JP7162546B2 - electric work machine - Google Patents

Description

The present disclosure relates to an electric working machine that controls a motor using Hall sensor signals.

2. Description of the Related Art An electric working machine, such as the electric tool described in Patent Document 1, is known that includes a Hall sensor that detects the position of a rotor of a motor and recognizes the rotation speed of the motor from a detection signal of the Hall sensor. Such an electric working machine uses the recognized rotational speed to control the rotation of the motor and to detect kickback. Kickback is a phenomenon in which the electric working machine bounces off the workpiece, causing a sudden drop in rotational speed.

Japanese Patent No. 5408416

The detection signal of the Hall sensor changes from low to high and from high to low according to the change in the magnetic pole of the rotor. The rotation speed of the motor is calculated from the edge interval of the detection signal. Therefore, if noise such as static electricity noise is mixed in the detection signal and the noise is detected as an edge, an incorrect rotational speed may be erroneously recognized. If the rotational speed of the motor is erroneously recognized, there is a risk that control based on the rotational speed, such as motor rotational speed control and kickback detection, will be hindered.

One aspect of the present disclosure provides an electric working machine capable of suppressing erroneous recognition of the rotation speed of the motor.

One aspect of the present disclosure is an electric working machine that includes a motor, a Hall sensor, a gap detection section, a speed calculation section, a threshold value setting section, and a noise detection section. The Hall sensor is configured to detect the rotational position of the rotor of the motor. The interval detector is configured to detect an edge interval of the detection signal of the Hall sensor. The speed calculator is configured to calculate the rotation speed of the motor using the edge interval detected by the interval detector. The threshold setting unit is configured to set an interval threshold for determining whether the edge interval is normal. The noise detection unit is configured to detect noise mixture when the edge interval for calculating the current rotational speed is equal to or less than the interval threshold value set by the threshold value setting unit. The speed calculation unit executes a special rotation speed calculation process that is different from the normal rotation speed calculation process when the noise detection unit detects noise contamination.

According to one aspect of the present disclosure, the edge interval of the detection signal of the Hall sensor is detected, and the rotation speed of the motor is calculated using the detected edge interval. Here, when noise is mixed in the detection signal, the edge interval is detected to be shorter than the original edge interval. Therefore, an interval threshold is set for determining whether the edge interval is normal or not, and noise mixture is detected when the edge interval is shorter than the set interval threshold. Then, when noise contamination is detected, a special calculation process different from the normal rotation speed calculation process is executed to calculate the rotation speed. Therefore, erroneous recognition of the rotation speed of the motor can be suppressed.

Further, in the normal calculation process, the speed calculation unit calculates the rotational speed from the interval average value obtained by dividing the interval total value of the interval set, which is the interval set of the predetermined number of edges continuously detected by the interval detection unit, by the predetermined number. You may

If noise contamination is not detected, normal calculation processing is executed to calculate the rotational speed. In the normal calculation process, the rotation speed is calculated from the interval average value obtained by averaging a predetermined number of edge intervals detected continuously. A stable rotation speed can be calculated by using the interval average value.

Further, in the special calculation process, the speed calculation unit may calculate the rotation speed by correcting the value used for calculating the rotation speed in the normal calculation process so as to eliminate the influence of noise mixed from the interval set.

When noise contamination is detected, special calculation processing is executed to correct the value used to calculate the rotational speed in the normal calculation processing so as to remove the influence of noise. Then, the rotational speed is calculated using the corrected value. As a result, even when noise is detected, erroneous recognition of the rotation speed can be suppressed.

Further, the threshold value setting unit may set the interval threshold value based on the interval average value used to calculate the previous rotational speed.
By setting the interval threshold value based on the interval average value used to calculate the previous rotational speed, it is possible to set an appropriate interval threshold value and detect the presence of noise with high accuracy.

Further, in the special calculation process, the velocity calculation unit may calculate a short interval, which is an edge interval equal to or smaller than the interval threshold, in the interval set other than at both ends, If the added value obtained by adding the interval and its adjacent edge interval is less than the addition threshold, the interval total value may be corrected by adding the previously calculated interval average value to the interval total value.

