STEERING

Abstract

Control (1) for a drive mechanism (2) which is driven by a plurality of motors (13, 23), the control comprising according to the motors (13, 23): a position command calculation unit (10) that calculates a position command value to drive the drive mechanism (2); a position detection unit (14, 24) that detects a position of the motor (13, 23); a speed command calculation unit (11, 21) that calculates a speed command value based on a position error value determined from the position command value calculated by the position command calculation unit (10) and a position sensing value sensed by the position sensing unit (14, 24); a speed detection unit (15, 25) that calculates a speed detection value from the position detection value acquired by the position detection unit (14, 24); and a torque command calculation unit (12, 22) which calculates a torque command value from a velocity error value determined from the velocity command value calculated by the velocity command calculation unit (11, 21) and the velocity sensing value sensed by the velocity sensing unit (15, 25) by using at least one integral element, wherein the position command calculation unit (10) supplies the common position command value to each of the motors (13, 23), and wherein the torque command calculation unit (12, 22) switches between an individualization control, which provides for individual execution of an output of the integral element of the torque command calculation unit (12, 22) to each of the plurality of motors (13, 23), and a common control, which provides for sharing the output of the integral element of the torque command calculation unit (12, 22) to the plurality of motors (13, 23); where, if it is determined that the operating state is a transitional state, individualization control is carried out; if, on the other hand, it is determined that the operating state is a steady state, joint control is carried out; wherein, when the position command calculation unit (10) supplies the position command value specified as an abrupt acceleration / deceleration process, the operating state is determined as a transition state, so that the individualization control is carried out.

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to a control system for a drive mechanism that is driven by a plurality of motors. Related state of the art

[0002] Patent documents 1 to 3 disclose a technology in which an integrator is conventionally used in a control system for controlling a tandem mechanism that drives a drive mechanism such as a robot or a machine tool with multiple motors, in order to avoid mutual interference between the motors (servo motors).

[0003] Patent document 1 discloses a configuration in which, in a motor control system that performs tandem control to drive a driven element with a plurality of motors, a position control unit, a speed control unit, a current control unit, a current amplifier, a speed detector and another control device includes a common means for the speed integrator for sharing the integral value of an integral element in the speed control unit for each of the motors, wherein the same position command is input into the control system of the motors performing the tandem control, and in which substantially the same integral value of the integral element in the speed control unit is maintained by the common means of the speed integrator.

[0004] Patent document 2 discloses a machine tool control comprising a noise-free compensator for reducing the mutual interference of a pair of servomotors, wherein the noise-free compensator comprises: a torsional stiffness estimation block that estimates the torsional stiffness of a workpiece based on a difference value of position feedback values ​​acquired individually by the pair of servomotors and a torque command value for a torsional stiffness measurement supplied to the pair of servomotors to generate torsion on the workpiece;and a torque command value compensation block that estimates a torque command compensation value to compensate for the torque command value for the pair of servo motors, based on a difference value of speed feedback values ​​acquired individually from the pair of servo motors and the torsional stiffness estimated by the torsional stiffness estimation block.

[0005] Patent document 3 discloses a motor control system for controlling two motors as follows. A first speed control unit comprises an integrator that calculates an integral value of a speed error between a speed command value and a rotational speed, and a torque command value based on the speed error, a previously determined value, a proportional gain, and an integral gain. A second speed control unit comprises an integrator that calculates an integral value of a speed error between a speed command value and a rotational speed, and a torque command value based on the speed error, a previously determined value, a proportional gain, and an integral gain.An integral value selection unit selects one of the integral values ​​as a previously determined value according to a driven state of a main motor and a driven state of an auxiliary motor. JP 2003 - 189 657 A: Patent document 1: Japanese unexamined patent application, JP 2009 - 83 074 A: Patent document 2: Japanese unexamined patent application, JP 2015 - 23 708 A: Patent document 3: Japanese unexamined patent application, DE 602 10 734 T2 relates to a controller for regulating the drive of a moving component. WO 2009 / 083 031 A1 concerns a regulator. SUMMARY OF THE INVENTION

[0006] In a tandem mechanism, several motors are connected to a common drive mechanism. Connecting sections between the individual motors and the drive mechanism can exhibit different mechanical properties, even if they are structurally identical, for example, in their assembly and the position of their center of gravity. During transient response (positioning or immediately after the application of a disturbance), a significant difference between the motors can easily occur.

