Actuator and actuator control method

Abstract

To provide an actuator which performs passive compliance control to stabilize behavior of a load body even when power transmission system of the actuator has nonlinear characteristics.SOLUTION: A controller (13, 25) controls output (ωM) of a driving source (23) to realize a target position (θLt) of a load body 32. The controller (13, 25) detects slack or loosening amount (θl) of a wire 36 based on the position (θLt) of the load body 32 and the position (θM) of the driving source (23). When the target output (ωM) of the driving source (23) is a value to activate the load body 32 in a return direction (ωMt<0) and when slack of the wire 36 is detected, the controller (13, 25) corrects control gain (Rc) used for output control of the driving source (23) based on the loosening amount (θl) of the wire 36 so as to resolve the slack thereof.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to an actuator having a power transmission system including a wire, and a method for controlling the actuator. [Background technology]

[0002] Passive compliance (passive flexibility) control is known, which provides compliance or flexibility to a robot arm so that the arm or its components are not damaged when the arm is subjected to an external force (for example, Patent Document 1).

[0003] The actuator described in Patent Document 1 appropriately adjusts the compliance of the link's movement in response to an external force, taking into account the environment and application. This actuator includes a drive mechanism (e.g., a drive source such as a motor), a load (e.g., a load such as a link), a flexible element interposed between the drive source and the load, and a control device that controls the operation of the drive source. The control device sets a target driven speed (target speed to be applied) of the drive source based on a target force to be applied to the load, the actual speed of the load, the actual positions of the drive source and the load, and a flexibility coefficient that represents the characteristics of the flexible element. The control device sets a drive command speed based on a combined target speed that is a combination of the target speed (speed command) of the load and the target driven speed, and controls the drive speed of the drive source based on the drive command speed. In other words, the actuator includes a flexible element with a flexibility coefficient (linear flexibility characteristic) in its power transmission system, and achieves passive compliance control through hybrid control that combines position and force. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-160687 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the passive compliance control described in Patent Document 1 is based on the premise that the flexible element present in the power transmission system has a flexibility coefficient (that is, a linear flexibility characteristic like a spring).

[0006] Here, when considering applying this passive compliance control to the control of a wire-driven actuator whose power transmission system includes a wire, the following problem arises: The wire of the power transmission system is affected by friction with the pulley around which the wire is wound and with friction with the outer tube (e.g., a coiled tube) in which the wire is housed. As a result, the characteristics of the power transmission system, specifically, the characteristics corresponding to the flexibility coefficient, which indicate the relationship between the position of the drive source and the force generated by the load, become nonlinear (characteristics including hysteresis, in which the characteristics change depending on the direction of movement).

[0007] Furthermore, in order to reduce the size of the power transmission system, it is conceivable to configure the actuator to have a unidirectional drive as follows. That is, the load is driven in one direction by the power of the drive source via a wire, and is driven in the return direction by the biasing force of a biasing member that biases the wire in the return direction opposite to the power transmission direction. However, in unidirectional drive, if slack occurs in the wire during the return motion by the biasing member (i.e., if the tension in the wire becomes less than 0 N), the transmission characteristics of the wire change significantly. This makes the load more likely to oscillate, and the operation of the load becomes unstable.

[0008] To avoid this situation, it is possible to set a positive lower limit for the wire's target tension so that the wire is always in tension. However, in this case, the biasing member operates against the wire's tensile force, which reduces responsiveness in the return direction. Responsiveness can be improved by setting the lower limit for the wire's target tension closer to 0, but this requires a sensor that can detect the wire's tension with high accuracy.

[0009] In view of the above background, an object of the present invention is to stabilize the operation of a load body while performing passive compliance control even when the power transmission system of an actuator has nonlinear characteristics. [Means for solving the problem]

[0010] In order to solve such a problem, one embodiment of the present invention is an actuator (30), which includes a drive source (23), a load (32) driven by the drive source, a wire (36) that transmits the power generated by the drive source to the load with tension in the drive direction, and a biasing member (42) (having linear characteristics) that constantly biases the wire with a biasing force in a return direction opposite to the drive direction; M ) and a drive source position sensor (43) for acquiring the position (θ L ) and velocity (ω L ) and a load position sensor (44) for acquiring a given target position (θ L The output (ω M ) and the control device controls the position (θ L ) and the position of the driving source (θ M ), the slack of the wire and the amount of slack (θl=θdif-θth1) are detected based on the target output (ω M t) is a value that operates the load body in the return direction, (ω M t<0) When the looseness of the wire is detected, the control gain (Rc) used for controlling the output of the drive source is corrected to the side that eliminates the looseness based on the amount of looseness of the wire.

[0011] With this configuration, even if the power transmission system includes a wire that is a flexible element, the control device can control the output of the drive source to achieve a given target position of the load, thereby performing passive compliance control that provides compliance to the load. If the control device detects slack in the wire when the target output of the drive source is a value that operates the load in the return direction, it can stabilize the operation of the load by correcting the control gain.

[0012] In the above aspect, the control device adjusts (ω M t≧0) If the slack in the wire is detected, the control gain (Rc) is not modified.

[0013] If the control device's accuracy in detecting slack in the wire is low, slack in the wire may be detected even when the target output of the drive source is a value that would move the load in the drive direction. However, in this case, the load is unlikely to oscillate. This configuration makes it possible to stabilize the operation of the load while suppressing a decrease in responsiveness in the return direction.

[0014] In the above aspect, the actuator further includes a tension sensor (39) for acquiring the tension (Fa(Ta)) of the wire, and the control device further includes a tension sensor (39) for acquiring the target position (θ L t) and the position of the load (θ L ), a target force (Tt) to be applied to the load is set based on the tension (Fa(Ta)) of the wire and the target force (Tt), a target additional speed (ωadd) of the drive source is set by multiplying the deviation (Terr) between the tension (Fa(Ta)) of the wire and the target force (Tt) by a force control gain (Ktp), and the output (ωadd) is calculated based on the target additional speed. M ) to control the

[0015] With this configuration, even if the power transmission system includes a wire that is a flexible element, the control device can set the target additional speed of the drive source by multiplying the deviation between the tension of the wire obtained by the tension sensor and the target force by the force control gain. Then, the control device controls the output of the drive source based on the target additional speed, thereby achieving passive compliance control that imparts compliance to the load body in the same way as in the conventional case.

