JP2010244266A - Electric motor driving system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To safely and surely decelerate and stop an electric motor by synchronizing the decelerating time of a controller and the output of a safety function device. <P>SOLUTION: This electric motor driving system includes a controller for performing the variable speed operation of the electric motor and a safety function device for outputting a stop command to the controller in order to safely stop the electric motor. The safety function device includes a means for outputting a deceleration command to decelerate the electric motor before stopping the electric motor to the controller; a clocking means for starting clocking from the output of the deceleration command; and a means for, when the clock means reaches a predetermined set time, outputting a stop command to the controller. The controller is configured to decelerate the electric motor in a deceleration time shorter than the set time when the deceleration command is input. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric motor drive system that can safely decelerate and stop when an abnormality occurs in a control device that controls an inverter, a servo amplifier, and the like.

  In recent years, power converters that drive a motor at a variable speed, such as inverters and servo amplifiers, have become widespread with the need for energy saving. On the other hand, accidents such as elevators and revolving doors have become a social problem, and abnormal operation of electrical and mechanical equipment can have a significant impact on the human body. Therefore, it is particularly safe to monitor equipment abnormalities and ensure safety and reliability when abnormalities are detected. The function to stop the equipment is important.

  When stopping the motor, there is a safe torque-off function (STO) that shuts off the energy supplied to the motor, but if the energy is cut off while the motor is rotating, the motor will continue to rotate due to inertia. Can be dangerous.

  For this reason, the conventional control device is provided with a function of stopping at a preset deceleration slope when an abnormality is detected. In Patent Document 1, a safety function device that monitors an abnormality of the control device is provided independently of a control device that generates a control signal for driving the electric motor, and the control signal is cut off when an abnormality is detected. Thus, an electric motor drive system for stopping the electric motor has been proposed.

US Pat. No. 7,253,577

  However, according to the above-described safety function device according to the prior art, the safety function device and the control device are separated, and the deceleration command is output to the control device side. It will exist separately. For this reason, a difference arises between the deceleration time of the control device and the set time of the safety function device, and after the start of deceleration, the vehicle decelerates regardless of the set time of the safety function device. As a result, there is a possibility that a stop command is output even though the motor is still rotating at a high speed, or a stop command is not output even though a state in which the electric motor is hardly rotating continues for a long time. If such a situation occurs, there is a possibility of damaging the device to be driven or damaging the human body, which is not preferable.

  The present invention has been made in view of the above-described circumstances, and in an electric motor drive system configured by a control device and a safety function device, by synchronizing the deceleration time of the control device and the output of the safety function device. An object of the present invention is to provide an electric motor drive system that can safely and reliably decelerate and stop an electric motor.

  In order to achieve the above object, an electric motor drive system according to the present invention includes an electric motor drive having a control device for variable speed operation of the electric motor and a safety function device for outputting a stop command to the control device in order to stop the electric motor safely. The safety function device includes: a means for outputting a deceleration command for decelerating the motor before stopping the motor to the control device; a timing means for starting measurement from the output of the deceleration command; and a timing means in advance Means for outputting a stop command to the control device when a predetermined set time is reached, and the control device is configured to decelerate the motor with a deceleration time shorter than the set time when the deceleration command is input. It is characterized by being.

  The control device calculates a deceleration gradient for decelerating the motor based on the motor speed command value and the deceleration time when the deceleration command is input, and decelerates the motor based on the deceleration gradient.

  In the present invention, the motor is smoothly and safely controlled by controlling the rotation speed of the motor to be zero in a time shorter than the time from when the safety function device outputs the deceleration command to when the stop command is output. Can be stopped.

  Preferably, if the time difference between the set time and the deceleration time can be adjusted according to the characteristics of the motor, the safety function device can be handled independently and can be used in combination with an existing control device.

  The safety function device for an electric motor drive system according to the present invention includes self-diagnosis means, and when an abnormality is detected by the self-diagnosis means, the control device determines whether or not the control device is executing a deceleration command. The motor is stopped by shutting off a control signal output to the motor.

  In the present invention, when an abnormality is detected by the self-diagnosis means, the motor is immediately stopped by cutting off the control signal output from the control device to the motor.

