Inertia estimation device, inertia estimation method, and motor control device

Abstract

To provide an inertia estimation device and an inertia estimation method capable of more accurately estimating inertia of a movable part.SOLUTION: An inertia estimation apparatus 12 for estimating inertia of a movable part 50 including a motor 52, a transmission 56, and a driven object 58 includes a controller 12 configured to estimate the inertia of the movable part 50 based on an acceleration α and an output torque τ of the motor 52 and a transmission gear ratio R (R = m / n) that is a ratio of an output-side speed m to an input-side speed n of the transmission 56 when the motor 52 is caused to perform an acceleration / deceleration operation for inertia estimation. The controller 12 is configured to execute the acceleration / deceleration operation for inertia estimation in a state where the transmission gear ratio R is changed to a transmission gear ratio for inertia estimation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This specification discloses an inertia estimation device, an inertia estimation method, and a motor control device that estimate the inertia of a moving part including a motor, a transmission, and a driven body. [Background technology]

[0002] Many techniques have been proposed for controlling the position or speed of a driven object driven by a motor with high precision. For example, in a machine tool, the position or speed of the driven object, which is the spindle and the workpiece attached to the spindle, must be controlled with high precision. To control the position or speed of the driven object with high precision, it is necessary to determine the control parameters of the motor based on the inertia of the moving parts, including the driven object and the motor. However, the inertia of the moving parts is not constant and may change as appropriate. For example, in the case of the spindle of a machine tool, when the workpiece attached to the spindle is changed, the inertia of the entire moving parts changes.

[0003] Therefore, techniques for estimating the inertia of a moving part at any time have been proposed. For example, Patent Document 1 discloses a technique for calculating the inertia of a moving part from the ratio of an integrated value of a torque command value to an integrated value of an acceleration detection value when a driven body is accelerated or decelerated. The technique in Patent Document 1 makes it possible to estimate the inertia of the moving part with a certain degree of accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6009397 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the estimated inertia value naturally contains an estimation error. This estimation error becomes larger as the gear ratio, which is the output speed of the moving part relative to the input speed, becomes smaller. However, in the prior art such as Patent Document 1, the relationship between the gear ratio and the error has not been considered. As a result, it has not been possible to estimate the inertia of the moving part with high accuracy.

[0006] Therefore, this specification discloses an inertia estimation device and an inertia estimation method that can more accurately estimate the inertia of a moving part. [Means for solving the problem]

[0007] The inertia estimation device disclosed in this specification is an inertia estimation device that estimates the inertia of a moving part including a motor, a transmission, and a driven body, and is characterized in that it includes a controller configured to estimate the inertia of the moving part based on the acceleration and output torque of the motor when the motor is made to perform an acceleration / deceleration operation for inertia estimation, and on the gear ratio of the transmission, which is the output side speed relative to the input side speed, and the controller is configured to execute the acceleration / deceleration operation for inertia estimation with the gear ratio changed to a gear ratio for inertia estimation.

[0008] In this case, the speed ratio for inertia estimation may be the maximum speed ratio of the transmission.

[0009] The speed ratio for inertia estimation may be a specified speed ratio designated by the user.

[0010] Furthermore, the controller may store the gear ratio of the transmission at that time as a pre-start gear ratio prior to the acceleration / deceleration operation for estimation, and change the gear ratio of the transmission to the pre-start gear ratio after the acceleration / deceleration operation for estimation is completed.

[0011] The controller is also configured to acquire a first total inertia, which is the motor shaft converted total inertia when a workpiece is removed from the driven body, and a second total inertia, which is the motor shaft converted total inertia when the workpiece is loaded on the driven body, and to calculate an estimated work inertia by subtracting the first total inertia from the second total inertia and dividing the result by the square of the gear ratio, and the motor shaft converted total inertia may be calculated by dividing the integrated value of the torque command of the motor in an integration interval in which the motor is accelerating or decelerating by the integrated value of the acceleration of the motor in the integration interval.

