Control device for actuator system, control method and actuator control system

Abstract

To provide a control device for an actuator system capable of compensating responsiveness of a hydraulic actuator by using an electric actuator regardless of a load direction, a control method and an actuator control system.SOLUTION: A control device 10 controls an actuator system 30 including: a hydraulic actuator 1; an electric actuator 2; a proportional valve 6; flow passages P1, P2 for connecting the hydraulic actuator and the proportional valve; and a thrust force measuring device 4 that measures actual thrust force obtained by totaling thrust force of the hydraulic actuator and thrust force of the electric actuator. The control device includes: a target thrust force input section to which target thrust force of the actuator system is input; a thrust force acquisition section that acquires actual thrust force on the basis of output from the thrust force measuring device; a difference calculation section that calculates a difference between the target thrust force and the actual thrust force; and a control section that controls an opening area of the proportional valve and the thrust force of the electric actuator on the basis of the difference.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device, a control method, and an actuator control system for an actuator system in which an electric actuator and a hydraulic actuator are arranged in parallel.

Background Art

[0002] In recent years, with the decline of the working population, automation of work by robots has been promoted. As a means for robots to replace human work, there are robots of the same size as humans and with output equal to or greater than that of humans. To realize such robots, small and high-output actuators are required. A hydraulic actuator is a small and high-output actuator, but since the response speed of a hydraulic actuator is about several Hz, there is a problem with responsiveness as an actuator applied to a robot that replaces human work.

[0003] Here, as a means for improving the responsiveness of a hydraulic actuator, a technique of combining an electric actuator with a high response speed can be considered. In relation to this technique, Patent Document 1 discloses an injection molding machine that combines a hydraulic actuator and an electric actuator.

[0004] For example, in the abstract of the same document, as a problem, it is described that "dramatically enhance the high speed, stability, responsiveness, and reproducibility when using an electric actuator, and at the same time, realize miniaturization and cost reduction of the electric drive unit and the hydraulic drive unit, and in addition, improve the performance and further enhance the developability of the injection molding machine." As a solution thereto, "when driving an injection molding machine including an electric drive unit 2 that drives a movable body forward by an electric actuator and a hydraulic drive unit 4 that pressurizes the movable body by a hydraulic actuator, the movable body is driven forward by controlling the electric drive unit 2, and the load pressure Po during the forward drive is detected to calculate an assist pressure Pa at a predetermined ratio K with respect to the load pressure Po, and the screw S is pressurized by the assist pressure Pa by controlling the hydraulic drive unit 4."

[0005] Further, in paragraph 0009 of the same document, it is described that "the assist ratio K can be made different for each control region. In particular, the assist ratio K in the acceleration section Z1 or the deceleration section Z2 in the speed control region is 80 to 100 [%], the assist ratio K in the constant speed section Z3 in the speed control region is 50 to 80 [%], and the assist ratio K in the pressure control region Z4 is desirably set to 60 to 70 [%] respectively."

Prior Art Document

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, in Patent Document 1, an injection molding machine has been proposed in which an assist pressure Pa obtained by multiplying the load pressure Po of the electric drive unit by a predetermined ratio K is generated by the hydraulic drive unit, and the output of the electric drive unit is assisted by the output of the hydraulic drive unit. Further, it has also been proposed to appropriately change the assist ratio K in accordance with the control region (operation sequence) of the injection molding machine.

[0008] However, in the control of Patent Document 1 in which the output ratio of the hydraulic drive unit to the output of the electric drive unit is constant, since the output of the hydraulic drive unit is controlled to be synchronized with the output of the electric drive unit, there is no problem if it is applied to a sequential operation in which the load magnitude is constant and its direction is also constant, such as an injection molding machine. However, when controlling a robot whose load magnitude is indefinite and the load direction changes at any time, a problem occurs in that the lack of responsiveness of the hydraulic drive unit cannot be compensated by the immediate responsiveness of the electric drive unit.

[0009] The present invention has been made in view of the above actual situation, and an object thereof is to provide a control device, a control method, and an actuator control system for an actuator system capable of compensating the responsiveness of a hydraulic actuator with an electric actuator regardless of the load direction.

