CN107994817B - Motor back electromotive force sampling system and method thereof - Google Patents
Motor back electromotive force sampling system and method thereof Download PDFInfo
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- CN107994817B CN107994817B CN201711163608.6A CN201711163608A CN107994817B CN 107994817 B CN107994817 B CN 107994817B CN 201711163608 A CN201711163608 A CN 201711163608A CN 107994817 B CN107994817 B CN 107994817B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
- H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings
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Abstract
The invention relates to a sampling system and a method for counter electromotive force of a motor, which comprises a sampling unit for counter electromotive force of the motor, wherein the sampling unit for counter electromotive force of the motor is connected with a sampling control unit for counter electromotive force of the motor, the sampling control unit for counter electromotive force of the motor acquires working state data of a wire feeding motor, controls the sampling unit for counter electromotive force of the motor, stops sampling the counter electromotive force of the motor during the power supply duration and the inductive load recovery time of a wire feeding loop, samples the counter electromotive force of the motor during the counter electromotive force generation time of the motor, samples the counter electromotive force to the maximum extent, is not influenced by the impedance of the wire feeding loop and the inductance of the loop, and further improves the accuracy of sampling the counter electromotive force. The invention directly utilizes the hardware circuit to realize the sampling control of the back electromotive force of the motor, the sampling method is simple and effective, the circuit is simplified, and the cost is reduced; meanwhile, the sampling precision of the counter electromotive force is ensured to the maximum extent, and the control precision of the wire feeding motor can be improved.
Description
Technical Field
The invention relates to the field of welding power supplies, in particular to a wire feeding speed regulating system part of a welding power supply, and specifically relates to a motor back electromotive force sampling system and a method thereof.
Background
Referring to fig. 1, a method for sampling a back electromotive force of a motor of a wire feeding speed regulating system in the prior art includes the following two steps:
the method comprises the following steps: and back electromotive force sampling is carried out at the moment before the power output of the wire feeding motor, the sampling pulse width is fixed, and the sampling time is short relative to the period. In the actual work of the wire feeding motor, the counter electromotive force has certain fluctuation, the sampling time of the counter electromotive force is short, and the sampling accuracy of the counter electromotive force is influenced.
The method 2 comprises the following steps: and calculating recovery time T1 through current, loop inductance and the like at the power output stop moment of the wire feeding motor, sampling back electromotive force at the time of T3 after delaying for a fixed time T2, and outputting power to the wire feeding motor after delaying for a fixed time T4. In actual use, the lengths of control lines between the wire feeding motors and the control loops of the wire feeding motors are different, the curling states of the control lines are different, and meanwhile, the inductance of different wire feeding motors is discrete, so that the loop impedance and the loop inductance of the wire feeding motors are correspondingly changed. Method 2 is inevitably affected by these factors, which in turn affects the back emf sampling accuracy.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a motor back electromotive force sampling system and a method thereof, which can achieve the maximum back electromotive force sampling time as far as possible and are not influenced by loop impedance and loop inductance of a wire feeding motor.
In order to achieve the above purpose, the system and the method for sampling the back electromotive force of the motor of the invention are specifically as follows:
the motor back electromotive force sampling system comprises a motor and is mainly characterized by further comprising a motor back electromotive force sampling unit and a motor back electromotive force sampling control unit connected with the motor back electromotive force sampling unit, wherein the motor back electromotive force sampling control unit acquires working state data of the motor and carries out acquisition state control on the motor back electromotive force sampling unit according to the acquired working state data, so that the motor back electromotive force sampling unit samples the back electromotive force of the motor in the time when the motor generates the back electromotive force.
Preferably, the motor back electromotive force sampling control unit includes three inputs, and acquires a PWM driving state, a motor voltage sampling potential and a motor current sampling potential of the motor through the three inputs, the three inputs are respectively connected to an output of the motor current sampling and converting unit, an output of the motor voltage sampling and converting unit and an output of the driving unit, the motor back electromotive force sampling unit is also connected to an output of the motor voltage sampling and converting unit, the working state data of the motor includes the PWM driving state, the motor voltage sampling potential and the motor current sampling potential of the motor, and the motor back electromotive force sampling control unit acquires the working state data of the motor in real time through the three inputs to control the sampling state of the motor back electromotive force sampling unit.