[0012] Furthermore, the motor control device disclosed in this specification may be configured to have the above-mentioned inertia estimation device, and the controller may be configured to calculate the inertia of a workpiece loaded on the driven body as an estimated workpiece inertia, and change a servo parameter, which is a control parameter of the motor, based on the estimated workpiece inertia.

[0013] The inertia estimation method disclosed in this specification is an inertia estimation method for estimating the inertia of a moving part including a motor, a transmission, and a driven body, and may involve changing a gear ratio, which is the output side speed relative to the input side speed of the transmission, to a gear ratio for inertia estimation, causing the motor to perform an acceleration / deceleration operation for inertia estimation, and estimating the inertia of the moving part based on the acceleration and output torque of the motor when the acceleration / deceleration operation for inertia estimation is performed, and the gear ratio. [Effects of the Invention]

[0014] According to the technology disclosed in this specification, the acceleration / deceleration operation for inertia estimation is performed with the gear ratio changed to the gear ratio for inertia estimation, which reduces the estimation error of the inertia of the moving part and allows for more accurate estimation of the inertia of the moving part. [Brief explanation of the drawings]

[0015] [Figure 1]FIG. 2 is a block diagram showing the configuration of a motor control device. [Figure 2] 10 is a flowchart showing a flow of calculation of an estimated workpiece inertia and setting of servo parameters by the motor control device. [Figure 3] FIG. 10 is a block diagram showing the configuration of another motor control device. [Figure 4] 4 is a flowchart showing a flow of estimating a workpiece inertia and changing servo parameters by the motor control device of FIG. 3. [Figure 5] FIG. 10 is a block diagram showing the configuration of another motor control device. [Figure 6] 6 is a flowchart showing a flow of estimating a workpiece inertia and changing servo parameters by the motor control device of FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0016] The configuration of a motor control device 10 will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the motor control device 10. The motor control device 10 controls the driving of a motor 52. The motor 52 is mechanically coupled to a driven body 58 via a transmission 56. The driven body 58 includes a workpiece 60 that is detachable and replaceable. Hereinafter, the motor 52, the driven body 58, and the transmission 56 will be collectively referred to as the "moving part 50." The moving part 50 can be considered to be the moving part of various devices. For example, the moving part 50 may be the moving part of a machine tool, such as the spindle of a lathe. In this case, the workpiece attached to the spindle and machined by the machine tool corresponds to the workpiece 60 in FIG. 1.

[0017] The position sensor 54 detects the position of the motor 52 or the driven body 58. The position sensor 54 is, for example, an encoder that optically or electromagnetically detects the position of the motor 52 or the driven body 58. The position of the motor 52 or the driven body 58 detected by the position sensor 54 is output to the motor control device 10 as a position detection value Pd.

[0018] As described above and shown in FIG. 1 , the movable part 50 includes a transmission 56. The transmission 56 changes the speed of the output power of the motor 52 and transmits it to the driven body 58. The transmission 56 in this example can change the gear ratio R in a stepwise or continuous manner. The gear ratio R is the ratio of the output speed m to the input speed n. That is, R=m / n. Hereinafter, the maximum gear ratio among the gear ratios R selectable by the transmission 56 is referred to as the "maximum gear ratio Rmx." The transmission 56 includes, for example, gears, pulleys, clutches, or a combination thereof. The transmission 56 may also have an electric actuator (not shown) for automatically switching the gear ratio R. The electric actuator, for example, switches a clutch or the like in response to a command from the gear ratio switching unit 22 (described later) to change the gear ratio R.

[0019] The motor control device 10 controls the position or speed of the motor 52, and therefore the driven body 58. The motor control device 10 is broadly divided into a controller 12 and a current controller 14. The current controller 14 is electrically connected to a power supply (not shown), and controls the current applied to the motor 52 in accordance with a torque command Tc output from the controller 12. The current controller 14 is, for example, an inverter.

[0020] Controller 12 controls the driving of motor 52 in response to a control command input from a higher-level control device. This controller 12 also functions as an inertia estimation device that estimates inertia. Physically, controller 12 is a computer having a processor and memory. For example, if moving part 50 is the spindle of a machine tool, controller 12 may be a numerical control device incorporated in the machine tool or a controller of the machine tool.

