Current control device

Abstract

To provide a current control device capable of obtaining a dither effect without superimposing a dither waveform on a target current value, and adjusting the dither amplitude while preventing current rise.SOLUTION: A duty ratio setting portion calculates a first duty ratio that is updated every first period equal to a switching period on the basis of a target current value set by a target current setting portion, a second duty ratio that is updated every second period that is a natural number multiple of the first period on the basis of the target current value set by the target current setting portion, and a third duty ratio is obtained by dividing the binary pulse waveform represented by the second duty ratio and the second period on the time axis for each first period, and calculated as integral rate for each first cycle, and generates periodic oscillations in the second period in an excitation current by instructing a drive circuit of a weighted average duty ratio calculated as a weighted average value of the first duty ratio and the third duty ratio.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates to a current control device that controls the current of a solenoid used for hydraulic control, which is mounted on vehicles such as construction machinery. [Background technology]

[0002] In recent years, construction machinery has seen an increase in the electronic integration of various control systems, aimed at improving construction efficiency through operator assistance and remote control.

[0003] Construction machinery operates using actuators in various parts, and its power source is hydraulics. Among the hydraulic components, the electromagnetic proportional valve plays a bridging role between electricity and hydraulics, switching and adjusting the hydraulic path according to the drive current applied to the internal solenoid.

[0004] Typically, the drive current of an electromagnetic proportional valve is controlled by switching the DC voltage of the alternator or battery. Furthermore, to improve hysteresis characteristics, it is common to use a drive current that oscillates at a specific frequency. Conventionally, a widely used method involves utilizing the current ripple caused by switching itself as the oscillation.

[0005] In recent years, a method has become known for driving at a higher switching frequency while periodically oscillating (dithering) the drive current at a lower frequency, and there are various examples of specific control methods for this, including those described in Patent Documents 1 and 2 below. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5761580 [Patent Document 2] Japanese Patent Publication No. 2020-068357 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] To obtain good responsiveness in hydraulic equipment, it is desirable to be able to adjust the amplitude of the dither according to the target current value and its rate of change. In the above-mentioned Patent Documents 1 and 2, the dither effect is obtained by directly superimposing a waveform signal that oscillates with a period longer than the PWM period onto the target current value. However, if the dither waveform is generated separately from the target current value and superimposed in conjunction with the target current value, the setting procedure may become complicated.

[0008] Furthermore, at low currents, it is difficult to ensure sufficient dither amplitude in principle, which may cause hysteresis and other effects on hydraulic equipment. As a countermeasure, it is conceivable to increase the amplitude of the dither waveform superimposed on the target current value, but this may cause a rise in current due to saturation at the duty cycle lower limit on the lower side of the periodic oscillation, potentially preventing the system from following the target current value.

[0009] The present invention has been made in view of the above problems, and aims to provide a current control device that can obtain the effect of dithering without superimposing a dither waveform on the target current value, and can adjust the amplitude of dithering while preventing the current from rising. [Means for solving the problem]

[0010] The current control device of the present invention, which solves the above problems, is a current control device for controlling the excitation current of a solenoid, comprising: a drive circuit for supplying the excitation current to the solenoid; a duty cycle setting unit for determining the duty cycle of a switching signal output by the drive circuit; and a target current setting unit for setting a target current value of the excitation current, wherein the duty cycle setting unit generates periodic oscillations in the excitation current in the second period by instructing the drive circuit to use a weighted average duty cycle calculated as the weighted average duty cycle of the first duty cycle and the third duty cycle, respectively, by dividing the binary pulse waveform represented by the second duty cycle and the second period on the time axis for each first period and calculating it as the integral ratio for each first period. [Effects of the Invention]

[0011] According to the present invention, the dithering effect can be obtained without superimposing a dither waveform on the target current value.

[0012] Furthermore, in this invention, the dither amplitude can be adjusted by changing only the weighted average ratio of the first duty cycle and the third duty cycle. Since both the first duty cycle and the third duty cycle, which contributes to the dither effect, are calculated based on the same target current value, it is possible to adjust the dither amplitude while preventing a rise in current.