[0007] In patent document 1, an integrator is used in the speed control unit, and although a time constant circuit is employed to stabilize the transition, since the integral values ​​must be considered constant, there is room for improvement in actively absorbing differences in the mechanical properties between the tandems. In this respect, patent document 2, although an attempt is made to eliminate differences in transmission properties (torsional stiffness) not through an integrator but through gain planning and adaptive control, since a mechanism is assumed that is little affected by backlash caused by a retarder, it cannot be said that mechanical properties are directly absorbed.In patent document 3, although the integration is certainly divided at some point in time, and it is reasonable to modify the division of an integrator by means of an acceleration serving as an inertial force, initially in a transitional state such as an acceleration process, the division of the integration itself may lead to a reduction in controllability.

[0008] One object of the present invention is to provide a control system which, when controlling a drive mechanism driven by a plurality of motors, incorporates mechanical properties between the drive mechanism and the individual motors in order to achieve both the stability of a steady state and an improvement in the response in a transition state.

[0009] The task, therefore, is to solve the problems mentioned above.

[0010] The above problems are solved by the subject matter of the independent patent claim. Advantageous further developments are the subject matter of the dependent patent claim. (1) The present invention relates to a control (for example, a control 1, which will be described later) for a drive mechanism (for example, a drive mechanism 2, which will be described later) which is driven by a plurality of motors (e.g., motors 13 and 23, which will be described later) and comprises, according to the motors: a position command calculation unit (for example, a position command calculation unit 10, which will be described later) that calculates a position command value to drive the drive mechanism; a position sensing unit (for example, a position sensing unit 14, 24, which will be described later) that senses the position of the motor; a velocity command calculation unit (for example, a velocity command calculation unit 11, 21, which will be described later) that calculates a velocity command value based on a position error value determined from the position command value calculated by the position command calculation unit and a position sensing value sensed by the position sensing unit; a velocity sensing unit (for example, a velocity sensing unit 15, 25, which will be described later), which calculates a speed sensing value from the position sensing value acquired by the position sensing unit; and a torque command calculation unit (for example, a torque command calculation unit 12, 22, which are described later) which calculates a torque command value from a speed error value determined from the speed command value calculated by the speed command calculation unit and the speed sensing value acquired by the speed sensing unit by using at least one integral element, wherein the position command calculation unit supplies the common position command value to each of the motors,and wherein the torque command calculation unit switches between the individualization control for individually executing an output of the integral element of the torque command calculation unit to each of the plurality of motors and a common control for sharing the output of the integral element of the torque command calculation unit to the plurality of motors, according to an operating state of the drive mechanism. (2) If the control described in (1) determines that the operating state is a transitional state, individualization control is carried out, whereas if the operating state is determined to be a steady state, common control is carried out. (3) If, in the control described in (2), the position command calculation unit supplies the position command value which is specified as an abrupt acceleration / deceleration process, the operating state is preferably determined as a transition state so that the individualization control is carried out. (4) If, in the control described in (2) or (3), the position command calculation unit supplies the position command value specified as stop or constant speed operation, the operating state is determined to be a steady state so that the joint control is executed.