[0021] 1, controller 12 is configured to function as a position command generator 16, subtractor 17, feedback controller 18, inertia calculator 20, gear ratio switch 22, and parameter calculator 24. Position command generator 16 outputs a position command value Pc in response to a control command from a higher-level control device. Subtractor 17 subtracts a position detection value Pd output from position sensor 54 from position command value Pc, and outputs the result as a position deviation ΔP.

[0022] The FB controller 18 calculates the torque command Tc based on the position deviation ΔP. For example, the FB controller 18 may calculate the torque command Tc by PID control. That is, the FB controller 18 may multiply the position deviation ΔP, the integral value of the position deviation ΔP, and the derivative value of the position deviation ΔP by a proportional gain, an integral gain, and a derivative gain, respectively, and calculate the sum of these values ​​as the torque command Tc. Furthermore, the manner in which the FB controller 18 calculates the torque command Tc is not particularly limited and may be changed as appropriate.

[0023] The controller 12 also functions as an inertia calculation unit 20, a parameter calculation unit 24, and a gear ratio switching unit 22. The reason for this configuration will be explained. The torque command Tc described above is the manipulated variable for the motor 52. Coefficients used to calculate this manipulated variable, such as proportional gain and integral gain, are parameters for controlling the motor 52, i.e., servo parameters Sp. In order to accurately control the position or speed of the motor 52 or the driven body 58, the servo parameters Sp must be set to values ​​corresponding to the inertia of the movable part 50. However, the inertia of the movable part 50 varies depending on the type of workpiece 60 placed on the driven body 58. Therefore, in order to set an appropriate servo parameter Sp, the controller 12 of this example periodically or irregularly calculates an estimated workpiece inertia Jw' and changes the servo parameter Sp. The calculation of the estimated workpiece inertia Jw' will be explained in detail below.

[0024] As is well known, torque τ is the product of inertia J and acceleration α, and is expressed by Equation 1. τ=J×α (1)

[0025] When estimating inertia, the above-mentioned formula 1 is used. Specifically, when estimating inertia, the position command generation unit 16 outputs a position command value Pc that causes the movable part 50 to accelerate or decelerate. The inertia calculation unit 20 sets the section in which the movable part 50 is accelerating or decelerating as an integration section, and calculates the motor shaft equivalent total inertia J from the motor torque τ and acceleration α in the integration section. Specifically, the motor shaft equivalent total inertia J is the value obtained by dividing the integrated value of the motor torque τ in the integration section by the integrated value of the acceleration α of the motor 52 in the integration section, and is expressed by formula 2. Note that the acceleration α is obtained, for example, by differentiating the position detection value Pd twice.

number

[0026] Hereinafter, the motor shaft converted total inertia J when no workpiece 60 is loaded on the driven body 58 will be referred to as the "first total inertia Jt," and the motor shaft converted total inertia J when a workpiece 60 is loaded will be referred to as the "second total inertia Jh." Here, the second total inertia Jh is the sum of the first total inertia Jt and the value obtained by multiplying the workpiece inertia Jw by the square of the gear ratio R. That is, the second total inertia Jh is expressed by the following equation 3. Jh=Jt+Jw×R 2 (3)

[0027] Therefore, the estimated workpiece inertia Jw' can be calculated by subtracting the first total inertia Jt from the second total inertia Jh and dividing the result by the square of the speed ratio R, as shown in Equation 4. Jw'=(Jh-Jt) / R 2 (4)

[0028] The first total inertia Jt can be obtained by accelerating and decelerating the movable part 50 with the workpiece 60 removed from the driven body 58, and applying the motor torque τ and acceleration α at that time to Equation 2. Similarly, the second total inertia Jh can be obtained by accelerating and decelerating the movable part 50 with the workpiece 60 loaded on the driven body 58, and applying the motor torque τ and acceleration α at that time to Equation 2.