When noise is included, an interval that should be detected as one edge interval is detected as two edge intervals. Then, when the short interval exists other than at both ends of the interval set, when the short interval exists at the end of the interval set, and when the sum of the short interval and the adjacent edge interval is less than the addition threshold, , it can be determined that both of the edge intervals divided into two due to noise inclusion are included in the interval set. In this case, the spacing set is short of one edge spacing. Therefore, the interval average value calculated last time is added to the interval total value obtained by totaling the predetermined number of edge intervals, and the interval total value is corrected. As a result, even when noise is detected, it is possible to suppress a decrease in the calculation accuracy of the rotational speed.

Further, in the special calculation process, the velocity calculation unit adds a short interval, which is an edge interval equal to or smaller than the interval threshold value, at the end of the interval set, and adds the short interval and the adjacent edge interval in the interval set. If the value is equal to or greater than the addition threshold, the difference between the previously calculated interval average value and the short interval may be added to the interval total value to correct the interval total value.

When noise is included, an interval that should be detected as one edge interval is detected as two edge intervals. Then, when the short interval exists at the end of the interval set and the sum of the short interval and the adjacent edge interval is equal to or greater than the addition threshold, only one of the two edge intervals divided by noise mixture is It can be determined that it is included in the interval set. In this case, the interval set lacks an edge interval corresponding to the other of the edge intervals divided into two due to noise contamination. Therefore, the difference between the interval average value calculated last time and the short interval is added to the interval total value obtained by totaling the predetermined number of edge intervals, and the interval total value is corrected. As a result, even when noise is detected, it is possible to suppress a decrease in the calculation accuracy of the rotational speed.

Further, in the special calculation process, the velocity calculation unit may calculate a short interval, which is an edge interval equal to or smaller than the interval threshold, in the interval set other than at both ends, If the added value obtained by adding the interval and its adjacent edge interval is less than the addition threshold, the predetermined number may be corrected to a value that is one less.

If the short interval exists outside the edge of the interval set, or if the short interval exists at the edge of the interval set and the sum of the short interval and its adjacent edge interval is less than the addition threshold, the interval The set is short of one edge spacing. Therefore, the predetermined number is corrected to a value that is one less. As a result, even when noise is detected, it is possible to suppress a decrease in the calculation accuracy of the rotational speed.

Further, in the special calculation process, the velocity calculation unit adds a short interval, which is an edge interval equal to or smaller than the interval threshold value, at the end of the interval set, and adds the short interval and the adjacent edge interval in the interval set. If the value is equal to or greater than the addition threshold, the short interval may be subtracted from the interval total to correct the interval total, and the predetermined number may be corrected to a value that is one less.

If the short interval exists at the end of the interval set and the sum of the short interval and its adjacent edge interval is equal to or greater than the addition threshold, it corresponds to the other edge interval divided into two due to noise contamination. Insufficient edge spacing. Therefore, the interval total value is corrected to a value obtained by subtracting the short interval from the interval total value, and the predetermined number is corrected to a value that is one less. As a result, even when noise is detected, it is possible to suppress a decrease in the calculation accuracy of the rotational speed.

Further, the speed calculation unit may calculate the rotation speed calculated last time as the current rotation speed in the special calculation process.
Normally, the rotation speed of the motor is often close to the value of the rotation speed calculated last time. Therefore, when noise contamination is detected, the rotation speed calculated last time is calculated as the current rotation speed. As a result, even when noise is detected, erroneous recognition of the rotation speed can be suppressed.