  The safety function device of the motor drive system according to the present invention is capable of detecting a plurality of abnormal modes by self-diagnosis means, and outputs a deceleration command to the control device at a different deceleration time for each detected abnormal mode. .

  In the present invention, since a deceleration command is output to the control device with a different deceleration time for each abnormal mode, appropriate deceleration / stop control can be performed according to the abnormal state.

  According to the present invention, a safety function device that realizes a safety function independent of a control device that generates a drive signal is provided, and a set time from when the safety function device outputs a deceleration command to when it outputs a stop command, Since a time difference is provided in the deceleration time from when the control device inputs a deceleration command until the rotational speed of the motor reaches zero and the deceleration is performed earlier than the set time, the motor can be safely stopped. This also ensures the safety of the machine such as the brake means attached to the electric motor.

  Furthermore, by outputting a deceleration command to the control device with a different deceleration time for each abnormal mode, it becomes possible to perform appropriate motor deceleration / stop control according to the abnormal state.

1 is a functional block diagram of an electric motor drive system 1 according to a first embodiment of the present invention. It is explanatory drawing which shows the comparison with the deceleration inclination in the case of decelerating by the deceleration command from the normal function according to embodiment of this invention, the deceleration command from a safety function apparatus, and setting time. It is a flowchart which shows the procedure of the deceleration process of the safety calculating means 21a, 21b of the safety function apparatus 20 of FIG. It is a flowchart which shows the process sequence of the control apparatus 10 of FIG. It is a functional block diagram of the electric motor drive system 1 by the 2nd Embodiment of this invention. It is a data block diagram of the setting time table of FIG. It is a flowchart which shows the procedure of the initialization process of the safe calculation means 21 of FIG. It is a flowchart which shows the process sequence at the time of abnormality detection of the safe calculation means 21 of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 8 are drawings for explaining an embodiment of the electric motor drive system of the present invention, and the present invention is not limited by these drawings.

  FIG. 1 is a functional block diagram of an electric motor drive system 1 according to the first embodiment. Here, the electric motor drive system 1 includes a control device 10 that performs variable speed control of the electric motor 4 and a safety function device 20 that outputs a signal such as a stop command to the control device 10 in order to stop the electric motor 4 safely.

  Further, the inverter 3 converts the power source 2 into a predetermined frequency by the PWM signal output from the control device 10 and supplies it to the motor 4 to control the load 8 such as an elevator at a variable speed. The load 8 has a brake mechanism 6 and is configured to stop by a brake command from the safety function device 20.

  The control device 10 includes a deceleration gradient calculating means 11 for calculating a deceleration gradient indicating the relationship between the rotational speed of the motor and the deceleration elapsed time during deceleration, and a speed signal for controlling the rotational speed of the motor based on the deceleration gradient. From the speed control means 12 that outputs the PWM signal, the PWM signal generation means 13 that generates a PWM signal by comparing the speed signal with the output value of the inverter 3 input via the current / voltage sensor 9, and the safety function device 20. There is a gate means 15 for cutting off the PWM signal by a stop command.

  Further, the safety function device 20 generates a deceleration time, a deceleration command, and a stop command until the rotation speed becomes zero based on a stop command and a deceleration command input from the outside, and outputs them to the control device 10. It is composed of a pair of safety calculation means 21a and 21b having a CPU function for outputting a brake command to the brake mechanism 6 of the load 8.

  Next, the normal operation of the electric motor drive system 1 having the above configuration will be described. When the control device 10 of the electric motor drive system 1 detects an operation command inputted from the outside, the speed control means 12 calculates the torque and electric power supplied to the electric motor 4 from the deviation between the command speed and the feedback speed of the encoder 5, The calculation result is output to the PWM generator 13. The PWM generator 13 compares the calculation result with the output value of the inverter 3 input via the current / voltage sensor 9 to generate a PWM signal for turning on / off the semiconductor switch of the inverter 3. This PWM signal is sent to the inverter 3 via the gate circuit 14. Thereby, the semiconductor switch of the inverter 3 is turned on and off, and the electric motor 4 is driven with an appropriate torque and electric power.