Means for Solving the Problems

[0010] In order to solve the above problems, the following configuration is adopted. A control device for controlling an actuator system including a hydraulic actuator, an electric actuator, a proportional valve, a flow path connecting the hydraulic actuator and the proportional valve, and a thrust measuring device for measuring an actual thrust obtained by summing the thrust of the hydraulic actuator and the thrust of the electric actuator, the control device including a target thrust input unit to which a target thrust of the actuator system is input, a thrust acquisition unit that acquires the actual thrust based on the output of the thrust measuring device, a difference calculation unit that calculates a difference between the target thrust and the actual thrust, and a control unit that controls the opening area of the proportional valve and the thrust of the electric actuator based on the difference.

Effects of the Invention

[0011] According to the present invention, the responsiveness of the hydraulic actuator can be compensated with the electric actuator regardless of the load direction.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9A

Figure 9B

Figure 9C

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment

[0014] First, the actuator control system 100 according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 4.

[0015] FIG. 1 is a configuration diagram of the actuator control system 100 of this embodiment. As shown here, the actuator control system 100 includes a control device 10, an interface 20, and an actuator system 30.

[0016] Specifically, the control device 10 is a computer including hardware such as an arithmetic unit like a CPU, a main memory device such as a semiconductor memory, an auxiliary storage device such as a hard disk, and a communication device. Then, the arithmetic unit executes a program while referring to a database to realize each function described later. However, hereinafter, such well-known technologies will be omitted as appropriate for explanation.

[0017] The interface 20 includes an input device such as a keyboard, a touch panel, and a mouse that a user operates when inputting system control parameters (such as target thrust), and an output device such as a display that presents desired information to the user during system operation.

[0018] The actuator system 30 is a hybrid actuator system including a plurality of types of linear actuators, and has a hydraulic cylinder 1, an electric linear motor 2, a connection part 3, a force sensor 4, end effectors 5a and 5b, a proportional valve 6, a tank 7, a pressure source 8, and flow paths P1 to P4. Then, on one surface of the plate-shaped connection part 3, the hydraulic cylinder 1 which is a type of linear hydraulic actuator and the electric linear motor 2 which is a type of linear electric actuator are arranged in parallel, and on the other surface of the connection part 3, the end effector 5a is connected via the force sensor 4. By configuring in this way, when the linear actuator operates, the force (thrust) applied to the end effector 5a is measured by the force sensor 4 which is a thrust measuring device, and an electric signal corresponding to the measured value is input to the control device 10. Hereinafter, the details of the main parts of the actuator system 30 will be sequentially described.

[0019] <Hydraulic cylinder 1, proportional valve 6> The hydraulic cylinder 1 includes a cap chamber 1a, a rod chamber 1b, a rod 1c, and a piston 1d. As is obvious from FIG. 1, on the pressure receiving surface of the piston 1d attached to the left end of the rod 1c on the cap chamber 1a side, a force corresponding to the product of the pressure receiving area and the hydraulic pressure in the cap chamber 1a acts, and on the pressure receiving surface on the rod chamber 1b side, a force corresponding to the product of the pressure receiving area and the hydraulic pressure in the rod chamber 1b acts. Therefore, based on the balance between the hydraulic pressure in the cap chamber 1a and the hydraulic pressure in the rod chamber 1b, the thrust output from the rod 1c is determined.

[0020] The hydraulic cylinder 1 is connected to the tank 7 and the pressure source 8 as follows through a proportional valve 6 such as a servo valve. That is, the cap chamber 1a of the hydraulic cylinder 1 is connected to the proportional valve 6 through the flow path P1, and the rod chamber 1b is connected to the proportional valve 6 through the flow path P2. Further, the proportional valve 6 is connected to the tank 7 through the flow path P3 and connected to the pressure source 8 through the flow path P4.

[0021] The proportional valve 6 is controlled as follows in response to the current input from the control device 10.

[0022] FIG. 2A shows the case where there is no current input from the control device 10. In this case, the proportional valve 6 is in the initial position state (the first state) where none of the flow paths P1 to P4 are connected.