Preferably, the input end of the motor voltage sampling and converting unit is connected with the motor, and the input end of the motor current sampling and converting unit is connected with the motor through a sampling resistor.
Preferably, the motor counter electromotive force sampling control unit obtains a motor current sampling potential after sampling conversion by the motor current sampling and converting unit through the motor current sampling and converting unit; the motor back electromotive force sampling control unit acquires a motor voltage sampling potential acquired after sampling and conversion by the motor voltage sampling and conversion unit through the motor voltage sampling and conversion unit; and the motor back electromotive force sampling control unit acquires the PWM driving state output by the driving unit through the driving unit.
Preferably, the motor back electromotive force sampling system is a wire feeding speed regulating system, and the motor is a wire feeding motor
The method for realizing the sampling of the counter electromotive force of the motor based on the counter electromotive force sampling system of the motor is mainly characterized by comprising the following steps:
(1) acquiring working state data of a motor;
(2) and judging the voltage states of the two ends of the motor according to the driving state of the PWM and the relation between the voltage sampling potential of the motor and the current sampling potential of the motor, thereby sampling the counter electromotive force of the motor according to the voltage states of the two ends of the motor.
Preferably, the step (1) is:
the working state data of the motor comprises a PWM driving state of the motor, a motor voltage sampling potential and a motor current sampling potential, and the motor counter electromotive force sampling control unit acquires the motor current sampling potential after sampling conversion is carried out by the motor current sampling and converting unit through the motor current sampling and converting unit; the motor back electromotive force sampling control unit acquires a motor voltage sampling potential acquired after sampling and conversion by the motor voltage sampling and conversion unit through the motor voltage sampling and conversion unit; and the motor back electromotive force sampling control unit acquires the PWM driving state output by the driving unit through the driving unit.
Preferably, the voltage states at two ends of the motor include a voltage state corresponding to a power supply voltage duration when the PWM driving state output by the driving unit is ON, a voltage state corresponding to a recovery of the inductive load of the motor circuit when the PWM driving state output by the driving unit is OFF, and a voltage state corresponding to a generation of a back electromotive force by the motor.
More preferably, the step (2) comprises:
(2, a) when the PWM driving state output by the driving unit is OFF, the motor counter electromotive force sampling control unit compares the acquired motor current sampling potential with the acquired motor voltage sampling potential to determine the time when the motor generates the counter electromotive force, and outputs a high level to the motor counter electromotive force sampling unit when the motor generates the counter electromotive force to control the motor counter electromotive force sampling unit to start sampling;
(2, b) the motor back electromotive force sampling control unit is blocked when the output PWM driving state of the driving unit is changed from OFF to ON, the output control level of the motor back electromotive force sampling control unit is changed from high level to low level, and the motor back electromotive force sampling unit stops sampling;
and (2, c) the motor back electromotive force sampling control unit is blocked when the power supply voltage output by the driving unit is continuous when the PWM driving state is ON and when the inductive load of the motor loop is recovered when the PWM state is OFF, the motor back electromotive force sampling control unit outputs low level to the motor back electromotive force sampling unit, and the motor back electromotive force sampling unit stops sampling.
Preferably, the motor current sampling potential and the motor voltage sampling potential obtained in (2.a) are compared, and the generation time of the motor back electromotive force is determined as follows:
the motor counter electromotive force acquisition control unit compares the acquired motor current sampling potential with the motor voltage sampling potential, and when the motor current sampling potential is lower than the voltage sampling potentials at two ends of the motor, the motor generates counter electromotive force.
By adopting the motor counter electromotive force sampling system and the method thereof, the counter electromotive force can be sampled to the maximum extent, the influence of the control line length of the wire feeding motor, the loop impedance and the loop inductance is avoided, the sampling accuracy of the counter electromotive force of the wire feeding motor is improved, the control complexity of the counter electromotive force sampling of the wire feeding motor is reduced, the counter electromotive force sampling system and the method are directly realized by using a hardware circuit, the sampling method is simple and effective, the circuit is simplified, and the cost is reduced; meanwhile, the sampling precision of the counter electromotive force is ensured to the maximum extent, and the control precision of the wire feeding motor can be improved.
Drawings
Fig. 1 is a schematic timing diagram of a conventional motor back electromotive force sampling method.