[0013] Other issues, configurations, and effects will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0014] [Figure 1] A side view showing a hydraulic excavator to which the present invention is applied. [Figure 2] Figure 1 shows the hydraulic system of a hydraulic excavator. [Figure 3] An explanatory diagram of an example of current dither control. [Figure 4] A diagram showing the functional configuration of the control unit 10 in the first embodiment of the present invention. [Figure 5] A diagram showing the control logic for the drive current in the first embodiment of the present invention. [Figure 6] Diagram illustrating the operation of the second duty cycle conversion unit 53. [Figure 7] Diagram illustrating the generation of the power supply instruction signal. [Figure 8] A diagram showing the functional configuration of the control unit 10 in a second embodiment of the present invention. [Figure 9] A diagram showing the control logic for the drive current in a second embodiment of the present invention. [Figure 10] A diagram showing the functional configuration of the control unit 10 in the third embodiment of the present invention. [Figure 11] A diagram illustrating the effect of the weighted average ratio α. [Figure 12A] A table showing examples of setting the weighted average ratio α in the third embodiment of the present invention. [Figure 12B] A processing flowchart according to the third embodiment of the present invention. [Figure 13] An explanatory diagram illustrating an example of the current value transition in the third embodiment of the present invention. [Figure 14] A diagram showing the functional configuration of the control unit 10 in the fourth embodiment of the present invention. [Figure 15A] A table showing examples of setting the weighted average ratio α in the fourth embodiment of the present invention. [Figure 15B] A flowchart illustrating the process in the fourth embodiment of the present invention. [Figure 16] An explanatory diagram illustrating an example of the current value transition in the fourth embodiment of the present invention. [Figure 17A] A table showing examples of setting the weighted average ratio α in the fifth embodiment of the present invention. [Figure 17B] A processing flowchart in the fifth embodiment of the present invention. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings. In each figure, parts having the same configuration or function are denoted by the same reference numerals, and their repeated descriptions may be omitted. In the following description, the invention will be applied to a hydraulic excavator, a type of construction machine, but it is not limited to hydraulic excavators and is of course applicable to various machines that control the current of a hydraulic control solenoid.

[0016] Figure 1 shows a hydraulic excavator to which the present invention is applied.

[0017] The basic structure of the hydraulic excavator 19 consists of three basic parts: a lower running body 7 that drives tracks for movement, an upper rotating body 8 that is rotatably mounted on the lower running body 7, and a front attachment 9 that is rotatably (vertically) attached to the upper rotating body 8.

[0018] The upper rotating body 8 is equipped with the prime mover 3, pump unit 4, and other components.

[0019] The components that directly generate power for the hydraulic excavator 19 to operate are called actuators. The hydraulic excavator 19 has multiple actuators, but in the figure, as specific examples, only the arm cylinder 1, which is the actuator for the movement of the arm of the front attachment 9, and the travel motor 2, which is the travel actuator for the lower travel body 7, are shown.

[0020] The hydraulic system of the hydraulic excavator shown in Figure 1 is shown in Figure 2.

[0021] The prime mover 3 provides rotational driving force to the pump unit 4, and the pump unit 4 supplies pressurized oil to the control valve 5 and the signal control valve 6, respectively.

[0022] The control valve 5 switches the hydraulic path by a spool (not shown) in order to drive a plurality of actuators including the arm cylinder 1 which is a hydraulic cylinder and the traveling motor 2 which is a hydraulic motor. The operation of the control valve 5 is mainly controlled by the pressure oil at a lower pressure than the actuator drive circuit, which is supplied from the signal control valve 6.

[0023] The pump unit 4, the control valve 5, and the signal control valve 6 are all controlled in part or in whole of their operations by the electromagnetic proportional valve 14 mounted thereon. All the electromagnetic proportional valves 14 operate by the current supplied from the electromagnetic proportional valve control unit (hereinafter sometimes simply referred to as the control unit) 10. The control unit 10 processes input signals from various external devices including the operation device 15 and controls the current supplied to the electromagnetic proportional valve 14.

[0024] The electromagnetic proportional valve 14 causes the spool to be displaced by the exciting current applied to the internal solenoid, and switches and adjusts the hydraulic circuit on the low-pressure side.

[0025] The electromagnetic proportional valve 14 generally has hysteresis in the current-hydraulic characteristics, but as a method for reducing the hysteresis, dither control for vibrating the current is generally performed.

[0026] The control unit 10 controls the current of the electromagnetic proportional valve 14, and the current dither control which is a premise in the present invention will be described using FIG. 3. In FIG. 3, i L1 , i L2 , i L3 are currents (drive currents), I L1 , I L2 , I L3 are the average values of i L1 , i L2 , i L3 respectively, and ΔI L1 , ΔI L2 , ΔI L3 are the amplitudes of i L1 , i L2 , i L3 respectively. The dither period T C is longer than the switching carrier period TD By applying periodic oscillations, the effect of dither control is obtained.

[0027] Typically, the dither period is a natural number multiple of the carrier period and is longer than the carrier period. In Figure 3, as an example, the dither period is set to 10 times the carrier period.

[0028] The following describes in detail, for each embodiment, the functional configuration of the control unit 10, which is a current control device that controls the current of the electromagnetic proportional valve 14.