[0029] Incidentally, the estimated workpiece inertia Jw' calculated by equation 4 naturally includes an estimation error. This estimation error becomes larger as the gear ratio R becomes smaller. This will be explained below. When the inertia estimation error rate of the first total inertia Jt generated due to variations in the motor torque constant, etc. is denoted by At, the inertia estimation error rate of the second total inertia Jh is denoted by Ah, and the true value of the workpiece inertia is denoted by Jw, the estimated workpiece inertia Jw' taking the errors into consideration is expressed by equation 5.

number

[0030] Therefore, the error rate B of the estimated work inertia Jw' with respect to the true value Jw can be expressed by Equation 6. As is clear from Equation 6, the error rate B is inversely proportional to the square of the gear ratio R. Therefore, the smaller the gear ratio R, the smaller the denominator on the right side of Equation 6 becomes, and the larger the error rate B becomes.

number

[0031] Note that when the servo parameter Sp is changed using the motor-shaft converted total inertia J rather than the work inertia Jw, the error rate remains constant regardless of the gear ratio R. However, when the motor-shaft converted total inertia J is used, it is necessary to calculate the motor-shaft converted total inertia J for each gear ratio R selectable by the transmission 56. Furthermore, the work inertia Jw must be calculated in the process of calculating the motor-shaft converted total inertia J2 calculated for a different gear ratio R2 based on the motor-shaft converted total inertia J1 calculated for a specific gear ratio R1. Furthermore, when the motor-shaft converted total inertia J is used, it is necessary to store the motor-shaft converted total inertia J and the gear ratio at which the motor-shaft converted total inertia J was calculated, which complicates control. Considering these circumstances, it can be said that it is more advantageous to use the work inertia Jw rather than the motor-shaft converted total inertia J. Therefore, in this example, the servo parameter Sp is changed based on the work inertia Jw rather than the motor-shaft converted total inertia J.

[0032] As described above, the smaller the gear ratio R, the larger the error rate B of the estimated workpiece inertia Jw'. Therefore, the motor control device 10 disclosed in this specification has a gear ratio switching unit 22 that switches the gear ratio R to the maximum gear ratio Rmx prior to estimating the workpiece inertia Jw. That is, this motor control device 10 uses the maximum gear ratio Rmx as the gear ratio for estimating the workpiece inertia Jw. Before causing the moving part 50 to perform an acceleration / deceleration operation for inertia estimation, an electrical signal for switching the gear ratio R is output to the transmission 56, changing the gear ratio R to the maximum gear ratio Rmx. Then, the inertia calculation unit 20 applies the motor torque τ and acceleration α obtained when R=Rmx, and the maximum gear ratio Rmx, to Equation 2 and Equation 4 to calculate the estimated workpiece inertia Jw'. This reduces the error rate B, resulting in a more accurate estimation of the estimated workpiece inertia Jw'.

[0033] 2 is a flowchart showing the flow of calculation of estimated workpiece inertia Jw' and setting of servo parameter Sp by motor control device 10. The processing shown in FIG. 2 may be executed, for example, at a timing specified by a user, or may be executed automatically by controller 12. For example, if movable part 50 is a machine tool, controller 12 may automatically start the processing of FIG. 2 based on the progress of a machining program being executed by the machine tool. For example, controller 12 may automatically execute the processing of FIG. 2 at the timing when an instruction is given in the machining program to change the type of workpiece to be machined by the machine tool.

[0034] When changing the servo parameter Sp, the controller 12 first switches the gear ratio R of the transmission 56 to the maximum gear ratio Rmx (S10). Next, the controller 12 executes an inertia estimation process in that state (S12). Specifically, the controller 12 causes the movable part 50 to perform an acceleration / deceleration operation with the workpiece 60 removed from the driven body 58 (S14). For example, the controller 12 may store data of the position command value Pc that causes acceleration or deceleration of the movable part 50 as an estimation profile, and may generate the position command value Pc based on this estimation profile during inertia estimation. Furthermore, prior to the acceleration / deceleration operation, the controller 12 may detect whether the driven body 58 has a workpiece 60 loaded thereon, and if so, may display a message to the user urging them to remove the workpiece 60.

