Vibration suppression device, robot system, and vibration suppression method

Abstract

A vibration suppression device (2) suppresses vibrations of a robot (3) that has: a sensor (24) which detects a state of the robot (3); a robot controller (21) which, on the basis of a state detection value output by the sensor (24) and a set operation procedure, outputs an operation command; and an actuator (22) which operates a mechanism (23) in accordance with the operation command. The vibration suppression device (2): outputs, to the robot controller (21), an identification command pertaining to an operation of the mechanism (23) when a system characteristic that is a characteristic of the mechanism (23) is identified; generates, on the basis of the system characteristic that is identified on the basis of a state detection value which is output by the sensor (24) when the mechanism (23) operates according to the identification command, a stability command that avoids an unstable operation cycle, which is an operation cycle of the mechanism (23) at the time when the operation of the mechanism (23) becomes unstable; and suppresses vibrations of the mechanism (23) by outputting the stability command to the robot controller (21).

Description

Vibration suppression device, robot system, and vibration suppression method

[0001] The present disclosure relates to a vibration suppression device, a robot system, and a vibration suppression method for suppressing vibrations of a robot.

[0002] There is a need for lightweight robots, such as industrial robots, from the perspective of ease of installation and maintenance. Reducing the weight of a robot's mechanism reduces the rigidity of the mechanism, which can make the mechanism more susceptible to vibration. To achieve both weight reduction and vibration reduction, design changes are sometimes made to components such as reducers, which can be sources of vibration. Furthermore, vibration suppression devices are sometimes applied to robots, which modify their motion commands to make them less susceptible to vibration.

[0003] Patent Document 1 discloses a vibration suppression device that reduces vibration by preventing transmission of vibrations at a preset frequency by modifying an operation command through the application of a biquad notch filter. The vibration suppression device disclosed in Patent Document 1 can suppress vibrations of a robot by setting the excitation frequency of the robot to the notch frequency of the biquad notch filter.

[0004] Patent No. 6254180

[0005] In the case of parametric resonance caused by a robot's reducer or the like, the pump frequency, which is the frequency of the parametric resonance, differs from the frequency of the motion command. According to the technology of Patent Document 1, the notch frequency cannot be determined unless the robot is operated to generate vibrations. Vibrations occurring in the robot, i.e., causing the robot to perform unstable motions, can cause malfunctions due to robot vibrations. Thus, the conventional technology disclosed in Patent Document 1 has a problem in that it is necessary to cause the robot to perform unstable motions in preparation for suppressing robot vibrations.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a vibration suppression device that makes it possible to avoid causing a robot to perform unstable movements when preparing to suppress the robot's vibrations.

[0007] In order to solve the above-mentioned problems and achieve the object, a vibration suppression device according to the present disclosure is a vibration suppression device that suppresses vibrations of a robot having a sensor that detects the state of the robot, a robot controller that outputs an operation command based on a state detection value output by the sensor and a set operation procedure, and an actuator that operates a mechanism of the robot in accordance with the operation command. The vibration suppression device according to the present disclosure outputs an identification command to the robot controller that is a command regarding the operation of the mechanism when identifying a system characteristic that is a characteristic of the mechanism, and generates a stability command that avoids an unstable operation period that is an operation period of the mechanism when operation of the mechanism becomes unstable based on the system characteristic identified on the basis of the state detection value output by the sensor when the mechanism operates in accordance with the identification command, and outputs the stability command to the robot controller to suppress vibrations of the mechanism.

[0008] The vibration suppression device according to the present disclosure has the advantage of being able to avoid causing the robot to perform unstable movements in preparation for suppressing vibrations of the robot.

[0009] FIG. 1 is a diagram showing an example of the configuration of a robot system according to the first embodiment; FIG. 2 is a flowchart showing an example of the operation procedure of the vibration suppression device according to the first embodiment; FIG. 3 is a diagram showing an example of parameters used in a simulation by the vibration suppression device according to the first embodiment; FIG. 4 is a diagram showing an example of the results of a simulation by the vibration suppression device according to the first embodiment; FIG. 5 is a diagram showing an example of the configuration of a hardware circuit according to the first embodiment;

[0010] A vibration suppression device, a robot system, and a vibration suppression method according to embodiments will be described in detail below with reference to the accompanying drawings.

[0011] First Embodiment. Fig. 1 is a diagram showing an example configuration of a robot system 1 according to a first embodiment. The robot system 1 includes a vibration suppression device 2 and a robot 3. The vibration suppression device 2 suppresses vibrations of the robot 3. The robot 3 is, for example, an industrial robot. Note that the vibration suppression device 2 has various built-in functions and various means, but in the first embodiment, only the functions and means related to the characteristic processing of the vibration suppression device 2 according to the present disclosure will be described.