Fig. 2 is a schematic block diagram of the back electromotive force sampling of the motor of the present invention.
Fig. 3 is a timing diagram of sampling the back electromotive force of the motor according to the present invention.
Fig. 4 is a schematic block diagram of a motor back emf sampling circuit of the present invention.
Detailed Description
In order to clearly understand the technical contents of the present invention, the following embodiments are specifically illustrated.
Referring to fig. 2, the motor back electromotive force sampling system includes a motor, a motor back electromotive force sampling unit, and a motor back electromotive force sampling control unit connected to the motor back electromotive force sampling unit, where the motor back electromotive force sampling control unit obtains working state data of the motor, and performs collection state control on the motor back electromotive force sampling unit according to the obtained working state data, so that the motor back electromotive force sampling unit samples back electromotive force of the motor within a time period in which the motor generates back electromotive force.
In a preferred embodiment, the motor back electromotive force sampling control unit comprises three input terminals, and the PWM driving state of the motor, the motor voltage sampling potential and the motor current sampling potential are obtained through the three input ends, the three input ends are respectively connected with the output end of the motor current sampling and converting unit, the output end of the motor voltage sampling and converting unit and the output end of the driving unit, the motor counter electromotive force sampling unit is also connected with the output end of the motor voltage sampling and converting unit, the working state data of the motor comprise a PWM driving state of the motor, a motor voltage sampling potential and a motor current sampling potential, and the motor back electromotive force sampling control unit acquires the working state data of the motor in real time through three input ends and controls the sampling state of the motor back electromotive force sampling unit.
In a specific embodiment, the three input ends can acquire the working state of the motor in real time. In a more preferred embodiment, the input terminal of the motor voltage sampling and converting unit is connected to the motor, and the input terminal of the motor current sampling and converting unit is connected to the motor through a sampling resistor.
In a better embodiment, the motor back electromotive force sampling control unit obtains a motor current sampling potential after sampling conversion by the motor current sampling and converting unit through the motor current sampling and converting unit; the motor back electromotive force sampling control unit acquires a motor voltage sampling potential acquired after sampling and conversion by the motor voltage sampling and conversion unit through the motor voltage sampling and conversion unit; and the motor back electromotive force sampling control unit acquires the PWM driving state output by the driving unit through the driving unit.
In a preferred embodiment, the motor back electromotive force sampling system is a wire feeding speed regulating system, and the motor is a wire feeding motor
The method for realizing the sampling of the counter electromotive force of the motor based on the counter electromotive force sampling system of the motor is mainly characterized by comprising the following steps:
(1) acquiring working state data of a motor;
(2) and judging the voltage states of the two ends of the motor according to the driving state of the PWM and the relation between the voltage sampling potential of the motor and the current sampling potential of the motor, thereby sampling the counter electromotive force of the motor according to the voltage states of the two ends of the motor.
In a preferred embodiment, the step (1) is:
the working state data of the motor comprises a PWM driving state of the motor, a motor voltage sampling potential and a motor current sampling potential, and the motor counter electromotive force sampling control unit acquires the motor current sampling potential after sampling conversion is carried out by the motor current sampling and converting unit through the motor current sampling and converting unit; the motor back electromotive force sampling control unit acquires a motor voltage sampling potential acquired after sampling and conversion by the motor voltage sampling and conversion unit through the motor voltage sampling and conversion unit; and the motor back electromotive force sampling control unit acquires the PWM driving state output by the driving unit through the driving unit.
In a more preferred embodiment, the voltage conditions at two ends of the motor include a voltage condition corresponding to the power supply voltage duration when the PWM driving condition output by the driving unit is ON, a voltage condition corresponding to the inductive load recovery of the motor circuit when the PWM driving condition output by the driving unit is OFF, and a voltage condition corresponding to the generation of the back electromotive force by the motor.
