STEERING

Abstract

Control for a drive mechanism (2) 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) which 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 sensing by the position sensing unit (14, 24); a speed detection unit (15, 25) which calculates a speed detection value from the position detection value detected by the position detection unit (14, 24); a torque command calculation unit (12, 22) that calculates a torque command value from a speed error value determined from the speed command value calculated by the speed command calculation unit (11, 21) and the speed sensing value detected by the speed sensing unit (15, 25); and a preload torque superposition unit (30) that superimposes a set preload torque onto the torque command value, wherein, when a state in which the output of the motors (13, 23) is zero shifts to a state in which the output is non-zero, such that the preload torque is provided by the preload torque superposition unit (30), at least one of the motors (13, 23) forms a contact section between the drive mechanism (2) and the motor (13, 23) by speed control based on the speed sensing value detected in the speed sensing unit (15, 25), such that the preload torque is provided; and wherein the control unit controls the motors (13, 23) such that in a state in which the contact section is designed to remove a gap between one side of the drive mechanism (2) and one side of the motor (13, 23), the motor (13, 23) subject to speed control is switched to position control based on the position command value calculated by the position command calculation unit (10), so that the preload torque is provided.

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 technology

[0002] A conventional technology is known in which, in a controller for a tandem mechanism that drives a drive mechanism such as a robot or a machine tool with multiple motors, a preload torque is added to a torque command value for controlling the motors in order to reduce backlash. Patent documents 1 to 3 disclose this type of technology.

[0003] Patent document 1 discloses a technology comprising two motors driving a driven element, a position control unit that performs computational processing on a position error value to output a speed command value, a speed control unit that performs processing based on the speed command value, a speed feedback value fed back by a speed detector with an integrated element and a proportional element to output a torque command value, a current control unit that controls a drive current for the motors based on the torque command value, a speed integrator sharing means that copies an output of one integral element to the other integral element in the speed control unit, and a compensation unit that adds a preload torque value to each torque command value to reduce the backlash between the two motors.and the compensation unit has a time constant circuit and gradually adds the preload torque value based on a predetermined time constant.

[0004] Patent document 2 discloses, as a motor control system, that when a driven element is driven by two motors, the backlash between a machine element and the driven element in a gear mechanism connected to the drive shafts of the motors can be reduced even during acceleration / deceleration of the motors. This technology comprises a first preload torque calculation unit, which calculates a preload torque value according to the acceleration of the main motor. This preload torque value is a torque value that is added in advance to a torque command value, such that the direction of a force exerted on the drive shaft of the main motor and the direction of a force exerted on the drive shaft of the sub-motor are opposite to each other. A second preload torque calculation unit also calculates a preload torque according to the acceleration of the sub-motor. This preload torque value is a torque value that is added in advance to a torque command value.so that the direction of the force exerted on the drive shaft of the main motor and the direction of the force exerted on the drive shaft of the sub-motor are opposite to each other.

[0005] Patent specification 3 discloses a technology in which, in a motor control system that performs tandem control for driving a moving unit, a position control unit, a speed control unit, and a current control unit are provided for each motor; a torque arbitration control unit is provided, which calculates a torque arbitration value for calculating an arbitration torque from a difference between a torque command calculated in the speed control unit and a torque command calculated in the speed control unit; and a preload control unit is provided, which adds a preload torque to the torque command; and the preload control unit calculates the minimum preload torque required to reduce backlash according to the position of the moving unit. JP 2010 - 172 054 A: Patent document 1: Japanese unexamined patent application JP 2014 - 178 753 A: Patent document 2: Japanese unexamined patent application JP 2014 - 207 770 A: Patent document 3: Japanese unexamined patent application DE 10 2014 010 576 A1 relates to a motor control system for controlling two motors to drive a single driven object. DE 11 2007 002 118 T5 relates to a servo controller that drives the drive of a feed screw of a machine tool. SUMMARY OF THE INVENTION

[0006] Even if a preload torque is added to a torque command value, it cannot function mechanically if a gap caused by structurally necessary clearance exists between a motor and a drive mechanism in an initial state, even if the preload torque is provided electrically. Although Patent Document 1 and Patent Document 2 disclose technologies where the preload is provided by speed control, since this presupposes a state in which the backlash is already eliminated by adding a fixed preload, there is potential for improvement in the appropriate provision of the preload torque in the initial state.