[0012] The robot 3 includes a robot controller 21, an actuator 22, a mechanism 23, and a sensor 24. The robot controller 21 controls the operation of the robot 3 by outputting operation commands to the actuator 22. The actuator 22 operates the mechanism 23 in accordance with the operation commands input to the actuator 22. The actuator 22 includes a servo motor as a drive source and a reducer. The mechanism 23 includes an arm with multiple joints and an end effector attached to the tip of the arm. The servo motor, reducer, arm, and end effector are not shown in the figures.

[0013] The sensor 24 detects the state of the robot 3. Specifically, the sensor 24 detects a physical quantity related to the posture of the robot 3 or the environment in which the robot 3 is installed. Examples of the sensor 24 that detects a physical quantity related to the posture of the robot 3 include a displacement sensor, a velocity sensor, an acceleration sensor, and an angular velocity sensor. Examples of physical quantities related to the posture of the robot 3 include position, velocity, and acceleration. An example of the sensor 24 that detects a physical quantity related to the environment in which the robot 3 is installed is a temperature sensor. An example of a physical quantity related to the environment in which the robot 3 is installed is temperature. The sensor 24 outputs a state detection value, which is a detected value of the physical quantity, to the robot controller 21. The robot controller 21 outputs an operation command based on the state detection value output by the sensor 24 and a set operation procedure. The set operation procedure is an operation procedure that is programmed in advance. Note that the physical quantities detected by the sensor 24 are not limited to the above physical quantities.

[0014] The vibration suppression device 2 and the robot 3 are connected to each other so that they can communicate with each other. The vibration suppression device 2 includes an identification command generator 11, a system characteristic identifier 12, a fluctuation characteristic calculator 13, an unstable operating period estimator 14, and a stability command generator 15.

[0015] The identification command generator 11 generates an identification command. The identification command is a command regarding the operation of the mechanism 23 when identifying the system characteristics, which are the characteristics of the mechanism 23. The identification command generator 11 outputs the identification command to each of the system characteristic identifier 12 and the robot controller 21.

[0016] The robot controller 21 outputs the identification command input to the robot controller 21 to the actuator 22. The actuator 22 operates the mechanism 23 in accordance with the identification command. The sensor 24 outputs a state detection value detected when the mechanism 23 is operated in accordance with the identification command to the system characteristic identifier 12.

[0017] The system characteristic identifier 12 identifies the system characteristic based on the identification command input to the system characteristic identifier 12 and the state detection value output by the sensor 24 when the mechanism 23 operates in accordance with the identification command. The system characteristic identifier 12 outputs information on the system characteristic to the fluctuation characteristic calculator 13.

[0018] The fluctuation characteristic calculator 13 divides the system characteristics identified by the system characteristic identifier 12 into fluctuation characteristics that change over time and non-variable characteristics that do not change over time. The fluctuation characteristic calculator 13 calculates normalized fluctuation characteristics, which are normalized fluctuation characteristics, and normalized non-variable characteristics, which are normalized non-variable characteristics. The fluctuation characteristic calculator 13 outputs information on the normalized fluctuation characteristics and information on the normalized non-variable characteristics to the unstable operating period estimator 14.

[0019] The unstable operation period estimator 14 estimates, based on the normalized fluctuation characteristic and the normalized non-fluctuation characteristic, an unstable operation period, which is the operation period of the mechanism 23 when the operation of the mechanism 23 becomes unstable due to parametric resonance of the mechanism 23. The unstable operation period estimator 14 outputs information on the unstable operation period to the stability command generator 15. In the first embodiment, the operation period is defined as the time from the start to the completion of each repeated operation when the robot 3 performs a repetitive operation.

[0020] The stability command generator 15 generates a stability command that avoids the unstable operating period estimated by the unstable operating period estimator 14. The stability command generator 15 outputs the stability command to the robot controller 21. The robot controller 21 outputs the stability command input to the robot controller 21 to the actuator 22. The actuator 22 operates the mechanism 23 in accordance with the stability command. The stability command can also be considered an operation command for causing the mechanism 23 to perform a stable operation.

[0021] In this way, the vibration suppression device 2 outputs to the robot controller 21 an identification command which is a command regarding the operation of the mechanism 23 when identifying the system characteristics which are the characteristics of the mechanism 23. The vibration suppression device 2 generates a stability command which avoids an unstable operation cycle which is the operation cycle of the mechanism 23 when the operation of the mechanism 23 becomes unstable, based on the system characteristics identified based on the state detection values ​​output by the sensor 24 when the mechanism 23 operates in accordance with the identification command. The vibration suppression device 2 suppresses vibration of the mechanism 23 by outputting the stability command to the robot controller 21.

