Drive state detection device

Abstract

To properly adjust a pass frequency band of a variable filter by following a change of a drive current waveform depending on the temperature change of an induction load.SOLUTION: A drive state detection device includes a current detection unit, a voltage detection unit, a variable filter, a signal generation unit, and a computation unit that detects the state of an induction load on the basis of a drive current, an inter-terminal voltage, and a pulse signal. The computation unit has an approximate equation calculation unit that calculates an approximate equation of a drive current waveform on the basis of a plurality of peak points extracted from the drive current waveform, a peak current calculation unit that calculates a peak current in the induction load from the approximate equation calculated by the approximate equation calculation unit, a resistance value calculation unit that calculates a resistance value of the induction load on the basis of the peak current calculated by the peak current calculation unit and the inter-terminal voltage detected by the voltage detection unit, and an adjustment unit that calculates a frequency corresponding to the resistance value calculated by the resistance value calculation unit, and adjusts a prescribed pass frequency band in the variable filter so as to allow the calculated frequency to pass.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a driving state detection device. [Background technology]

[0002] The following Patent Document 1 suggests that a motor current having ripple fluctuations takes on an exponential form, and that a blocking current can be estimated from the exponential form.

[0003] The following Patent Document 2 describes that the number of samplings, n, is six, and that this is used to detect the inrush current that flows when a DC motor is started, and that the waveform of the inrush current may have two peaks or only one peak, depending on the rotor position at start-up. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 11-514094 [Patent Document 2] Japanese Patent Application Publication No. 8-25198 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, a technique has been devised in the past in which a predetermined pass frequency band in a variable filter is adjusted based on the frequency of a ripple component in the waveform of a motor's drive current so that the frequency of the ripple component is included, so that the ripple component passes through the variable filter and is converted into a pulse signal, and the ripple component converted into a pulse signal is detected.

[0006] However, with this technology, changes in the waveform of the motor's drive current occur in response to changes in the resistance value due to changes in the motor's temperature, and as a result, the frequency of the ripple component fluctuates.If the specified pass frequency band in the variable filter is not appropriately adjusted, the frequency of the ripple component will no longer be included, and there is a risk that the ripple component will not be detected. [Means for solving the problem]

[0007] A drive state detection device according to one embodiment includes a current detection unit that detects a drive current when an inductive load is driven, a voltage detection unit that detects a terminal-to-terminal voltage when the inductive load is driven, a variable filter that passes components of a predetermined pass frequency band of the drive current detected by the current detection unit, a signal generation unit that generates a pulse signal from the waveform of the drive current after passing through the variable filter, and a calculation unit that detects the state of the inductive load based on the drive current detected by the current detection unit, the terminal-to-terminal voltage detected by the voltage detection unit, and the pulse signal generated by the signal generation unit. The calculation unit includes an approximate equation calculation unit that calculates an approximate equation of the waveform of the drive current based on a plurality of peak points extracted from the waveform of the drive current, a peak current calculation unit that calculates a peak current of the inductive load from the approximate equation calculated by the approximate equation calculation unit, a resistance value calculation unit that calculates a resistance value of the inductive load based on the peak current calculated by the peak current calculation unit and the terminal-to-terminal voltage detected by the voltage detection unit, and an adjustment unit that calculates a frequency corresponding to the resistance value calculated by the resistance value calculation unit and adjusts the predetermined pass frequency band of the variable filter so as to pass the calculated frequency. [Effects of the Invention]

[0008] According to the drive state detection device of one embodiment, the pass frequency band of the variable filter can be appropriately adjusted in accordance with changes in the drive current waveform caused by temperature changes in the inductive load. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of a drive control device according to an embodiment; [Figure 2] FIG. 1 is a block diagram illustrating an example of the functional configuration of a calculation unit included in a driving state detection device according to an embodiment. [Figure 3] 1 is a flowchart illustrating an example of a processing procedure performed by a calculation unit included in a driving state detection device according to an embodiment. [Figure 4] 10 is a graph illustrating a method (first example) for calculating the resistance value of a motor by a calculation unit included in a driving state detection device according to an embodiment. [Figure 5] Graph for explaining a method (second example) for calculating the resistance value of the motor by the calculation unit included in the driving state detection device according to one embodiment. [Figure 6] FIG. 10 is a diagram showing an example of a waveform of a drive current when a motor is locked in a drive control device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] A drive control device 10 according to one embodiment will be described below with reference to the drawings.