[0023] FIG. 2B shows the case where there is a positive current input from the control device 10. In this case, the proportional valve 6 is in the closed operation state (the second state) where the flow path P1 and the flow path P4 are connected and the flow path P2 and the flow path P3 are connected. In the second state, the hydraulic oil flows from the pressure source 8 into the cap chamber 1a, and the hydraulic oil flows out from the rod chamber 1b to the tank 7, so that the rod 1c applies a force in the closing direction to the end effectors 5a and 5b through the connection portion 3.

[0024] FIG. 2C shows the case where there is a negative current input from the control device 10. In this case, the proportional valve 6 is in the open operation state (the third state) where the flow path P1 and the flow path P3 are connected and the flow path P2 and the flow path P4 are connected. In the third state, the hydraulic oil flows from the pressure source 8 into the rod chamber 1b, and the hydraulic oil flows out from the cap chamber 1a to the tank 7, so that the rod 1c applies a force in the opening direction to the end effectors 5a and 5b through the connection portion 3.

[0025] When the current flowing from the control device 10 to the proportional valve 6 increases, the cross-sectional area of the opening in the proportional valve 6 that connects the flow paths in the second state and the third state increases. When the opening area increases, the inflow and outflow flow rates to each part increase, the pressure in the cap chamber 1a or the rod chamber 1b increases integrally with the supply pressure of the pressure source 8 as the upper limit, and the thrust of the rod 1c also increases integrally.

[0026] <Electric direct-acting motor 2> The electric direct-acting motor 2 is composed of a coil part 2a and a mover 2b. When a current flows through the coil part 2a, a thrust is generated on the mover 2b. The mover 2b is connected to the connection part 3. When there is a positive-direction current input from the control device 10 to the coil part 2a, the mover 2b applies a force in the direction to close the end effectors 5a and 5b via the connection part 3. Also, when there is a negative-direction current input from the control device 10 to the coil part 2a, the mover 2b applies a force in the direction to open the end effectors 5a and 5b via the connection part 3. And when the current flowing from the control device 10 to the coil part 2a increases, the force applied by the mover 2b to the connection part 3 increases proportionally.

[0027] <Control device 10> Fig. 3 shows a functional block diagram of the control device 10. As shown here, the control device 10 includes a controller 11 and an amplifier 12, and controls the input current to the electric direct-acting motor 2 and the proportional valve 6 based on the measurement result of the force sensor 4.

[0028] <<Controller 11>> The controller 11 includes a target thrust input unit 11a, an actual thrust calculator 11b, an overall thrust calculator 11c, a motor current calculator 11d, and a proportional valve current calculator 11e.

[0029] The target thrust input unit 11a outputs the target thrust of the actuator system 30 input from the interface 20 to the overall thrust calculator 11c.

[0030] The actual thrust calculator 11b calculates the actual thrust of the actuator system 30 from the electrical signal corresponding to the thrust measured by the force sensor 4, and outputs the calculation result to the overall thrust calculator 11c.

[0031] The overall thrust calculator 11c calculates the thrusts that should be output by the hydraulic cylinder 1 and the electric direct-acting motor 2 respectively from the target thrust acquired from the target thrust input device 11a and the actual thrust calculated by the actual thrust calculator 11b. For example, the difference calculation unit calculates the difference between the target thrust and the actual thrust, and determines whether the difference is equal to or greater than an arbitrary threshold value. If the difference is equal to or greater than the arbitrary threshold value, the control unit configures feedback control that multiplies the difference by a proportional gain for each of the hydraulic cylinder 1 (proportional valve 6) and the electric direct-acting motor 2, and may calculate the opening command of the proportional valve 6 and the target thrust command of the electric direct-acting motor 2. The target thrust command of the electric direct-acting motor 2 calculated in this way is input to the motor current calculator 11d, and the opening command of the proportional valve 6 is input to the proportional valve current calculator 11e.

[0032] Based on the target thrust of the electric direct-acting motor 2 calculated by the overall thrust calculator 11c, the motor current calculator 11d calculates the current flowing through the electric direct-acting motor 2, and inputs the target value of the current to the electric motor amplifier 12a.

[0033] Based on the opening command of the proportional valve 6 calculated by the overall thrust calculator 11c, the proportional valve current calculator 11e calculates the current flowing through the proportional valve 6, and inputs the target value of the current to the proportional valve amplifier 12b.