[0022] Next, a detailed description will be given of the operating principle of the vibration suppression device 2 according to the embodiment 1. The following equation (1) is an equation of motion normalized by the moment of inertia about one axis of the mechanism 23.

[0023]

[0024] where x represents the joint angle, which is the angle of the joint of the mechanism 23. The unit of x is rad. β(t) represents the coefficient of the first derivative term. The unit of β(t) is rad / s. ω 2(t) represents the coefficient of the zeroth-order differential term. 2 (t) is in rad 2 / s 2 is.

[0025] Here, a coordinate transformation expressed by the following equation (2) is introduced: Hereinafter, q(t) will be referred to as the transformed coordinate.

[0026]

[0027] D(t) in equation (2) is expressed by the following equation (3).

[0028]

[0029] The identification command generator 11 generates an identification command to reduce the operating speed of the mechanism 23 to a speed lower than the speed at which parametric resonance occurs, thereby enabling the vibration suppression device 2 to operate the mechanism 23 in a manner that does not cause parametric resonance when identifying the system characteristics.

[0030] The system characteristic identifier 12 identifies, as system characteristics, the coefficients of the first-order differential terms and the coefficients of the zeroth-order differential terms in the normalized equations of motion that are normalized with respect to inertia and are equations of motion for each of the multiple axes of the mechanism 23. That is, the system characteristic identifier 12 identifies the coefficients of the β(t) and ω shown in equation (1) 2 The system characteristic identifier 12 identifies β(t) and ω(t) based on the detected state values. 2 The system characteristic identifier 12 identifies β(t) and ω based on the detected state values. 2 The method for identifying (t) is arbitrary.

[0031] When equation (1) is subjected to coordinate transformation using equation (2), the following equation (4) is obtained.

[0032]

[0033] However, Ω 2 (t) is expressed by the following equation (5).

[0034]

[0035] β(t) can be expressed as the following equation (6): 2 (t) can be expressed as the following equation (7).

[0036]

[0037]

[0038] where ω0 represents the damped natural frequency, b represents the normalized non-varying characteristic, g(t) represents the first normalized varying characteristic, and h(t) represents the second normalized varying characteristic.

[0039] Ω shown in equation (5) 2 (t) can be expressed as the following equation (8).

[0040]

[0041] where f(t) represents the third normalized fluctuation characteristic. n 2 By comparing equations (5) and (8), ω is expressed by the following equation (9). n represents the natural frequency in the normalized equation of motion after coordinate transformation.

[0042]

[0043] The fluctuation characteristic calculator 13 calculates the normalized fluctuation characteristics, i.e., the first normalized fluctuation characteristic, the second normalized fluctuation characteristic, and the third normalized fluctuation characteristic, as well as the normalized non-fluctuation characteristic. That is, the fluctuation characteristic calculator 13 calculates g(t), h(t), f(t), and b.

[0044] From equations (5) to (8), f(t) is expressed by the following equation (10).

[0045]

[0046] By substituting equation (8) into equation (4), the following equation (11) is obtained.

[0047]

[0048] Equation (11) can be rewritten as the following equation (12).

[0049]

[0050] Assume that the parametric resonance occurring in mechanism 23 is caused by the reducer. In this case, the number of contact points between the teeth of the reducer changes periodically. The first normalized variation characteristic g(t) and the second normalized variation characteristic h(t) can be approximated by square waves with the same period and phase. Therefore, according to equation (10), the third normalized variation characteristic f(t) has the same period as the excitation period and is a periodic function composed of a square wave and an impulse, which is the first-order differential term in equation (10).

[0051] The transformed coordinate q(t) is approximated as in the following equation (13).

[0052]

[0053] The third normalized fluctuation characteristic f(t) can be expressed as in the following equation (14). k (t) is expressed by the following equation (15).

[0054]

[0055]

[0056] However, f k (t) represents the k-th frequency component of f(t). k -(t) represents the term of f(t) other than the k-th frequency component. k represents the k-th spectral amplitude of the fluctuation part in the coefficient of the zeroth-order differential term of the normalized equation of motion after coordinate transformation. p represents the pump frequency, which is the frequency of the parametric resonance. In the first embodiment, the pump frequency is set to ω e In the first embodiment, the pump frequency can also be said to be the frequency of parametric excitation.

[0057] From equation (13), q, which is the second derivative of the transformed coordinate with respect to time, .. When (t) is calculated, the following equation (16) is obtained. .. " is written with "q" above it. .. " represents a symbol followed by ".

[0058]

[0059] By substituting equations (14) to (16) into equation (11), the following equation (17) is obtained.

[0060]

[0061] Here, l(t) is expressed by the following equation (18).

[0062]

[0063] In equation (17), the frequency is ω p By comparing the coefficients of the cosine and sine terms, the following equations (19) and (20) are derived. p Each of the cosine and sine terms, k -ω p =ω p The term "is" is included.