In a more preferred embodiment, the step (2) comprises:
(2, a) when the PWM driving state output by the driving unit is OFF, the motor counter electromotive force sampling control unit compares the acquired motor current sampling potential with the acquired motor voltage sampling potential to determine the time when the motor generates the counter electromotive force, and outputs a high level to the motor counter electromotive force sampling unit when the motor generates the counter electromotive force to control the motor counter electromotive force sampling unit to start sampling;
(2, b) the motor back electromotive force sampling control unit is blocked when the output PWM driving state of the driving unit is changed from OFF to ON, the output control level of the motor back electromotive force sampling control unit is changed from high level to low level, and the motor back electromotive force sampling unit stops sampling;
and (2, c) the motor back electromotive force sampling control unit is blocked when the power supply voltage output by the driving unit is continuous when the PWM driving state is ON and when the inductive load of the motor loop is recovered when the PWM state is OFF, the motor back electromotive force sampling control unit outputs low level to the motor back electromotive force sampling unit, and the motor back electromotive force sampling unit stops sampling.
In a more preferred embodiment, the motor current sampling potential and the motor voltage sampling potential obtained in (2.a) are compared, and the generation time of the motor back electromotive force is determined as follows:
the motor counter electromotive force acquisition control unit compares the acquired motor current sampling potential with the motor voltage sampling potential, and when the motor current sampling potential is lower than the voltage sampling potentials at two ends of the motor, the motor generates counter electromotive force.
In a specific implementation mode, the sampling system of the counter electromotive force of the motor is used for a wire feeding speed regulating system, and collects the counter electromotive force of a wire feeding motor, and the sampling system comprises a sampling unit of the counter electromotive force of the motor, a sampling control unit of the counter electromotive force of the motor, a sampling and converting unit of the voltage of the motor, a sampling and converting unit of the current of the motor, a driving unit, a driving power tube, a braking unit and a braking power tube, wherein:
the motor counter electromotive force sampling unit comprises two input ends, wherein the first input end is connected with the output end of the motor voltage sampling and converting unit and used for receiving the input of the motor voltage sampling potential, and the second input end is connected with the output end of the motor counter electromotive force sampling control unit and used for receiving the output control signal of the motor counter electromotive force sampling control unit;
the motor counter electromotive force sampling control unit comprises three input ends, wherein the first input end is connected with the output end of the driving unit, the second input end is connected with the output end of the motor voltage sampling and converting unit, and the third input end is connected with the output end of the motor current sampling and converting unit and is used for outputting corresponding control signals according to the PWM driving state output by the driving unit, the motor voltage sampling potential and the motor current sampling potential;
the input end of the motor voltage sampling and converting unit is connected with the wire feeding motor and used for collecting voltages at two ends of the motor and carrying out motor voltage sampling and sampling voltage conversion, and the output end of the motor voltage sampling and converting unit is connected with the input end of the motor counter electromotive force sampling control unit and used for controlling the working state of the motor counter electromotive force sampling control unit;
the input end of the motor current sampling and converting unit is connected to the wire feeding motor through a sampling resistor, receives the potential of the current sampling resistor, and the output end of the motor current sampling and converting unit is connected with the input end of the motor counter electromotive force sampling control unit and is used for controlling the working state of the motor counter electromotive force sampling control unit;
the driving unit comprises two output ends, wherein the first output end of the driving unit is connected with the input end of the motor back electromotive force sampling control unit and is used for controlling the working state of the motor back electromotive force sampling control unit, and the second output end of the driving unit is connected with the control end of the driving power tube and is used for controlling the working state of the driving power tube;
the output end of the brake unit is connected with the control end of the brake power tube and is used for controlling the brake power tube to work; the power supply unit provides energy for the control unit and the motor.
The time of the voltage state at the two ends of the wire feeding motor comprises the power supply voltage duration when the output PWM state of the driving unit is ON, the inductive load recovery time of a wire feeding motor loop when the output PWM state of the driving unit is OFF and the back electromotive force time of the wire feeding motor.
When the output PWM state of the driving unit is OFF, the generation time of the back electromotive force of the wire feeding motor is judged according to the output of the motor voltage sampling and converting unit and the output of the motor current sampling and converting unit. During inductive load recovery of a wire feeding motor loop, the output of a motor current sampling and converting unit is greater than the output of a motor voltage sampling and converting unit, a motor counter electromotive force sampling control unit outputs low level, and the motor counter electromotive force sampling unit does not sample the motor voltage; when the motor counter electromotive force is generated, the output of the motor current sampling and converting unit is smaller than the output of the motor voltage sampling and converting unit, the motor counter electromotive force sampling control unit outputs high level, and the motor counter electromotive force sampling unit starts to sample the motor voltage.
