JP2001265433A - Method for detecting failure of servo controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting the failure of a servo controller having high failure detecting capabilities by reducing any influence on a post stage system. SOLUTION: A servo controller is provided with a current driver part 3 and a torque motor 21 operating according to a current command, a servo actuator 20 operating according to the output of the torque motor 21, an integrating element 68 interposed between the torque motor 21 and the actuator 20, a position sensor 41a for detecting the displacement of the outputting part of the actuator 20, and a subtractor 61 for subtracting the detection signal of the position sensor 41a from an actuator position command inputted from the outside part and for outputting the subtracted value as a current command. Then, a dummy signal is superimposed on the current command, and the output change of the current driver part 3 and the toque motor 21 is monitored synchronously with the superimposing timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a failure in a servo control device having two or more operating portions, such as a servo actuator that servo-controls a hydraulic actuator by driving a hydraulic valve with a motor.

[0002]

2. Description of the Related Art Conventionally, in a servo control device such as a servo actuator or a process constant value control device such as a chemical plant, in order to detect a failure of a feedback sensor or a drive circuit, a value considered not to occur in a normal state is detected by a sensor signal. Countermeasures have been taken such as detecting whether it appears independently in values, state variables, and operation inputs, or as a combination of these.

[0003]

In these methods, it is difficult to determine whether or not a failure has occurred by focusing on features and situations where the normal state and the failure state are significantly different. This is advantageous in preventing detection and in the event of a failure, quickly detecting the failure and taking appropriate measures. However, such a setting may be difficult.

In order to increase the response and robustness against fluctuations in a position servo system, a control system having multiple inner feedback loops such as a current loop and a speed loop is used. The effect appears late in the final output. Therefore, when the failure is detected from the abnormality of the final output, the failure progresses to a state where it cannot be easily restored, and the system is likely to have a transient influence on a subsequent system to which the output is connected. Therefore, failure of the inner feedback loop such as the current control circuit
As far as possible independently, it is necessary to detect and isolate faults before adversely affecting the output.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting a failure in a servo control device having a small influence on a subsequent system and having a high failure detection capability.

[0006]

According to the present invention, there is provided a first operation section which operates in response to a first command signal, a second operation section which operates in accordance with an output of the first operation section, and a first operation section. Subtracting the detection signal of the position sensor from an integral element interposed between the second operation unit, a position sensor for detecting displacement of an output unit of the second operation unit, and a second command signal input from the outside; , A subtraction element for outputting a subtraction value as the first command signal.
A failure detection method for a servo control device, wherein the failure detection method is superimposed on a command signal and a change in output of a first operating unit is monitored in synchronization with the superimposition timing.

According to the present invention, the dummy signal is superimposed on the first command signal, and the output change of the first operating unit is monitored in synchronization with the superimposition timing, whereby the dummy signal and the output of the first operating unit are monitored. From the relationship with the change, it is possible to determine with high reliability whether the first operating section is in the normal state or the failure state.

Further, since the integrating element is interposed between the first operating section and the second operating section, it is difficult for the output of the first operating section to be transmitted to the second operating section even if the output changes sharply. Therefore, when a steep pulse signal is superimposed as a dummy signal, the first
A pulse signal can be set so that a change corresponding to the transfer characteristic of the first operating unit appears in the output of the operating unit, but the change is hardly transmitted to the second operating unit. Therefore, even in a state where the servo control device continues the normal operation, the fault detection can be performed with high reliability without affecting the final output due to the superposition of the dummy signal.

According to the present invention, there is provided a first operation section which operates according to a first command signal and has a multiple feedback loop;
A second operating unit that operates according to the output of the first operating unit;
An integral element interposed between the operating section and the second operating section;
A position sensor for detecting a displacement of an output unit of the operation unit, and a subtraction element for subtracting a detection signal of the position sensor from a second command signal input from the outside and outputting a subtraction value as the first command signal A method of detecting a failure of a servo control device, comprising: superimposing a dummy signal on one of feedback loop signals of a first operating unit, and changing a change of another feedback loop signal of the first operating unit to a superimposition timing. This is a failure detection method for a servo control device, wherein the failure is monitored in synchronization.