[0011] (Configuration of drive control device 10) Fig. 1 is a diagram showing the configuration of a drive control device 10 according to one embodiment. The drive control device 10 shown in Fig. 1 is a device that adjusts the position of a seat provided in a vehicle such as an automobile. As shown in Fig. 1, the drive control device 10 includes a motor 23, a resistor 24, a drive control unit 50, and a drive state detection device 100.

[0012] The motor 23 is an example of an “inductive load.” The motor 23 is a direct current (DC) motor that adjusts the position of a part of the seat (for example, the seat portion, the backrest, etc.).

[0013] The resistor 24 is connected in series with the motor 23 and is a sensing resistor used to detect the current of the motor 23 .

[0014] The drive condition detection device 100 detects the terminal voltage and ripple current of the motor 23, and generates a motor condition signal indicating the state of the motor based on the ripple current. The drive condition detection device 100 then outputs the generated motor condition signal to the drive control unit 50.

[0015] The drive control unit 50 adjusts the posture of a part of the seat by driving the motor 23 in response to the operation of a switch (not shown). At this time, the drive control unit 50 drives the motor 23 based on the motor state signal output from the drive state detection device 100.

[0016] The drive control device 10 is not limited to being used for adjusting the seat position, and may also be used for other purposes (for example, for opening and closing an electric sunroof, for adjusting the angle of an electric door mirror, for opening and closing a power window, etc.).

[0017] Here, a specific description will be given of the configuration of the drive state detection device 100. As shown in Fig. 1, the drive state detection device 100 has a voltage detection unit 111, a current detection unit 112, a filter 121, a filter 122, a variable filter 130, a filter 140, a ripple pulse generation unit 150, and a calculation unit 160.

[0018] The voltage detection unit 111 is connected to two terminals of the motor 23, and detects the voltage between the terminals when the motor 23 is driven. The voltage detection unit 111 then outputs the detected voltage between the terminals when the motor 23 is driven to the filter 121. The voltage detection unit 111 can be, for example, a voltage detection circuit configured with an amplifier.

[0019] The current detection unit 112 detects the drive current when the motor 23 is driven. Then, the current detection unit 112 outputs the detected drive current when the motor 23 is driven to the calculation unit 160 and the filter 122.

[0020] The filter 121 is a low pass filter (LPF). The filter 121 removes frequency components (noise components) higher than a predetermined cutoff frequency from the terminal voltage of the motor 23 detected by the voltage detection unit 111. The terminal voltage of the motor 23 output from the filter 121 is converted into a digital signal by an analog to digital (A / D) converter (not shown) and then input to the calculation unit 160.

[0021] The filter 122 is an LPF. The filter 122 removes frequency components (noise components) higher than a predetermined cutoff frequency from the drive current detected by the current detection unit 112 when the motor 23 is driven, and the result is input to the variable filter 130.

[0022] The variable filter 130 is a BPF (Band Pass Filter). The variable filter 130 passes frequency components in a predetermined pass frequency band from the drive current when the motor 23 is driven, which is output from the filter 122. The drive current when the motor 23 is driven (the drive current after passing through the variable filter) output from the variable filter 130 is input to the filter 140. The predetermined pass frequency band of the variable filter 130 can be controlled by the calculation unit 160.

[0023] The filter 140 is a high pass filter (HPF). The filter 140 removes frequency components (noise components) lower than a predetermined cutoff frequency from the drive current when the motor 23 is driven, which is output from the variable filter 130. The drive current when the motor 23 is driven, which is output from the filter 140, is input to the ripple pulse generating unit 150.

[0024] The ripple pulse generating unit 150 is an example of a "signal generating unit." The ripple pulse generating unit 150 detects a ripple component contained in the drive current output from the filter 140 when the motor 23 is driven. The ripple pulse generating unit 150 then converts the detected ripple component into a pulse signal and outputs the pulse signal to the calculating unit 160.

[0025] The calculation unit 160 detects the state of the motor 23 based on the drive current when the motor 23 is driven, detected by the current detection unit 112, the terminal voltage when the motor 23 is driven, detected by the voltage detection unit 111, and the pulse signal generated by the ripple pulse generation unit 150. The calculation unit 160 then outputs a motor state signal indicating the detected state of the motor 23 to the drive control unit 50. For example, the calculation unit 160 detects the rotation speed of the motor as an example of the state of the motor 23, based on the pulse signal generated by the ripple pulse generation unit 150. The calculation unit 160 then outputs a motor state signal based on the detected rotation speed of the motor 23 to the drive control unit 50.