[0011] According to the control system of the present invention, it is possible, when controlling a drive mechanism driven by a plurality of motors, to absorb mechanical properties between the drive mechanism and the individual motors in order to achieve both the stability of a steady state and an improvement in the response in a transition state. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic view showing a configuration for performing tandem control in a controller according to an embodiment of the present invention; Fig. 2 is a block diagram of the tandem control in the control system of the present embodiment; Fig. Figure 3 is a schematic view showing an example where an integrator is divided in a comparative example so that individual motors are controlled; Fig. Figure 4 is a schematic view showing a control for selecting a case in which integrators are used jointly in the control of the present embodiment, or a case in which they are individualized; Fig. Figure 5 is a flowchart showing the first half of the total control flow at a drive mechanism performed by the control unit of the present embodiment; and Fig. Figure 6 is a flowchart showing the second half of the overall flow of the control of the drive mechanism performed by the control system of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] A preferred embodiment of the present invention is described below with reference to the drawings.

[0013] First, a device configuration is described in which a controller 1 of the present embodiment is used. Fig. Figure 1 is a schematic view showing a configuration for performing tandem control in the controller 1 according to the embodiment of the present invention. The device configuration with reference to Fig. 1 is an example, and the device configuration to be applied to control 1 is not based on the one in Fig. The example shown is limited to one.

[0014] The control unit 1 is designed to implement a tandem control system in which a drive mechanism 2 is driven by several (two) motors 13 and 23. The drive mechanism 2 is a robot, a machine tool, or the like, which is configured with a moving element 101 and mechanical parts 102 and 103 such as gears. A driving force is transmitted from motor 13 through mechanical part 102 to the moving element 101, and a driving force is transmitted from motor 23 through mechanical part 103 to the moving element 101.

[0015] The control system 1 of the present embodiment comprises a numerical control unit 3 and a motor control unit 4. The numerical control unit 3 is a CNC (Computerized Numerical Control) and performs various processing operations to control the drive mechanism 2. Based on a command from the numerical control 20, the motor control unit 4 performs current control of motor 13 through an amplifier 5 and current control of motor 23 through an amplifier 6. Motors 13 and 23 are servo motors, and the motor control unit 4 receives feedback signals to determine the position and speed of each motor 13 and 23.

[0016] Fig. Figure 2 is a block diagram of the tandem control in the control unit 1 of the present embodiment. As in Fig. As shown in Figure 2, the control unit 1 comprises a position command calculation unit 10, position detection units 14 and 24, velocity detection units 15 and 25, velocity command calculation units 11 and 21, and torque command calculation units 12 and 22.

[0017] The position command calculation unit 10, the position detection units 14 and 24, the velocity detection units 15 and 25, the velocity command calculation units 11 and 21, and the torque command calculation units 12 and 22 are implemented by hardware such as the numerical control unit 3, the motor control unit 4, and the motors 13 and 23. The configurations of these individual units in the controller 1 are not limited to either the numerical control unit 3 or the motor control unit 4, and the functions of the individual units can be achieved through the interaction of the numerical control unit 3 and the motor control unit 4, or the functions of the individual units can be achieved by an external device connected via a network.

[0018] The position command calculation unit 10 calculates a position command value based on a predetermined program to move the movable element 101 of the drive mechanism 2 to a predetermined position.

[0019] The position detection unit 14 detects the position (angle of rotation) of the motor 13, and the position detection unit 24 detects the position (angle of rotation) of the motor 23. The position detection units 14 and 24 of the present embodiment are each individually equipped with encoders for the motors 13 and 23.

[0020] The speed sensing unit 15 acquires a speed sensing value corresponding to motor 13 based on a position sensing value acquired by the position sensing unit 14, and the speed sensing unit 25 acquires a speed sensing value corresponding to motor 23 based on a position sensing value acquired by the position sensing unit 24.

[0021] The speed command calculation unit 11 calculates a speed command value based on the position command value input from the position command calculation unit 10 and the position sensing value acquired by the position sensing unit 14. Similarly, the speed command calculation unit 21 calculates a speed command value based on the position command value input from the position command calculation unit 10 and the position sensing value acquired by the position sensing unit 24. The speed command value is calculated by the P-controller taking a proportional element into account.The speed command value can be calculated, for example, by a PID controller taking into account a proportional element, an integral element, and a derivative element; and a suitable method for calculating the speed command value can be selected according to the circumstances.