According to the present invention, when the first operating section has a multiple feedback loop, the dummy signal is superimposed on one of the feedback loops of the first operating section, and another dummy feedback loop of the first operating section is used. By monitoring the change in synchronization with the superimposition timing, it is possible to determine with high reliability whether the first operating section is in the normal state or the failure state from the relationship between the change in the dummy signal and the loop signal.

Further, since the integrating element is interposed between the first operating section and the second operating section, even if the output of the first operating section changes sharply, it is difficult to transmit the output to the second operating section. Therefore, when a steep pulse signal is superimposed, for example, as a dummy signal, a change corresponding to the transfer characteristic of the first operating unit appears in the output of the first operating unit, but the change is hardly transmitted to the second operating unit. . Therefore, even in a state where the servo control device continues the normal operation, the failure detection can be performed with high reliability by the superposition of the dummy signal.

Further, according to the present invention, the dummy signal is a single pulse, and the amplitude and time width of the pulse are such that the response amount Qa from the superimposed point of the dummy signal to the monitoring point is the output of the second operating unit from the superimposed point of the dummy signal. The response amount is set to be smaller than the response amount Qb.

According to the present invention, the transfer characteristic of the first operating section can be measured over a high band by using a single pulse as the dummy signal.

The amplitude and time width of the pulse are set so that the response amount Qa from the superimposition point of the dummy signal to the monitoring point is smaller than the response amount Qb from the superimposition point of the dummy signal to the output of the second operating section. Thereby, the influence on the output of the second operating unit can be reduced as much as possible while improving the failure detection capability of the first operating unit. The response amount can be defined by the ratio of the change amount to the control full scale.

Further, in the present invention, the dummy signal is a positive / negative pulse, and the amplitude and time width of the pulse are such that the response amount Qa from the superimposition point of the dummy signal to the monitoring point is the output of the second operating unit from the superimposition point of the dummy signal. The response amount is set to be smaller than the response amount Qb.

According to the present invention, the transfer characteristic of the first operating section can be measured over a high band by using positive and negative pulses as the dummy signal. In addition, the effects of the positive and negative pulses cancel each other out,
The influence on the output of the second operating unit is reduced.

The pulse amplitude and time width are set so that the response amount Qa from the superimposition point of the dummy signal to the monitoring point is smaller than the response amount Qb from the superimposition point of the dummy signal to the output of the second operating section. Thereby, the influence on the output of the second operating unit can be reduced as much as possible while improving the failure detection capability of the first operating unit. The response amount can be defined by the ratio of the change amount to the control full scale.

Further, according to the present invention, the dummy signal has a high frequency, and the amplitude and cycle of the high frequency are such that the response amount Qa from the superimposition point of the dummy signal to the monitoring point is the second time from the superimposition point of the dummy signal.
It is characterized in that it is set to be smaller than the response amount Qb up to the output of the operating section.

According to the present invention, by using a high frequency as a dummy signal, an abnormality can be measured by focusing on a specific frequency which exhibits an abnormality due to a failure among the transfer characteristics of the first operating section.

The amplitude and cycle of the high frequency are set so that the response Qa from the superimposition point of the dummy signal to the monitoring point is smaller than the response Qb from the superimposition point of the dummy signal to the output of the second operating section. Thereby, the influence on the output of the second operating unit can be reduced as much as possible while improving the failure detection capability of the first operating unit. The response amount can be defined by the ratio of the change amount to the control full scale.

[0021]

FIG. 1 is a mechanical configuration diagram showing an example of a servo actuator to which the present invention can be applied.
1A is a plan view, and FIG. 1B is a front view. The servo actuator 20 is configured as a DDV (Direct Drive Valve) hydraulic servo actuator in which an electric motor directly drives a hydraulic valve, and includes a first hydraulic system including a control valve 33a and an actuator 40a, and a control hydraulic valve 33b and an actuator 40b. Driving force is supplied from two independent hydraulic systems called a second hydraulic system.