[0026] (An example of the functional configuration of the calculation unit 160) 2 is a block diagram showing an example of the functional configuration of the calculation unit 160 included in the drive state detection device 100 according to an embodiment. As shown in FIG. 2, the calculation unit 160 includes an approximate expression calculation unit 161, a peak current calculation unit 162, a resistance value calculation unit 163, and an adjustment unit 164.

[0027] The approximate expression calculation unit 161 extracts a plurality of peak points from the waveform of the drive current when the motor 23 is driven, which is detected by the current detection unit 112. Then, the approximate expression calculation unit 161 calculates an approximate expression (an exponential curve expression) of the waveform of the drive current when the motor 23 is driven, based on the extracted plurality of peak points.

[0028] As an example, the approximate expression calculation unit 161 extracts a plurality of minimum points from the waveform of the drive current when the motor 23 is driven, which is detected by the current detection unit 112. Then, the approximate expression calculation unit 161 calculates an approximate expression of the waveform of the drive current when the motor 23 is driven, based on the extracted plurality of minimum points.

[0029] As another example, the approximate expression calculation unit 161 extracts a plurality of maximum points from the waveform of the drive current when the motor 23 is driven, which is detected by the current detection unit 112. Then, the approximate expression calculation unit 161 calculates an approximate expression of the waveform of the drive current when the motor 23 is driven, based on the extracted plurality of maximum points.

[0030] The peak current calculation unit 162 calculates the peak current of the motor 23 from the approximate expression of the waveform of the drive current when the motor 23 is driven, calculated by the approximate expression calculation unit 161 .

[0031] The resistance value calculation unit 163 calculates the resistance value of the motor 23 based on the peak current of the motor 23 calculated by the peak current calculation unit 162 and the terminal voltage of the motor 23 detected by the voltage detection unit 111 when the motor 23 is driven.

[0032] The adjustment unit 164 adjusts the predetermined pass frequency band of the variable filter 130 based on the resistance value of the motor 23 calculated by the resistance value calculation unit 163. Specifically, the adjustment unit 164 calculates the frequency of a ripple component corresponding to the resistance value of the motor 23 calculated by the resistance value calculation unit 163. Then, the adjustment unit 164 adjusts the predetermined pass frequency band of the variable filter 130 so that the frequency of the calculated ripple component is included in the predetermined pass frequency band. By adjusting the predetermined pass frequency band, it is possible to reliably pass the frequency of the calculated ripple component included in the waveform of the drive current.

[0033] The calculation unit 160 is realized by, for example, an IC (Integrated Circuit) such as a microcomputer. Each functional unit included in the calculation unit 160 is realized by a processor (for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), etc.) executing a program stored in a memory (for example, a DRAM (Dynamic Random Access Memory), an SRAM (Static Random Access Memory), a flash memory, etc.) in the IC.

[0034] (Example of processing procedure by the calculation unit 160) FIG. 3 is a flowchart showing an example of a processing procedure by the calculation unit 160 included in the driving state detection device 100 according to an embodiment.

[0035] First, the approximate expression calculation unit 161 extracts a plurality of peak points (minimum points or maximum points) from the waveform of the drive current when the motor 23 is driven, which is detected by the current detection unit 112 (step S301).

[0036] Next, the approximate expression calculation unit 161 calculates an approximate expression of the waveform of the drive current when the motor 23 is driven, based on the plurality of peak points extracted in step S301 (step S302).

[0037] Next, the peak current calculation unit 162 calculates the peak current of the motor 23 from the approximation formula of the waveform of the drive current when the motor 23 is driven, calculated in step S302 (step S303).

[0038] Next, the resistance value calculation unit 163 calculates the resistance value of the motor 23 based on the peak current of the motor 23 calculated in step S303 and the inter-terminal voltage of the motor 23 when it is driven, detected by the voltage detection unit 111 (step S304).

[0039] Next, based on the resistance value of the motor 23 calculated in step S304, the adjustment unit 164 calculates the frequency of the ripple component corresponding to the resistance value (step S305).

[0040] Next, the adjusting unit 164 adjusts the predetermined pass frequency band of the variable filter 130 so that the frequency of the ripple component calculated in step S305 is included in the predetermined pass frequency band (step S306).

[0041] (Method of Calculating Resistance Value of Motor 23 by Calculation Unit 160 (First Example)) FIG. 4 is a graph for explaining a method (first example) of calculating the resistance value of the motor 23 by the calculation unit 160 included in the driving state detection device 100 according to one embodiment.