[0007] Although patent document 3 discloses that the preload torque is provided by the position control, since the individual motors attempt to remain in their positions in a state where a gap exists, there are cases in which contact sections (contact surfaces) of the motors and the drive mechanism are not formed within the clearance of the structure. As described above, if the contact sections (contact surfaces) are not formed, the preload torque intended for control does not have a physical effect.

[0008] One objective of the present invention is to provide a configuration in which a preload (preload torque) can be applied stably and uniformly in a controller that controls a drive mechanism driven by a plurality of motors. The object is therefore to solve the problems mentioned above. The above problems are solved by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claim. (1) The present invention relates to a control unit (e.g., a control unit 1, which will be described later) for a drive mechanism (e.g., a drive mechanism 2, which will be described later) driven by a plurality of motors (e.g., motors 13 and 23, which will be described later), comprising, according to the motors: a position command calculation unit (e.g., a position command calculation unit 10, which will be described later) that calculates a position command value for driving the drive mechanism; a position sensing unit (e.g., a position sensing unit 14, 24, which will be described later) that senses the position of the motor; a speed command calculation unit (e.g.,a speed command calculation unit 11, 21 (which will be described later) 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 and a position sensing value acquired by the position sensing unit; a speed sensing unit (e.g., a speed sensing unit 15, 25, which will be described later) that calculates a speed sensing value from the position sensing value acquired by the position sensing unit; a torque command calculation unit (e.g., a torque command calculation unit 12, 22, which will be described later) that 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; and a preload torque superposition unit (e.g., a preload torque superposition unit 11, 21 ...).B. a preload torque superposition unit 30, which will be described later), which superimposes a set preload torque on the torque command value, wherein, when a state in which there is no output from the motors shifts to a state in which the output is non-zero, such that the preload torque is provided by the preload torque superposition unit, at least one of the motors forms a contact section between the drive mechanism and the motor by speed control based on the speed sensing value detected in the speed sensing unit, such that the preload torque is provided. (2) In the control described in (1), if a state in which there is no output from the motors shifts to a state in which the output is non-zero, such that the preload torque is provided by the preload torque superposition unit, position control can be performed on at least one of the motors (13, 23) based on the position sensing value detected in the position sensing unit (14, 24), and speed control can be performed on at least one of the motors (13, 23) to form the contact section, and in a state in which the contact section is formed, the preload torque is provided by the preload torque superposition unit (30). (3) In the control described in (1) or (2), the control can control the motors such that, in a state where the contact section is designed to remove a gap between the side of the drive mechanism and the side of the motor, the motor subject to speed control is switched to position control based on the position command value calculated by the position control calculation unit, so that the preload torque is provided.

[0009] According to the present invention, it is possible to apply a preload stably and uniformly in a control system that controls a drive mechanism driven by a plurality of motors. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 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 that represents the signal flow at the time of speed feedback in the control system of the present embodiment; Fig. Figure 3 is a block diagram illustrating the signal flow at the time of position feedback in the control system of the present embodiment; Fig. Figure 4 is a schematic view showing a case in which, in the position feedback of a comparative example, the control of a drive mechanism is carried out before and after excitation; Fig. 5 is a schematic view showing a case in which, in the speed feedback of the present embodiment, the control of a drive mechanism is carried out before and after excitation; Fig. 6 is a flowchart illustrating the entire switching sequence of the control of the drive mechanism by the control system of the present embodiment; and Fig. Figure 7 is a flowchart showing a specific example of the switching processing of the feedback control by the control system of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] A preferred embodiment of the present invention is described below with reference to drawings.

[0011] First, a device configuration is described in which a controller 1 of the present embodiment is used. Fig. Figure 1 is a schematic view illustrating a configuration for implementing 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 which control 1 is applied is not the one in Fig. The example shown is limited to one.