[0016] In the above aspect, the force control gain (Ktp) is the product of the flexibility coefficient (1 / Kspr) of the power transmission system and the speed gain (Kp2).

[0017] According to this configuration, since the force control gain includes a flexibility coefficient, a value obtained by multiplying the deviation between the wire tension and the target force by the flexibility coefficient is calculated as a value corresponding to the displacement difference (Δθ) between the actual wire displacement and the target wire displacement. Then, this wire displacement difference is multiplied by the speed gain to calculate the target additional speed of the drive source.

[0018] In the above aspect, the control device is configured to adjust the velocity (ω L ) is converted into the driven drive source speed (ωf) and the target additional speed (ωadd) of the drive source, and the target speed (ω M t) and set the output (ω M ) should be controlled.

[0019] According to this configuration, the control device can control the output of the drive source based on the target force and the tension of the wire, using the target speed of the drive source as a control medium.

[0020] In the above aspect, the power transmission system may further include a biasing member (42) (having linear characteristics) that constantly biases the wire in a direction opposite to the direction in which the tension of the wire acts, and the control device may set the target force by adding a force (Tc) that counteracts the biasing force of the biasing member.

[0021] With this configuration, the wire is arranged to transmit tension in only one direction, and even if a force in the other direction is applied by the biasing member, the output of the drive source can be controlled so that the target force acts on the load. Also, since there is no need to arrange the wire so that it can drive the load in both directions, it is possible to prevent the actuator from becoming too large.

[0022] In the above aspect, it is preferable that at least one joint (12) is provided between the drive source and the load body, the wire is arranged to pass through the joint, and the tension sensor is arranged on the drive source side with respect to the joint.

[0023] According to this configuration, there is no need to provide a tension sensor on the load body side of the joint, so that the size of the load body side portion of the actuator can be prevented from increasing.

[0024] In order to solve the problem, one embodiment of the present invention is a control method for an actuator (30) including a drive source (23), a load (32) driven by the drive source, and a power transmission system (33) including a wire (36) that transmits power generated by the drive source to the load, the method comprising: L The output (ω M ) and the position (θ L ) and the position of the driving source (θ M ), the slack of the wire and the amount of slack (θl=θdif-θth1) are detected based on the target output (ω M t) is a value that operates the load body in the return direction, (ω M t<0) When the looseness of the wire is detected, the control gain (Rc) used for controlling the output of the drive source is corrected to the side that eliminates the looseness based on the amount of looseness of the wire.

[0025] With this configuration, even if the power transmission system of the actuator includes a wire that is a flexible element, it is possible to perform passive compliance control, which controls the output of the drive source to achieve a given target position of the load and provides compliance to the load. If slack in the wire is detected when the target output of the drive source is a value that operates the load in the return direction, the operation of the load can be stabilized by correcting the control gain. [Effects of the Invention]

[0026] As described above, according to the present invention, passive compliance control is possible even if the power transmission system of the actuator has nonlinear characteristics. [Brief explanation of the drawings]

[0027] [Figure 1] Schematic configuration diagram of a robot according to an embodiment [Figure 2] Schematic diagram of the robot's hand [Figure 3] Model of the hand actuator [Figure 4] System configuration diagram of the hand actuator [Figure 5] Schematic functional block diagram of the hand actuator [Figure 6] Functional block diagram of the main part of the controller related to the actuator [Figure 7] (A) Conventional technology, (B) Control diagram of the present invention [Figure 8] 10 is a Bode diagram showing the effect of response due to the control according to the embodiment; [Figure 9] Time chart showing actuator response [Figure 10] 1 is a time chart showing a response by a control system according to an embodiment; [Figure 11] Graph showing tension control gain in output correction according to an embodiment. [Figure 12] 10 is a time chart showing a response of a comparative example in which output correction according to an embodiment is not performed. [Figure 13] 10 is a time chart showing a response of an example in which output correction is performed according to an embodiment; [Figure 14] 10 is a model diagram of an actuator according to another embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0029] FIG. 1 is a schematic diagram of a robot 1 according to an embodiment. As shown in FIG. 1, the robot 1 is a humanoid robot. The robot 1 includes a base 2, a head 3 disposed above the base 2, left and right arms 4 extending from the upper part of the base 2, hands 5 provided at the tips of the arms 4, left and right legs 6 extending from the lower part of the base 2, and feet 7 provided at the tips of the legs 6. In the following description, the front-to-back direction of the robot 1 is referred to as the X-axis, the left-to-right direction as the Y-axis, and the up-to-down direction as the Z-axis.

[0030] The base body 2 is composed of an upper part and a lower part that are connected vertically so that they can rotate relatively around the Z axis. The head part 3 can move relative to the base body 2, for example, by rotating around the Z axis.

[0031] The arm 4 includes an upper arm link 8 and a forearm link 9. The body 2 and the upper arm link 8 are connected via a shoulder joint 10, the upper arm link 8 and the forearm link 9 are connected via an elbow joint 11, and the forearm link 9 and the hand 5 are connected via a wrist joint 12. The shoulder joint 10 has degrees of freedom of rotation about the X-axis, Y-axis, and Z-axis, the elbow joint 11 has degrees of freedom of rotation about the Y-axis, and the wrist joint 12 has degrees of freedom of rotation about the X-axis, Y-axis, and Z-axis. The body 2 is provided with a first control device 13 that controls the overall operation of the robot 1.

[0032] As shown in FIG. 2, the hand 5 includes a palm 14 and a plurality of fingers 15 extending from the palm 14. Each finger 15 includes a first finger link 16, a second finger link 17, and a third finger link 18. The palm 14 and the first finger link 16 are connected via a first finger joint 19, the first finger link 16 and the second finger link 17 are connected via a second finger joint 20, and the second finger link 17 and the third finger link 18 are connected via a third finger joint 21. The first finger joint 19 to the third finger joint 21 have a degree of freedom of rotation about the Y axis. The first finger joint 19 of the finger 15 corresponding to the thumb also has a degree of freedom of rotation about the X axis. The forearm link 9, palm 14, the first finger link 16 to the third finger link 18, the wrist joint 12, and the first finger joint 19 to the third finger joint 21 are covered by an outer case 22.

[0033] The forearm link 9 is provided with a plurality of motors 23 (drive sources) for driving the joints of each finger, and a second control device 25 for controlling the operation of these motors 23. In this embodiment, the third finger joint 21 is configured to move in conjunction with the second finger joint 20, and two motors 23 are used for each finger 15: one motor 23 for driving the first finger joint 19, and another motor 23 for driving the second finger joint 20 and the third finger joint 21. The second control device 25 drives the motors 23 of all the fingers 15 and is common to the plurality of actuators 30.