[0042] In the graph shown in Figure 4, the waveform of the drive current when the motor 23 is driven, detected by the current detection unit 112, is shown by a solid line, and the exp curve representing the approximate equation of the waveform of the drive current when the motor 23 is driven, calculated by the approximate equation calculation unit 161, is shown by a dotted line.

[0043] Here, the approximate formula of the waveform of the drive current when the motor 23 is driven, calculated by the approximate formula calculation unit 161, is expressed by the following formula (1). However, the convergence value Δ included in the following formula (1) is an example of a "steady value", and a current value extracted from the waveform of the drive current when the motor 23 is in a steady driving state (a state in which the motor 23 is rotating stably) can be used.

[0044]

number

[0045] When the above formula (1) is converted, the following formula (2) is obtained.

[0046]

number

[0047] The peak current calculation unit 162 can calculate the peak current ImPeak (i.e., rush current) at the start of the motor 23 using the following formula (3), which is derived from the above formulas (1) and (2). Im(t) represents the current value at time t when the waveform of the drive current reaches its maximum point.

[0048]

number

[0049] Here, as shown in Figure 4, if the current value at time t1 (maximum point of the driving current waveform) is Im1 and the current value at time t2 (maximum point of the driving current waveform) is Im2, the above formula (3) becomes the following formulas (4) and (5).

[0050]

number

[0051]

number

[0052] Therefore, the peak current calculation section 162 can obtain T in the above formula (3) by the following formula (6) which is derived from the above formulas (4) and (5).

[0053]

number

[0054] Then, the resistance value calculation unit 163 can calculate the resistance value Rm' of the motor 23 using the following formula (7) based on the peak current ImPeak at the time of startup of the motor 23 calculated using the above formula (3) and the inter-terminal voltage Vm at the time of driving of the motor 23 detected by the voltage detection unit 111.

[0055]

number

[0056] Based on the resistance value Rm' of the motor 23 calculated by the above formula (7), the adjustment unit 164 can calculate the frequency f of the ripple component corresponding to the resistance value Rm' by the following formula (8).

[0057]

number

[0058] In the above formula (8), Eb represents the power supply voltage [V], Im represents the motor current [A], Ke represents the power generation coefficient [V / rps], and s represents the number of ripples per one rotation of the motor.

[0059] The adjusting unit 164 can calculate the frequency f of the ripple component according to the resistance value Rm′ of the motor 23 by calculating the frequency f of the ripple component using the above equation (8).

[0060] Then, the adjustment unit 164 adjusts the predetermined pass frequency band of the variable filter 130 so that the frequency f of the ripple component calculated by the above formula (8) is included in the predetermined pass frequency band, thereby ensuring that the ripple component contained in the waveform of the drive current when the motor 23 is driven passes through the variable filter 130, thereby preventing the ripple component from being missed when detected.

[0061] As described above, in the drive state detection device 100 according to one embodiment, the calculation unit 160 includes an approximate equation calculation unit 161 that calculates an approximate equation of the waveform of the drive current based on a plurality of peak points extracted from the waveform of the drive current, a peak current calculation unit 162 that calculates the peak current of the motor 23 from the approximate equation calculated by the approximate equation calculation unit 161, a resistance value calculation unit 163 that calculates the resistance value of the motor 23 based on the peak current calculated by the peak current calculation unit 162 and the inter-terminal voltage detected by the voltage detection unit 111, and an adjustment unit 164 that adjusts a predetermined pass frequency band of the variable filter 130 based on the resistance value calculated by the resistance value calculation unit 163.

[0062] As a result, the drive state detection device 100 of one embodiment can appropriately adjust the pass frequency band of the variable filter 130 so as to follow changes in the drive current waveform due to temperature changes in the motor 23 and pass the frequencies of the ripple components contained in the drive current waveform.

[0063] In particular, the conventional method of calculating the resistance value of motor 23 based on the waveform of the peak current of motor 23 makes it impossible to calculate the peak current of motor 23 with high accuracy because the waveform of the peak current varies depending on the position of the brushes and commutator of motor 23.

[0064] On the other hand, the driving state detection device 100 according to one embodiment calculates the resistance value of the motor 23 using an approximation equation for the driving current waveform based on multiple peak points extracted from the driving current waveform of the motor 23, and is therefore able to calculate the peak current of the motor 23 with high accuracy.