Also, the noise detection unit may limit the number of detected noises to be one or less in the edge interval used to calculate the rotational speed.
The frequency of noise mixing in the predetermined number of edge intervals is sufficiently low, and the possibility of the edge interval becoming shorter due to the acceleration of the rotational speed is more likely than the possibility of two or more noises mixing in the predetermined number of edge intervals. is high. Therefore, if two or more noises are detected, there is a possibility that the rotation speed is erroneously recognized. Therefore, by limiting the noise mixture to be detected to one or less, it is possible to cope with changes in the rotation speed while suppressing erroneous recognition of the rotation speed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows the external appearance of the mower of 1st Embodiment. It is a figure which shows the circuit structure of the controller of 1st Embodiment. 4 is a flowchart showing main processing executed by a control circuit according to the first embodiment; 4 is a flowchart showing motor control processing executed by a control circuit according to the first embodiment; 6 is a flowchart showing motor rotation speed calculation processing according to the first embodiment. FIG. 10 is a diagram showing edge intervals used in normal calculation processing; FIG. 10 is a diagram showing edge intervals used in special calculation processing when noise is mixed in the first example; FIG. 10 is a diagram showing captured values of respective edge intervals and corresponding rotation speeds when noise is mixed in the first example; FIG. 10 is a diagram showing edge intervals used in special calculation processing when noise is mixed in the second example; FIG. 11 is a diagram showing edge intervals used in special calculation processing when noise is mixed in the third example; FIG. 10 is a diagram showing changes in capture values of average intervals during acceleration of rotational speed; 7 is a graph showing capture values and rotation speeds at each edge interval when noise is mixed once; It is a graph which shows the time change of the rotation speed calculated at the time of noise mixing once. FIG. 10 is a graph showing capture values and rotation speeds at respective edge intervals when noise is mixed twice; FIG. FIG. 10 is a graph showing the time change of the rotational speed calculated when noise is mixed twice. FIG. FIG. 11 is a flowchart showing motor rotation speed calculation processing according to the second embodiment; FIG.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this disclosure is demonstrated, referring drawings.
(First embodiment)
<1. Configuration>
<1-1. Overall configuration>
First, the overall configuration of a mower 1 according to this embodiment will be described with reference to FIG. Grass cutter 1 corresponds to an example of a working machine in one aspect of the present disclosure.

A lawn mower 1 includes a main pipe 2 , a control unit 3 , a drive unit 4 , a cover 5 and a handle 6 .
The main pipe 2 is formed in a long and hollow rod shape. A control unit 3 is provided on the rear end side of the main pipe 2 , and a drive unit 4 and a cover 5 are provided on the front end side of the main pipe 2 .

The drive unit 4 has a motor housing 16 and a cutting blade 17 . The cutting blade 17 is a working tool for cutting objects such as grass and trees with a small diameter, and is detachably attached to the motor housing 16 . The cutting blade 17 is made of metal, has a disk shape, and has serrated teeth formed over the entire outer circumference. The cover 5 is provided to prevent grass or the like cut by the cutting blade 17 from flying toward the user of the mower 1 .

A motor 15 is mounted inside the motor housing 16 to generate a rotational force for rotating the cutting blade 17 . The rotational force generated by driving the motor 15 is transmitted to the work tool rotating shaft on which the cutting blade 17 is mounted via a speed reducing mechanism. Motor 15 is a three-phase brushless motor that includes a rotor and a stator.

The handle 6 is U-shaped and is connected to the main pipe 2 near the middle position in the length direction of the main pipe 2 . A first end of the handle 6 is provided with a right grip 7 that is held with the right hand of the operator, and a second end of the handle 6 is provided with a left grip 8 that is held with the left hand of the operator.

A display section 9 , a lock-off button 10 and a trigger 11 are provided on the tip side of the right grip 7 . The display unit 9 is provided so as to be visible to the user, and displays information about the mower 1 . The information about the lawn mower 1 includes, for example, the remaining capacity of the battery 20, the rotation speed of the motor 15, the operation mode of the motor 15, and the like, which will be described later. A direction changeover switch 51 (see FIG. 2) for switching the rotation direction of the motor 15 between forward rotation and reverse rotation is also provided on the tip side of the right grip 7 .

The trigger 11 is an operation member operated by the operator to instruct rotation or stop of the cutting blade 17 . A trigger switch 12 that operates in conjunction with the trigger 11 is arranged inside the right grip 7 . The trigger switch 12 is turned on when the trigger 11 is operated, turned off when the trigger 11 is not operated, and outputs a trigger signal indicating its on state or off state. The lock-off button 10 is a button for preventing or suppressing malfunction of the cutting blade 17 .

A control wiring pipe 13 is provided between the lower end of the right grip 7 and the front end of the control unit 3 . The control wiring pipe 13 is formed in a hollow tube shape and has elasticity. A control harness is arranged inside the control wiring pipe 13 . The control harness is wiring for electrically connecting the display section 9 and the trigger switch 12 to the control unit 3 .