[0034] <<Amplifier 12>> The amplifier 12 includes an electric motor amplifier 12a and a proportional valve amplifier 12b.

[0035] Based on the value of the target current calculated by the motor current calculator 11d, the electric motor amplifier 12a controls the current input to the electric direct-acting motor 2.

[0036] Based on the value of the target current calculated by the proportional valve current calculator 11e, the proportional valve amplifier 12b controls the current input to the proportional valve 6.

[0037] <Control Example of Actuator System 30> Here, taking the case where the end effectors 5a and 5b are made to perform a closing operation (see Fig. 2B) as an example, a specific control example of the actuator system 30 will be described.

[0038] Fig. 4 shows the time-series changes of (a) the opening degree of the proportional valve 6, (b) the thrust of the hydraulic cylinder 1, (c) the thrust of the electric direct-acting motor 2, and (d) the total thrust (actual thrust) of the hydraulic cylinder 1 and the electric direct-acting motor 2 when the target thrust is stepped up from f1 to f2.

[0039] As shown in the figure, from time t0 to t1, the target thrust is low at f1, and it steps up to the high target thrust f2 at time t1.

[0040] In that case, (a) the opening degree of the proportional valve 6 is kept at 0 from time t0 to t1 (see Fig. 2A), but as the target thrust changes stepwise at time t1, the opening degree changes to increase from time t1 to t2 (see Fig. 2B). As the thrust of the hydraulic cylinder 1 increases and approaches the target thrust f2 from time t2 to t3, the opening degree of the proportional valve 6 approaches 0. Then, after time t3, the opening degree is kept at 0 (see Fig. 2A).

[0041] As a result, (b) the thrust of the hydraulic cylinder 1 is kept at the target thrust f1 from time t0 to t1 and increases as the opening degree of the proportional valve 6 increases from time t1 to t2. At this time, the thrust of the hydraulic cylinder 1 rises slightly later than the opening degree of the proportional valve 6 due to the influence of the delay generally possessed by the hydraulic system. It continues to rise until the opening degree of the proportional valve 6 becomes 0 from time t2 to t3. The target thrust f2 is reached at time t3, and after time t3, it is kept at the target thrust f2.

[0042] In addition, the thrust of the (c) electric direct-acting motor 2 is maintained at 0 from time t0 to t2. However, as the target thrust changes stepwise at time t1, it increases by proportional control based on the difference between the target thrust and the actual thrust. Here, since the hydraulic cylinder 1 has output the target thrust f1 by time t1, the electric direct-acting motor 2 only needs to compensate for the difference between the target thrust f2 and the target thrust f1. That is, when the fluctuation of the target thrust is small, the required thrust of the electric direct-acting motor 2 may be small, so the electric actuator can be miniaturized. From time t2 to t3, as the thrust of the hydraulic cylinder 1 increases and approaches the target thrust f2, the thrust of the electric direct-acting motor 2 becomes 0.

[0043] The (d) actual thrust obtained by summing the thrusts of both actuators increases with the thrust of the electric direct-acting motor 2 being dominant from time t1 to t2, and increases with the thrust of the hydraulic cylinder 1 being dominant from time t2 to t3, changing from the target thrust f1 to the target thrust f2. After time t3, it is maintained constant.

[0044] With the above configuration, compared with the case of controlling the thrust with the hydraulic cylinder 1 alone, the rise time of the thrust immediately after the target thrust changes due to the thrust of the electric direct-acting motor 2 can be shortened. Also, since the final target thrust is output by the hydraulic cylinder 1, the steady output of the electric direct-acting motor 2 becomes 0, and the power consumption can be suppressed. Further, when the steadily output thrust is large and the fluctuation range of the thrust is small, the thrust of the electric direct-acting motor 2 with respect to the hydraulic cylinder 1 may be small, so the electric direct-acting motor 2 can be miniaturized.

[0045] Note that in FIG. 4, an example where the target thrust rises stepwise from f1 to f2 is shown assuming that the end effectors 5a, 5b execute a closing operation (see FIG. 2B). However, if the end effectors 5a, 5b execute an opening operation (see FIG. 2C), after stepwise decreasing the target thrust from, for example, f2 to f1, the same control as above may be implemented. Therefore, according to this embodiment, the same effect can be obtained regardless of the load direction.