[0012] The controller 1 is designed to implement tandem control, in which a drive mechanism 2 is driven by a plurality of (two) motors 13 and 23. The drive mechanism 2 is a robot, a machine tool, or the like, comprising 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.

[0013] 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 types of processing for the operation of the drive mechanism 2. Based on a command from a numerical control 20, the motor control unit 4 performs current control at motor 13 via an amplifier 5 and current control at motor 23 via an amplifier 6. Motors 13 and 23 are servo motors, and the motor control unit 4 receives feedback to determine the position and speed of each motor 13 and 23.

[0014] Fig. Figure 2 is a block diagram that shows the signal flow at the time of speed feedback in the control unit 1 of the present embodiment. Fig. Figure 3 is a block diagram illustrating the signal flow at the time of position feedback in the controller 1 of the present embodiment. As shown in the Fig. 2 and Fig. As shown in Figure 3, the control unit 1 comprises a position command calculation unit 10, the position detection units 14 and 24, the speed detection units 15 and 25, the speed command calculation units 11 and 21, the torque command calculation units 12 and 22 and a preload torque superposition unit 30.

[0015] The position command calculation unit 10, the position detection units 14 and 24, the speed detection units 15 and 25, the speed command calculation units 11 and 21, the torque command calculation units 12 and 22, and the preload torque superposition unit 30 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 units 3 or 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.

[0016] 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 into a predetermined position.

[0017] 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 individually equipped with encoders for the motors 13 and 23.

[0018] The speed detection unit 15 detects a speed detection value corresponding to the motor 13 based on a position detection value detected by the position detection unit 14, and the speed detection unit 25 detects a speed detection value corresponding to the motor 23 based on a position detection value detected by the position detection unit 24.

[0019] 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 acquisition value acquired by the position acquisition unit 14. Similarly, the speed command calculation unit 21 calculates a position command value based on the position command value input from the position command calculation unit 10 and the position acquisition value acquired by the position acquisition unit 24. The speed command value is calculated by the P-controller using a proportional element. The speed command value can be calculated similarly to a PID controller, using a proportional element, an integral element, or a derived element. Depending on the circumstances, a suitable method for calculating the speed command value can be selected.

[0020] 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 sensing value acquired 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 sensing value acquired 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 a control system that includes at least the integral element, so that in an internal model principle a continuous error is set to zero.

[0021] The preload torque superposition unit 30 adds a set preload torque to the torque command value. During preload processing to provide a preload, the motor 13 is driven and controlled based on a value obtained by superimposing the preload torque with the torque command value calculated by the torque command calculation unit 12, and the motor 23 is driven and controlled based on a value obtained by superimposing the preload torque with the torque command value calculated by the torque command calculation unit 22.

[0022] If the preload torque is provided by an electrical control, the preload torque does not physically act in a state where the motors 13 and 23 and the drive mechanism 2 do not form contact sections (contact surfaces) in a first operating step, despite being electrically applied. This state is described with reference to Fig. 4 described. Fig. Figure 4 is a schematic view showing a case in which, in the position feedback of a comparative example, the control of the drive mechanism 2 is carried out before and after excitation. As in Fig. As shown in Figure 4, when position control is performed in a state where the contact sections are not formed by the mechanical parts 102 and 103 of the motors 13 and 23 and the moving element 101, the mechanical parts 102 and 103 of the drive mechanism 2 attempt to remain in their original positions. Thus, a state is maintained in which gaps are formed between the mechanical parts 102 and 103 and the moving element 101. Therefore, the contact sections cannot be formed, so the preload torque is provided control-wise, but not physically.

[0023] Fig. Figure 5 is a schematic view showing a case in which, in the speed feedback of the present embodiment, the control of the drive mechanism 2 is carried out before and after excitation. With speed feedback, coasting occurs during positioning, since the position control is not as strict compared to position feedback. Additionally, applying the preload corresponds to the stage disturbance for speed control. Therefore, during initial operation, speed control is carried out until the speed becomes zero in a disturbance state, thus making it possible to establish contact sections with the mechanical parts 102 and 103 of the motors 13 and 23 and the moving element 101 of the drive mechanism 2.