The control unit 3 has a rear end housing 21 and a battery pack 22 . The battery pack 22 is detachably attached to the rear end portion of the rear end housing 21 .
As shown in FIG. 2, the battery pack 22 incorporates a battery 20 and a battery control circuit 25 . Battery 20 is a rechargeable power source for supplying DC power to components within rear end housing 21 and to motor 15 . Battery 20 is, for example, a lithium ion secondary battery. The battery control circuit 25 includes a CPU 25a, memory 25b, I/O, etc., and controls charging and discharging of the battery 20. FIG. The battery control circuit 25 outputs a discharge permission signal or a discharge prohibition signal to the mower 1 via the battery communication terminal 26 according to the state of the battery 20 .

A speed change dial 23 and a main switch 24 are provided on the front end side of the rear end housing 21 so as to be operable by the operator. A variable speed dial 23 is provided for the user to variably set the rotation speed of the motor 15 . The main switch 24 is a switch for making the lawn mower 1 ready for use by starting power supply from the battery 20 to each part. A controller 30, which will be described later, is arranged inside the rear end housing 21. As shown in FIG. The controller 30 controls driving of the motor 15 by controlling energization of the motor 15 .

<1-1. Circuit configuration>
Next, the circuit configuration of the controller 30 will be described with reference to FIG.
The controller 30 includes a control circuit 31 , a gate circuit 32 , a drive circuit 33 , a regulator 41 , a controller communication terminal 55 , a Hall sensor 61 , a current detector 62 and a battery voltage detector 42 . The positive and negative terminals of the controller 30 are connected to the positive and negative terminals of the battery pack 22, respectively.

The drive circuit 33 is a circuit that receives power supply from the battery 20 and applies current to each winding corresponding to each phase of the motor 15 . Specifically, the drive circuit 33 is a three-phase full bridge circuit including high-side switching elements Q1 to Q3 and low-side switching elements Q4 to Q6. Each switching element Q1 to Q6 is composed of, for example, a MOSFET, but is not limited to this.

The gate circuit 32 turns on or off each of the switching elements Q1 to Q6 in accordance with the control signal output from the control circuit 31, and causes current to flow sequentially through each phase winding of the motor 15, thereby causing the motor 15 to rotate. Note that when all the switching elements Q1 to Q6 are turned off, the motor 15 is in a free-running state. Further, when all of the switching elements Q1 to Q3 are turned off and all of the switching elements Q4 to Q6 are turned on, the motor 15 is in a so-called short-circuit braking state.

When the main switch 24 is on, the regulator 41 receives power from the battery 20 and generates a constant power supply voltage Vcc (for example, 5 VDC) required to operate the control circuit 31 .

A Hall sensor 61 is arranged near the motor 15 and detects the rotational position of the rotor. Specifically, the Hall sensor 61 includes Hall elements corresponding to the number of phases of the motor 15, that is, three Hall elements. The three Hall elements are arranged at intervals of 120 degrees on the stator side facing the magnetic poles of the rotor. Each Hall element produces an element detection signal that varies from low to high and from high to low in response to changes in rotor magnetic poles. The Hall sensor 61 outputs to the control circuit 31 a sensor detection signal obtained by synthesizing the element detection signals generated by the three Hall elements.

The current detection unit 62 is provided on an energization path from the drive circuit 33 to the negative pole of the controller 30 , detects the value of the current flowing through the motor 15 , and outputs a current detection signal to the control circuit 31 .

Battery voltage detection unit 42 detects the voltage between the positive terminal and the negative terminal of controller 30 , that is, the value of the voltage of battery 20 , and outputs a voltage detection signal to control circuit 31 .
Controller communication terminal 55 is connected to battery communication terminal 26 . A discharge permission signal or discharge inhibition signal output from the battery control circuit 25 is input to the control circuit 31 via the battery communication terminal 26 and the controller communication terminal 55 .

The control circuit 31 includes a CPU 31a, a memory 31b, an I/O, and the like, and receives power from the regulator 41 to operate. The control circuit 31 is connected to the hall sensor 61 , the current detection section 62 , the battery voltage detection section 42 , the controller communication terminal 55 , the main switch 24 , the trigger switch 12 , the direction changeover switch 51 and the display section 9 . Also connected to the control circuit 31 are a mode selection switch and the like for the user to set the operation mode of the motor 15 according to the work.

The control circuit 31 calculates the rotation speed of the motor 15 from the sensor detection signal. The control circuit 31 generates a control signal for controlling driving of the motor 15 based on the input various signals and the calculated rotational speed, and outputs the generated control signal to the gate circuit 32 .