[0034] The second control device 25 receives commands from the first control device 13 (FIG. 1) mounted on the base 2, and drives all of the fingers 15 of the hand 5 by controlling the operation of the motors 23 based on the commands. The motors 23 are powered by power supplied from a battery (not shown) mounted on the robot 1. Each of the fingers 15 constitutes an actuator 30. In other words, the portion from the upper arm link 8 to the palm 14 forms an arm 31 supported on the base 2 via a shoulder joint 10, and the palm 14 is connected to a forearm link 9, which forms the base of the arm 31, via a carpal joint 12, forming a hand that supports the fingers 15.

[0035] In this embodiment, the finger 15 has multiple joints (19-21) driven by multiple motors 23. In other words, the finger 15 of this embodiment includes multiple actuators 30. The actuator 30 that drives the first finger joint 19 drives the entire finger 15 to rotate around the Y-axis relative to the palm 14. The actuator 30 that drives the second finger joint 20 drives the second finger link 17 and the third finger link 18 to rotate around the Y-axis relative to the first finger link 16. Hereinafter, the finger 15, the second finger link 17, and the third finger link 18, which are driven by the actuator 30, are simply referred to as loads 32 (see FIG. 3). Each load 32 is provided so as to be displaceable relative to the arm 31, either directly or indirectly via another load 32. In other embodiments, a finger may be driven by only one motor 23.

[0036] 3 is a model diagram of the actuator 30 of the hand portion 5. As shown in FIG. 3, the actuator 30 includes a motor 23 provided in the forearm link 9, a load 32 driven by the motor 23, and a power transmission system 33 that transmits the power generated by the motor 23 to the load 32. The power transmission system 33 includes a drive pulley 34 that is rotationally driven by the motor 23, a driven pulley 35 that is integrally formed with the load 32 around the rotation axis of the load 32, and a wire 36 that is wound around the drive pulley 34 and the driven pulley 35. The wire 36 connects the drive pulley 34 and the driven pulley 35 so as to be able to transmit the bending-side tension Fb.

[0037] The wire 36 extends from one end fixed to the drive pulley 34 and is wound around the driven pulley 35, with the other end fixed to the palm portion 14 (hand portion, FIG. 2). A biasing member 42 that constantly biases the wire 36 toward the palm portion 14 is provided on the other end of the wire 36 relative to the driven pulley 35. The biasing member 42 may be, for example, a tension coil spring or a helical spring. When the wire 36 is pulled by the drive pulley 34, the bending-side tension Fb transmits torque to the driven pulley 35 in a direction that bends the load body 32. When the wire 36 is biased by the biasing member 42 in a direction opposite to the direction in which the bending-side tension Fb from the drive pulley 34 acts, the biasing force transmits torque to the driven pulley 35 in a direction that stretches the load body 32.

[0038] In this embodiment, a tension sensor 39 for obtaining the tension F of the wire 36, i.e., a tension sensor 39 for detecting the bending side tension Fb of the wire 36, is provided on the wire 36 between the drive pulley 34 and the driven pulley 35. The tension sensor 39 is provided on the forearm link 9 (FIG. 2). The portion of the wire 36 between the tension sensor 39 and the driven pulley 35 passes through the wrist joint 12 (FIG. 2). An outer tube (not shown) is provided at the portion of the wire 36 that passes through the wrist joint 12.

[0039] A reducer 40 having a predetermined reduction ratio RR is provided between the motor 23 and the drive pulley 34. Here, the radius of the drive pulley 34 and the radius of the driven pulley 35 are set to be the same, and the drive pulley 34 and the driven pulley 35 rotate at the same speed. In other embodiments, a speed reduction mechanism based on the radius ratio of the drive pulley 34 and the driven pulley 35 may be added. The output shaft of the motor 23 is directly coupled (rigidly coupled) to the drive pulley 34. The power transmission system 33 includes the wire 36, and therefore has a flexibility coefficient 1 / Kspr, which is the reciprocal of the wire stiffness. The flexibility coefficient is the reciprocal of the spring stiffness Kspr (spring constant) of the power transmission system 33.

[0040] 4 is a system configuration diagram of the actuator 30 of the hand section 5. As shown in FIG. 4, the actuator system of the hand section 5 provided in the robot 1 includes a first control device 13, a second control device 25, a plurality of motors 23, a plurality of motor angle sensors 43, a plurality of tension sensors 39, and a plurality of joint angle sensors 44. The second control device 25 is connected to the first control device 13 via a communication line 45. The plurality of motors 23, the motor angle sensors 43, and the joint angle sensors 44 are connected to the second control device 25 via the communication line 45.

[0041] The first control device 13 is an electronic control device composed of a CPU, ROM, RAM, I / O, analog circuits, etc. The first control device 13 performs various motion controls by executing arithmetic processing according to a program using the CPU. The first control device 13 may be configured as a single piece of hardware, or may be configured as a unit consisting of multiple pieces of hardware. A "motion control program" for causing the first control device 13 to function as a control device for the robot 1 may be pre-stored in a storage device such as a ROM. Alternatively, this program may be distributed from a server via a network or broadcast at any time and stored in the storage device of the first control device 13, or may be stored on the server and used by the first control device 13 via a network or broadcast. The first control device 13 executes arithmetic processing according to the motion control program to set a motion target value of the load 32 of each actuator 30 and set a target torque Tt of the load 32 based on the motion target value.

[0042] The second control device 25 is an electronic control device composed of a programmable logic device, a motor driver, an I / O, an analog circuit, etc. The programmable logic device controls the operation of the actuator 30 by executing arithmetic processing according to a program, and may be, for example, an FPGA (field-programmable gate array). An "operation control program" for causing the second control device 25 to function as a control device for the actuator 30 is pre-stored in the programmable logic device. The second control device 25 operates the actuator 30 by controlling the output of the motor 23 in accordance with a command for the target torque Tt of the load 32 received from the first control device 13. That is, the second control device 25, in cooperation with the first control device 13, controls the output of the motor 23 so as to realize a given target position of the load 32.