Next, an outline of the operation when the motor drive system 1 is stopped will be described.
When an abnormality is detected by an abnormality monitoring device (not shown) provided outside, a stop command is sent to the safety function device 20 of the electric motor drive system 1. When a stop command is input, the safety function device 20 detects this by the safety calculation means 21a and 21b, and outputs a deceleration command and a deceleration time until the rotation speed is made zero to the control device 10. Further, the safety function device 20 creates a stop command for stopping the PWM signal after the set time, and outputs the stop command to the control device 10. When this stop command is input, the control device 10 generates logic that turns off all the semiconductor switches of the inverter 3 regardless of the presence or absence of the PWM signal by the gate means 15 configured by a logic circuit. Then, the output to the inverter 3 is stopped.

  The safety calculation means 21a and 21b perform self-diagnosis and mutual diagnosis. As a self-diagnosis, for example, when an abnormal mode such as a clock abnormality occurs, a stop command is output and the control signal is stopped by turning off the gate means 15 of the control device 10.

  A load 8 is connected to the electric motor 4. The safety calculation means 21a and 21b output a brake command to the brake mechanism 6 when the load 8 is stopped. The brake commands output from the respective safety calculation means 21a and 21b are input to the brake mechanism 6 under the OR condition by the relay circuit 7, whereby the brake mechanism 6 operates.

  In FIG. 1, two safety calculation means are provided, and even when one of the safety calculation means fails, the control signal (PWM signal) is stopped by the other safety calculation means. This duplex configuration uses an existing technology such as a dual configuration or a duplex configuration.

  Note that it is possible to increase the self-diagnosis function and reduce the failure rate to a level that conforms to safety standards, etc., with a single configuration of the safety calculation means. Since it is not, description is abbreviate | omitted.

  Next, main deceleration processing according to the present embodiment will be described with reference to FIGS. FIG. 2 shows a case where the control device 10 decelerates according to the rate of change of the rotational speed of the motor (hereinafter referred to as a deceleration gradient) when stopping by a normal deceleration / stop operation and a deceleration command from the safety function device 20. A comparison of deceleration slopes is shown. The vertical axis represents the rotation speed of the electric motor 4, and the horizontal axis represents time.

  When there is no deceleration command from the safety function device 20 (normal time), the control device 10 performs speed control so that the feedback speed is the same as the command speed. The deceleration inclination set on the control device 10 side indicated by the dotted line in FIG. 2 is the deceleration inclination when stopping at normal time, and the rotation speed of the electric motor registered in advance as an initial value in the control device 10 is zero. It is calculated from the deceleration time and the deceleration time set during normal acceleration / deceleration operation regardless of the safety function.

  Moreover, the relationship between the time (set time) from when the stop command is input from the outside by the safety function device 20 to when the stop command is output to the control device 10 and the deceleration time passed to the control device 10 is shown in FIG. Thus, the deceleration time is slightly shorter than the set time. This time difference varies depending on the characteristics of the electric motor and the load.

  When a deceleration command and a deceleration time are input from the safety function device 20, the deceleration inclination calculating means 11 of the control device 10 calculates a deceleration inclination from the deceleration time and the current rotational speed state.

If the deceleration time passed from the safety function device 20 is Tstop, the sample period of the control device 10 is Ts, and the rotational speed at the start of deceleration is ω _r , a speed command for deceleration during one control sample (control signal calculation period) Δω _r is _expressed by equation (1).

Here, Δω _r is a positive value if the rotational speed ω _r at the start of deceleration is positive (when the motor rotates in the direction defined as the normal rotation in advance), and negative (reverse rotation). ) Is a negative value.

Thus, the speed command value omega ^* _r for each calculation cycle used in the speed control unit 12, be determined by the equation (1) [Delta] [omega _r and using the first control sample prior to the speed command value omega ^* _r0 (2) below Can do.

  FIG. 3 is a flowchart showing the procedure of the deceleration process of the safety calculation means 21a, 21b of the safety function device 20.