[0035] Next, the controller 12 calculates the motor shaft equivalent total inertia in a state where no workpiece 60 is loaded, i.e., the first total inertia Jt, based on the position detection value Pd and the torque command Tc collected during the acceleration / deceleration operation (S16). Specifically, the controller 12 collects the position detection value Pd and the torque command Tc during the acceleration / deceleration operation. The controller 12 then calculates the acceleration by differentiating the position detection value Pd twice, and identifies the section where acceleration or deceleration is occurring as an integration section based on this acceleration. The controller 12 then calculates the first total inertia Jt by dividing the integrated value of the motor torque τ in the integration section by the integrated value of the acceleration α of the motor 52 in the integration section based on Equation 2.

[0036] Note that the first total inertia Jt, i.e., the value of the motor shaft converted total inertia when the workpiece 60 is removed, may change slightly in apparent inertia due to changes in sliding resistance that occur over several years, but will hardly change in the short term. Therefore, steps S14 and S16 in Fig. 2 may be omitted, and a value calculated in advance may be used as the first total inertia Jt. In this case, the value of the first total inertia Jt may be updated only at long-term intervals (for example, every year) or after an operation that changes the first total inertia Jt (for example, after changing the chuck setup).

[0037] Once the first total inertia Jt is obtained, the controller 12 obtains the second total inertia Jh (S18, S20). The procedure for obtaining the second total inertia Jh is the same as the procedure for obtaining the first total inertia Jt, except that the acceleration / deceleration operation of the movable part 50 is performed with the workpiece 60 loaded, and therefore a detailed description thereof will be omitted here. Prior to starting the acceleration / deceleration operation in step S18, the controller 12 may detect whether or not the workpiece 60 is attached to the driven body 58, and if the workpiece 60 is not attached, may display a message to the user urging them to attach the workpiece 60.

[0038] Once the first total inertia Jt and the second total inertia Jh are obtained, the controller 12 calculates the estimated workpiece inertia Jw' based on equation 4 (S22). That is, the controller 12 calculates the estimated workpiece inertia Jw' by dividing the value obtained by subtracting the first total inertia Jt from the second total inertia Jh by the square of the gear ratio R. Here, the gear ratio R at this time is the maximum gear ratio Rmx, so the error rate B can be kept small, as described with reference to equation 6.

[0039] Once the estimated workpiece inertia Jw' is obtained, the controller 12 calculates the servo parameter Sp based on the estimated workpiece inertia Jw' (S24), and changes the servo parameter Sp to a changed value (S26). Then, by setting the servo parameter Sp according to the estimated workpiece inertia Jw' estimated with high accuracy in this way, the moving part 50 can be controlled with higher accuracy.

[0040] Next, the configuration of another motor control device 10 will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the configuration of another motor control device 10. This motor control device 10 differs from the motor control device 10 of Fig. 1 in that the controller 12 also functions as a gear ratio storage unit 26. The gear ratio storage unit 26 stores the gear ratio R before the gear ratio R of the transmission 56 is switched to the maximum gear ratio Rmx as a pre-start gear ratio Ra. Once the acquisition of the estimated work inertia Jw' is completed, the gear ratio switching unit 22 acquires the pre-start gear ratio Ra stored in the gear ratio storage unit 26 and changes the gear ratio R back from the maximum gear ratio Rmx to the pre-start gear ratio Ra.

[0041] Fig. 4 is a flowchart showing the flow of calculation of estimated workpiece inertia Jw' and change of servo parameter Sp by motor control device 10 of Fig. 3. As shown in Fig. 4, in this case, prior to switching gear ratio R to maximum gear ratio Rmx (S32), controller 12 stores the current gear ratio R of transmission 56 as a pre-start gear ratio Ra (S30). Next, controller 12 switches gear ratio R to maximum gear ratio Rmx (S32) and executes inertia estimation processing in that state (S12). The contents of the inertia estimation processing are the same as steps S14 to S22 in Fig. 2, so a detailed description will be omitted here.