In addition, the control circuit 31 uses the calculated rotational speed to determine whether or not kickback has occurred. Kickback is a phenomenon in which the cutting blade 17 of the lawn mower 1 bounces back when it hits a hard object such as a rock or tree. When the kickback occurs, the rotation speed of the motor 15 drops rapidly. Therefore, the control circuit 31 can detect the occurrence of kickback based on the calculated rotational speed. The control circuit 31 may stop driving the motor 15 when it is determined that kickback has occurred.
In the present embodiment, the control circuit 31 implements the functions of the interval detection section, the speed calculation section, the threshold value setting section, and the noise detection section by executing the program stored in the memory 31b by the CPU 31a.

<2. Processing>
<2-1. Main processing>
Next, the main processing executed by the control circuit 31 will be described with reference to the flowchart of FIG.

First, in S10, it is determined whether or not the time base has elapsed. If the time base has not elapsed, the process waits, and if the time base has elapsed, the process proceeds to S20. The time base corresponds to the processing period of the control circuit 31 . In this embodiment, the processing period is 1 ms.

Subsequently, in S20, operation detection processing of the trigger switch 12 is executed. Specifically, the control circuit 31 detects whether the trigger switch 12 is on or off based on the signal from the trigger switch 12 .

Subsequently, in S30, AD conversion processing is executed. Specifically, the control circuit 31 AD-converts the detection signals input from the battery voltage detection unit 42, the current detection unit 62, and the like. Thereby, the control circuit 31 acquires the current value flowing through the motor 15, the voltage value of the battery 20, and the like.

Subsequently, in S40, an abnormality detection process is executed. More specifically, the control circuit 31 compares the current value, voltage value, etc. acquired in S30 with respective threshold values to detect abnormalities such as overcurrent and battery voltage drop.

Subsequently, in S50, mode and direction setting processing is executed. Specifically, the control circuit 31 sets the operation mode and rotation direction of the motor 15 according to input signals from various switches.
Subsequently, in S60, motor control processing is executed based on the processing results of S20 to S50. Details of the motor control processing will be described later.

Subsequently, in S70, a display process is executed. Specifically, the control circuit 31 displays the operating mode of the motor 15, the remaining capacity of the battery 20, the detected abnormality, etc. on the display unit 9 to notify the user. This completes the processing.

<2-2. Motor control processing>
Next, motor control processing executed by the control circuit 31 will be described with reference to the flowchart of FIG.

First, in S100, a sensor detection signal output from the hall sensor 61 is used to execute rotational speed calculation processing. Details of the rotation speed calculation process will be described later.
Subsequently, in S110, it is determined whether or not the trigger switch 12 is turned on. The control circuit 31 proceeds to the processing of S120 when the trigger switch 12 is on, and proceeds to the processing of S140 when the trigger switch 12 is off.

In S120, it is determined whether the motor 15, the controller 30, and the battery pack 22 are abnormal or not detected. Further, the control circuit 31 determines whether or not kickback occurs based on the rotational speed calculated in S100. If no abnormality is detected and it is determined that no kickback has occurred, the process proceeds to S130. On the other hand, if any abnormality is detected, or if it is determined that kickback has occurred, the process proceeds to S140.

In S130, control processing for the motor 15 is executed. Specifically, using the rotation speed of the motor 15 calculated in S100, the rotation speed of the drive circuit 33 is adjusted so that the rotation speed of the motor 15 in the rotation direction set in S50 converges to the target rotation speed corresponding to the set operation mode. Calculate the Pulse Width Modulation (PWM) duty ratio of each switching element. Furthermore, the control circuit 31 outputs a control signal corresponding to the calculated PWM duty ratio to the gate circuit 32, and ends this processing.

On the other hand, in S140, it is determined whether or not to execute brake control. Specifically, the control circuit 31 determines to execute the brake control when the motor 15 is rotating and the controller 30 is not affected even if the motor 15 is caused to generate a braking force. In this case, the control circuit 31 sets the brake flag in S150 and terminates this process. As a result, power supply from the battery 20 to the motor 15 is stopped, and short-circuit braking is performed.

In S140, the control circuit 31 performs brake control when the motor 15 is not rotating, or when the motor 15 is rotating but generating a braking force in the motor 15 affects the controller 30. will not be implemented. In this case, the control circuit 31 clears the brake flag in S160 and terminates this process. As a result, power supply from the battery 20 to the motor 15 is stopped. Then, when the motor 15 is rotating, a free run or the like is executed.