  In FIG. 3, when a stop command is input (S101: “Yes”), the safety calculation means 21a, 21b of the safety function device 20 outputs a deceleration command to the control device 10 (S102), and sets a deceleration time Tstop. It outputs to the control apparatus 10 (S103). The deceleration time Tstop is a time determined in advance by a time during which the load can be safely stopped within a range of electric power that can be output by the inverter 3 to brake the electric motor. It is assumed that the deceleration time Tstop is stored in advance in a memory (not shown) in the safety function device 20 or the safety calculation means 21a, 21b.

  Then, the safety calculation means 21a and 21b determine whether or not the safety function device 20 is decelerating (S104), and if not decelerating ("No" in S104), the safety calculation means 21a and 21b have timers. A count value corresponding to the set time is set (S106). On the other hand, if the vehicle is decelerating (“Yes” in S104), the countdown is performed (S105), and the process continues until the count value becomes zero (S107).

  Whether or not the vehicle is decelerating can be determined by using a flag. That is, the deceleration flag is reset as an initial state, and if the deceleration flag is in the reset state in step S104, the timer is set and the deceleration flag is set to indicate that the vehicle is not decelerating. On the other hand, the timer count is continued when the deceleration flag is set.

  When the count value becomes zero in step S107, the safety calculation means 21a, 21b outputs a stop command to the control device 10 (S108), and outputs a brake command for operating the brake when the brake mechanism 6 exists. (S109). The brake command is output from each of the pair of safety calculation means 21a and 21b, and is output to the brake mechanism 6 by the relay circuit 7 under an OR condition. Thereafter, the safety calculation means 21a and 21b cancel the deceleration command and stop command output to the control device 10 (S110).

  Next, the operations of the deceleration inclination calculating means 11 and the speed control means 12 of the control device 10 will be described with reference to FIG.

When a deceleration command is input from the safety function device 20 (S201), the deceleration inclination calculating means 11 of the control device 10 is input from the encoder 5 when the deceleration command is first input ("Yes" in S202). Using the rotational speed ω _r of the electric motor 4 _{, the} deceleration time Tstop, and a preset sample period Ts, the deceleration gradient is calculated by the equation (1) and output to the speed control means 12 (S203, S204). The speed control means 12 determines whether or not the speed command value ω ^* _r has reached zero (S205). If it has not reached (“Yes” in S205), a new speed command value ω is obtained from the equation (2). ^* _r is calculated and output to the PWM generation means 13 (S207). As a result, the electric motor 4 is decelerated.

If the speed command value reaches zero in step S205, the speed control means 12 continues operation at zero speed (S206). Then, the gate circuit 14 is turned OFF by the stop command from the safety function device 20, and the operation is stopped (S209). When there is no deceleration command from the safety function device 20 in step S201, normal operation is executed (S210).
As described above, according to the present embodiment, the deceleration time Tstop used in the control device 10 is set slightly shorter than the set time used in the safety function device 20, so that the control device 10 and the safety function device 20 Even if there is an error in the calculation time, the stop process can be performed after the rotational speed is reliably controlled to be near zero.

  In addition, as shown in the processing procedure of FIG. 4, since the deceleration / stop operation and the normal operation are separated depending on the presence / absence of the deceleration command from the safety function device 20, the control device 10 receives the deceleration command from the safety function device 20. When the deceleration operation is performed, the safety function device 20 can surely realize the stop without stopping itself even if the rotation speed is low until the safety function device 20 gives a stop command. it can.

In the present embodiment, the speed command value Δω _r for decelerating between one control sample is obtained using the feedback speed ω at the start of deceleration in the calculation of equation (1). If the equation (1) is calculated based on the speed command value when the deceleration command from the safety function device 20 is input, the same effect can be obtained. Further, in the case of the control device 10 with no speed control means 12 without using the equation (2), the deceleration gradient calculated based on the above-mentioned speed command value [Delta] [omega _r, the output voltage of the PWM generating means 13 This can be achieved by reducing the command frequency.

  Next, a second embodiment of the present invention will be described. FIG. 5 is a functional block diagram of the electric motor drive system 1 according to the second embodiment. In the present embodiment, the case where the safety calculation means 21 is single will be described. However, if necessary, a multiplexing configuration can be adopted as in the first embodiment.