[0043] The motor angle sensor 43 detects the motor angle θ, which is the angle of the output shaft of the corresponding motor 23. M (position) and motor angular velocity ω M (speed) to obtain the motor angle θ M That is, the motor angle sensor 43 is a drive position sensor that detects the position of the drive source to obtain the position and speed of the drive source. The motor angle sensor 43 may be, for example, an encoder, and detects the motor angle θ M The controller 100 outputs a signal according to the received signal.

[0044] The tension sensor 39 detects the bending side tension Fb of the wire 36 (see FIG. 5). The tension sensor 39 outputs a signal corresponding to the tension F of the wire 36.

[0045] The joint angle sensor 44 detects the angular position of the load 32 driven by the motor 23 relative to the support member, i.e., the joint angle θ L (position) and joint angular velocity ω L To obtain the velocity, the joint angle θ LThat is, the joint angle sensor 44 is a load position sensor that detects the position of the load 32 to obtain the position and velocity of the load 32. The joint angle sensor 44 may be, for example, an encoder, and is configured to detect the joint angle θ L The controller 100 outputs a signal according to the received signal.

[0046] As described above, the first control device 13 is disposed on the base 2 of the robot 1, and the second control device 25 and the plurality of motors 23 are disposed on the forearm link 9 of the robot 1. Therefore, the shoulder joint 10 and the elbow joint 11 are interposed between the first control device 13 and the second control device 25.

[0047] FIG. 5 is a schematic functional block diagram of the actuator 30 of the hand portion 5. As shown in FIG. 5, the first control device 13 has a joint target value setting unit 51 and a target tension setting unit 52. The joint target value setting unit 51 executes calculation processing in accordance with the motion control program to set a motion target value of the load body 32. The motion target value of the load body 32 includes a target joint angle θ L t and target joint angular velocity ω L t. The motion target value of the load 32 may include a joint torque command.

[0048] The target tension setting unit 52 sets the target joint angle θ L t and target joint angular velocity ω L t and the joint angle θ obtained from the tension sensor 39 L and joint angular velocity ω L The target tension setting unit 52 performs impedance control to set a target torque Tt as a target force of the load 32 based on the deviation of these input values. In this way, the target tension setting unit 52 sets at least the target joint angle θ L t (target position) and joint angle θ L A target force to be applied to the load 32 is set based on the position of the load 32.

[0049] The second control device 25 has a tension control unit 53, a motor control unit 54, a current control unit 55, and a sensor data acquisition unit 56. The sensor data acquisition unit 56 is equipped with a differentiator 57. The sensor data acquisition unit 56 acquires signals output from the tension sensors 39 (39A, 39B), the motor angle sensor 43, and the joint angle sensor 44, performs necessary processing, and then distributes these signals to each required functional unit. The differentiator 57 calculates the motor angle θ acquired from the motor angle sensor 43. M The motor angular velocity ω is calculated by differentiating the signal corresponding to M and calculates the joint angle θ L The joint angular velocity ω is calculated by differentiating the signal corresponding to L Calculate.

[0050] The sensor data acquisition unit 56 acquires the motor angle θ M is transmitted to the motor control unit 54, and the tension F (Fb) of the wire 36 and the joint angular velocity ω L is transmitted to the tension control unit 53, and the joint angle θ L and joint angular velocity ω L to the target tension setting unit 52 of the first control device 13. It should be noted that the actuator 30 transmits the bending-side tension Fb to the tension control unit 53.

[0051] The tension control unit 53 receives the target torque Tt set by the target tension setting unit 52, the tension F (Fb) transmitted from the sensor data acquisition unit 56, and the joint angular velocity ω L Based on this, the target motor angular velocity ω M Set t.

[0052] The motor control unit 54 controls the target motor angular velocity ω set by the tension control unit 53. M t, and the motor angular velocity ω transmitted from the sensor data acquisition unit 56 M The current control unit 55 controls the current I flowing from the battery to the motor 23 so that the target current It set by the motor control unit 54 is supplied to the motor 23. In this way, the second control device 25 controls the motor angular velocity ω MHereinafter, the first control device 13 and the second control device 25 will be collectively referred to as the controller.

[0053] 6 is a functional block diagram of the main part of the controller for the actuator 30. The target tension setting unit 52 of the first control device 13 includes a first subtractor 61, a second subtractor 62, an integrator 63, and an adder 64. The first subtractor 61 subtracts the target joint angle θ set by the joint target value setting unit 51. L t, the joint angle θ at the time of actual measurement detected by the joint angle sensor 44 L By subtracting L The second subtractor 62 calculates the target joint angular velocity ω set by the joint target value setting unit 51. L t, the joint angular velocity ω at the time of actual measurement detected by the joint angle sensor 44 L By subtracting L The integrator 63 calculates the joint angle difference Δθ L The target tension setting unit 52 integrates the joint angle difference Δθ L is multiplied by a proportional gain Kp to convert it into a torque value of the load 32, and the joint angular velocity ω L is multiplied by the differential gain Kd to convert it into the torque value of the load body 32, and the joint angle difference Δθ L The integral value of is multiplied by the integral gain Ki to convert it into the torque value of the load 32. The adder 64 adds these three values ​​together to obtain the torque target value T L Calculate t.

[0054] The target tension setting unit 52 also includes a drive-side torque conversion unit 65 and a limiting unit 66. The drive-side torque conversion unit 65 converts the torque target value T L In this embodiment, there is no speed reducing mechanism between the load 32 and the wire 36, and the torque of the load 32 and the torque of the wire 36 portion of the power transmission system 33 are the same. Therefore, the drive-side torque conversion unit 65 converts the torque target value T LOutput t as the target torque Tt directly to the limiting unit 66. The limiting unit 66 limits the target torque Tt such that -C2 < Tt < C1. C2 is a positive value smaller than C1 and is the lower limit value to prevent the wire 36 from loosening. Here, C1 is a positive value and is the upper limit value of the torque at which the wire 36 does not break in this power transmission system 33. C1 may be set to, for example, 1 N according to the measurement accuracy of the tension sensor 39. After performing the limiting process on the target torque Tt, the limiting unit 66 outputs the target torque Tt to the tension control unit 53.

[0055] The target tension setting unit 52 can change the characteristics of the actuator 30 by changing these proportional gain Kp, derivative gain Kd, and integral gain Ki to adjust the mechanical impedance (spring stiffness Kspr) of the actuator 30. Specifically, even if the wire 36 is included in the power transmission system 33, by increasing these gains, the position responsiveness of the load body 32 can be enhanced. Also, by decreasing these gains, the flexibility of the load body 32 of the hand part 5 can be enhanced, for example, the shock absorption performance can be enhanced.