[0022] The torque command calculation unit 12 calculates the torque command value for the motor 13 based on the speed command value calculated by the speed command calculation unit 11 and the speed detection value detected by the speed sensing unit 15. The torque command calculation unit 22 calculates the torque command value for the motor 23 based on the speed command value calculated by the speed command calculation unit 11, or the speed command value calculated by the speed command calculation unit 21 and the speed detection value detected by the speed sensing unit 25. The torque command value is calculated by the PID controller taking into account the proportional, integral, and derivative elements, or by the PI controller taking into account the proportional and integral elements.The torque command value is preferably calculated by control with at least the integral element, so that a stationary error in an internal model principle is set to zero.

[0023] In the present embodiment, the division and individualization of the integrators in the torque command calculation units 12 and 22, corresponding to the motors 13 and 23, are performed selectively based on an operating pattern and the transition thereto. Here, the selective control in the present embodiment is described using a conventional technology as a comparative example.

[0024] Fig. Figure 3 is a schematic view showing an example where an integrator in the comparison example is divided in such a way that individual motors are controlled. In a Fig. The state shown in Figure 3 is an example in which there is no motion command to move the movable element 101 of the drive mechanism 2, where position P-control is performed using the proportional element, and where velocity PI-control is performed using the proportional and integral elements. In a state where motors 13 and 23 are stationary without the motion command, after a long time, feedback fluctuations bring the state to a condition in which both (motors 13 and 23) repel each other due to the integral element of the velocity PI control.In the comparative example, the integrator used in the speed PI control corresponding to motor 13 and the integrator used in the speed PI control corresponding to motor 23 are shared, thus avoiding their rejection and maintaining stability. In a transitional state, which is easily influenced by a difference in the mechanical properties of motors 13 and 23, the accuracy of the control could be affected by sharing the integrators.

[0025] Therefore, in the present embodiment, processing is performed to select the shared use or individualization of the integrators, depending on whether the state is the transition state or the steady state. Fig. Figure 4 is a schematic view showing a control for selecting a case in which the integrators in control 1 of the present embodiment are shared, or a case in which they are individualized. As shown in Fig. As shown in Figure 4, the controller 1 performs the processing to switch between the shared use and the individualization of the integrators according to an operating state.

[0026] If the operating state of the drive mechanism 2 is the steady state, a path (1) is selected which leads to Fig. 4 is indicated by a continuous line, and an integrator (copy) common to the integrator in the torque command calculation unit 12 corresponding to the motor 13 is used to calculate the torque command value for the motor 23. The steady state here refers, for example, to a state in which the drive mechanism 2 is operated at a constant speed in a stop state or in a state in which no disturbance is generated.

[0027] If the operating state of the drive mechanism 2 is the transition state, a path (2) is selected which leads into Fig. 4 is indicated by a dashed line, and an integrator in the torque command calculation unit 22, corresponding to motor 23, is used; thus, a torque command value for motor 23 is calculated individually. The transition state here refers to a condition in which abrupt operation is performed, such as positioning immediately after the application of a disturbance or an acceleration / deceleration process that is easily influenced by the mechanical properties between motors 13 and 23. For example, a case in which a predetermined acceleration, a predetermined speed range, a predetermined load, a predetermined torque, or the like is exceeded can be defined as a transition state.Alternatively, the CNC program of the numerical control unit 3 is decoded, and based on the result, the steady state, the transition state, the other state, or the like can be determined.

[0028] The specific processing sequence for individualizing or dividing the integrators, performed by the controller 1 of the present embodiment, is described next. The flow of the first half, until the torque command values ​​for the motors 13 and 23 are calculated, is first described with reference to Fig. 5 described. Fig. Figure 5 is a flowchart showing the first half of the total control flow at the drive mechanism 2, which is carried out by the controller 1 of the present embodiment.

[0029] The position command calculation unit 10 calculates the position command value (step S101). The position sensing unit 14 senses the position sensing value of motor 13, and the position sensing unit 24 senses the position sensing value of motor 23 (step S102).