  The main difference from FIG. 1 is that the safety function device 20 latches the deceleration time output from the safety calculation means 21, the deceleration time holding means 22 that latches the time difference between the deceleration time and the set time, the deceleration A deceleration time gate circuit 24 that outputs a deceleration time in response to a read request from the inclination calculating means 11, a deceleration command holding means 25 that latches a deceleration command from the safety calculating means 21, a watchdog timer circuit (WDT) 26, and an internal clock It is provided with a time measuring means 28 that is an operating counter and a set time table 29 for storing information such as set time. In the set time table 29, as shown in FIG. 6, the time difference between the deceleration time to be output to the control device 10 for each abnormal mode and the set time is stored in advance. Here, the abnormality modes 1 to N correspond to the abnormality detection signals 1 to N detected from the outside or in the safety function device and inputted to the safety calculation means 21, respectively. The CPU stall error is an error in which the WDT 26 reset by a reset signal periodically output by the CPU detects that the reset signal does not come for a certain period of time.

  Thus, in the set time table 29, the deceleration time and the time difference are stored in advance in association with each error mode. In this deceleration time, all lower bits (for example, 4 digits from the LSB) of a predetermined digit are all zero, and the time difference is a numerical value represented only by the lower bits of the predetermined digit. Note that the value of the deceleration time and the time difference are determined based on the period of the internal clock.

Next, operation | movement of the safety function apparatus 20 is demonstrated using FIG. 7, FIG.
(Initialization process)
In the initialization process, the safety calculation means 21 reads the deceleration time and the time difference corresponding to the CPU stall error from the set time table 29 (S301), and performs a write operation to the deceleration time holding means 22 and the time difference holding means 23, respectively. It performs (S302, S303). The deceleration time holding means 22 latches only the upper digit corresponding to the effective bit of the deceleration time, and the time difference holding means 23 latches only the lower digit.

  Of these latched values, the deceleration time is input to the upper digit of the time measuring means 28 configured by a hardware circuit, and the time difference is input to the lower digit of the time measuring means 28. The output of the deceleration time holding means 22, that is, the upper digit of the latched deceleration time becomes the input of the upper digit of the deceleration time gate circuit 24. On the other hand, the lower digit of the input of the deceleration time gate circuit 24 is set to zero.

  The above is the time setting initialization process. It should be noted that a more reliable system can be constructed by starting the control device 10 by the permission signal from the safety calculation means 21 after the initialization process is completed.

(Abnormality detection processing)
In this state, when the safety calculation means 21 detects any of the abnormality detection signals 1 to N, it determines which abnormality detection signal is input (S401), and refers to the set time table 29 to indicate the abnormality. The deceleration time and time difference in the abnormal mode corresponding to the detection signal are extracted (S402), and written in the deceleration time holding means 22 and the time difference holding means 23 by the same processing as in steps S302 and S303, respectively (S403 and S404). Of the written values, the deceleration time is input to the upper digits of the timing means 28 and the deceleration time gate circuit 24, and the time difference is input to the lower digits of the timing means 28.

  Next, the safety calculation means 21 writes “1” in the deceleration command holding means 25 (S405). As a result, the deceleration command holding means 25 is turned on, and a deceleration command is output to the deceleration inclination calculating means 11 of the control device 10.

  When this deceleration command is input, the deceleration inclination calculating means 11 reads the deceleration time from the deceleration time gate circuit 24 and executes the deceleration operation by the processing shown in FIG.

  On the other hand, the safety calculation means 21 activates the time counting means 28 simultaneously with outputting the deceleration command (S406). The start command output from the safety calculating means 21 is sent to the time measuring means 28 via the OR circuit 27, and the time measuring means 28 detects this and takes in the difference between the deceleration time as an input signal, that is, the set time. Start counting down from that value. When it reaches zero, a stop command is output. If necessary, calculate the one's complement of the deceleration time and the time difference, input that value to the timing means 28, start counting up from the input value with the start signal (load / enable), and stop with the carry signal A command may be output.

  The stop command output from the time measuring means 28 is sent to the OR circuit 30 and the gate circuit 14 of the control device 10. The gate circuit 14 is turned off by the stop command, and the PWM signal is cut off. On the other hand, the output of the OR circuit 30 is transmitted to the brake mechanism 6 and the load 8 is braked.