<2-3. Rotation Speed Calculation Processing>
Next, the rotation speed calculation process of the motor 15 executed by the control circuit 31 will be described with reference to the flowchart of FIG.

First, in S200, it is determined whether or not the sensor detection signal contains noise. FIG. 6 shows a sensor detection signal without noise.
The control circuit 31 has a timer function, starts counting of the timer at the timing of the edge of the sensor detection signal, resets the timer at the timing of the next edge, and starts counting again. The count value of the timer between edges is called the capture value. The edge timing of the sensor detection signal is the timing at which the sensor detection signal changes from low to high or from high to low.

If the motor 15 is a two pole (ie one pole pair) motor, one edge separation corresponds to the time it takes for the rotor to rotate 60 degrees. Also, if the motor 15 is a 4-pole (ie, 2-pole pair) motor, one edge interval corresponds to the time it takes for the rotor to rotate 30 degrees.

In general, if the rotation speed is calculated from the capture value of one edge interval, the variation becomes large and unstable. is calculated, and the rotation speed is calculated from the calculated interval average value. In this embodiment, as shown in FIG. 6, an average interval obtained by averaging capture values of consecutive edge intervals #1 to #8 is used.

In addition, although the predetermined number is eight in the present embodiment, the predetermined number is not limited to eight. The smaller the predetermined number, the faster the calculated rotational speed responds to changes in the actual rotational speed, but the less stable it is. On the other hand, the greater the predetermined number, the slower the response to changes in the actual rotation speed, but the higher the stability of the calculated rotation speed. Therefore, the predetermined number should be appropriately set in consideration of the stability and reactivity required for the rotation speed used for control. Here, if the predetermined number is an integral multiple of the number of phases and the number of poles of the motor 15, when there is a positional deviation in the three Hall elements, the edge intervals are averaged to obtain the number of captures corresponding to the positional deviation. difference is cancelled. Therefore, the predetermined number may be an integral multiple of the number of phases and the number of poles of the motor 15 .

As shown in FIG. 6, when the rotation speed is constant and noise is not mixed, the eight edge intervals are almost equal. On the other hand, FIG. 7 shows a first example of a sensor detection signal mixed with noise. In the case of the first example shown in FIG. 7, noise is mixed after the edge interval #6. Such noise is, for example, static electricity noise, and is generated when the cutting blade 17 cuts a workpiece made of a material that easily generates static electricity.

If noise is mixed in the sensor detection signal, the control circuit 31 recognizes the noise as an edge. Therefore, in the first example shown in FIG. 7, the interval that should originally be acquired as one edge interval #7 is acquired as two intervals, edge interval #7 and edge interval #8. As a result, as shown in FIG. 8, the interval set average value is calculated to be smaller than the original interval average value, and the rotation speed is calculated to be higher than the original rotation speed. Specifically, the rotational speed is calculated to be approximately 6000 rpm higher than the original rotational speed of approximately 38000 rpm.

In this way, if the rotation speed is erroneously recognized as being higher than the original rotation speed, the rotation control of the motor 15 may be hindered, and the rotation speed of the motor 15 may not be converged to the target rotation speed. Further, after the rotation speed influenced by noise is calculated, the correct rotation speed is calculated when the noise influence disappears in the interval set. In this case, the control circuit 31 may determine that the rotation speed has suddenly decreased. As a result, the control circuit 31 may erroneously determine that kickback has occurred.

Therefore, in S200, the control circuit 31 determines whether or not the interval set contains noise. As described above, when noise is mixed in the edge interval, the edge interval becomes shorter than the original edge interval. Therefore, the control circuit 31 compares each edge interval included in the interval set with an interval threshold for judging whether the edge interval is normal or not, and detects noise mixture when the edge interval is equal to or less than the interval threshold.

The control circuit 31 sets the interval threshold value based on the edge interval (specifically, interval average value) used to calculate the rotation speed in the previous processing cycle (that is, 1 ms ago). For example, the control circuit 31 sets the interval threshold value to the previous interval average value×0.6.