[0029] << First Embodiment >> Figure 4 shows the functional configuration of the control unit 10 in carrying out the first embodiment of the present invention. The control unit 10 mainly controls the electromagnetic proportional valve 14, and although multiple electromagnetic proportional valves are connected, only the electromagnetic proportional valve 14 is shown as a representative.

[0030] The control unit 10 receives signals from the operating device 15, sensors 16, etc., and the signals processed by the internal input signal processing unit 21 are sent to the central processing unit 20.

[0031] The electromagnetic proportional valve drive unit 204 supplies a drive current 207 to the electromagnetic proportional valve 14 based on a drive signal coming from the central processing unit 20. The drive current 207 is supplied by the electromagnetic proportional valve drive unit 204 via switching from a voltage source +VB. In other words, the electromagnetic proportional valve drive unit 204 functions as a drive circuit for supplying the drive current (excitation current) 207 to the electromagnetic proportional valve 14 (and its solenoid), and outputs a switching signal with a duty cycle described later to the electromagnetic proportional valve 14 (and its solenoid).

[0032] The current detection unit 205 detects the drive current 207 and transmits it to the central processing unit 20.

[0033] The central processing unit 20 instructs the electromagnetic proportional valve drive unit 204 to issue a drive signal based on signals from the operating device 15 and the current detection unit 205. Based on input from the operating device 15, the target current setting unit 201 generates a target drive current value (target current value of the excitation current) 206 for the electromagnetic proportional valve 14 and transmits it to the electromagnetic proportional valve control unit 202. The current calculation unit 203 calculates the current value based on the signal transmitted from the current detection unit 205 and transmits it to the electromagnetic proportional valve control unit 202. The electromagnetic proportional valve control unit 202 generates a drive signal to instruct the electromagnetic proportional valve drive unit 204 based on signals transmitted from the target current setting unit 201 and the current calculation unit 203.

[0034] In this embodiment, the electromagnetic proportional valve control unit 202 functions as a duty cycle setting unit that determines the duty cycle of the switching signal output by the electromagnetic proportional valve drive unit 204, which acts as a drive circuit. The functions of each unit will be explained later with reference to Figure 5, but the electromagnetic proportional valve control unit 202 includes a first duty cycle calculation unit 511, a second duty cycle calculation unit 512, a second duty cycle conversion unit 53, and a weighted average unit 54. In addition, corresponding to the configuration of the electromagnetic proportional valve control unit 202, the current calculation unit 203 includes a first average value calculation unit 521 and a second average value calculation unit 522.

[0035] The drive current control logic in this embodiment is shown in Figure 5. Each block constituting the control logic in Figure 5 corresponds to the part with the same symbol and name in the control unit 10 in Figure 4.

[0036] The input to the entire control logic is the target current I r The output is the actual current I a The output is fed back to the input and reflected in the control, but there are two feedback loops. These correspond to the dashed lines 50a and 50b in Figure 5, respectively, and feedback control is performed at different periods, namely the first period and the second period.

[0037] The 50a loop performs feedback control for each first period. The first period is the same as the carrier period of the switching (PWM), as illustrated in Figure 3. CThis applies (hereafter, the first period will be referred to as the carrier period). The first average value calculation unit 521 receives feedback of the actual current I a Based on this, the average value of the actual current for each carrier cycle is calculated by sampling and averaging. The current value I calculated by the first average value calculation unit 521 a1 This is fed back to the preceding stage of the first duty cycle calculation unit 511, and the deviation for each carrier period is input to the first duty cycle calculation unit 511.

[0038] The 50b loop implements feedback control every second period. The second period is the same as the dither period, as illustrated in Figure 3. D This applies (hereafter, the second period will be referred to as the dither period). The second average value calculation unit 522 receives feedback of the actual current I a Based on this, the average value of the actual current for each dither period is calculated by sampling and averaging. The current value I calculated by the second average value calculation unit 522 a2 This is fed back to the preceding stage of the second duty cycle calculation unit 512, and the deviation for each dither period is input to the second duty cycle calculation unit 512. The second duty cycle D2 generated by the second duty cycle calculation unit 512 is the duty cycle for each dither period, and the second duty cycle conversion unit 53 performs the process of converting this to the duty cycle for each carrier period and generating the third duty cycle D3.

[0039] Examples of implementations for the first duty cycle calculation unit 511 and the second duty cycle calculation unit 512 include PID controllers, where their outputs D1 and D2 correspond to the switching duty cycles.

[0040] The duty cycles D1 and D3 calculated in 50a and 50b respectively are input to the weighted average unit 54. D3 is multiplied by a constant α (0≦α≦1) (or 0%≦α≦100%) in 542, and D1 is multiplied by 1-α (or 100%-α) in 541. The sum of these results is then output.