[0064]

[0065]

[0066] Equations (19) and (20) can be rewritten as the following equation (21).

[0067]

[0068] The vector and matrix in equation (21) are expressed as in the following equation (22).

[0069]

[0070] By using equation (22), equation (21) can be rewritten as the following equation (23).

[0071]

[0072] Equation (22) can be rewritten as the equation of state, which is the following equation (24).

[0073]

[0074] The s described below iis the i-th eigenvalue of H expressed by the following equation (25).

[0075]

[0076] The excitation frequency ω is set so that the following equation (26) holds. e By selecting ω, the operation of the mechanism 23 expressed by the formula (1) can be stabilized. e =ω p It is assumed that

[0077]

[0078] Here, Re(X) represents the real part of X when X is a complex number. . satisfies the following formula (27). . " is written with "D" above it. . " indicates a symbol with ".

[0079]

[0080] However, g min represents the minimum value of g(t), which is the first normalized fluctuation characteristic.

[0081] By using equations (26) and (27), the sufficiently stable condition shown in equation (28) is derived. In the first embodiment, the sufficiently stable condition is a sufficient condition for stabilizing the operation of mechanism 23.

[0082]

[0083] However, the left side of equation (28) represents the attenuation rate.

[0084] In order to stabilize the operation of the mechanism 23 expressed by the formula (1), it is necessary to set ω to satisfy the formula (28). e (=ω p ) should be selected.

[0085] The unstable operation period estimator 14 calculates ω e (=ω p ) and repeat the above calculation, eFor each of the pump frequencies, it is determined whether it is a stable pump frequency or an unstable pump frequency. A stable pump frequency is a pump frequency that satisfies the sufficiently stable condition. An unstable pump frequency is a pump frequency that does not satisfy the sufficiently stable condition. The unstable duty cycle estimator 14 determines T when the equation (28) is not satisfied. e is estimated to be an unstable operating period. e represents the excitation period. e = 2 π / ω e holds true.

[0086] In this way, the unstable operating period estimator 14 determines whether the pump frequency, which is the frequency of parametric resonance, satisfies the conditional expression (28), and calculates the unstable operating period by finding the pump frequency that does not satisfy the conditional expression. The unstable operating period estimator 14 outputs information about the unstable operating period to the stability command generator 15.

[0087] The stability command generator 15 generates a stability command that represents an operation adjusted to avoid the unstable operation period estimated by the unstable operation period estimator 14. The stability command generator 15 outputs the generated stability command to the robot controller 21. The robot controller 21 outputs the stability command to the actuator 22. The actuator 22 operates the mechanism 23 in accordance with the stability command. This makes it possible to cause the mechanism 23 to perform the operation desired by the user of the robot 3 without causing parametric resonance.

[0088] Next, a description will be given of the operation procedure of the vibration suppression device 2 according to embodiment 1. Fig. 2 is a flowchart showing an example of the operation procedure of the vibration suppression device 2 according to embodiment 1.

[0089] In step S1, the identification command generator 11 generates and outputs an identification command. The identification command generator 11 generates an identification command that causes the mechanism 23 to operate at a speed that is slower than the operating speed according to the operation command when the robot 3 is actually used. In this way, the identification command generator 11 generates an identification command that causes the mechanism 23 to operate in a manner that does not cause parametric resonance.

[0090] In step S2, the system characteristic identifier 12 identifies the system characteristic based on the identification command generated in step S1 and the state detection value output by the sensor 24 when the mechanism 23 operates in accordance with the identification command. The system characteristic identifier 12 identifies the system characteristic based on β(t) and ω 2 Identify (t).

[0091] In step S3, the variation characteristic calculator 13 calculates normalized variation characteristics and normalized non-variable characteristics based on the system characteristics identified in step S2. The variation characteristic calculator 13 divides the system characteristics identified in step S2 into variation characteristics and non-variable characteristics, and obtains the normalized variation characteristics and normalized non-variable characteristics. The variation characteristic calculator 13 calculates the normalized variation characteristics g(t), h(t), and f(t), and the normalized non-variable characteristic b.

[0092] Steps S4 and S5 are steps for estimating an unstable operating period based on the normalized varying characteristic and normalized non-varying characteristic obtained in step S3. In step S4, the unstable operating period estimator 14 determines a stable pump frequency and an unstable pump frequency based on a sufficiently stable condition. The unstable operating period estimator 14 calculates ω e (=ω p ) is changed, and by determining whether the sufficiently stable condition is satisfied, a stable pump frequency and an unstable pump frequency are determined.

[0093] In step S5, the unstable operating period estimator 14 calculates the unstable operating period. The unstable operating period estimator 14 calculates T when the equation (28) is not satisfied. e is estimated to be the unstable operating period, thereby calculating the unstable operating period.