[0030] In motor 13, the speed command calculation unit 11 calculates the speed command value based on a position error value obtained from the position command value and the position sensing value, and in motor 23, the speed command calculation unit 21 calculates the speed command value based on a position error value obtained from the position command value and the position sensing value (step S103).

[0031] The speed sensing unit 15 calculates the speed sensing value of the motor 13 from the position sensing value of the position sensing unit 14, and the speed sensing unit 25 calculates the speed sensing value of the motor 23 from the position sensing value of the position sensing unit 24 (step S104).

[0032] On the side of motor 13, the torque command calculation unit 12 calculates the torque command value based on a speed error value obtained from the speed command value of the speed command calculation unit 11 and the speed sensing value of the speed sensing unit 15, and on the side of motor 23, the torque command calculation unit 22 calculates the torque command value based on a speed error value obtained from the speed command value of the speed command calculation unit 21 and the speed sensing value of the speed sensing unit 25 (step S105).

[0033] The flow of a second half, after the torque command values ​​for motors 13 and 23 have been calculated, will next be described with reference to Fig. 6 described. Fig.Figure 6 is a flowchart showing the second half of the overall flow of the control of the drive mechanism 2, which is carried out by the control 1 of the present embodiment.

[0034] The controller 1 determines whether the position command value indicates a steady state or not (step S106). As previously described, the steady state refers to the stop state or the state in which the drive mechanism 2 operates at a constant speed. Based on the position command value and the operating conditions, the controller 1 determines whether the state is a steady state or not. If the steady state is indicated in the determination of step S107, processing is performed to divide the output of the integral element of the torque command calculation units 12 and 22 in the motors 13 and 23 (step S107).

[0035] If no steady state is commanded in step S107, it is determined whether the position command value is in a transition state or not (step S108). As described previously, the transition state refers to the state in which the drive mechanism 2 is actuated by an abrupt operation such as an acceleration / deceleration operation, i.e., a state in which at least the steady state is not specified. The controller 1 determines whether the state is a transition state or not based on the position command value and the operating conditions.

[0036] If, during the determination of step S108, the position command value is in the transition state, the output of the integral elements of the torque command calculation units 12 and 22 is individualized such that the motor 13 is controlled by the torque command value calculated in the torque command calculation unit 12, and that the motor 23 is controlled by the torque command value calculated in the torque command calculation unit 22 (step S109).

[0037] If, in step S108, the position command value is not in a transition state via a time constant circuit, the output of the integral elements of the torque command calculation units 12 and 22 of motors 13 and 23 is shared (step S109). When the position command value, which indicates a transition state between the transition state and the steady state, is fed to the position command calculation unit 10, the sharing between motors 13 and 23 is performed over a given time period, while the output of the integral element of the torque command calculation unit 12 is delayed by the time constant circuit. Multiplication by a suitable time constant is performed to prevent the control amount from being discontinuous.

[0038] In the embodiment described above, the following effects are achieved. In particular, the control unit 1, according to the individual motors 13 and 23, comprises: the position command calculation unit 10, which calculates the position command value for driving the drive mechanism 2; the position sensing units 14 and 24, which sens the positions of the motors 13 and 23; the velocity command calculation units 11 and 21, which calculate the velocity command value based on the position error value determined from the position command value calculated by the position command calculation unit 10 and the position sensing value acquired by the position sensing units 14 and 24; the velocity sensing units 15 and 25, which calculate the velocity sensing value from the position sensing value acquired by the position sensing units 14 and 24;and the torque command calculation units 12 and 22, which calculate the torque command value from the velocity error value, which is determined from the velocity command value calculated by the velocity command calculation units 11 and 21 and the velocity detection value detected by the velocity sensing units 15 and 25 by using at least the integral element. The position command calculation unit 10 provides the common position command value to each of the motors 13 and 23, and the torque command calculation units 12 and 22 switch, according to the operating state of the drive mechanism 2, between the individualization control for individually executing the output of the integral elements of the torque command calculation units 12 and 22 to each of the motors 13 and 23, and a common control for sharing the output of the integral element of the torque command calculation unit 12 for the motors 13 and 23.