[0056] The tension control unit 53 of the second control device 25 includes a drive-side torque conversion unit 72, a subtractor 73, and an adder 74. The drive-side torque conversion unit 72 receives the bending-side tension Fb (actual torque tension Fa of the wire 36) acquired from the tension sensor 39. The drive-side torque conversion unit 72 calculates the actual torque Ta of the wire 36 part of the power transmission system 33 by multiplying the bending-side tension Fb by the radius of the drive pulley 34. The subtractor 73 calculates the torque deviation Terr to be added to the load body 32 by subtracting the actual torque Ta from the target torque Tt set by the target tension setting unit 52.

[0057] The actual torque tension Fa calculated by the drive-side torque conversion unit 72 includes a force that counteracts the biasing force of the biasing member 42 in FIG. 3. Therefore, the target tension setting unit 52 of the first control device 13 further includes a biasing force compensation unit 67. In the target tension setting unit 52 of the first control device 13, the biasing force compensation unit 67 uses the joint angle θ corresponding to the elongation displacement of the biasing member 42 Lis multiplied by a compensation coefficient corresponding to the spring constant of the biasing member 42 to calculate an opposing torque Tc corresponding to the opposing force to the biasing force of the biasing member 42. The target tension setting unit 52 multiplies the opposing torque Tc by the torque feedforward gain Ktff to convert it into a torque value of the load 32. This value is input to an adder 64 and added to the other three values. This cancels out the biasing force of the biasing member 42.

[0058] The tension control unit 53 calculates a target additional angular velocity ωadd, which is an additional velocity command (target additional velocity) for the drive source, by multiplying the torque deviation Terr calculated by the subtractor 73 by a force control gain Ktp. The target additional angular velocity ωadd is input to an adder 74. Here, the force control gain Ktp is obtained by multiplying the flexibility coefficient (1 / Kspr) of the power transmission system 33 by a proportional gain Kp2, which is a velocity gain for converting an angle, which is a position command, into an angular velocity, which is a velocity command. The force control gain Ktp will be described in detail below.

[0059] FIG. 7 is an explanatory diagram of the control of (A) the prior art and (B) the present invention. In the conventional passive compliance control shown in Patent Document 1, the flexible element intervening in the power transmission system 33 has a linear flexible characteristic. Therefore, as shown in FIG. 7(A), the angle command value θt, which is a position command, is calculated by multiplying the target torque Tt, which is a torque command, by the flexibility coefficient (1 / Kspr) of the flexible element. In addition, the angle between the drive side and the load side (angle difference "θ") is calculated from the angle command value θt. M -θ L The angular difference Δθ was calculated by subtracting the angular difference Δθ from the angular velocity command. The angular velocity command was then calculated by multiplying this angular difference Δθ by a proportional gain Kp2, which is used to convert the angle command into an angular velocity command.

[0060] In contrast to this, in this embodiment, the power transmission system 33 includes the wire 36, so the characteristics of the power transmission system 33 become nonlinear. Therefore, the tension control unit 53 calculates the angle between the drive side and the load side (angle difference "θ M -θ LThe actual torque Ta between the drive side and the load side, obtained by multiplying the actual torque Ta ("") by the spring stiffness Kspr of the power transmission system 33, is obtained from the detection value of the tension sensor 39. The actual torque Ta is then subtracted from the target torque Tt, which is the torque command, to calculate the torque deviation Terr. The torque deviation Terr is then multiplied by the flexibility coefficient (1 / Kspr) of the power transmission system 33 to calculate a value equivalent to the conventional angular difference Δθ, and this value is multiplied by the proportional gain Kp2 to calculate the angular velocity command. In this way, the tension control unit 53 performs similar processing using force (actual torque Ta) rather than position through equivalent exchange, thereby being able to calculate the velocity command (target angular velocity ωt) without having to model the spring characteristics of the power transmission system 33, which has hysteresis.

[0061] Continuing the explanation, returning to FIG. 6, the tension control unit 53 further includes a drive-side speed conversion unit 75. The drive-side speed conversion unit 75 converts the joint angular velocity ω L Specifically, the drive-side velocity converter 75 converts the joint angular velocity ω L is multiplied by the reduction ratio RR of the reducer 40 to obtain the joint angular velocity ω L Here, the driven motor angular velocity ωf is calculated based on the joint angular velocity ω of the load 32 that rotates driven by the driving of the motor 23. L The motor angular velocity ω M is the angular velocity equivalent to the driven drive source velocity obtained by converting

[0062] The tension control unit 53 optimizes the driven motor angular velocity ωf by multiplying the driven motor angular velocity ωf by a control gain Kvff. The control gain Kvff is normally set to 1, and is also set to 1 in this embodiment. The driven motor angular velocity ωf is input to an adder 74 as a feedforward term. The adder 74 adds the driven motor angular velocity ωf to the target additional angular velocity ωadd to calculate a target motor angular velocity ω M Calculate the target motor angular velocity ω M t is supplied to the motor control unit 54, and as described above, the motor control unit 54 controls the motor angular velocity ω MAngular velocity control is performed to set the target current It based on

[0063] In this way, the second control device 25 and the control method therefor multiply the torque deviation Terr, which is the deviation between the actual torque Ta corresponding to the actual torque tension Fa of the wire 36 and the target torque Tt, by the force control gain Ktp to set the target additional angular velocity ωadd, which is the target angular velocity ωt of the drive source. Then, the second control device 25 calculates the motor angular velocity ωadd, which is the output of the drive source, based on the target additional angular velocity ωadd. M By controlling the load 32, passive compliance control that applies compliance to the load 32 can be realized in the same manner as in the conventional case.

[0064] As described above, the force control gain Ktp is the product of the flexibility coefficient (1 / Kspr) of the power transmission system 33 and the proportional gain Kp2 as a speed gain. In other words, since the force control gain Ktp includes the flexibility coefficient (1 / Kspr), the value obtained by multiplying the torque deviation Terr by the flexibility coefficient (1 / Kspr) is calculated as the angle between the drive side and the load side (angle difference Δθ in FIG. 7) corresponding to the displacement difference between the actual displacement of the wire 36 and the target displacement of the wire 36. Then, the target additional angular velocity ωadd of the drive source is calculated by multiplying this displacement difference of the wire 36 (angle difference Δθ in FIG. 7) by the proportional gain Kp2.