[0094] In step S6, the stability command generator 15 generates a stability command and outputs the stability command. The stability command generator 15 generates a stability command that represents an operation adjusted to avoid the unstable operation period calculated in step S5. The stability command generator 15 outputs the generated stability command to the robot controller 21. With the above, the vibration suppression device 2 ends the operation according to the procedure shown in FIG. 2.

[0095] Next, an example of calculation of an unstable operation period by the vibration suppression device 2 according to embodiment 1 will be described. Hereinafter, calculation of an unstable operation period by the vibration suppression device 2 will be referred to as a simulation by the vibration suppression device 2. In the following description, it is assumed that the robot 3 operates only one axis.

[0096] Fig. 3 is a diagram showing examples of parameters used in a simulation by the vibration suppression device 2 according to embodiment 1. Fig. 3 shows symbols representing the parameters, the meanings of the parameters, and example values ​​of the parameters.

[0097] 3, the parameter "g" represents the first normalized fluctuation characteristic g(t). In the example shown in FIG. 3, g(t) is p That is, the frequency of g(t) is the pump frequency, ω p 3, the parameter "h" represents the second normalized fluctuation characteristic h(t). In the example shown in FIG. 3, h(t) is the second normalized fluctuation characteristic h(t) when the frequency is 500 Ω. p That is, the frequency of h(t) is the pump frequency, ω p It is 500 times larger than that.

[0098] Fig. 4 is a first diagram showing an example of the results of a simulation performed by the vibration suppression device 2 according to the first embodiment. Fig. 4 shows a graph representing the relationship between the k-th spectral amplitude of f(t), which is the third normalized fluctuation characteristic, and the excitation frequency. The vertical axis of the graph shown in Fig. 4 represents the k-th spectral amplitude of f(t). The horizontal axis of the graph shown in Fig. 4 represents the excitation frequency.

[0099] In FIG. 4, the k-th spectral amplitude of f(t), i.e., f k is the excitation frequency, ω e This is because when the right side of equation (12) is 0.4 [Hz], that is, when the excitation period is 2.5 [s], f k This shows that the

[0100] Fig. 5 is a second diagram showing an example of the results of a simulation using the vibration suppression device 2 according to the first embodiment. Fig. 5 shows a graph representing the relationship between the damping rate and the excitation period. The vertical axis of the graph shown in Fig. 5 represents the damping rate. The damping rate is expressed by the left side of equation (28). The horizontal axis of the graph shown in Fig. 5 represents the excitation period.

[0101] In FIG. 5, the excitation period T e is near 1.4 [s], 1.5 [s], 2.5 [s], and 4.2 [s], the damping rate is a positive number. When the damping rate is a positive number, the operation of the mechanism 23 becomes unstable. The stability command generator 15 generates a stability command in which the excitation frequency is adjusted so as to avoid the excitation period when the operation of the mechanism 23 becomes unstable.

[0102] In the above, for ease of explanation, g(t) and h(t) are each represented by a square wave. However, g(t) and h(t) may also be represented by something other than a square wave. For example, the waveforms representing g(t) and h(t) may be any step-shaped waveform that corresponds to the movement pattern desired for the robot 3. The above processing by the vibration suppression device 2 can also be applied when g(t) and h(t) are each represented by something other than a square wave.

[0103] In the above description, the parametric resonance occurring in the mechanism 23 is attributed to the reducer. However, the parametric resonance may be attributed to a system characteristic that changes over time other than the reducer. In this case, the above processing by the vibration suppression device 2 can be applied even when each of g(t) and h(t) is expressed by a wave other than a square wave.

[0104] In the above, it is assumed that the robot 3 operates only one axis. When multiple axes of the mechanism 23 are moved, the vibration suppression device 2 applies the above method to all axes. In this case, the stability command generator 15 generates a stability command for each of the multiple axes based on the union of the unstable operating periods estimated for each of the multiple axes of the mechanism 23. The vibration suppression device 2 can suppress vibrations when multiple axes are moved by generating a stability command for each axis based on the union of the unstable operating periods calculated for all axes.

[0105] According to the first embodiment, the vibration suppression device 2 operates the mechanism 23 by outputting an identification command to identify system characteristics, and generates a stability command that avoids unstable operating periods based on the identified system characteristics. When operating the mechanism 23 based on the identification command, there is no need to generate parametric resonance. When making adjustments to suppress vibrations of the robot 3, the robot 3 can be made to operate quietly and stably. In other words, the vibration suppression device 2 can generate a stability command for suppressing vibrations of the robot 3 without causing vibrations in the robot 3. Therefore, the vibration suppression device 2 can avoid making the robot 3 perform unstable operations in preparation for suppressing vibrations of the robot 3. The vibration suppression device 2 can avoid problems that arise from making the robot 3 perform unstable operations.