When drive unit's output PWM state is ON, motor back electromotive force sampling control unit's output becomes the low level by the high level, and motor back electromotive force sampling unit stops to motor voltage sampling to this maximize of guaranteeing sampling time promotes the back electromotive force sampling accuracy of motor, and then improves the precision of sending a motor control.
Referring to fig. 3 and 4, in a specific embodiment, the voltage across the wire feeding motor is sampled by dividing the voltage through a resistor R7 and a resistor R8, the sampled potential of the resistor R8 is input to a linear isolation circuit composed of resistors R13 to R15, a linear optocoupler IC9, and an operational amplifier IC21B through a follower composed of an operational amplifier IC41B, and the 7 th pin of the operational amplifier IC21B outputs a potential equal to the sampled potential of the resistor R8. During the working period of the wire feeding motor, the potential consists of the sampling potential of the power supply of the wire feeding motor, the sampling potential when the inductive load of the wire feeding motor loop is recovered and the sampling potential during the generation period of the counter electromotive force of the wire feeding motor. The motor counter electromotive force sampling unit samples the potential output by the 7 th pin of the operational amplifier IC21B during the generation of the wire feeding motor counter electromotive force, and the sampling of the wire feeding motor counter electromotive force can be realized.
When the PWM signal output by the driving unit changes from low level to high level, on one hand, the PWM signal is input to the control end of the transistor Q10 in the driving isolation unit, so that the transistor Q10 is turned on, the power supply V + is connected to ground through the 1 st pin, the 3 rd pin, the resistor R3 and the transistor Q10 of the optocoupler IC11, the control end of the optocoupler IC11 is connected, the lower output control tube (the control tube between the 5 th pin and the 4 th pin) of the optocoupler IC11 is turned off, the upper output control tube (the control tube between the 6 th pin and the 5 th pin) of the optocoupler IC11 is connected, the power supply V1+ is connected to the gate of the MOS transistor Q1 through the 6 th pin and the 5 th pin of the optocoupler IC11 and the resistor R4, the power MOS transistor Q1 is connected, and the power supply outputs; on one hand, the output voltage is input into the motor counter electromotive force sampling control unit, and before the conduction moment of the power MOS transistor Q1, the output of the motor counter electromotive force sampling control unit is blocked, so that the motor counter electromotive force sampling control unit outputs low level, and the motor counter electromotive force sampling control unit is controlled to stop sampling. When the driving unit outputs the PWM signal in a high-level period, the control of the motor back electromotive force sampling control unit is invalid through the motor current sampling potential output by the 14 th pin of the operational amplifier IC5D and the motor voltage sampling potential sampled through the resistor R7 and the resistor R8, the motor back electromotive force sampling control unit outputs a blocking state, namely, the output end of the motor back electromotive force sampling control unit maintains a low level from the time t1 to the time t2, and the motor back electromotive force sampling control unit stops sampling.
When the PWM signal output by the driving unit is changed from high level to low level, on one hand, the PWM signal is input to a control end of a transistor Q10 in the driving isolation unit, so that the transistor Q10 is cut off, a control end of an optical coupler IC11 is cut off, an upper output control tube (a control tube between a pin 6 and a pin 5) of the optical coupler IC11 is cut off, a lower output control tube (a control tube between a pin 5 and a pin 4) of the optical coupler IC11 is switched on, a grid electrode of an MOS tube Q1 is pulled down to the ground by a resistor R4 and a lower output control tube of the optical coupler IC11, a power MOS tube Q1 is cut off, and energy output to the wire feeding motor is stopped; on one hand, the output of the motor back electromotive force sampling control unit is input into the motor back electromotive force sampling control unit, the blocking of the output of the motor back electromotive force sampling control unit is released, and the output of the motor back electromotive force sampling control unit is determined by the sampling potential of the motor voltage sampling resistor R8 and the output potential of the follower IC5D in the current sampling and converting unit.