[0041] The duty cycle generated by the weighted average unit 54 is transmitted to the electromagnetic proportional valve drive unit 204 and supplied to the electromagnetic proportional valve 14 as the actual current I a The final output is determined accordingly.

[0042] The function of the second duty cycle conversion unit 53 in loop 50b in Figure 5 is explained in Figure 6.

[0043] The second duty cycle D2 is the dither period T D This represents the duty cycle, i.e., the proportion of time the current is applied. The change in the second duty cycle D2 is shown in Figure 6(a). Also, the relationship between the second duty cycle D2 and the dither period T D The current-on instruction waveform based on this is shown in Figure 6(b).

[0044] Dither period T D The carrier period is T C Although it is longer than the carrier period T, the switching itself is of a longer carrier period T. C Because it is performed every time, the carrier cycle T C A process is needed to convert each current into a power supply signal. This is performed by the second duty cycle conversion unit 53, which converts the dither period T based on the second duty cycle D2. D Outputs the third duty cycle D3, converted as a periodic fluctuation within the system.

[0045] The second duty cycle conversion unit 53 has an internal counter variable C, the transition of which is shown in Figure 6(c). The counter variable C is the carrier period T C It is incremented in sync with the progress of the dither period T. Also, the counter variable C is reset to 0 as soon as it reaches its maximum value N. The maximum counter value N is determined by the dither period T. D and carrier cycle T C It is a natural number that can be expressed as a ratio of two values.

[0046] Furthermore, the second duty cycle conversion unit 53 performs calculations to assign the second duty cycle D2, which is the input from the previous stage, to the duty cycle for each carrier period, and calculates the third duty cycle D3. Specifically, it performs the calculations shown in equations (1) and (2) below.

number

[0047] D3, D in the above formulas (1) and (2) TMP In all cases, the unit is "%".

[0048] The change in the third duty cycle D3 is shown in Figure 6(d). By performing the calculations of equations (1) and (2) on D2, the carrier period T is obtained. C Each D3 has a dither period T D When coupled continuously over the length of time, an energized signal equivalent to D2 will be obtained in terms of the time-averaged value. Another way to express the third duty cycle D3 is the dither period T D A binary pulse waveform represented by the second duty cycle D2, with a carrier period T C This can be expressed as the integral factor over time, or as the dither period T. D And a binary pulse waveform represented by the second duty cycle D2 with carrier period T C The time axis is divided into segments, and the carrier period T C This is calculated as the integral factor for each step.

[0049] The effect obtained by the third duty cycle D3 generated by the second duty cycle conversion unit 53, as explained in Figure 6, and the weighted average of it and the first duty cycle D1, will be explained using Figure 7. Figure 7 shows the case where the dither period is 5 times the carrier period.

[0050] The duty cycle D1 generated by the first duty cycle calculation unit 511 is updated with each carrier cycle by feedback control and is assumed to change as shown in Figure 7(a). The second duty cycle D2 generated by the second duty cycle calculation unit 512 is converted into a third duty cycle D3, which is updated with each carrier cycle by the second duty cycle conversion unit 53 and is assumed to change as shown in Figure 7(b).

[0051] The first duty cycle calculation unit 511 and the second duty cycle calculation unit 512 each calculate the target current I rThey are common to all, and the actual current I a A value based on this is fed back. Therefore, although the update cycles are different, the generated first duty cycle D1 and the second duty cycle D2 (not shown) are correlated with each other.

[0052] The change in the weighted average value (weighted average duty cycle) αD3+(1-α)D1 of D1 and D3 by the weighted average unit 54 is similarly shown in Figure 7(c). The weighted average ratio α is set to any value in the range of 0≦α≦1 such that the sum of the two is 1. Alternatively, the weighted average ratio α is set to any value in the range of 0%≦α≦100% such that the sum of the two is 100%. The weighted average value (weighted average duty cycle) αD3+(1-α)D1 is the carrier period T C The duty cycle value is updated each time, and according to this value, the electromagnetic proportional valve drive unit 204 supplies current to the electromagnetic proportional valve 14.

[0053] The waveforms of the applied voltage (drive voltage) and drive current to the electromagnetic proportional valve 14 are similarly shown in Figure 7(d). Carrier period T C For each duty cycle D1, the dither period T D By weighting and averaging D3, which has the oscillation component, the dither effect, i.e., the dither period T, is applied to the drive current. D Obtain periodic oscillations.

[0054] This embodiment makes it possible to obtain the effect of dithering without superimposing the dither waveform onto the target current value.

[0055] << Second Embodiment >> Figure 8 shows the functional configuration of the control unit 10 in carrying out the second embodiment of the present invention.