[0065] The second control device 25 also detects the joint angular velocity ω of the load 32 acquired from the joint angle sensor 44. L The target motor angular velocity ω is calculated based on the driven motor angular velocity ωf obtained by converting the target additional angular velocity ωadd. M Then, the second control device 25 sets the target motor angular velocity ω M The motor angular velocity ω is set to achieve t. M Therefore, the second control device 25 controls the target motor angular velocity ω based on the target torque Tt and the actual torque Ta corresponding to the actual torque tension Fa of the wire 36. M t is the control medium and the motor angular velocity ω M can be controlled.

[0066] 3, in the actuator 30, the power transmission system 33 includes a biasing member 42 having linear characteristics that constantly biases the wire 36 in a direction opposite to the direction in which the tension F of the wire 36 acts. Then, as shown in FIG. 6, the first control device 13 sets the target torque Tt by adding a counter torque Tc corresponding to the biasing force of the biasing member 42.

[0067] The conventional passive compliance control shown in Patent Document 1 is based on the premise that the power transmission system 33 is continuous via a flexible element such as a metal spring and can transmit force in both positive and negative directions. Therefore, if the wire 36 is arranged to transmit tension F in only one direction and the force in the other direction is applied by the biasing member 42, conventional control cannot be used.

[0068] In this embodiment, the wire 36 is arranged to transmit the tension F to only one side, and even if a force to the other side is applied by the biasing member 42 having a linear characteristic, the controller controls the motor angular velocity ω to apply the target torque Tt to the load 32. M Furthermore, since there is no need to arrange the wires 36 so as to be able to drive the load body 32 in both directions, the actuator 30 can be prevented from becoming large.

[0069] 8 is a Bode diagram showing the effect of responsiveness by the control according to the embodiment. The dashed line in the graph indicates the amount of tension that the target tension setting unit 52 of the first control device 13 determines based on the joint angle difference Δθ L The figure shows the frequency characteristics when the torque value of the load 32 converted by multiplying the integral value of the load 32 by the integral gain Ki is not added to the adder 64, that is, when PD control is performed. The solid line shows the frequency characteristics of the control according to the embodiment. L When PD control is performed using the above, as shown by the dashed line, a resonance point occurs in the frequency range of 0.5 to 1 Hz, and while the gain increases, a phase delay occurs, resulting in a decrease in responsiveness. In contrast, in this embodiment, resonance in this frequency range is suppressed, improving responsiveness.

[0070] 9 is a time chart showing the response of the actuator 30. The vertical axis represents the joint angle θ L The dashed line in the chart indicates the joint angle θ L The command value (target joint angle θ L t), and the solid line shows the actual measured value of the present invention (joint angle θ L ), and the dashed line indicates the actual measured value of the comparative example. In the comparative example, the target tension setting unit 52 (FIG. 6) L is converted to the primary side (drive side) driven motor angular velocity ωf by the drive side speed conversion unit 75, and the value multiplied by the control gain Kvff is not added as a feedforward term by the adder 74.

[0071] As shown in FIG. 9, in the comparative example, the joint angle θ L When the command value of changes slightly (when the rotation command is to the extension side), the joint angle θ L In contrast, in the present invention, the target tension setting unit 52 sets the joint angular velocity ω L The target motor angular velocity ω is calculated by adding a feedforward term related to the driven motor angular velocity ω based on M By calculating t, the joint angle θ L changes following the command value, just like when the command is given to the flexion side, and the joint angle θ L In other words, even if the wire 36 is arranged to transmit the tension F to only one side and a force to the other side is applied by the biasing member 42, the joint angular velocity ω of the load body 32 acquired by the second control device 25 from the joint angle sensor 44 is L The target motor angular velocity ω is calculated based on the driven motor angular velocity ωf obtained by converting the target additional angular velocity ωadd. M By setting t, the response of the load 32 is improved.

[0072] 10 is a time chart showing the response of the control system according to the embodiment. The vertical axis represents the joint angle θ L The dashed line in the chart indicates the joint angle θ L The command value (target joint angle θ L t), and the solid line shows the actual measured value of the present invention (joint angle θ L) and the dashed dotted line indicates the measured value of the comparative example.

[0073] The comparative example is based on the configuration of a conventional system. Here, the configuration of the conventional system will be explained to clarify the differences from the present invention. In the conventional system, the second control device 25 only functions as a motor driver that controls the output of the motor 23. In other words, the motor angular velocity ω M The tension control section 53 that controls the joint angle θ of the load body 32 is provided in the first control device 13. L is obtained from the joint angle sensor 44, and the joint angle θ L to joint angular velocity ω L is calculated and provided to the tension control unit 53.

[0074] In contrast, in the present invention, as shown in FIG. 5, the motor angular velocity ω M The tension control section 53 is integrally provided in the second control device 25, which is a motor driver for controlling the load 32. The tension control section 53 of the second control device 25 controls the joint angle θ L is obtained directly from the joint angle sensor 44, and the joint angle θ L Based on this, the joint angular velocity ω of the load body 32 L Then, the second control device 25 calculates the actual torque Ta corresponding to the tension F of the wire 36 and the joint angular velocity ω of the load 32. L and the joint angular velocity ω, which is the output of the motor 23, based on L As a result, the second control device 25 controls the joint angular velocity ω of the load 32. L is calculated in a short time and the motor angular velocity ω M The target motor angular velocity ω M t, and the operation of the load 32 becomes smooth.

[0075] 6, in the second control device 25, the tension control unit 53 sets the target additional angular velocity ωadd of the motor 23 based on the target torque Tt and the actual torque Ta of the wire 36 portion of the power transmission system 33, which corresponds to the actual torque tension Fa of the wire 36. The tension control unit 53 calculates the target additional angular velocity ωadd and the joint angular velocity ω of the load 32. L Based on the driven motor angular velocity ωf obtained by converting M Then, the motor control unit 54 sets the target motor angular velocity ω M In this way, the second control device 25 drives the motor 23 based on the target motor angular velocity ωt set by the first control device 13 and the actual torque Ta. M The output of the motor 23 is controlled using t as a control medium. This allows the controller to achieve conventional passive compliance control that provides compliance to the load 32, even if the power transmission system 33 includes the wire 36, which is a flexible element.