[0042] Once the estimated workpiece inertia Jw' has been calculated, the controller 12 calculates and changes the servo parameter Sp based on the obtained estimated workpiece inertia Jw' (S34, S36). Finally, the controller 12 switches the gear ratio R of the transmission 56 to the pre-start gear ratio Ra (S38).

[0043] With this configuration, the servo parameter Sp can be appropriately set while maintaining the speed change state desired by the user. That is, in this example, in order to obtain the estimated workpiece inertia Jw', the speed change ratio R is forcibly changed to the maximum speed change ratio Rmx. However, when the speed change ratio R is changed, the output torque and speed range of the driven body 58 change. For example, if the movable part 50 is the spindle of a machine tool, changes in the output torque and speed range make it impossible to perform the machining desired by the user. Therefore, in this example, once the estimated workpiece inertia Jw' is obtained, the speed change ratio R is returned to its original state. As a result, after obtaining the estimated workpiece inertia Jw', the movable part 50 can be operated in the state desired by the user.

[0044] Next, the configuration of another motor control device 10 will be described with reference to Fig. 5. Fig. 5 is a block diagram showing the configuration of another motor control device 10. This motor control device 10 differs from the motor control device 10 of Fig. 3 in that the controller 12 also functions as a gear ratio specifying unit 28.

[0045] Gear ratio specifying unit 28 determines the gear ratio to be used in estimating work inertia Jw, i.e., the estimation gear ratio, and notifies gear ratio switching unit 22. That is, as described above, in order to reduce error rate B of estimated work inertia Jw', it is sufficient to make gear ratio R as large as possible. However, there are cases where the maximum gear ratio Rmx cannot be selected due to a malfunction of the machine, etc. In such cases, gear ratio specifying unit 28 determines the gear ratio specified by the user as the estimation gear ratio.

[0046] For example, gear ratio designation unit 28 may store in advance a gear ratio designated by the user as a designated gear ratio Rb, and determine this designated gear ratio Rb as the estimation gear ratio when instructed by the user or when the maximum gear ratio Rmx is not available. As another embodiment, gear ratio designation unit 28 may inquire of the user whether or not to set the designated gear ratio Rb each time the work inertia Jw is estimated. Then, if the user inputs the designated gear ratio Rb, gear ratio designation unit 28 may determine the designated gear ratio Rb as the estimation gear ratio, and if no input is received, gear ratio designation unit 28 may determine the maximum gear ratio Rmx as the designated gear ratio Rb. When estimating the work inertia Jw, gear ratio switching unit 22 switches the gear ratio R of transmission 56 to the notified estimation gear ratio.

[0047] FIG. 6 is a flowchart showing the flow of calculation of estimated workpiece inertia Jw' and change of servo parameter Sp by motor control device 10 of FIG. 5. As shown in FIG. 6, in this case, prior to switching gear ratio R (S48), controller 12 checks whether or not it is necessary to adopt designated gear ratio Rb (S40). If maximum gear ratio Rmx cannot be used, or if the user has instructed that designated gear ratio Rb be used, controller 12 determines that it is necessary to adopt designated gear ratio Rb (Yes in S40). In this case, controller 12 sets this designated gear ratio Rb as the estimation gear ratio (S44). On the other hand, if it is not necessary to adopt designated gear ratio Rb, controller 12 sets maximum gear ratio Rmx as the estimation gear ratio (S42).

[0048] Next, the controller 12 stores the current gear ratio as the pre-start gear ratio Ra in the gear ratio storage unit 26 (S46). Thereafter, the controller 12 switches the gear ratio R to the specified gear ratio Rb (S48) and executes the inertia estimation process in that state (S12). The contents of the inertia estimation process (S12) are the same as steps S14 to S22 in FIG. 2, so a detailed description thereof will be omitted here. Furthermore, the processes (S50 to S54) after calculation of the estimated work inertia Jw' are the same as steps S34 to S38 in FIG. 4, so a description thereof will also be omitted.