[0056] The basic functional configuration of the second embodiment is the same as that of the first embodiment shown in Figure 4, but in the second embodiment, the first average value correction unit 521a is located inside the electromagnetic proportional valve control unit 202.

[0057] The drive current control logic in the second embodiment is shown in Figure 9. Each block constituting the control logic in Figure 9 corresponds to the part with the same symbol and name in the control unit 10 in Figure 8.

[0058] In the second embodiment, the first average value correction unit 521a is added between the first average value calculation unit 521 and the first duty cycle calculation unit 511. The first average value correction unit 521a subtracts from the calculation result by the first average value calculation unit 521 an amount proportional to the value obtained by multiplying the third duty cycle D3 by the weighted average ratio α. This function corrects the expected fluctuation in the calculation result of the first average value calculation unit 521 caused by the weighted average of D1 and D3. That is, the first average value correction unit 521a corrects the target current I r When calculating the first duty cycle D1 from the detected excitation current (actual current I a The fluctuations based on the weighted average with the third duty cycle D3 are offset. As a result, the influence of the third duty cycle D3 on the first duty cycle D1, which is the result of the first duty cycle calculation unit 511, can be reduced, and the accuracy of current control can be improved.

[0059] << Third Embodiment >> Figure 10 shows the functional configuration of the control unit 10 in carrying out the third embodiment of the present invention.

[0060] The basic functional configuration of the third embodiment is the same as in Figure 4 of the first embodiment, and the control logic is also the same as in Figure 5 of the first embodiment. However, in the third embodiment, a weighted average setting unit 202b is added to the weighted average unit 54. Alternatively, the first average value correction unit 521a, as explained in Figure 8 of the second embodiment, may be introduced, and the control logic in Figure 9 may be used.

[0061] As described in the first embodiment, the duty cycle instructed to the electromagnetic proportional valve drive unit 204 is the weighted average of the duty cycles calculated from the feedback based on the carrier period and the feedback based on the dither period. The weighted average ratio α can be arbitrarily set within the range of 0 ≤ α ≤ 1 (or 0% ≤ α ≤ 100%), and Figure 11 shows the waveforms of the drive voltage and drive current for each weighted average ratio. For the sake of simplicity, the target current value is assumed to be constant.

[0062] When α = 0 (minimum value) (upper panel of Figure 11), and the target current value is constant, the carrier period T C Switching is performed with a constant duty cycle. The duty cycle of the electromagnetic proportional valve control unit 202 is set to the dither period T. D The waveform component is not included. In other words, the electromagnetic proportional valve drive unit 204 has a carrier period T that does not include the aforementioned periodic vibration. C The drive is performed with the first duty cycle D1. On the other hand, when α=1 (maximum value) (lower diagram in Figure 11), the switching calculation itself is performed with a carrier period T C Even if executed every time, the generated duty cycle will be the dither period T. D The value is based on the dither period T D This becomes equal to the waveform used for switching. In other words, the electromagnetic proportional valve drive unit 204 has a dither period T D The drive is performed with a second duty cycle D2. In this case, the dither amplitude is theoretically the largest.

[0063] In this way, by arbitrarily setting the magnitude of the weighted average ratio α, it is possible to adjust the dither amplitude (the amplitude of periodic oscillations at the dither period).

[0064] Furthermore, the magnitude of the achievable dither amplitude of the drive current is, in principle, determined by the carrier period T. C It depends on the carrier period T C The longer the dither period, the easier it is to obtain a larger dither amplitude. When the weighted average ratio α=1, the duty cycle instructed to the drive circuit becomes equal to D3, which is as explained in Figures 6 and 7 of the first embodiment, and the dither period T DThis is essentially the same as switching in [the specified location]. Therefore, the largest dither amplitude is obtained at a weighted average ratio α=1.

[0065] In a third embodiment of the present invention, the weighted average ratio α is switched according to the target current value. There is no limit to the number of thresholds, but for simplicity of explanation, I rth1 , I rth2 The two methods used are shown in Figure 12A, where the weighted average ratio α is set.

[0066] Dither control is performed to reduce hysteresis as a hydraulic characteristic of electromagnetic proportional valves, but generally, it is difficult to obtain a large dither amplitude when the drive current is small. A weighted average ratio α as shown in Figure 12A is assigned to each target current magnitude, and the smaller the target current, the larger the value of the weighted average ratio α. That is, the smaller the target current, the larger the value of the weighted average ratio α, and the larger the proportion of the third duty cycle D3 in the duty cycle (weighted average duty cycle) generated by the weighted average unit 54, making it easier to obtain a dither amplitude. Also, the larger the target current, the smaller the value of the weighted average ratio α, and the larger the proportion of the first duty cycle D1 in the duty cycle (weighted average duty cycle) generated by the weighted average unit 54.