[0106] Furthermore, the vibration suppression device 2 can output a stability command through processing that takes a shorter time than when performing a convolution operation on multiple signals. When parameters change rapidly, the vibration suppression device 2 can generate a stability command that matches the change in the parameters. The vibration suppression device 2 can suppress parametric resonance caused by parameters that change rapidly. The vibration suppression device 2 can suppress parametric resonance even when there is a time change in inertia, friction, or stiffness in each axis of the robot 3.

[0107] In the above description, the robot 3 is an industrial robot, but is not limited to this. The robot 3 may also be a service robot, rescue robot, medical robot, care robot, entertainment robot, forestry robot, agricultural robot, or the like. Furthermore, the vibration suppression device 2 can be applied to suppressing vibrations in any device that includes a controller that outputs an operation command based on a state detection value and a set operation procedure, and an actuator that operates a mechanism according to the operation procedure. The robot 3 according to the first embodiment is understood to include such devices in general.

[0108] Next, a description will be given of hardware that realizes the vibration suppression device 2. The vibration suppression device 2 is realized by using a processing circuit. The processing circuit may be a dedicated circuit or a circuit in which a processor executes software.

[0109] When the processing circuit is a dedicated circuit, the vibration suppression device 2 is realized by, for example, the hardware circuit shown in Fig. 6. Fig. 6 is a diagram showing an example of the configuration of the hardware circuit 30 according to the first embodiment. The hardware circuit 30 includes an input unit 31, a processing circuit 32, and an output unit 33.

[0110] The input unit 31 is an interface circuit that receives data input from outside the hardware circuit 30 and provides the data to the processing circuit 32. The output unit 33 is an interface circuit that sends data from the processing circuit 32 to outside the hardware circuit 30.

[0111] The processing units of the vibration suppression device 2, namely, the identification command generator 11, the system characteristic identifier 12, the fluctuation characteristic calculator 13, the unstable operating period estimator 14, and the stability command generator 15, are realized by a dedicated circuit, the processing circuit 32. The processing circuit 32 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit combining these. The processing units of the vibration suppression device 2 may be realized by the processing circuit 32 on a function-by-function basis, or all functions may be realized collectively by the processing circuit 32.

[0112] When the processing circuit is realized by software, the processing circuit is, for example, the control circuit shown in Fig. 7. Fig. 7 is a diagram showing an example configuration of a control circuit 34 according to the first embodiment. The control circuit 34 includes an input unit 31, an output unit 33, a processor 35, and a memory 36. The input unit 31 of the control circuit 34 is an interface circuit that receives data input from outside the control circuit 34 and provides the data to the processor 35. The output unit 33 of the control circuit 34 is an interface circuit that sends data from the processor 35 or the memory 36 to outside the control circuit 34.

[0113] When the processing circuit is the control circuit 34 shown in FIG. 7 , the processing unit of the vibration suppression device 2 is realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in memory 36. The processing circuit realizes the functions of the processing unit of the vibration suppression device 2 by having the processor 35 read and execute the program stored in memory 36. In other words, the processing circuit includes memory 36 for storing programs that result in the processing of the vibration suppression device 2 being executed. It can also be said that these programs cause a computer to execute the procedures and methods of the vibration suppression device 2.

[0114] The processor 35 is a central processing unit (CPU). The processor 35 may be a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (digital signal processor). The memory 36 may be, for example, a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM (registered trademark)), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a digital versatile disk (DVD). The processing unit of the vibration suppression device 2 may be realized by combining the control circuit 34 and the processing circuit 32 shown in FIG. 6.

[0115] The program stored in the memory 36 may be provided in a state stored on a recording medium such as a CD (Compact Disc)-ROM or a DVD-ROM, or may be provided via a communication line.

[0116] Next, hardware for realizing the robot controller 21 shown in Fig. 1 will be described. The robot controller 21 is realized by using a processing circuit, similar to the vibration suppression device 2. The robot controller 21 has the configuration of the hardware circuit 30 shown in Fig. 6, or a configuration similar to the control circuit 34 shown in Fig. 7. The functions of the robot controller 21 may be realized by combining a configuration similar to the processing circuit 32 shown in Fig. 6 with a configuration similar to the control circuit 34 shown in Fig. 7.

[0117] The vibration suppression device 2 may be connected to the robot 3 via a network. The network may be, for example, a wide area network (WAN) such as the Internet, or a local area network (LAN). The vibration suppression device 2 may be configured by a server built in a cloud environment.