The control valve 33a includes a sleeve 34a and a spool 30a, and the control valve 33b includes a sleeve 34b and a spool 30b. The two control valves 33a and 33b are arranged in parallel with each other.

The torque motor 21 has a double shaft structure and has two eccentric output shafts 22a and 22b. Spool 30a
And the output shaft 22a are connected via a rotary linear conversion mechanism 31a that converts the angular displacement of the output shaft 22a into a linear displacement. Similarly, the spool 30b and the output shaft 22b are connected to the output shaft 22b.
Rotary linear conversion mechanism 31b that converts the angular displacement of the object into a linear displacement
Are connected via Also, the torque motor 21
It has three mutually independent drive coils 21a to 21c to form a triple system.

The other end of the spool 30a has a spool 30
a position sensor 32a for measuring the amount of displacement of the spool 30b.
A position sensor 32b for measuring the amount of displacement of b is attached. The position sensors 32a and 32b output two electrically independent position signals, respectively. Of the four position signals, three position signals Sa to Sc are feedback signals corresponding to the drive coils 21a to 21c of the torque motor 21. Used as

The sleeves 34a and 34b have a pipeline (not shown) for introducing hydraulic oil supplied from a hydraulic pump, a pipeline (not shown) for returning hydraulic oil to the oil tank, and actuators 40a and 40b. Is connected to a pipeline (not shown) for guiding hydraulic oil.

The two actuators 40a and 40b are arranged in parallel and connected to the output shaft 42 so that the piston in the cylinder is displaced integrally. The piston in each cylinder is driven by the pressure difference of the working oil. A passage is formed in the sleeves 34a and 34b and the spools 30a and 30b for switching the direction of the hydraulic oil and adjusting the flow rate.

As shown in FIG. 1B, each actuator 40a, 40b is provided below each actuator 40a, 40b.
Position sensors 41a and 41b for independently detecting the displacement amounts of a and 40b are provided. Position sensors 41a, 41
b outputs two electrically independent position signals, and three position signals Pa to P out of a total of four position signals.
c is used as a feedback signal of the output shaft displacement.

The position sensors 32a, 32b, 41
a, 41b as LDVT (Linear Variable Differe
Various displacement sensors such as ntial Transformer) can be used.

FIG. 2A is a block diagram showing an example of the servo control device according to the present invention, and FIG. 2B is an equivalent circuit diagram of the current driver 3. The controller 1 that controls the servo actuator 20 includes a sensor signal processing unit 2
, A current driver unit 3, a servo control unit 4, a failure determination unit 5, an addition command signal generation unit 6, and the like. The controller 1 can be configured by an analog circuit or a digital circuit using a computer.

The sensor signal processing section 2 processes a sensor signal from the servo actuator 20. Servo control unit 4
Outputs a current command to the current driver 3 based on the output of the sensor signal processor 2. The current driver 3 drives the torque motor 21 according to the current command.

The failure judging unit 5 takes in various signals such as the output of the sensor signal processing unit 2 and the driving current of the current driver unit 3 and instructs the addition command signal generating unit 6 to superimpose a dummy signal. The addition command signal generation unit 6 is configured to
A dummy signal is superimposed on various signals of the servo control unit 4.

As shown in FIG. 2B, the torque motor 2
One system includes a motor resistance Rm and a motor inductance R
m and a series circuit of the motor back electromotive voltage Em.
The differential current amplifier 3a amplifies the difference between the current command from the servo controller 4 and the motor current value detected by the current sensor 3b, and operates so that the current command matches the motor current. In the triple torque motor 21 shown in FIG. 1, three drive circuits are provided.

For example, when a disconnection failure of the motor winding occurs as a failure state of the torque motor 21, the motor current Im becomes zero. In this case, since the motor current is fed back so as to follow the command current, the motor voltage Vm output from the differential current amplifier 3a increases and saturates near the power supply voltage. On the other hand, when a short-circuit fault occurs in the motor winding, the motor voltage Vm decreases to a voltage across the short-circuit resistor. In this case, since the motor current is fed back so as to follow the command current, the motor current Im substantially matches the current command.