[0067] Figure 12B shows the processing of the weighted average setting unit 202b for each carrier period. The processing in Figure 12B updates the weighted average ratio α for each dither period based on the counter variable C operated by the second duty cycle conversion unit 53, as described in the first embodiment.

[0068] When the weighted average setting unit 202b starts the α setting process (S1000), it determines whether the counter variable C = N-1 (S1001). If Yes, it proceeds to S1002; otherwise, it terminates the α setting process (S1007). In S1002, the target current I r Threshold I rth1 Determine if it is less than or equal to the target current I. If yes, proceed to S1004; otherwise, proceed to S1003. In S1003, the target current I r Threshold I rth1 The threshold I rth2The system determines whether the following conditions apply; if yes, proceed to S1005; otherwise, proceed to S1006. In S1004, α=1 is set; in S1005, α=0.7; and in S1006, α=0.3 is set, and the α setting process ends (S1007).

[0069] In relation to Figures 12A and 12B, Figure 13 shows the target current I r and actual current I a An example of the progression is shown. In Figure 13, at time t1, the target current I r is threshold I rth1 Once the dithering period ends, the weighted average setting unit 202b assigns a different weighted average ratio by following “No” at S1002 in the flowchart of Figure 12B. At time t1, the value, which had been set to α=1.0, is switched to α=0.7.

[0070] Also, at time t2 in Figure 13, the target current I r is threshold I rth2 Once the dithering period ends, the weighted average setting unit 202b assigns a different weighted average ratio by following "No" at S1003 in the flowchart of Figure 12B. At time t2, the setting, which had been α=0.7, is switched to α=0.3.

[0071] Target current I r Similarly, for t3 and t4 in Figure 13, where the ratio is decreasing, the weighted average ratio α is switched using the same process shown in the flowchart in Figure 12B.

[0072] This embodiment makes it possible to adjust the dither current amplitude according to the target current value without superimposing the dither waveform onto the target current value.

[0073] << Fourth Embodiment >> In carrying out the fourth embodiment of the present invention, the functional configuration of the control unit 10 is shown in Figure 14.

[0074] The basic functional configuration of the fourth embodiment is the same as that of the third embodiment shown in Figure 10, but in the fourth embodiment, a target differential value calculation unit 202c is added to the weighted average setting unit 202b. Alternatively, the first average value correction unit 521a, as described in Figure 8 of the second embodiment, may be introduced, and the control logic shown in Figure 9 may be used.

[0075] As mentioned above, the dither amplitude can be adjusted by the weighted average ratio α, and the larger the weighted average ratio α, the larger the dither amplitude. In terms of tracking performance, the smaller the weighted average ratio α, the more dominant the tracking becomes in terms of carrier cycles, making it easier to achieve high-speed tracking. Conversely, the larger the weighted average ratio α, the more dominant the tracking becomes in terms of dither cycles, limiting the tracking speed.

[0076] In this fourth embodiment, the time derivative of the target current is calculated by the target derivative calculation unit 202c. If the derivative is positive and its magnitude is greater than the reference value, the weighted average ratio α is reduced for the purpose of improving responsiveness. In other words, the proportion of the first duty cycle D1 in the duty cycle (weighted average duty cycle) generated by the weighted average unit 54 is increased. On the other hand, if the derivative is negative and its magnitude is greater than the reference value, the weighted average ratio α is set to be larger for the purpose of improving hysteresis characteristics by ensuring dither amplitude. In other words, the proportion of the third duty cycle D3 in the duty cycle (weighted average duty cycle) generated by the weighted average unit 54 is increased.

[0077] The setting of the weighted average ratio α in this fourth embodiment is shown in Figure 15A. There is no limit to the number of threshold values ​​for the target current derivative, but for simplicity of explanation, -ΔI rt ΔI rt Two threshold values ​​are used. In Figure 15A, the value of α when the magnitude of the target current derivative exceeds the reference value is set to a maximum value of 1 or a minimum value of 0, but it can be implemented with any other arbitrary value.

[0078] Figure 15B shows the processing of the weighted average setting unit 202b for each carrier period. The processing in Figure 15B updates the weighted average ratio α for each dither period based on the counter variable C operated by the second duty cycle conversion unit 53, as described in the first embodiment.