[0046] According to the actuator control system 100 of the present embodiment described above, the responsiveness of the hydraulic actuator can be compensated by the electric actuator regardless of the load direction.

Embodiment

[0047] Next, the actuator control system 100 according to Embodiment 2 of the present invention will be described with reference to FIGS. 5 to 7. Note that the description of elements common to Embodiment 1 will be omitted.

[0048] FIG. 5 is a configuration diagram of the actuator control system 100 of the present embodiment. As shown here, in the actuator system 30 of the present embodiment, a pressure sensor 9a for measuring the hydraulic pressure in the flow path P1 and the cap chamber 1a and a pressure sensor 9b for measuring the hydraulic pressure in the flow path P2 and the rod chamber 1b are added to each configuration described in Embodiment 1, and the measurement results of each are input to the control device 10.

[0049] As described above, since a force corresponding to the product of the pressure receiving area and the hydraulic pressure in the cap chamber 1a acts on the pressure receiving surface on the cap chamber 1a side of the piston 1d, and a force corresponding to the product of the pressure receiving area and the hydraulic pressure in the rod chamber 1b acts on the pressure receiving surface on the rod chamber 1b side, the control device 10 can calculate the thrust of the hydraulic cylinder 1 output from the rod 1c based on the balance between the hydraulic pressure in the cap chamber 1a and the hydraulic pressure in the rod chamber 1b.

[0050] By using these pressure sensors 9a and 9b, in the actuator control system 100 of this embodiment, the high or low pressure rigidity of the hydraulic cylinder 1 can be appropriately controlled. Here, the state with high pressure rigidity means a state in which the pressures in both the cap chamber 1a and the rod chamber 1b of the hydraulic cylinder 1 are kept high, and even when an external force is applied to the hydraulic cylinder 1 (that is, even when an external force is applied to the end effector 5a), it indicates a state where the piston 1d is difficult to displace. Also, the state with low pressure rigidity means a state in which the pressure on one side of the cap chamber 1a and the rod chamber 1b of the hydraulic cylinder 1 is kept low, and when an external force is applied in the direction of the lower pressure side of the hydraulic cylinder 1 (that is, when an external force is applied in the opening or closing direction of the end effector 5a), it indicates a state where the piston 1d is easy to displace. Therefore, the pressure rigidity can be measured by the displacement amount of the piston 1d when an external force is applied to the hydraulic cylinder 1.

[0051] FIG. 6 is a functional block diagram of the control device 10 of this embodiment. As shown here, the controller 11 of this embodiment includes a target pressure balance calculator 11h, in addition to a proportional valve current calculator 11e from the target thrust inputter 11a shown in FIG. 3, a target hydraulic pressure rigidity inputter 11f, and a cylinder pressure calculator 11g.

[0052] The target hydraulic pressure rigidity inputter 11f outputs the target effective pressure rigidity of the hydraulic cylinder 1, which is input from the interface 20, to the target pressure balance calculator 11h.

[0053] The cylinder pressure calculator 11g calculates the pressure inside the hydraulic cylinder 1 from the electrical signals corresponding to the hydraulic pressures measured by the pressure sensors 9a and 9b, and outputs the calculation result to the target pressure balance calculator 11h.

[0054] The overall thrust calculator 11c calculates the thrusts to be output by the hydraulic cylinder 1 and the electric direct-acting motor 2 respectively from the target thrust acquired from the target thrust input unit 11a and the actual thrust calculated by the actual thrust calculator 11b. For example, the difference calculation unit calculates the difference between the target thrust and the actual thrust, and determines whether the difference is equal to or greater than an arbitrary threshold value. If the difference is equal to or greater than the arbitrary threshold value, the control unit configures feedback control in which the difference is multiplied by a proportional gain for each of the hydraulic cylinder 1 (proportional valve 6) and the electric direct-acting motor 2, and may calculate the target thrust command for the hydraulic cylinder 1 and the target thrust command for the electric direct-acting motor 2. The target thrust command for the electric direct-acting motor 2 calculated in this way is input to the motor current calculator 11d, and the target thrust command for the hydraulic cylinder 1 is input to the target pressure balance calculator 11h.