[0039] In this way, since the method for outputting the integral element can be selected according to the operating conditions, the integrators are used jointly in a state where infinite time is problematic, thus achieving control stability; while in a state where a significant difference in the mechanical properties between motors 13 and 23 is generated, the integrators are individualized in such a way that a difference in the mechanical properties between motors 13 and 23 is absorbed, and thus an improvement in response can be achieved.

[0040] If, in the control unit 1 of the present embodiment, it is determined that the operating state is the transition state, the individualization control is carried out; if, on the other hand, it is determined that the operating state is the steady state, the common control is carried out.

[0041] In this way, the form of the speed control is switched accordingly, whether the operating state is the transition state or the steady state, and thus a configuration is realized in which, at the time of a settling time, individual properties of individual controllers are absorbed, while at the time of a uniform response, the properties of both are unified by unifying the integrators.

[0042] When, in the control unit 1 of the present embodiment, the position command calculation unit 10 supplies the position command value, which is specified as an abrupt acceleration / deceleration process, the operating state is determined as a transition state, and thus the individualization control is carried out. In this way, it is possible with simple processing to determine precisely whether the operating state is the transition state or not.

[0043] When the position command calculation unit 10 in the control unit 1 of the present embodiment supplies the position command value specified as stop or constant speed operation, the operating state is determined to be a steady state, so that the joint control is carried out. In this way, it is possible with simple processing to accurately determine whether the operating state is a steady state or not.

[0044] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above, and modifications are possible as required. For example, although in the embodiment described above, joint processing is performed by the time constant circuit in step S110, there is no restriction on this configuration. In other words, multiplication by a time constant can be performed at the time of the transition from the transition state to the steady state or from the steady state to the transition state, or the individualization control and the joint control can be switched without any multiplication by a time constant. EXPLANATION OF REFERENCE SYMBOLS 1 Control 2 Drive mechanism 11, 21 Speed ​​command calculation unit 12, 22 Torque command calculation unit 13, 23 Engine 14, 24 Position detection unit 15, 25 Speed ​​detection unit

Claims

[1] Control (1) for a drive mechanism (2) which is driven by a plurality of motors (13, 23), the control comprising according to the motors (13, 23): a position command calculation unit (10) that calculates a position command value to drive the drive mechanism (2); a position detection unit (14, 24) that detects a position of the motor (13, 23); a speed command calculation unit (11, 21) that calculates a speed command value based on a position error value determined from the position command value calculated by the position command calculation unit (10) and a position sensing value sensed by the position sensing unit (14, 24); a speed detection unit (15, 25) that calculates a speed detection value from the position detection value acquired by the position detection unit (14, 24); and a torque command calculation unit (12, 22) which calculates a torque command value from a velocity error value determined from the velocity command value calculated by the velocity command calculation unit (11, 21) and the velocity sensing value sensed by the velocity sensing unit (15, 25) by using at least one integral element, wherein the position command calculation unit (10) supplies the common position command value to each of the motors (13, 23), and wherein the torque command calculation unit (12, 22) switches between an individualization control, which provides for individual execution of an output of the integral element of the torque command calculation unit (12, 22) to each of the plurality of motors (13, 23), and a common control, which provides for sharing the output of the integral element of the torque command calculation unit (12, 22) to the plurality of motors (13, 23); where, if it is determined that the operating state is a transitional state, individualization control is carried out; if, on the other hand, it is determined that the operating state is a steady state, joint control is carried out; wherein, when the position command calculation unit (10) supplies the position command value specified as an abrupt acceleration / deceleration process, the operating state is determined as a transition state, so that the individualization control is carried out. [2] Control according to claim 1, wherein when the position command calculation unit (10) supplies the position command value specified as stop or constant speed operation, the operating state is determined as a steady state, so that the joint control is carried out.

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