[0076] In the arm 31 shown in FIG. 2, the palm 14, which forms the hand supporting the load 32, is connected to the forearm link 9, which forms the base of the arm, via the wrist joint 12. Therefore, the wire 36 shown in FIG. 3 is arranged to pass through the wrist joint 12. Meanwhile, since the second control device 25 and the tension sensor 39 (39A, 39B) are both provided on the forearm link 9 as described above, the time required for tension control processing by the second control device 25 is reduced. This allows the load 32 to move smoothly. Furthermore, the palm 14 does not need to be large due to the incorporation of devices and sensors.

[0077] In other words, the tension sensors 39 (39A, 39B) are disposed on the motor 23 side relative to the wrist joint 12. This eliminates the need to provide the tension sensors 39 (39A, 39B) on the load 32 side relative to the wrist joint 12, thereby preventing the portion of the actuator 30 on the load 32 side from becoming larger.

[0078] The actuator 30 of this embodiment has a unidirectional drive configuration as shown in Fig. 3. That is, the load 32 is driven in one direction by the power of the drive source via the wire 36, and is driven in the return direction by the biasing force of the biasing member 42 that biases the wire 36 in the return direction opposite to the power transmission direction. Therefore, if slack occurs in the wire 36 during the return operation by the biasing member 42 (i.e., if the tension F of the wire 36 becomes less than 0 N), the transmission characteristics of the wire 36 change significantly. This makes the load 32 more likely to oscillate, and the operation of the load 32 becomes unstable.

[0079] For this reason, as shown in FIG. 6, the tension control section 53 of the second control device 25 includes a wire slack detection section 77 and an output correction section 78.

[0080] The wire loosening detection unit 77 detects the joint angle θ L and the motor angle θ, which is the position of the drive source detected by the motor angle sensor 43. M Specifically, the wire slack detection unit 77 detects the slack and the amount of slack θl of the wire 36 based on the joint angle θ L is converted into the estimated angle θest of the motor 23 by multiplying it by the reduction ratio RR of the reducer 40. The wire slack detection unit 77 converts the estimated angle θest of the motor 23 into the motor angle θ M The difference angle θdif is obtained by subtracting θdif=θest-θ M ···(1) When the angle difference θdif is greater than a predetermined first threshold θth1, it is determined that there is slack in the wire 36. The first threshold θth1 may be, for example, 1°. As shown in the following equation (2), the value obtained by subtracting the first threshold θth1 from the angle difference θdif (θdif-θth1) represents the amount of slack θl of the wire 36. θl=θdif-θth1 (2)

[0081] The output corrector 78 calculates the target motor angular velocity ω, which is the target output of the motor controller 54, in accordance with the slack of the wire 36 and the amount of slack θl.M Specifically, the output corrector 78 uses the graph shown in FIG. 11 to obtain the tension control gain Rc based on the amount of slack θl of the wire 36. The tension control gain Rc is calculated based on the target motor angular velocity ωt used for output control (tension control) of the motor 23. M t is a correction gain for correcting t. The tension control gain Rc is set to 1 when the differential angle θdif is equal to or less than the first threshold θth1. The first threshold θth1 may be, for example, 0°. When the differential angle θdif exceeds the first threshold θth1, the tension control gain Rc is set to decrease as the differential angle θdif increases, i.e., as the amount of slack θl of the wire 36 increases. In the illustrated example, the tension control gain Rc decreases linearly from the first threshold θth1 to the second threshold θth2, and is set to 0 at the second threshold θth2. The second threshold θth2 may be, for example, 10°. The tension control gain Rc is set to 0 when the differential angle θdif is equal to or greater than the second threshold θth2, which is 10°. The output correction unit 78 calculates the tension control gain Rc based on the target motor angular velocity ω M The target motor angular velocity ω is calculated by multiplying t by the tension control gain Rc. M Fix t.

[0082] The output corrector 78 calculates the target motor angular velocity ω by multiplying the torque deviation Terr to be applied to the load 32 by the force control gain Ktp, and adding the result to the value obtained by multiplying the torque deviation Terr by the control gain Kvff. M This value is corrected according to the value of t. Target motor angular velocity ω M The value of t indicates the driving direction of the motor 23. That is, the target motor angular velocity ω M When t is smaller than 0, this means that the tension control unit 53 drives the load 32 in the return direction by the biasing member 42. If slack occurs in the wire 36 during such a return operation (i.e., if the tension F of the wire 36 becomes less than 0 N), the transmission characteristics of the wire 36 change significantly. This makes the load 32 more likely to oscillate, and the operation of the load 32 becomes unstable.

[0083] Therefore, the output corrector 78 calculates the target motor angular velocity ω M When t is less than 0, the target motor angular velocity ω M The target motor angular velocity ω is calculated by multiplying t by the tension control gain Rc based on the slack amount θl of the wire 36. M Correct t. Target motor angular velocity ω M The absolute value of t is corrected to be smaller by multiplying it by the tension control gain Rc, that is, corrected to the side that eliminates the slack. M If slack in the wire 36 is detected when t is a value that moves the load 32 in the return direction, the second control device 25 corrects the tension control gain Rc to the side that eliminates the slack, based on the amount of slack θl of the wire 36. This stabilizes the operation of the load 32. In addition, the second control device 25 adjusts the target joint angle θ of the load 32. L The motor angular velocity ω, which is the output of the motor 23, is calculated so as to realize t. M and performs passive compliance control to provide compliance to the load 32.

[0084] On the other hand, when the accuracy of detecting the looseness of the wire 36 by the wire looseness detection unit 77 of the second control device 25 is low, the target motor angular velocity ω M A loose wire 36 may be detected even when t is a value that moves the load 32 in the drive direction. However, in this case, the load 32 is unlikely to oscillate. Therefore, the second control device 25 determines the target motor angular velocity ω M When t is equal to or greater than 0, that is, when the output of the motor 23 is a value that moves the load 32 in the drive direction, the tension control gain Rc is not modified even if slack is detected in the wire 36. In this way, the second control device 25 can stabilize the operation of the load 32 while suppressing a decrease in responsiveness in the return direction by setting a small value for C2, which is the lower limit value at which the wire 36 does not slacken.

[0085] Next, the effect of the output correction performed by the second control device 25 will be described using specific examples. Fig. 12 is a time chart showing the response of a comparative example in which the output correction according to the embodiment is not performed. Fig. 13 is a time chart showing the response of an example in which the output correction according to the embodiment is performed.