[0055] The target pressure balance calculator 11h receives the target thrust of the hydraulic cylinder 1 calculated by the overall thrust calculator 11c, the target pressure stiffness set by the target pressure stiffness input unit 11f, and the actual pressure in the hydraulic cylinder 1 calculated by the cylinder pressure calculator 11g. Then, the target pressure balance calculator 11h calculates the target pressure of the hydraulic cylinder 1 from the target thrust and the target pressure stiffness of the hydraulic cylinder 1. The target pressure balance calculator 11h calculates an opening command for the proportional valve 6 for controlling the pressure on the higher side of the target pressure of the hydraulic cylinder 1 calculated. For example, feedback control in which a proportional gain is multiplied by the difference between the target pressure and the actual pressure may be configured to calculate the opening command for the proportional valve 6. The calculated opening command for the proportional valve 6 is input to the proportional valve opening command calculator.

[0056] Here, the feedback control will be described. As a control method for the hydraulic cylinder, for example, there is the feedback control shown in FIG. 10. K H (s) is a controller, and P H (s) is the hydraulic cylinder which is the control object. The input of the controller K H (s) is the difference e between the target thrust r and the actual thrust y, and is represented by Equation 1.

[0057] e(s)=y(s)-r(s) ··· (Equation 1) Also, the output is the input current u to the servo valve fbH and is represented by Equation 2

[0058] u fbH = K H (s)e(s) ··· (Equation 2) The input to the hydraulic cylinder P H (s) is the current u to the servo valve fbH and the output is the thrust y of the hydraulic cylinder H In the configuration of the hydraulic cylinder shown in Fig. 10, the thrust y of the hydraulic cylinder H becomes the overall thrust y. From the viewpoint of eliminating the neutral point shift and dead zone of the servo valve, etc., the controller K H (s) is effectively a PI controller including an integral element

[0059] K H (s) = (K PH + K IH / s) ··· (Equation 3) The feedback control extended for the actuator system is shown in Fig. 11. K fbE (s) is the controller of the electric actuator, and P E (s) is the electric actuator. The input to the controller K fbE (s) is the difference e between the target thrust r and the actual thrust y, and the output is the input current u to the electric actuator fbE

[0060] u fbE = K fbE (s)e(s) ··· (Equation 4) The input to the electric actuator P E (s) is the current u fbE and the output is the thrust y of the electric actuator E In this system, the sum of the thrust y of the hydraulic cylinder H and the thrust y of the electric actuator E becomes the overall thrust y

[0061] y(s) = y H (s) + y E (s) ··· (Equation 5) ​As described above, the controller K of the electric actuator fbE (s) is a P control, so K fbE (s)=K PfbE ···(Equation 6) becomes

[0062] A two-degree-of-freedom control system with feedforward control added to feedback control may be constructed to compensate for the delay. The two-degree-of-freedom control system with a feedforward element added is shown in Fig. 12. As a feedforward term, to compensate for the delay of the hydraulic cylinder P H (s), a model G H (s) that approximates the hydraulic cylinder P mH (s) is used to determine the feedforward input u ffE so as to compensate for the difference.

[0063] u ffE =K ffE (s)(1 - G mH (s))r(s)···(Equation 7) Here, proportional control is added to the feedforward controller K ffE (s) to adjust the sensitivity of the feedforward element.

[0064] K ffE (s)=K PffE ···(Equation 8) As described above, by configuring the actuator control system, immediately after the target thrust changes, the electric actuator can output the change in thrust, and the target thrust can be output by the hydraulic cylinder. This can compensate for the responsiveness of the hydraulic cylinder by the electric actuator. Also, since the electric actuator only compensates for the fluctuation range of the target thrust, the rated output can be reduced compared to the hydraulic cylinder, and miniaturization of the electric actuator can be achieved.

[0065] <Control Example of Actuator System 30> Here, taking the state where the end effectors 5a and 5b are made to perform a closing operation (see Fig. 2B) and gripping some object as an example, a specific control example of the actuator system 30 will be described.