[0079] When the weighted average setting unit 202b starts the α setting process (S2000), it determines whether the counter variable C = N-1 (S2001). If Yes, it proceeds to S2002; otherwise, it terminates the α setting process (S2007). In S2002, the target current derivative is the threshold - ΔI. rt Determine if it is less than the threshold value. If yes, proceed to S2004; otherwise, proceed to S2003. In S2003, the target current derivative is the threshold value -ΔI. rt The threshold ΔI rt The system determines whether the following conditions apply; if yes, proceed to S2005; otherwise, proceed to S2006. In S2004, α=1; in S2005, α=0.5; and in S2006, α=0, and the α setting process ends (S2007).

[0080] In other words, when the magnitude of the target current derivative is small, α = 0.5 is set by following the steps of No at S2002 and Yes at S2003 in Figure 15B.

[0081] In relation to Figures 15A and 15B, the target current I r and actual current I a An example of the progression is shown in Figure 16. In Figure 16, the target current value changes between t1 and t2 and between t5 and t6, but because the magnitude of the derivative is small, the setting value of α does not change from 0.5.

[0082] Between t3 and t4, the derivative of the target current is positive and its magnitude is greater than the reference value. Therefore, by following No at S2002 and No at S2003 in Figure 15B, α=0 is set.

[0083] Between t7 and t8, the derivative of the target current is negative and its magnitude is greater than the reference value, and by following the Yes path in S2002 in Figure 15B, α=1 is set.

[0084] This embodiment improves the responsiveness of hydraulic equipment by primarily using high-speed tracking for each carrier cycle when the target current value rises significantly (when the time derivative of the target current value is positive and its magnitude is greater than the reference value), and by ensuring the dither current amplitude when the target current value falls significantly (when the time derivative of the target current is negative and its magnitude is greater than the reference value).

[0085] << Fifth Embodiment >> In carrying out the fifth embodiment of the present invention, the functional configuration of the control unit 10 is the same as in Figure 14 of the fourth embodiment.

[0086] In the fifth embodiment, the setting of the weighted average ratio α according to the target current value, as described in the third embodiment, and the setting of the weighted average ratio α according to the target current derivative, as described in the fourth embodiment, are combined and implemented. The settings of the weighted average ratio α according to the target current value and the target current derivative are shown in Figure 17A.

[0087] In the fifth embodiment, the main purpose is to change the weighted average ratio α according to both the target current value and the target current derivative, and the threshold and its number are arbitrary. In the example setting shown in Figure 17A, the target current I r Threshold I rth1 If it is smaller than the target current I r Assuming that is on an increasing trend (not a decreasing trend), a positive value is set as the threshold for the derivative of the target current, and the target current I r Threshold I rth2 If it is greater than the target current I r Assuming that the value is decreasing (not increasing), a negative value is set as the threshold for the target current derivative.

[0088] Figure 17B shows the processing of the weighted average setting unit 202b for each carrier period. The processing in Figure 17B updates the weighted average ratio α for each dither period based on the counter variable C operated by the second duty cycle conversion unit 53, as described in the first embodiment.

[0089] Although detailed descriptions of each of steps S3000 to S3019 in FIG. 17B are omitted, for example, S3002 and S3003 in FIG. 17B correspond to S1002 and S1003 in FIG. 12B, and S3004, S3005, S3009, S3010, S3014, and S3015 in FIG. 17B correspond to S2002 and S2003 in FIG. 15B.

[0090] In the description of this fifth embodiment, the description of the target current value of the current waveform and the current waveform is omitted. However, the change in the weighted average ratio α with respect to the target current value is the same as that in the third embodiment, and the change in the weighted average ratio α with respect to the target current differential value is the same as that in the fourth embodiment.

[0091] In a region where the target current value is small, similar to the description in the third embodiment, the current amplitude of the dither can be ensured, and the hysteresis in the low current region can be improved. Also, similar to the description in the fourth embodiment, when the target current value increases significantly, the main focus is on following each carrier period, and when the target current value decreases significantly, the main focus is on ensuring the current amplitude of the dither, thereby improving the responsiveness of the hydraulic equipment.

[0092] << Summary >> As described above, the current control device (control unit 10) of the present embodiment is a current control device that controls the excitation current of the solenoid, and includes a drive circuit (electromagnetic proportional valve drive unit 204) for supplying the excitation current to the solenoid, a duty ratio setting unit (electromagnetic proportional valve control unit 202) that determines the duty ratio of the switching signal output by the drive circuit, and a target current setting unit 201 that sets the target current value of the excitation current. The duty ratio setting unit (electromagnetic proportional valve control unit 202) is based on the target current value set by the target current setting unit 201, a first duty ratio D1 updated every first period (carrier period T C ) equal to the switching period, and based on the target current value set by the target current setting unit 201, a second period (dither period T C ) that is a natural multiple of the first period (carrier period T DThe second duty ratio D2 updated every time, and the second duty ratio D2 and the second period (dither period T D ) The binary pulse waveform represented by is divided on the time axis for each of the first periods (carrier periods T C ) to calculate the third duty ratio D3 calculated as the integration rate for each of the first periods (carrier periods T C ) (first duty ratio calculation unit 511, second duty ratio calculation unit 512, second duty ratio conversion unit 53), and the weighted average duty ratio calculated as the weighted average value of the first duty ratio D1 and the third duty ratio D3 is used as the drive circuit. By instructing (weighted average unit 54), periodic vibration in the second period (dither period T D ) is generated in the excitation current.