  As a result of the above processing, since the deceleration time and the set time have a time difference as shown in FIG. 2, the speed control means 12 of the control device 10 reliably decelerates until the motor rotation speed becomes zero, and then the gate circuit 14 is turned off to stop the operation, and the load 8 is braked. If necessary, a time difference may be provided between the stop process and the brake drive process.

  When a plurality of abnormality detection signals are simultaneously turned ON, the safety calculation means 21 refers to the set time table 29 and the deceleration time is the longest among the abnormality modes in which the abnormality detection signal is ON. By selecting a short mode value, appropriate deceleration / stop processing can be performed according to the degree of urgency.

(Process when CPU stalls)
When the CPU stalls after the initialization process, the WDT 26 detects this and performs an abnormal output. This signal activates the timing means 28 via the OR circuit 27 and turns on the deceleration command holding means 25 via the OR circuit 31. Thereby, the control apparatus 10 performs a deceleration process according to the process sequence of FIG. Since the deceleration time gate circuit 24 is set with a deceleration time corresponding to the CPU stall at the time of initialization, the deceleration process is performed so that the rotational speed becomes zero during this deceleration time. In addition, the time measuring means 28 outputs a stop command after the set time has elapsed, turns off the gate circuit 14 and brakes the load 8.

  As described above, according to the present embodiment, the set time table stores the deceleration time for each abnormal mode including the CPU stall in advance and the time difference between the deceleration time and the set time, and supports the CPU stall at the time of initialization. Since the deceleration time and the time difference are set, the time corresponding to the abnormal mode corresponding to the signal is reset by inputting the abnormality detection signal, and the deceleration command and the stop command are output. Therefore, the CPU of the safety function device 20 Even if stalled during monitoring, the deceleration / stop processing can be performed reliably. If necessary, an abnormality such as a CPU stall of the control device 10 is assigned to one of the abnormality detection signals and monitored so that even if the CPU of the control device 10 does not function normally, a stop is output after a set time. By the command, the gate circuit 14 as the final stage is turned off and the load brake is applied, so that the load 8 can be stopped reliably.

DESCRIPTION OF SYMBOLS 1 Electric motor drive system 2 Power supply 3 Inverter 4 Electric motor 5 Encoder 6 Brake mechanism 8 Load 9 Current / voltage sensor 10 Control apparatus 11 Deceleration inclination calculation means 12 Speed control means 13 PWM generation means 14 Gate circuit 20 Safety function apparatus 21, 21a, 21b Safety calculation means 22 Deceleration time holding means 23 Time difference holding means 24 Deceleration time gate circuit 25 Deceleration command holding means 26 Watchdog timer (WDT)
27, 30, 31 OR circuit 28 Time measuring means 29 Set time table

Claims (4)

An electric motor drive system having a control device that operates an electric motor at a variable speed, and a safety function device that outputs a stop command to the control device in order to stop the electric motor safely,
The safety function device is:
Means for outputting a deceleration command for decelerating the electric motor to the control device before stopping the electric motor;
Timing means for starting measurement from the output of the deceleration command;
Means for outputting the stop command to the control device when the time measuring means reaches a predetermined set time,
The motor drive system is configured to decelerate the motor in a deceleration time shorter than the set time when the deceleration command is input.   2. The motor drive system according to claim 1, wherein the safety function device includes a self-diagnosis unit, and when an abnormality is detected by the self-diagnosis unit, whether the control device is executing the deceleration command or not. Regardless, the motor drive system is characterized in that the motor is stopped by interrupting a control signal output from the control device to the motor.   The motor drive system according to claim 1, wherein the control device calculates a deceleration slope for decelerating the motor based on a motor speed command value and the deceleration time when the deceleration command is input. An electric motor drive system characterized by decelerating the electric motor by the deceleration inclination.   4. The electric motor drive system according to claim 1, wherein the safety function device is capable of detecting a plurality of abnormal modes by the self-diagnosis unit, and the deceleration time is different for each detected abnormal mode. An electric motor drive system characterized by outputting a deceleration command to a control device.

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