Therefore, the failure state of the torque motor 21 can be determined by analyzing the changes in the motor voltage Vm and the motor current Im.

FIG. 3 is a control block diagram of the controller 1. The controller 1 includes a subtracter 61 for amplifying a difference between an externally input actuator position command and an actuator position signal from the position sensor 41a, an amplifier 62 for amplifying an output of the subtractor 61 with a gain G1, and an amplifier 62. 63 that amplifies the difference between the output of the subtractor 63 and the DDV position signal from the position sensor 32a, an amplifier 64 that amplifies the output of the subtractor 63 with a gain G2, and a difference that inputs the output of the amplifier 64 as a current command. A dynamic current amplifier 3a;
The motor current value constituted by the torque motor 21 and the current sensor 3b described above is converted to a torque value by a motor torque coefficient Kt, and the torque value is integrated to become a DDV speed value, and the DDV speed value is integrated to obtain a DDV position value. Become. D
The DV position value corresponds to the opening of the valve, but when the load is low, a flow proportional to the opening flows into the actuator piston, and this is integrated to become an actuator position output. A back electromotive voltage is generated by the coefficient KE based on the DDV speed value. In the integral elements 66 to 68, s is a Laplace operator, and a, b, and c are constants.

In this way, the motor current value is changed to the differential current amplifier 3
A servo control device includes a current feedback loop that negatively feeds back to a, a first position feedback loop that negatively feeds the DDV position to the amplifier 64, and a second position feedback loop that negatively feeds back the actuator position to the amplifier 62. .

FIG. 4 is a flowchart showing a failure detecting operation of the controller 1. First, in step s1, the failure determination unit 5 monitors various outputs of the sensor signal processing unit 2, fetches a predetermined failure determination signal, and
It is determined whether the failure determination signal is within a predetermined allowable range. If the failure determination signal is within the permissible range, it is determined to be in a normal state, and the process returns to step s1 again to perform failure determination at the next timing.

When the failure determination signal is out of the allowable range,
The process proceeds to step s3 to determine whether or not the value of the timer for determining the superimposition timing of the dummy signal has reached a predetermined value, and if not, returns to step s1 again. If the timer value has reached the predetermined value, the process proceeds to step s4, where the failure determination unit 5 instructs the addition command signal generation unit 6, and the addition command signal generation unit 6 generates an addition pulse signal as a dummy signal. Superimposed on current command. Then, the timer is reset in step s5.

Next, in step s6, the failure judgment unit 5
Monitors the change in the motor current value in synchronization with the superimposition timing of the dummy signal, and determines whether or not the amount of change is within a predetermined allowable range. If the amount of change is within the allowable range, it is determined to be normal,
Returning to step s1, the failure judgment is executed at the next timing.

If the variation is out of the allowable range, the process proceeds to step s7, where the failure determination unit 5 determines that a failure has occurred, and further, in step s8, separates the failed system from the triple system, and only the remaining system Then, the system is reconfigured so as to continue the servo control, and the process returns to step s1 again to execute the failure judgment at the next timing.

FIG. 5 is a diagram showing various waveforms of a dummy signal applicable to the present invention. FIG. 5A shows a case where a single positive pulse is superimposed as a dummy signal. By monitoring changes in the motor current value and the voltage value in synchronization with the superimposition timing, the transfer characteristic of the current driver unit 3 is improved. It can be measured over a band. The dummy signal may be a single negative pulse.

FIG. 5B shows a case where positive and negative pulses in which a positive pulse and a negative pulse are successively superimposed are superimposed as a dummy signal. Changes in the motor current value and the voltage value are monitored in synchronization with the superimposition timing. Current driver 3
Can be measured over a high band.

FIG. 5 (c) shows a case where a high frequency is superimposed as a dummy signal. By monitoring a change in the motor current value in synchronization with the high frequency, an abnormality relating to a specific frequency in the transfer characteristics of the first operating portion is obtained. Can be measured.

The amplitude and the time width of the pulse and the amplitude and the period of the high frequency wave are determined by the response Qa from the superimposition point (here, the current command) of the dummy signal to the monitoring point (here, the motor current). It is preferable that the setting is made so as to be smaller than the response amount Qb up to the output of the two operating units (here, the servo actuator 20).