[0024] In the present embodiment, the control of the drive mechanism 2 in the first operation is achieved by a speed feedback according to Fig. 2 is carried out to reach a state where the preload is physically applied, and then the processing is carried out to control the position feedback according to Fig. 3 to move on. Fig. Figure 6 is a flowchart that illustrates the entire switching sequence of the control of the drive mechanism 2 by the control unit 1 of the present embodiment.

[0025] As in Fig. As shown in Figure 6, the control of the drive mechanism 2 is initiated immediately before and after the excitation of motors 13 and 23 by a speed control (step S101). The preload is applied to motors 13 and 23 (step S102). Subsequently, a transient response (up to 100 ms) to the application of the preload is detected (step S103). The contact sections in the moving element 101 are formed by this settling (step S104). The processing of steps S103 and S104 accounts for a delay due to a mechanical response time in motors 13 and 23 and ensures the formation of contact sections between the mechanical parts 102 and 103 of motors 13 and 23 and the moving element 101 of the drive mechanism 2 (a state on the right side of the plane of Fig. 5) The contact sections are formed by contact of the mechanical parts 102 and 103 of the motors 13 and 23 and the movable element 101 of the drive mechanism 2, and then the control of the drive mechanism 2 is switched to position feedback (step S105).

[0026] Fig. Figure 7 is a flowchart showing a specific example of the switching processing of the feedback control by the controller 1 of the present embodiment. The specific processing of individual configurations in the controller 1 when switching the feedback is now described with reference to Fig. 2 and Fig. 3 described.

[0027] To determine whether a voltage is applied to motors 13 and 23 or not, the output is first monitored to see if it is zero or not (step S201), and thus it is determined whether a zero output has been shifted to a non-zero output or not (step S202).

[0028] If the output changes to a non-zero state during the determination of step S202, the process continues with step S203. In step S203, a common speed command value is supplied to the other motor 23 to perform the speed feedback. Specifically, the controller 1 controls the first motor 13 and the second motor 23 based on a speed command value calculated by the speed command calculation unit 11, which in turn uses the position command value from the position command calculation unit 10 and the position sensing value from the position sensing unit 14 (see Figure 1). Fig. 2).

[0029] After processing in step S203, the preload torque superimposition unit 30 continues to superimpose the preload torque (step S204), and it is determined whether the backlash in the drive mechanism 2 is eliminated to such an extent that the position error and speed of motors 13 and 23 have become zero (step S205). The preload torque continues to be superimposed until the backlash in the drive mechanism 2 is eliminated to such an extent that the position error and speed of motors 13 and 23 have become zero. If the backlash in the drive mechanism 2 is eliminated during processing in step S205 so that the position error and speed of motors 13 and 23 become zero, the process continues with step S206.

[0030] In step S206, position feedback is performed at the first motor 13, and a common position command value is supplied to the other motor 23 to perform position feedback. Specifically, after switching from speed control to position control, controller 1 controls motors 13 and 23 (see Fig. 3) based on the common position command value calculated by the position command calculation unit 10.

[0031] If the output in step S202 does not change to a non-zero state, processing is performed in which the preload torque is superimposed by the preload torque superposition unit 30 without speed feedback, where both motors 13 and 23 have position feedback (step S207). If the motor output remains zero during the processing of step S201, the flow terminates without the process proceeding to the processing of step S202.

[0032] 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 speed command calculation units 11 and 21, which calculate the speed command values ​​based on the position error values ​​determined from the position command value calculated by the position command calculation unit 10 and the position sensing values ​​acquired by the position sensing units 14 and 24; the speed sensing units 15 and 25, which calculate the speed sensing values ​​from the position sensing values ​​acquired by the position sensing units 14 and 24;the torque command calculation units 12 and 22, which calculate the torque command values ​​from the speed command values ​​determined from the speed command values ​​calculated by the speed command calculation units 11 and 21 and the speed detection values ​​detected by the speed detection units 15 and 25;and the preload torque superposition unit 30, which superimposes the set preload torque on the torque command value. When, in the controller 1, a state in which the output of motors 13 and 23 is zero transitions to a state in which the output is non-zero, such that the preload torque is provided by the preload torque superposition unit 30, at least one of the motors 23 forms contact sections between the drive mechanism 2 and the motors 13 and 23 by speed control based on the speed sensing value detected in the speed sensing unit 15, and in a state in which the contact sections are formed, the preload torque is provided by the preload torque superposition unit 30.