[0065] Furthermore, in the driving state detection device 100 according to one embodiment, the approximate expression calculation unit 161 calculates an approximate expression including a convergence value Δ, which is the steady-state value of the current value extracted from the waveform of the driving current when the motor 23 is in a steady driving state.

[0066] As a result, the driving state detection device 100 according to one embodiment can calculate the approximate equation calculated by the approximate equation calculation unit 161 in accordance with the waveform of the driving current when the motor 23 is driven, as shown in FIG. 4, and therefore can calculate the peak current when the motor 23 is started with high accuracy.

[0067] In particular, in the first example shown in Figure 4, the approximate equation calculation unit 161 calculates an approximate equation (the above formula (3)) of the waveform of the drive current when the motor 23 is driven based on multiple maximum points of the waveform of the drive current, so the calculated approximate equation can be made to match the waveform of the drive current when the motor 23 is driven, as shown in Figure 4, and therefore the peak current at the start of the motor 23 can be calculated with high accuracy.

[0068] 4, the approximation formula expressed by the above formula (3) may be further improved by subtracting W (the amplitude of the current value when the motor 23 is locked (see FIG. 6)) ÷ 2 (an example of a lock current value based on the amplitude of the current value when the motor 23 is locked). This allows the resistance value calculation unit 163 to more accurately calculate the peak current ImPeak at the start of the motor 23 using the improved formula (3).

[0069] (Method of Calculating Resistance Value of Motor 23 by Calculation Unit 160 (Second Example)) FIG. 5 is a graph for explaining a method (second example) of calculating the resistance value of the motor 23 by the calculation unit 160 included in the driving state detection device 100 according to one embodiment.

[0070] In the graph shown in Figure 5, as in the graph shown in Figure 4, the waveform of the drive current when the motor 23 is driven, detected by the current detection unit 112, is shown by a solid line, and the exp curve representing the approximate equation of the waveform of the drive current when the motor 23 is driven, calculated by the approximate equation calculation unit 161, is shown by a dotted line.

[0071] However, the second example shown in Fig. 5 differs from the first example shown in Fig. 4 in that the approximate expression calculation unit 161 calculates the following mathematical expression (9), which is an approximate expression of the waveform of the drive current when the motor 23 is driven, based on multiple minimum points of the waveform of the drive current. Note that Im_bottom(t) indicates the current value at time t when the waveform of the drive current reaches a minimum point.

[0072]

number

[0073] As a result, in the second example shown in FIG. 5, the approximate expression calculation unit 161 can calculate an exp curve along a plurality of minimum points of the waveform of the drive current as an approximate expression of the waveform of the drive current when the motor 23 is driven.

[0074] However, the approximation expressed by the above formula (9) differs from the approximation expressed by the above formula (3) in that it is obtained by adding W (the amplitude of the current value when the motor 23 is locked (see Figure 6)) ÷ 2 (an example of a lock current value based on the amplitude of the current value when the motor 23 is locked).

[0075] In the first example shown in FIG. 4, the approximate equation calculation unit 161 calculates an approximate equation (the above-mentioned formula (3)) of the waveform of the drive current when the motor 23 is driven based on multiple maximum points of the waveform of the drive current. In this case, if there is variation in amplitude between multiple ripple components, the approximate equation calculated based on the multiple maximum points may not match the waveform of the drive current when the motor 23 is driven, and it may not be possible to calculate the peak current at the start of the motor 23 with high accuracy.

[0076] On the other hand, in the second example shown in FIG. 5, the approximate equation calculation unit 161 calculates an approximate equation (the above-mentioned formula (9)) of the waveform of the drive current when the motor 23 is driven based on multiple minimum points of the waveform of the drive current. Therefore, even if there is variation in amplitude between multiple ripple components, the approximate equation calculated based on the multiple minimum points will be in line with the waveform of the drive current when the motor 23 is driven, and the peak current at the start of the motor 23 can be calculated with high accuracy.

[0077] In particular, in the second example shown in Figure 5, the approximation formula (the above formula (9)) of the waveform of the drive current when the motor 23 is driven is obtained by adding W (the amplitude of the current value when the motor 23 is locked) ÷ 2 (an example of a lock current value based on the amplitude of the current value when the motor 23 is locked), so the resistance value calculation unit 163 can calculate the peak current ImPeak at the start of the motor 23 with higher accuracy using the above formula (9).

[0078] (Example of drive current waveform when the motor is locked) FIG. 6 is a diagram showing an example of a waveform of the drive current when the motor 23 is locked in the drive control device 10 according to one embodiment.