FIG. 6 is a block diagram schematically showing the transfer characteristics of the controller 1. The input X is a subtractor 91,
The output Y finally passes through an amplifier 92 having a gain Ga, a subtractor 93, an amplifier 94 having a gain Gb, and an amplifier 95 having a gain Gc. On the way, the output of the amplifier 94 is fed back to the subtractor 93 to form an inner feedback loop. The output of the amplifier 95 is fed back to the subtractor 91 to form an outer feedback loop.

The transfer function Gzy from the dummy signal addition point Z to the output Y is represented by the following equation (1).

[0047]

(Equation 1)

In the equation (1), Gzu is a transfer function from the dummy signal addition point z to the inner loop output point u of the Gb section, and is expressed by the following equation (2).

[0049]

(Equation 2)

The ratio between the transfer function Gzy and the transfer function Gzu is expressed by the following equation (3).

[0051]

(Equation 3)

When the dummy signal is superimposed on the output of the amplifier 92, when the controller 1 has a characteristic of generating an output signal in a delayed manner with respect to a steep input such as an integral element in Ga or Gc as a transfer characteristic, , The effect of the dummy signal hardly appears on the output Y.

In the above configuration, the dummy signal is superimposed on the current command output from the amplifier 64, and the current sensor 3
Although the method of monitoring the motor current value output by b has been described, if the superimposition point and the change monitoring point of the dummy signal are anywhere from the command input unit of the subtractor 61 to just before the integration element 68, failure detection will be performed. Will be possible.

Further, in a configuration in which a multiplex feedback loop exists from the command input section of the subtractor 61 to a position before the integration element 68, a dummy signal is superimposed on one of the multiplex feedback loops and another feedback loop is formed. The failure can be detected also by monitoring the change in synchronization with the superposition timing.

FIG. 7 is a graph showing a signal change when a dummy signal is superimposed on an actuator position command. The horizontal axis represents time, and each graph shows a position command, a motor voltage, a motor current, a DDV position, and an actuator position in order from the top. As shown in FIG. 7A, at time t1
When a single pulse having a width of 10 msec is superimposed on the position command as a dummy signal, the motor voltage and the motor current change as shown in FIGS. 7B and 7C, and further, as shown in FIG. The DDV position changes with a delay due to the integration elements 66 and 67 caused by the inertia and the like. However, as shown in FIG. 7E, the amount of change in the DDV position becomes the actuator position via the integration characteristic due to the integration element 68 caused by the mechanical inertia of the hydraulic system. Thus, it can be seen that the actual actuator position has hardly changed.

Therefore, changes in the motor voltage and the motor current are monitored in synchronization with the superimposition timing of the dummy signal.
For example, if the motor voltage Vm is equal to or higher than the threshold value Vmax and the motor current Im is equal to or lower than the threshold value Imin, it can be estimated that the motor has a disconnection failure. If the motor voltage Vm is equal to or lower than the threshold value Vmin and the motor current Im is equal to or higher than the threshold value Imax, it can be estimated that there is a short-circuit failure of the motor.

Such a threshold value is set so as not to be erroneously detected as a failure in a normal state, and to quickly determine a failure in a failure state. In the case of a motor driven at a low current, a fuzz signal or the like is set. Therefore, such setting is difficult, and there is a possibility that the use may be continued in a state where the performance is deteriorated. In the present embodiment, a failure can be quickly detected with high reliability by generating a situation in which it is easy to determine whether or not a failure has occurred by using a dummy signal without affecting the final output. Becomes possible.

If a failure is determined only by one pulse, there is a possibility of erroneous determination due to the influence of noise or the like. Therefore, a single pulse is generated a plurality of times at a predetermined cycle to increase the number of failure determinations. And accurate failure judgment can be made.

[0059]

As described above in detail, according to the present invention, the dummy signal is superimposed on the first command signal, and the output change of the first operating section is monitored in synchronization with the superimposition timing, whereby the dummy signal is superposed. It is possible to determine whether the first operating unit is in a normal state or a failure state from the relationship between the first operating unit and the output change of the first operating unit.