Then, the control circuit 31 proceeds to the process of S210 when noise mixture is not detected, and proceeds to the process of S220 when noise mixture is detected.
In S210, the interval average value of the interval set is calculated by normal calculation processing. Specifically, the control circuit 31 divides the total interval value of the eight edge intervals included in the interval set by 8, which is a predetermined number, to calculate the average interval value. That is, in the normal calculation process, the average interval value is calculated using the total interval value and the predetermined number without correction. After that, the process proceeds to S230.

On the other hand, in S220, the interval average value of the interval set is calculated by special calculation processing. In the special calculation process, at least one of the total interval value and the predetermined number used in the normal calculation process is corrected so as to remove the influence of noise mixed from the interval set, and the average interval value is calculated. After that, the process proceeds to S230.

Specifically, in the case of the first example shown in FIG. 7, edge intervals equal to or smaller than the interval threshold (hereinafter referred to as short intervals) exist at the ends of the interval set. If a short interval is at the edge of the interval set, then the pair of edge intervals that originally combine with the short interval into one edge interval may or may not be included in the interval set. In the first example, both edge spacing #8 and paired edge spacing #7, which are short spacings, are included in the spacing set.

If the interval set contains a pair of edge intervals, the short interval plus its adjacent edge interval in the interval set adds up to one edge interval. On the other hand, if the interval set does not include a pair of edge intervals, the added value is a value obtained by adding the short interval to one edge interval.

Therefore, the addition value and the addition threshold value are compared to determine whether the paired edge interval is included in the interval set. For example, the control circuit 31 sets the addition threshold to the previous interval average value×1.2.

In the case of the first example, the added value is less than the addition threshold, and it is determined that the interval set includes the paired edge interval. That is, the interval set includes seven edge intervals, which is one edge interval short.

Therefore, in the first example, the interval total value is corrected by adding the interval average value calculated last time to the interval total value. Then, the corrected interval total value is divided by a predetermined number to calculate the interval average value. Alternatively, the predetermined number is corrected to a value obtained by subtracting "1" from the predetermined number. Then, the average interval value is calculated by dividing the total interval value by the corrected predetermined number.

Also, in the case of the second example of noise contamination shown in FIG. 9, there is a short interval at the end of the interval set. However, unlike the first example, closely spaced pairwise edge spacings are not included in the spacing set. In the case of the second example, the added value is greater than or equal to the addition threshold, and it is determined that the interval set does not include the paired edge interval. That is, the interval set includes seven edge intervals and short intervals, and is short of the interval corresponding to the pair of edge intervals.

Therefore, in the second example, the interval total value is corrected by adding the difference between the interval average value calculated last time and the short interval to the interval total value. Then, the corrected interval total value is divided by a predetermined number to calculate the interval average value. Alternatively, the total interval value is corrected by subtracting the short interval from the total interval value, and the predetermined number is corrected to a value obtained by subtracting "1" from the predetermined number. Then, the corrected interval total value is divided by the corrected predetermined number to calculate the interval average value.

In addition, in the case of the third example of noise mixture shown in FIG. 10, there are short intervals other than at both ends of the interval set. Specifically, edge interval #3 is a short interval. If a short interval exists other than at both ends of the interval set, the edge interval paired with the short interval is also included in the interval set. In the case of the third example, originally one edge interval is divided into edge interval #3 and edge interval #4, and both edge interval #3 and edge interval #4 are included in the interval set. That is, the interval set includes seven edge intervals, which is one edge interval short.

Therefore, in the third example, similarly to the first example, the interval total value is corrected by adding the interval average value calculated last time to the interval total value. Then, the corrected interval total value is divided by a predetermined number to calculate the interval average value. Alternatively, the predetermined number is corrected to a value obtained by subtracting "1" from the predetermined number. Then, the average interval value is calculated by dividing the total interval value by the corrected predetermined number.

Here, the control circuit 31 limits the noise mixture detected in the interval set to one or less. Even if the interval set includes a plurality of short intervals that are not adjacent to each other, the control circuit 31 detects one noise mixture without detecting multiple noise mixtures. That is, no more than one noise is excluded from the interval set.

As shown in FIG. 11, when the rotation speed is accelerating, the edge interval capture value decreases. As a result, the edge spacing may be smaller than the spacing threshold even without noise. And the frequency of noise in the interval set is sufficiently low. Therefore, if an interval set contains multiple short intervals, it is more likely that at least one of the short intervals is caused by acceleration of the rotational speed, rather than the possibility that multiple noises are mixed in the interval set. considered to be high. If the short interval is caused by the acceleration of the rotational speed, executing the special calculation process for correction may result in erroneous recognition of the rotational speed. Therefore, in the interval set, the detected noise mixture is limited to one or less.