[0118] According to the first embodiment, the vibration suppression device 2 outputs an identification command to the robot controller 21, and generates a stability command that avoids an unstable operation cycle, which is an operation cycle of the mechanism 23 when the operation of the mechanism 23 becomes unstable, based on the system characteristics identified based on the state detection values ​​output by the sensor 24 when the mechanism 23 operates in accordance with the identification command, and suppresses vibration of the mechanism 23 by outputting the stability command to the robot controller 21. The vibration suppression device 2 can generate a stability command for suppressing vibration of the robot 3 without causing vibration in the robot 3 during preparatory operation. This makes it possible for the vibration suppression device 2 to avoid causing the robot 3 to perform unstable operations during preparation for suppressing vibration of the robot 3.

[0119] The vibration suppression device 2 also includes an identification command generator 11 that generates an identification command, a system characteristic identifier 12 that identifies system characteristics based on the identification command and state detection values ​​output by the sensor 24 when the mechanism 23 operates in accordance with the identification command, a fluctuation characteristic calculator 13 that divides the identified system characteristics into fluctuation characteristics and non-fluctuating characteristics and outputs information on normalized fluctuation characteristics and information on the normalized non-fluctuating characteristics, an unstable operation period estimator 14 that estimates an unstable operation period based on the normalized fluctuation characteristics and the normalized non-fluctuating characteristics, and a stability command generator 15 that generates a stability command that avoids the estimated unstable operation period. This allows the vibration suppression device 2 to generate a stability command for suppressing vibration of the robot 3 without causing vibration in the robot 3 during the preparatory operation. The vibration suppression device 2 can also suppress parametric resonance caused by rapidly changing parameters.

[0120] Furthermore, the identification command generator 11 generates an identification command to reduce the operating speed of the mechanism 23 below a speed at which parametric resonance may occur, thereby enabling the vibration suppression device 2 to avoid the occurrence of parametric resonance in preparation for suppressing vibrations of the robot 3.

[0121] The system characteristic identifier 12 identifies, as system characteristics, the coefficients of the first-order differential terms and the zeroth-order differential terms in the normalized equations of motion that are normalized with respect to inertia and are equations of motion for each of the multiple axes of the mechanism 23. The coefficient of the first-order differential term, β(t), is expressed by the above equation (6). The coefficient of the zeroth-order differential term, ω, is expressed by the above equation (6). 2 (t) is expressed by the above formula (7). As a result, the vibration suppression device 2 can suppress parametric resonance even when there is a time change in inertia, friction, or stiffness in each axis of the robot 3.

[0122] The unstable operating period estimator 14 determines whether the pump frequency, which is the frequency of the parametric resonance, satisfies the conditional expression, and calculates the unstable operating period by finding the pump frequency that does not satisfy the conditional expression. The conditional expression is expressed by the above expression (28). This allows the vibration suppression device 2 to estimate the unstable operating period based on the normalized fluctuation characteristic and the normalized non-fluctuation characteristic.

[0123] Furthermore, the pump frequency is set to the excitation frequency of the mechanism 23. This allows the vibration suppression device 2 to generate a stability command that avoids an unstable operating period.

[0124] Furthermore, the stability command generator 15 generates a stability command for each of the multiple axes based on the union of the unstable operating periods estimated for each of the multiple axes of the mechanism 23. This allows the vibration suppression device 2 to suppress vibrations when the multiple axes of the mechanism 23 are moved.

[0125] The configurations described in the above embodiments are examples of the contents of the present disclosure. The configurations of the embodiments can be combined with other known technologies. Part of the configurations of the embodiments can be omitted or modified without departing from the gist of the present disclosure.

[0126] 1 Robot system, 2 Vibration suppression device, 3 Robot, 11 Identification command generator, 12 System characteristic identifier, 13 Fluctuation characteristic calculator, 14 Unstable operation period estimator, 15 Stability command generator, 21 Robot controller, 22 Actuator, 23 Mechanism, 24 Sensor, 30 Hardware circuit, 31 Input unit, 32 Processing circuit, 33 Output unit, 34 Control circuit, 35 Processor, 36 Memory.

Claims

1. A vibration suppression device that suppresses vibrations of a robot having a sensor that detects the state of the robot, a robot controller that outputs operation commands based on the state detection values output by the sensor and a set operation procedure, and an actuator that operates the robot's mechanism in accordance with the operation commands, characterized in that the vibration suppression device outputs an identification command to the robot controller that is a command regarding the operation of the mechanism when identifying system characteristics that are characteristics of the mechanism, generates a stability command that avoids unstable operation periods that are operation periods of the mechanism when operation of the mechanism becomes unstable based on the system characteristics identified on the basis of the state detection values output by the sensor when the mechanism operates in accordance with the identification command, and outputs the stability command to the robot controller to suppress vibrations of the mechanism.