[0079] In this embodiment, the range from when the motor 23 is in a steady rotation state until it actually locks is defined as "when the motor is locked." As shown in FIG. 6, when the motor 23 is locked, the current value of the drive current of the motor 23 gradually increases from the current value in the steady rotation state and then becomes a substantially constant current value. At this time, as shown in FIG. 6, the current value of the drive current of the motor 23 has an amplitude W between a peak value (maximum value) and the peak value (minimum value) immediately before that. In the above-described formula (9), this amplitude W is used to calculate an approximation of the waveform of the drive current when the motor 23 is driven. Then, when the motor 23 actually locks, the current value of the drive current of the motor 23 no longer fluctuates in amplitude, as shown in FIG. 6.

[0080] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0081] For example, in the drive state detection device 100 according to one embodiment, the approximate equation calculation unit 161 may extract maximum and minimum points from the waveform of the drive current when the motor 23 is driven, and calculate an approximate equation for the waveform of the drive current when the motor 23 is driven based on the average value of the extracted maximum and minimum points.

[0082] In this case, too, the driving state detection device 100 according to one embodiment can make the approximate equation calculated by the approximate equation calculation unit 161 conform to the waveform of the driving current when the motor 23 is driven, and therefore can calculate the peak current when the motor 23 is started with high accuracy. [Explanation of symbols]

[0083] 10 Drive control device 23 Motor 24 resistor 50 Drive control unit 100 Driving state detection device 111 Voltage detection unit 112 Current detection unit 121 filters 122 filters 130 Variable Filter 140 filters 150 Ripple pulse generator 160 Arithmetic section 161 Approximate formula calculation part 162 Peak current calculation section 163 Resistance value calculation section 164 Adjustment section

Claims

1. a current detection unit that detects a drive current when driving an inductive load; a voltage detection unit that detects a voltage between the terminals of the inductive load when the inductive load is driven; a variable filter that passes components of a predetermined pass frequency band of the drive current detected by the current detection unit; a signal generating unit that generates a pulse signal from the waveform of the drive current that has passed through the variable filter; a calculation unit that detects a state of the inductive load based on the drive current detected by the current detection unit, the inter-terminal voltage detected by the voltage detection unit, and the pulse signal generated by the signal generation unit; and Equipped with The calculation unit an approximate expression calculation unit that calculates an approximate expression of the waveform of the driving current based on a plurality of peak points extracted from the waveform of the driving current; a peak current calculation unit that calculates a peak current of the inductive load from the approximate expression calculated by the approximate expression calculation unit; a resistance value calculation unit that calculates a resistance value of the inductive load based on the peak current calculated by the peak current calculation unit and the inter-terminal voltage detected by the voltage detection unit; an adjustment unit that calculates a frequency corresponding to the resistance value calculated by the resistance value calculation unit, and adjusts the predetermined pass frequency band of the variable filter so as to pass the calculated frequency; A driving state detection device comprising:

2. The approximate expression calculation unit An approximation formula of the waveform of the drive current is calculated, the approximation formula including a steady-state value extracted from the waveform of the drive current when the inductive load is in a steady-state driving state.

2. The driving state detection device according to claim 1.

3. The approximate expression calculation unit An approximation formula for the waveform of the drive current is calculated based on a plurality of peak points extracted from the waveform of the drive current and a lock current value based on the amplitude of the current value when the inductive load is locked.

2. The driving state detection device according to claim 1.

4. The peak point is a minimum point.

2. The driving state detection device according to claim 1.

5. The approximate expression calculation unit An approximation formula for the waveform of the drive current is calculated based on a plurality of minimum points extracted from the waveform of the drive current, to which a lock current value based on the amplitude of the current value when the inductive load is locked is added.

5. The driving state detection device according to claim 4.

6. The peak point is a local maximum point.

2. The driving state detection device according to claim 1.

7. The approximate expression calculation unit An approximation formula for the waveform of the drive current is calculated based on a plurality of maximum points extracted from the waveform of the drive current, from which a lock current value based on the amplitude of the current value when the inductive load is locked is subtracted.

7. The driving state detection device according to claim 6.

8. The peak points are local maximum points and local minimum points, The approximate expression calculation unit An approximation formula of the waveform of the driving current is calculated based on an average value of the maximum point and the minimum point extracted from the waveform of the driving current.

2. The driving state detection device according to claim 1.

Images