When the driving power MOS tube Q1 is cut off, the energy output to the wire feeding motor is stopped, because the wire feeding motor is an inductive load, the stored energy flows from the negative end of the wire feeding motor to the positive end of the wire feeding motor through the current sampling resistor R25 and the diode inside the brake power MOS tube Q2, the potentials at the two ends of the voltage sampling resistors R7 and R8 are clamped by the diode inside the brake power MOS tube Q2, the sampling potential of the voltage sampling resistor R8 is close to zero potential, meanwhile, the sampling potential of the current sampling resistor R25 is a positive potential, and after passing through the follower IC4C, the amplifying circuit formed by IC5C and the follower IC5D, the potential higher than the R8 sampling potential is output at the output end of the follower IC5D, from the time t2 to the time t3, the sampling potential of the voltage sampling resistor R8 is lower than the potential of the output end of the follower IC5D, the output end of the motor counter electromotive force sampling control unit still maintains low level, and the motor counter electromotive force sampling unit maintains a sampling stop state; after the inductive load of the wire feeding motor is recovered, under the action of inertia, the wire feeding motor works to a power generation mode, namely, counter electromotive force is generated, the counter electromotive force returns to the negative end of the wire feeding motor from the positive end of the wire feeding motor through the resistor R7, the resistor R8 and the resistor R25, at the moment, the potential of the resistor R25 is a negative potential close to zero potential, after passing through the follower IC4C, the amplifying circuit formed by the IC5C and the follower IC5D, the 14 th pin of the follower IC5D outputs a potential close to zero, the sampling potential of the resistor R8 is a positive potential higher than the output potential of the follower IC5D, namely, from the time t3 to the time t4, the sampling potential of the voltage sampling resistor R8 is higher than the output end potential of the follower IC5D, the output end of the counter electromotive force sampling control unit of the motor is changed from a low level to a high level, and the counter electromotive force sampling unit of the motor is.
The system and the method for sampling the counter electromotive force of the motor can realize accurate sampling of the counter electromotive force of the motor by directly utilizing a simple hardware circuit; the sampling starting time of the counter electromotive force of the motor is determined according to the relation between the current sampling potential of the motor and the voltage sampling potential of the motor, and the sampling ending time of the counter electromotive force of the motor is determined when the PWM is driven to change from a low level to a high level, so that the maximization of the counter electromotive force sampling time of the motor is realized; the inductive load recovery time of the wire feeding motor loop and the motor back electromotive force generation time can be accurately judged through the sampling potential of the motor current sampling resistor, and the influence of the wire feeding motor loop impedance and the loop inductance is overcome. The sampling method is simple and effective, simplifies the circuit and reduces the cost; meanwhile, the sampling precision of the counter electromotive force is ensured to the maximum extent, and the sampling accuracy of the counter electromotive force of the wire feeding motor under different use environments or use conditions is improved; thereby improving the performance of the wire feeding speed regulating system.
In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
Claims (9)
1. The motor back electromotive force sampling system comprises a motor and is characterized by further comprising a motor back electromotive force sampling unit and a motor back electromotive force sampling control unit connected with the motor back electromotive force sampling unit, wherein the motor back electromotive force sampling control unit acquires working state data of the motor and performs acquisition state control on the motor back electromotive force sampling unit according to the acquired working state data, so that the motor back electromotive force sampling unit samples the back electromotive force of the motor within the time of generating the back electromotive force by the motor;
the motor back electromotive force sampling control unit comprises three input ends, and acquires a PWM driving state, a motor voltage sampling potential and a motor current sampling potential of the motor through the three input ends, the three input ends are respectively connected with the output end of the motor current sampling and converting unit, the output end of the motor voltage sampling and converting unit and the output end of the driving unit, the motor back electromotive force sampling unit is also connected with the output end of the motor voltage sampling and converting unit, the working state data of the motor comprises the PWM driving state, the motor voltage sampling potential and the motor current sampling potential of the motor, and the motor back electromotive force sampling control unit acquires the working state data of the motor in real time through the three input ends and controls the sampling state of the motor back electromotive force sampling unit;
when the output PWM state of the driving unit is OFF, the time when the motor generates the counter electromotive force is judged according to the output of the motor voltage sampling and converting unit and the output of the motor current sampling and converting unit; during the inductive load recovery period of the motor loop, the output of the motor current sampling and converting unit is greater than the output of the motor voltage sampling and converting unit, the motor counter electromotive force sampling control unit outputs low level, and the motor counter electromotive force sampling unit does not sample the motor voltage; when the motor generates the counter electromotive force, the output of the motor current sampling and converting unit is smaller than the output of the motor voltage sampling and converting unit, the motor counter electromotive force sampling control unit outputs high level, and the motor counter electromotive force sampling unit starts to sample the motor voltage.