In addition, since the integration element is interposed between the first operating section and the second operating section, a dummy signal is set so that almost no change is transmitted to the second operating section.
Even in a state where the servo controller continues the normal operation, the failure can be detected by superimposing the dummy signal.

Further, when the first operating section has a multiple feedback loop, the dummy signal is superimposed on one of the feedback loops of the first operating section, and the change of another feedback loop of the first operating section is superimposed on the superposition timing. , It is possible to determine with high reliability whether the first operating unit is in a normal state or a fault state from the relationship between the dummy signal and the change in the loop signal.

[Brief description of the drawings]

FIG. 1 is a mechanical configuration diagram showing an example of a servo actuator to which the present invention can be applied. FIG. 1A is a plan view, and FIG. 1B is a front view.

FIG. 2A is a block diagram illustrating an example of a servo control device according to the present invention, and FIG. 2B is an equivalent circuit diagram of a current driver unit 3.

FIG. 3 is a control block diagram of the controller 1.

FIG. 4 is a flowchart showing a failure detection operation of the controller 1.

FIG. 5 is a diagram showing various waveforms of a dummy signal applicable to the present invention.

FIG. 6 is a block diagram schematically showing a transfer characteristic of the controller 1.

FIG. 7 is a graph showing a signal change when a dummy signal is superimposed on an actuator position command.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Controller 2 Sensor signal processing part 3 Current driver part 3a Differential current amplifier 3b Current sensor 4 Servo control part 5 Failure judgment part 6 Addition command signal generation part 20 Servo actuator 21 Torque motor 30a, 30b Spool 32a, 32b, 41a, 41b Position sensor 33a, 33b Control valve 34a, 34b Sleeve 40a, 40b Actuator 42 Output shaft 61, 63 Subtractor 62, 64 Amplifier 65, 69 Converter 66-68 Integral element

Claims (5)

[Claims] A first operating unit that operates in response to a first command signal; a second operating unit that operates in accordance with an output of the first operating unit; and a first operating unit and a second operating unit. An intervening integral element, a position sensor for detecting displacement of an output section of the second operating section, and a detection signal of the position sensor subtracted from a second command signal input from the outside, and the subtracted value is calculated by the first method. A failure detection method for a servo control device comprising a subtraction element that outputs a command signal, wherein a dummy signal is superimposed on a first command signal, and an output change of a first operation unit is monitored in synchronization with the superimposition timing. A method for detecting a failure of a servo control device. 2. A first operation unit that operates according to a first command signal and has a multiple feedback loop, a second operation unit that operates according to an output of the first operation unit, a first operation unit, and a second operation unit. An integral element interposed between the operating unit, a position sensor for detecting a displacement of an output unit of the second operating unit, and a detection signal of the position sensor subtracted from a second command signal input from the outside, and A subtraction element for outputting a calculated value as the first command signal, wherein the dummy signal is superimposed on one of the feedback loop signals of the first operating section, A failure detection method for a servo control device, wherein a change in another feedback loop signal of the operation unit is monitored in synchronization with the superimposition timing. 3. The dummy signal is a single pulse, and the amplitude and time width of the pulse are such that the response amount Qa from the superimposition point of the dummy signal to the monitoring point is a response from the superimposition point of the dummy signal to the output of the second operating unit. 3. The method according to claim 1, wherein the value is set to be smaller than the amount Qb. 4. The dummy signal is a positive / negative pulse, and the amplitude and time width of the pulse are such that the response amount Qa from the superimposition point of the dummy signal to the monitoring point is a response from the superimposition point of the dummy signal to the output of the second operating unit. 3. The method according to claim 1, wherein the value is set to be smaller than the amount Qb. 5. The dummy signal is of a high frequency, and the amplitude and cycle of the high frequency are such that the response amount Qa from the dummy signal superimposition point to the monitoring point is the response amount Qb from the dummy signal superimposition point to the output of the second operating unit. 3. The method according to claim 1, wherein the setting is made smaller.