[0049] As described above, in this example, the work inertia Jw can be estimated using the gear ratio R specified by the user. Therefore, even if the maximum gear ratio Rmx cannot be selected due to a malfunction of the machine or the like, the work inertia Jw can be appropriately estimated.

[0050] Note that the configurations described so far are merely examples, and other configurations may be modified as long as the configurations of the independent claims are included. For example, in the above description, the motor shaft converted total inertia is calculated by dividing the integrated value of the torque command Tc of the motor 52 in an integration interval in which the motor 52 is accelerating or decelerating by the integrated value of the acceleration α of the motor 52 in the integration interval. However, as long as the motor shaft converted total inertia can be obtained, the calculation formula may be modified as appropriate. Also, in the above description, the servo parameter Sp is changed based on the estimated workpiece inertia Jw'. However, the servo parameter Sp may be changed taking into account other parameters in addition to the estimated workpiece inertia Jw'. [Explanation of symbols]

[0051] 10 motor control device, 12 controller, 14 current controller, 16 position command generation unit, 17 subtractor, 18 FB controller, 20 inertia calculation unit, 22 gear ratio switching unit, 24 parameter calculation unit, 26 gear ratio storage unit, 28 gear ratio designation unit, 50 moving part, 52 motor, 54 position sensor, 56 transmission, 58 driven body, 60 work, Jw work inertia, Jw' estimated work inertia, R gear ratio, Ra gear ratio before start, Rb designated gear ratio, Rmx maximum gear ratio, Sp servo parameter.

Claims

1. An inertia estimation device that estimates the inertia of a moving part including a motor, a transmission, and a driven body, comprising: a controller configured to estimate the inertia of the moving part based on the acceleration and output torque of the motor when the motor is caused to perform an acceleration / deceleration operation for inertia estimation, and a speed ratio which is an output side speed relative to an input side speed of the transmission, the controller is configured to execute the acceleration / deceleration operation for inertia estimation in a state in which the speed ratio is changed to a speed ratio for inertia estimation. An inertia estimation device characterized by:

2. 2. The inertia estimation device according to claim 1, 10. The inertia estimation device, wherein the speed ratio for inertia estimation is a maximum speed ratio of the transmission.

3. 2. The inertia estimation device according to claim 1, The inertia estimation device is characterized in that the speed ratio for inertia estimation is a designated speed ratio designated by a user.

4. 2. The inertia estimation device according to claim 1, the controller is configured to store the gear ratio of the transmission at that time as a pre-start gear ratio prior to the acceleration / deceleration operation for estimation, and to change the gear ratio of the transmission to the pre-start gear ratio after the acceleration / deceleration operation for estimation is completed.

5. 2. The inertia estimation device according to claim 1, The controller a first total inertia, which is a motor shaft converted total inertia in a state where the workpiece is removed from the driven body, and a second total inertia, which is a motor shaft converted total inertia in a state where the workpiece is loaded on the driven body, are obtained; a value obtained by subtracting the first total inertia from the second total inertia and dividing the result by a square of a gear ratio is calculated as an estimated work inertia; It is structured as follows: The motor shaft converted total inertia is calculated by dividing an integrated value of a torque command of the motor in an integration interval in which the motor is accelerating or decelerating by an integrated value of acceleration of the motor in the integration interval. An inertia estimation device characterized by:

6. A motor control device for controlling the driving of the motor, The inertia estimation device according to any one of claims 1 to 5 is provided, The controller Calculating the inertia of the workpiece loaded on the driven body as an estimated workpiece inertia; changing a servo parameter, which is a control parameter of the motor, based on the estimated work inertia; A motor control device characterized by being configured as follows.

7. An inertia estimation method for estimating the inertia of a moving part including a motor, a transmission, and a driven body, comprising: a speed ratio, which is an output side speed relative to an input side speed of the transmission, is changed to a speed ratio for inertia estimation, and the motor is caused to perform an acceleration / deceleration operation for inertia estimation; the inertia of the movable part is estimated based on the acceleration and output torque of the motor when the motor is accelerated and decelerated for estimating the inertia, and the gear ratio.

2. A method for estimating inertia, comprising:

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