[0066] Fig. 6 shows the time-series changes of (a) the internal pressure of the hydraulic cylinder 1, (b) the thrust of the hydraulic cylinder 1, (c) the thrust of the electric direct-acting motor 2, and (d) the total thrust of the hydraulic cylinder 1 and the electric direct-acting motor 2 when the target pressure rigidity is increased stepwise (i.e., when it becomes difficult to displace the end effector 5a).

[0067] As shown in the figure, from time t0 to t1, a low target pressure rigidity is set, and at time t1, it steps up to a high target pressure rigidity.

[0068] In that case, (a) for the internal pressure of the hydraulic cylinder 1, from time t0 to t1, since the target pressure rigidity is set low, the pressure in the rod chamber 1b is kept lower than the pressure in the cap chamber 1a. When the target pressure rigidity changes to a high state at time t1, the target pressure balance calculator 11h calculates the pressure balance inside the hydraulic cylinder 1 and calculates an opening command for the proportional valve 6 to control the higher pressure side. In this embodiment, for example, if the pressure in the cap chamber 1a is high, an opening command for the proportional valve 6 is input so that the pressure in the cap chamber 1a increases. As a result, as shown in Fig. 7(a), the pressure in the cap chamber 1a increases from time t1 to t2.

[0069] Also, (b) the thrust of the hydraulic cylinder 1 is kept constant from time t0 to t1, but from time t1 to time t2, the thrust increases because the pressure in the cap chamber 1a increases. This is because the pressure in the cap chamber 1a increases while the pressure in the rod chamber 1b does not change.

[0070] Here, (c) the thrust of the electric direct-acting motor 2 is kept at 0 from time t0 to t1, but from time t1 to t2, as the thrust of the hydraulic cylinder 1 increases, in order to keep the total thrust unchanged, a thrust is generated on the minus side to compensate for the increase in the thrust of the hydraulic cylinder 1.

[0071] As described above, the pressure in the cap chamber 1a increases from time t1 to time t2 due to the opening of the proportional valve 6 (see FIG. 2B), but temporarily becomes higher than the target cap chamber 1a pressure due to the influence of the thrust of the electric direct-acting motor 2. Therefore, from time t2 to t3, an opening command for the proportional valve 6 is input so as to lower the pressure in the cap chamber 1a. At this time, since the proportional valve 6 opens so as to connect the cap chamber 1a to the tank 7 and the rod chamber 1b to the pressure source 8, the pressure in the cap chamber 1a decreases, but the pressure in the rod chamber 1b increases.

[0072] The thrust of the hydraulic cylinder 1 decreases to the same thrust as at time t0 as the pressure in the cap chamber 1a decreases and the pressure in the rod chamber 1b increases from time t2 to t3.

[0073] Also, the thrust of the electric direct-acting motor 2 changes to 0 as the thrust of the hydraulic cylinder 1 decreases from time t2 to t3.

[0074] By changing as described above, it becomes possible to change the balance of the internal pressure of the hydraulic cylinder 1, that is, the pressure rigidity, without significantly changing the (d) actual thrust obtained by summing the thrusts of both actuators.

Embodiment

[0075] Next, the actuator control system 100 according to Embodiment 3 of the present invention will be described with reference to FIGS. 8 and 9. Note that descriptions of elements common to the above embodiments are omitted.

[0076] In Examples 1 and 2, both the hydraulic actuator and the electric actuator were linear actuators, but in this example, both are rotary actuators. Therefore, in this example, as shown in FIG. 8, a hydraulic rotary motor 1' that substitutes for the function of the hydraulic cylinder 1 and an electric rotary motor 2' that substitutes for the function of the electric linear motor 2 are used, and a torque sensor 4' that substitutes for the function of the force sensor 4 is used. Needless to say, the functional block diagram of the control device 10 in this example is obtained by replacing the force sensor 4 on the input side in FIGS. 3 and 6 with the torque sensor 4' and replacing the electric linear motor 2 with the electric rotary motor 2'.

[0077] Also in this case, as shown in FIGS. 9A to 9C, the actuator system 30 can be controlled so as to adopt the initial position (first state), the closing operation (second state), and the opening operation (third state).

[0078] Also in the actuator control system of this example described above, by appropriately controlling the proportional valve 6 and the electric rotary motor 2' according to the relationship between the target thrust and the output of the torque sensor 4', the same effects as in Example 1 and Example 2 can be obtained.