2.A motor back electromotive force sampling system according to claim 1, wherein an input terminal of the motor voltage sampling and converting unit is connected to the motor, and an input terminal of the motor current sampling and converting unit is connected to the motor through a sampling resistor.
3. The motor back electromotive force sampling system according to claim 2, wherein the motor back electromotive force sampling control unit obtains a motor current sampling potential after sampling conversion by the motor current sampling and converting unit through the motor current sampling and converting unit; the motor back electromotive force sampling control unit acquires a motor voltage sampling potential acquired after sampling and conversion by the motor voltage sampling and conversion unit through the motor voltage sampling and conversion unit; and the motor back electromotive force sampling control unit acquires the PWM driving state output by the driving unit through the driving unit.
4. The motor back electromotive force sampling system according to claim 1, wherein the motor back electromotive force sampling system is a wire feed speed regulating system, and the motor is a wire feed motor.
5. A method for realizing motor back electromotive force sampling based on the motor back electromotive force sampling system of any one of claims 1 to 4, characterized in that the method comprises the following steps:
(1) acquiring working state data of a motor and a motor current sampling potential;
(2) and judging the voltage states of the two ends of the motor according to the driving state of the PWM and the relation between the voltage sampling potential of the motor and the current sampling potential of the motor, thereby sampling the counter electromotive force of the motor according to the voltage states of the two ends of the motor.
6. The method for sampling the back electromotive force of a motor based on the sampling system of the back electromotive force of the motor according to claim 5,
the step (1) is as follows:
the working state data of the motor comprises a PWM driving state of the motor, a motor voltage sampling potential and a motor current sampling potential, and the motor counter electromotive force sampling control unit acquires the motor current sampling potential after sampling conversion is carried out by the motor current sampling and converting unit through the motor current sampling and converting unit; the motor back electromotive force sampling control unit acquires a motor voltage sampling potential acquired after sampling and conversion by the motor voltage sampling and conversion unit through the motor voltage sampling and conversion unit; and the motor back electromotive force sampling control unit acquires the PWM driving state output by the driving unit through the driving unit.
7. The method as claimed in claim 6, wherein the voltage conditions at two ends of the motor include a voltage condition corresponding to a power voltage duration when the PWM driving condition output by the driving unit is ON, a voltage condition corresponding to a recovery of an inductive load of the motor circuit when the PWM driving condition output by the driving unit is OFF, and a voltage condition corresponding to a generation of a back electromotive force by the motor.
8. The method for sampling the back electromotive force of a motor based on a back electromotive force sampling system of a motor according to claim 7, wherein the step (2) comprises:
(2, a) when the PWM driving state output by the driving unit is OFF, the motor counter electromotive force sampling control unit compares the acquired motor current sampling potential with the acquired motor voltage sampling potential to determine the time when the motor generates the counter electromotive force, and outputs a high level to the motor counter electromotive force sampling unit when the motor generates the counter electromotive force to control the motor counter electromotive force sampling unit to start sampling;
(2, b) the motor back electromotive force sampling control unit is blocked when the output PWM driving state of the driving unit is changed from OFF to ON, the output control level of the motor back electromotive force sampling control unit is changed from high level to low level, and the motor back electromotive force sampling unit stops sampling;
and (2, c) the motor back electromotive force sampling control unit is blocked when the power supply voltage output by the driving unit is continuous when the PWM driving state is ON and when the inductive load of the motor loop is recovered when the PWM state is OFF, the motor back electromotive force sampling control unit outputs low level to the motor back electromotive force sampling unit, and the motor back electromotive force sampling unit stops sampling.
9. The method for sampling the back electromotive force of the motor based on the back electromotive force sampling system of the motor according to claim 8, wherein the sampled potentials of the motor current and the motor voltage obtained in (2.a) are compared to determine the back electromotive force generation time of the motor as follows:
the motor counter electromotive force acquisition control unit compares the acquired motor current sampling potential with the motor voltage sampling potential, and when the motor current sampling potential is lower than the voltage sampling potentials at two ends of the motor, the motor generates counter electromotive force.
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| CN110611462B (en) * | 2019-10-17 | 2021-01-15 | 江苏科技大学 | Three-stage rotating speed indicating device and method for brushless direct current motor |
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