of actuators, wherein the control device includes a control unit for synchronizing the operation of the plurality of actuators, and the control unit: for each actuator included in the plurality of actuators, generates a reference command value which is information on position command values for each predetermined reference period commonly used for the plurality of actuators as an actuator trajectory which is a trajectory of the actuator; determines a transmission command value which is a position command value for each control period of the actuator using the reference command value; transmits the determined transmission command value to the actuator; and when the control period of the actuator is different from the reference period, the control unit omits the reference command value not corresponding to the control period and sets the reference command value corresponding to the control period as the transmission command value. Control system.

11. The control system according to claim 10, wherein the plurality of actuators include a robot arm and a robot hand attached to the robot arm. Control system.

12. A control method for synchronizing the operations of a plurality of actuators operating at different control periods, wherein for each actuator included in the plurality of actuators: generates a reference command value which is information on position command values for each predetermined reference period commonly used for the plurality of actuators as an actuator trajectory which is a trajectory of the actuator; determines a transmission command value which is a position command value for each control period of the actuator using the reference command value; transmits the determined transmission command value to the actuator; and in determining the transmission command value, when the control period of the actuator is different from the reference period, the reference command value not corresponding to the control period is omitted and the reference command value corresponding to the control period is set as the transmission command value. Control method.

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