[0033] In this way, contact sections can also be formed at gaps between the side of motors 13 and 23 (the mechanical parts 102 and 103) and the side of the drive mechanism 2 (the moving element 101) at the time the power supply is switched on or when starting up after an emergency stop, by utilizing the coasting caused by the speed control. Thus, in the configuration of the present embodiment, it can be ensured at the time of commissioning that the preload torque has an effect not only from a control perspective but also physically.

[0034] Furthermore, in the control unit 1 of the present embodiment, when a state in which the output of motors 13 and 23 is zero shifts to a state in which the output is not zero, so that the preload torque is provided by the preload torque superposition unit 30, position control is performed on the first motor 13 based on the position sensing value detected in the position sensing unit 14 and speed control is performed on the second motor 23 to form the contact sections, and in a state in which the contact sections are formed, the preload torque is provided by the preload torque superposition unit 30.

[0035] In this way, it becomes easier to perform position control by implementing position control on one of the motors 13 and 23. For example, if in a machine tool where the moving element 101 is a feed axis, a motor 13 is present which performs position control in a first operation, it is possible to implement simple position management, leading to an advantageous effect with regard to control.

[0036] The control unit 1 of the present embodiment controls the motors 13 and 23 such that, in a state in which the contact sections for removing the gaps between the side of the drive mechanism 2 and the side of the motors 13 and 23 are formed, the motors 13 and 23 subject to speed control are switched to position control based on the position command value calculated by the position command calculation unit 10, and thus the preload torque is provided.

[0037] In this way, the drive mechanism 2 can be driven by precise position control in a state in which the preload torque is physically guaranteed.

[0038] Although the preferred embodiment of the present invention is described above, the present invention is not limited to the embodiment described above, and modifications can be made if necessary. For example, although in the embodiment described above, processing is carried out in step S203 in which position control is performed on motor 13 and speed control is performed on motor 23, there is no limitation to this processing. A modification can be made to the processing of step S203 such that the speed control on the two motors 13 and 23 is performed based on the speeds detected by the speed sensing units 15 and 25. EXPLANATION OF THE REFERENCE NUMBERS 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 30 Preload torque superposition unit

Claims

[1] Control for a drive mechanism (2) 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) which 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 sensing by the position sensing unit (14, 24); a speed detection unit (15, 25) which calculates a speed detection value from the position detection value detected by the position detection unit (14, 24); a torque command calculation unit (12, 22) that calculates a torque command value from a speed error value determined from the speed command value calculated by the speed command calculation unit (11, 21) and the speed sensing value detected by the speed sensing unit (15, 25); and a preload torque superposition unit (30) that superimposes a set preload torque onto the torque command value, wherein, when a state in which the output of the motors (13, 23) is zero shifts to a state in which the output is non-zero, such that the preload torque is provided by the preload torque superposition unit (30), at least one of the motors (13, 23) forms a contact section between the drive mechanism (2) and the motor (13, 23) by speed control based on the speed sensing value detected in the speed sensing unit (15, 25), such that the preload torque is provided; and wherein the control unit controls the motors (13, 23) such that in a state in which the contact section is designed to remove a gap between one side of the drive mechanism (2) and one side of the motor (13, 23), the motor (13, 23) subject to speed control is switched to position control based on the position command value calculated by the position command calculation unit (10), so that the preload torque is provided. [2] Control according to claim 1, wherein when the state in which the output of the motors (13, 23) is zero shifts to the state in which the output is not equal to zero, so that the preload torque is provided by the preload torque superposition unit (30), position control is performed on at least one of the motors (13, 23) based on the position sensing value detected in the position sensing unit (14, 24) and speed control is performed on at least one of the motors (13, 23) to form the contact section, and in a state in which the contact section is formed, the preload torque is provided by the preload torque superposition unit (30).

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