[0086] As shown in FIG. 12(A), at time t1, the target joint angle θ L When t decreases from a positive value (operates in the return direction), the target torque Tt of the load 32 (B) becomes approximately 0. The tension F of the wire 36 detected by the tension sensor 39 (D) also becomes approximately 0 N. However, if the second control device 25 does not perform output correction, after the time t2 when the tension F of the wire 36 (D) becomes 0, the actual joint angle θ of the load 32 detected by the joint angle sensor 44 L does not track the target value.

[0087] On the other hand, as shown in FIG. 13(A), the joint angle θ L is smaller than that in FIG. 12. At time t12, the difference angle θdif of (F) (the difference between the estimated angle θest of the motor 23 and the actual angle of the motor θ M When the difference angle θdif (the value obtained by subtracting θdif) exceeds the first threshold value θth1, the tension control gain Rc (E) becomes smaller than 1. When the difference angle θdif (F) becomes equal to or larger than the second threshold value θth2 at time t13, the tension control gain Rc becomes 0. As the tension control gain Rc decreases, the target torque Tt (B) gradually decreases, and the actual joint angle θ of the load 32 (A) L becomes 0 without oscillating the load 32. In this way, between time t12 and time t13, the drive in the direction in which the wire 36 loosens is weakened in accordance with the detected amount of loosening θl of the wire 36, thereby reducing the joint angle θ of the load 32. L In addition, by utilizing the effect of suppressing the behavior of the wire 36 in the direction of loosening, the negative value of C2, which is the lower limit value at which the wire 36 does not loosen, can be set as the lower limit of the target torque Tt, thereby making it possible to improve the responsiveness of the actuator 30 while suppressing oscillation of the load 32.

[0088] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and can be widely modified and implemented. For example, in the above embodiment, the present invention has been described as being applied to the actuator 30 of the hand 5 of the robot 1 as an example, but the present invention can be widely applied to parts other than the hand 5 and to robots 1 other than humanoid robots.

[0089] In another embodiment, the actuator 30 may be configured as shown in Fig. 14. In this actuator 30, an idler pulley 37 and a tensioner 38 are provided at appropriate positions on a wire 36 of a power transmission system 33. In the illustrated example, one idler pulley 37 and one tensioner 38 are provided in a portion that transmits bending side tension Fb of the wire 36. In this way, an idler pulley 37 and a tensioner 38 may be added to the power transmission system 33.

[0090] Furthermore, in the above embodiment, the first control device 13 is disposed on the base 2 of the robot 1, but the first control device 13 may also be disposed on the forearm link 9 of the robot 1, and the location of each device is not limited to this. In addition, the specific configuration, location, quantity, angle, procedure, etc. of each member or part can be changed as appropriate within a range that does not deviate from the spirit of the present invention. Meanwhile, not all of the components shown in the above embodiment are necessarily required, and can be selected as appropriate. [Explanation of symbols]

[0091] 12: Carpal joint 13: First control device 23: Motor (drive source) 25: Second control device 30: Actuator 32: Load body 33: Power transmission system 36: Wire 39: Tension sensor 42: biasing member 43: Motor angle sensor (drive source position sensor) 44: Joint angle sensor (load position sensor) F:Tension Fa: Actual torque tension Fb: Bending side tension Kp2: Proportional gain (speed gain) Kspr: Spring stiffness 1 / Kspr: flexibility coefficient Rc: Tension control gain (control gain) Ta: Actual torque Tc: Counter torque (force that counters the biasing force) Terr: Torque deviation Tt: Target torque Δθ: angle difference (displacement difference) θ L : Joint angle (position) θ L t: target joint angle (target position) θ M : Motor angle (position) θdif: difference angle θl: Amount of looseness θth1: First threshold ω L : Joint angular velocity (velocity) ω L t: target joint angular velocity ω M : Motor angular velocity (speed, drive source output) ω M t: Target motor angular velocity (target speed) ωadd: Target additional angular velocity (target additional velocity) ωf: Angular velocity of driven motor (speed of driven drive source)

Claims

1. An actuator, A driving source; a load driven by the drive source; a power transmission system including a wire that transmits power generated by the drive source to the load body with tension in a drive direction, and a biasing member that constantly biases the wire with a biasing force in a return direction opposite to the drive direction; a drive source position sensor for acquiring the position of the drive source; a load position sensor for acquiring the position and velocity of the load; a control device that controls the output of the drive source so as to realize a given target position of the load body, The control device detecting the slack and the amount of slack in the wire based on the position of the load body and the position of the drive source; An actuator that, when slack in the wire is detected when the target output of the drive source is a value that operates the load body in the return direction, corrects a control gain used to control the output of the drive source to a side that eliminates the slack based on the amount of slack in the wire.

2. 2. The actuator according to claim 1, wherein the control device does not modify the control gain if looseness of the wire is detected when the target output of the drive source is a value that moves the load in the drive direction.

3. a tension sensor for acquiring the tension of the wire; 3. The actuator according to claim 1, wherein the control device sets a target force to be applied to the load body based on the target position and a position of the load body, and controls the output based on a value obtained by multiplying a deviation between the tension of the wire and the target force by a force control gain.

4. 4. The actuator according to claim 3, wherein the force control gain is a product of a flexibility coefficient and a velocity gain of the power transmission system.

5. 5. The actuator according to claim 3, wherein the control device sets a target speed of the drive source based on a driven drive source speed obtained by converting the speed of the load obtained from the load position sensor and a target additional speed of the drive source, and controls the output so as to realize the target speed.

6. 6. The actuator according to claim 3, wherein the control device sets the target force by adding a force opposing the biasing force of the biasing member.

7. 7. The actuator according to claim 3, wherein at least one joint is provided between the drive source and the load body, the wire is provided to pass through the joint, and the tension sensor is disposed on the drive source side with respect to the joint.

8. A control method for an actuator including a drive source, a load body driven by the drive source, a wire that transmits power generated by the drive source to the load body with tension in a drive direction, and a power transmission system including a biasing member that constantly biases the wire with a biasing force in a return direction opposite to the drive direction, controlling the output of the drive source so as to realize a given target position of the load; detecting the slack and the amount of slack in the wire based on the position of the load body and the position of the drive source; A method for controlling an actuator in which, when slack in the wire is detected when the target output of the drive source is a value that operates the load body in the return direction, a control gain used to control the output of the drive source is corrected to a side that eliminates the slack based on the amount of slack in the wire.

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