[0093] The respective weighted average ratios of the first duty ratio D1 and the third duty ratio D3 are set to arbitrary values within the range of 0 to 1 where the sum of the two is 1, or within the range of 0% to 100% where the sum of the two is 100%. Adjust the amplitude of the periodic vibration in the second period (dither period T D ) of the excitation current.

[0094] At the minimum or maximum value of the weighted average ratio, the drive circuit is the first period (carrier period T) that does not include the periodic vibration. C ) Drive at the first duty ratio D1, or the second period (dither period T D ) Implement either drive at the second duty ratio D2.

[0095] According to this embodiment, the dither waveform is not superimposed on the target current value, and the effect of dither can be obtained.

[0096] Furthermore, in this embodiment, the dither amplitude (amplitude of periodic oscillations at the dither period) can be adjusted by changing only the weighted average ratio α of the first duty cycle D1 and the third duty cycle D3. Since both the first duty cycle D1 and the third duty cycle D3, which contributes to the dither effect, are calculated based on the same target current value, it is possible to adjust the dither amplitude while preventing a rise in current.

[0097] It should be noted that the present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0098] Furthermore, some or all of the functions of the controller in the above-described embodiment may be implemented in hardware, for example, by designing them as integrated circuits. Alternatively, they may be implemented in software by having a processor interpret and execute programs that implement each function. Information such as programs, tables, and files that implement each function can be stored in storage devices such as hard disks, SSDs (Solid State Drives), or recording media such as IC cards, SD cards, or DVDs, in addition to the storage device within the controller. [Explanation of Symbols]

[0099] 10. Control Unit (Current Control Device) 14 Solenoid proportional valve 20 Central Processing Unit 201 Target Current Setting Unit 202 Electromagnetic proportional valve control unit (duty cycle setting unit) 203 Current Calculation Unit 204 Electromagnetic proportional valve drive unit (drive circuit) 205 Current detection unit 511 First Duty Calculation Unit 512 Second Duty Calculation Unit 521 First Average Value Calculation Unit 522 Second Average Value Calculation Unit 53 Second Duty Cycle Conversion Unit 54 Weighted average part

Claims

1. A current control device for controlling the excitation current of a solenoid, A drive circuit for supplying the excitation current to the solenoid, A duty cycle setting unit that determines the duty cycle of the switching signal output by the drive circuit, A target current setting unit for setting a target current value for the excitation current, Equipped with, The duty cycle setting unit is, Based on the target current value set by the target current setting unit, the first duty cycle is updated every first cycle, which is equal to the switching cycle, Based on the target current value set by the target current setting unit, the second duty cycle is updated every second cycle, which is a natural number multiple of the first cycle, The binary pulse waveform represented by the second duty cycle and the second period is divided on the time axis for each first period, and the third duty cycle, calculated as the integral ratio for each first period, is calculated. A current control device characterized by generating periodic oscillations in the excitation current during the second period by instructing the drive circuit to use a weighted average duty cycle calculated as a weighted average of the first duty cycle and the third duty cycle.

2. The weighted average percentages of the first duty cycle and the third duty cycle are set to any value in the range of 0 to 1 such that their sum is 1, or to any value in the range of 0% to 100% such that their sum is 100%. The current control device according to claim 1, characterized in that it adjusts the amplitude of the periodic oscillation of the excitation current in the second period.

3. The current control device according to claim 2, characterized in that, at the minimum or maximum value of the weighted average ratio, the drive circuit performs either driving with a first duty cycle in the first period that does not include the periodic oscillation, or driving with a second duty cycle in the second period.

4. The current control device according to claim 2, characterized in that the weighted average ratio is changed according to the value of the target current value.

5. The current control device according to claim 2, characterized in that the weighted average ratio is changed according to the time derivative of the target current value.

6. The current control device according to claim 2, characterized in that the weighted average ratio is changed according to both the target current value and the time derivative of the target current value.

7. The current control device according to claim 1, characterized in that when the duty cycle setting unit calculates the first duty cycle from the target current value, it cancels out the fluctuations based on the weighted average of the detected excitation current value and the third duty cycle.

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