2. A vibration suppression device according to claim 1, comprising: an identification command generator that generates the identification command; a system characteristic identifier that identifies the system characteristic based on the identification command and the state detection value output by the sensor when the mechanism operates in accordance with the identification command; a fluctuation characteristic calculator that divides the identified system characteristic into fluctuating characteristics that change with time and non-fluctuating characteristics that do not change with time, and outputs information on normalized fluctuation characteristics that are the normalized fluctuating characteristics and information on normalized non-fluctuating characteristics that are the normalized non-fluctuating characteristics; an unstable operation period estimator that estimates, based on the normalized fluctuation characteristics and the normalized non-fluctuating characteristics, the unstable operation period of the mechanism when operation of the mechanism becomes unstable due to parametric resonance of the mechanism; and a stability command generator that generates the stability command in which the estimated unstable operation period is avoided.

3. The vibration suppression device according to claim 2, characterized in that the identification command generator generates the identification command to reduce the speed of the mechanism's operation below the speed at which the parametric resonance occurs.

4. The vibration suppression device according to claim 2, characterized in that the system characteristic identifier identifies, as the system characteristics, the coefficients of the first-order differential terms and the zeroth-order differential terms in the equations of motion for each of the multiple axes of the mechanism, which are normalized with respect to inertia.

5. When the damped natural frequency is ω0, the normalized fluctuation characteristics, ie, the first normalized fluctuation characteristic and the second normalized fluctuation characteristic, are g(t) and h(t), respectively, and the normalized non-fluctuation characteristic is b, the coefficient of the first-order differential term, β(t), is expressed by the following equation (1), and the coefficient of the zeroth-order differential term, ω 2 5. The vibration suppression device according to claim 4, wherein (t) is expressed by the following equation (2).

6. The vibration suppression device according to claim 4, characterized in that the unstable operating period estimator determines whether or not the pump frequency, which is the frequency of the parametric resonance, satisfies a conditional expression, and calculates the unstable operating period by determining the pump frequency that does not satisfy the conditional expression.

7. When X is a complex number, the real part of X is Re(X), and the i-th eigenvalue in H expressed by the following equations (4) and (5) is s. i , the damped natural frequency is ω0, the normalized non-variable characteristic is b, the first normalized variation characteristic which is the normalized variation characteristic is g(t), and the minimum value of g(t) is g min , the pump frequency is ω p , the natural frequency in the normalized equation of motion after coordinate transformation is ω n , and the k-th spectral amplitude of the fluctuation part in the coefficient of the zeroth-order differential term of the normalized equation of motion after coordinate transformation is defined as f k The vibration suppression device according to claim 6, wherein the conditional expression is expressed by the following expression (3):

8. The vibration suppression device according to claim 6, wherein the pump frequency is set as an excitation frequency of the mechanism.

9. The vibration suppression device described in claim 2, characterized in that the stability command generator generates the stability command for each of the multiple axes based on the union of the unstable operating periods estimated for each of the multiple axes of the mechanism.

10. A robot system comprising: a robot; and a vibration suppression device that suppresses vibrations of the robot, wherein the robot has a sensor that detects the state of the robot, a robot controller that outputs operation commands based on state detection values output by the sensor and a set operation procedure, and an actuator that operates a mechanism of the robot in accordance with the operation commands, wherein the vibration suppression device outputs to the robot controller an identification command that is a command regarding the operation of the mechanism when identifying system characteristics that are characteristics of the mechanism, and generates a stability command that avoids unstable operation periods that are operation periods of the mechanism when operation of the mechanism becomes unstable, based on the system characteristics identified on the basis of the state detection values output by the sensor when the mechanism operates in accordance with the identification command, and suppresses vibrations of the mechanism by outputting the stability command to the robot controller.

11. A vibration suppression method for suppressing vibrations of a robot having a sensor for detecting the state of the robot, a robot controller for outputting operation commands based on state detection values output by the sensor and a set operation procedure, and an actuator for operating a mechanism of the robot in accordance with the operation commands, comprising the steps of: generating an identification command which is a command for the operation of the mechanism when identifying a system characteristic which is a characteristic of the mechanism, and outputting the identification command to the robot controller; identifying the system characteristic based on the identification command and the state detection value output by the sensor when the mechanism operates in accordance with the identification command; dividing the identified system characteristic into a fluctuating characteristic which changes with time and a non-fluctuating characteristic which does not change with time, and determining a normalized fluctuating characteristic which is a normalized fluctuating characteristic and a normalized non-fluctuating characteristic which is a normalized non-fluctuating characteristic; and estimating an unstable operation period which is the operation period of the mechanism when operation of the mechanism becomes unstable due to parametric resonance of the mechanism, based on the normalized fluctuating characteristic and the normalized non-fluctuating characteristic; generating a stability command that avoids the estimated unstable operating period, and outputting the stability command to the robot controller to suppress vibration of the mechanism.

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