Explanation of Signs

[0079] 100 Actuator control system 10 Control device 11 Controller 11a Target thrust input device 11b Actual thrust calculator 11c Total thrust calculator 11d Motor current calculator 11e Proportional valve current calculator 11f Target hydraulic rigidity input device 11g Cylinder pressure calculator 11h Target pressure balance calculator 12 Amplifier 12a Electric motor amplifier 12b Proportional valve amplifier 20 Interface 30 Actuator system 1 Hydraulic cylinder 1a Cap chamber 1b Rod chamber 1c Rod 1d Piston 2 Electric direct-acting motor 2a Coil part 2b Mover 3 Connection part 4 Force sensor 5a, 5b End effector 6 Proportional valve 7 Tank 8 Pressure source 9a, 9b Pressure sensor

Claims

1. A hydraulic actuator, an electric actuator, a proportional valve, a flow path connecting the hydraulic actuator and the proportional valve, a thrust measuring device for measuring the actual thrust obtained by summing the thrusts of the hydraulic actuator and the electric actuator, A control device for controlling an actuator system comprising: a target thrust input unit to which a target thrust of the actuator system is input; a thrust acquisition unit for acquiring the actual thrust based on the output of the thrust measuring device; a difference calculation unit for calculating the difference between the target thrust and the actual thrust; a control unit for controlling the opening area of the proportional valve and the thrust of the electric actuator based on the difference; A control device characterized by comprising:

2. In the control device according to Claim 1, the control unit controls the opening area of the proportional valve by changing the cross-sectional area of the connection portion between the proportional valve and the flow path. A control device characterized by this.

3. In the control device according to Claim 1, the control unit determines and controls the opening area of the proportional valve and the thrust of the electric actuator at an arbitrary ratio based on the difference between the target thrust and the actual thrust. A control device characterized by this.

4. In the control device according to Claim 1, the hydraulic actuator is a hydraulic cylinder or a hydraulic rotary motor. A control device characterized by this.

5. In the control device according to Claim 1, the electric actuator is an electric linear motor or an electric rotary motor. A control device characterized by this.

6. In the control device according to Claim 1, the actuator system has a pressure sensor for measuring the hydraulic pressures in the cap chamber and the rod chamber of the hydraulic actuator in the flow path, The control device estimates the thrust of the hydraulic actuator based on the hydraulic pressure measured by the pressure sensor and the pressure receiving area of the hydraulic actuator. A control device characterized by this.

7. In the control device according to Claim 2, a target pressure stiffness input unit to which the target pressure stiffness of the hydraulic actuator is input; a target pressure balance calculator for calculating the target pressure inside the hydraulic actuator based on the target thrust and the target pressure stiffness, and comprising: The control unit controls the proportional valve based on the target pressure. A control device characterized by this.

8. A hydraulic actuator, an electric actuator, a proportional valve, A flow path connecting the hydraulic actuator and the proportional valve, A thrust measuring device that measures the actual thrust obtained by summing the thrust of the hydraulic actuator and the thrust of the electric actuator, A control method for controlling an actuator system comprising: A target thrust input step for inputting a target thrust of the actuator system, A thrust acquisition step for acquiring the actual thrust based on the output of the thrust measuring device, A difference calculation step for calculating the difference between the target thrust and the actual thrust, A control step for controlling the opening area of the proportional valve or the thrust of the electric actuator based on the difference, A control device characterized by comprising the above.

9. An actuator control system having an actuator system and a control device, wherein The actuator system includes A hydraulic actuator, An electric actuator, A proportional valve, A flow path connecting the hydraulic actuator and the proportional valve, A thrust measuring device that measures the actual thrust obtained by summing the thrust of the hydraulic actuator and the thrust of the electric actuator, And is provided with The control device includes A target thrust input unit for inputting a target thrust of the actuator system, A thrust acquisition unit for acquiring the actual thrust based on the output of the thrust measuring device, A difference calculation unit for calculating the difference between the target thrust and the actual thrust, A control unit for controlling the opening area of the proportional valve or the thrust of the electric actuator based on the difference, An actuator control system characterized by comprising the above.

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