Subsequently, in S230, the rotation speed (rpm) of the motor 15 is calculated by dividing the constant N by the interval average value calculated in S210 or S220. Here, assuming that the number of poles of the motor 15 is P and the capture timer clock cycle is Tc (sec), the constant N=60 (sec)/(3P×Tc (sec)).

<3. Operation>
The operation of the rotation speed calculation process according to this embodiment will be described with reference to FIGS. 12 to 15. FIG. FIG. 12 shows each captured value of eight edge intervals included in the interval set when noise is mixed in the interval set once, and the rotation calculated from each captured value (that is, the captured value that is not averaged) Speed and indicate. A portion surrounded by a dashed line is a noise mixture portion. FIG. 13 shows the corrected rotation speed and the uncorrected rotation speed when noise is mixed once in the interval set.

FIG. 14 shows captured values of edge intervals included in the interval set and rotation speeds calculated from the captured values when noise is mixed in the interval set twice. A portion surrounded by a dashed line is a noise mixture portion. FIG. 5 shows the rotational speed corrected to remove the influence of one noise and the uncorrected rotational speed when noise is mixed twice in the interval set.

In FIG. 12, originally one edge interval is divided into edge interval #1 and edge interval #2. As a result, the edge interval #2 becomes a short interval, and the rotation speed calculated from the edge interval #2 without correction is higher than the rotation speeds calculated from the other edge intervals. In this case, the interval total value is corrected to a value obtained by adding the previous interval average value to the interval total value, or to a value that is less than the predetermined number by "1". As a result, as shown in FIG. 13, the protruding high rotation speed is corrected, and a plausible rotation speed is calculated.

On the other hand, in FIG. 14, originally one edge interval is divided into edge interval #1 and the edge interval immediately preceding edge interval #1 not included in the interval set, and originally one edge interval is divided into edge interval #8 and the edge interval immediately following edge interval #8 that is not included in the interval set. In this case, correction is made to remove only one of the two noise inclusions, for example, only the influence of noise introduced on the leading end side of the interval set. That is, the total interval value is corrected to a value obtained by adding the difference between the previous average interval value and the edge interval #1 to the total interval value. Alternatively, the total interval value is corrected to a value obtained by subtracting the edge interval #1 from the total interval value, and the predetermined number is corrected to a value smaller by "1". As a result, as shown in FIG. 15, the protruding high rotational speed is corrected by about half.

<4. Effect>
According to the first embodiment described above, the following effects are obtained.
(1) Edge intervals of the sensor detection signal are detected, and the rotational speed of the motor 15 is calculated using the detected edge intervals. Also, an interval threshold is set based on the edge interval used for the previous rotation speed calculation, and noise mixture is detected when the edge interval is shorter than the set interval threshold. Then, when noise contamination is detected, a special calculation process different from the normal rotation speed calculation process is executed to calculate the rotation speed. Therefore, erroneous recognition of the rotation speed of the motor 15 can be suppressed.

(2) When noise contamination is not detected, normal calculation processing is executed to calculate the rotational speed. In the normal calculation process, the rotation speed is calculated from the interval average value obtained by averaging a predetermined number of edge intervals detected continuously. A stable rotation speed can be calculated by using the interval average value.

(3) When noise contamination is detected, a special calculation process is performed to correct at least one of the total interval value and a predetermined number of values so as to remove the influence of noise, and the corrected value is used. A rotation speed is calculated. As a result, even when noise is detected, erroneous recognition of the rotation speed can be suppressed.

(4) The interval threshold value is set based on the interval average value used to calculate the rotational speed in the previous processing cycle, thereby setting an appropriate interval threshold value and detecting noise contamination with high accuracy. can be done.

(5) When the short interval exists at a location other than both ends of the interval set, when the short interval exists at the edge of the interval set, and when the sum of the short interval and its adjacent edge interval is less than the addition threshold is determined to include both short intervals and their paired edge intervals in the interval set. In this case, the spacing set is short of one edge spacing. Therefore, the interval average value calculated last time is added to the interval total value obtained by totaling the predetermined number of edge intervals, and the interval total value is corrected. Alternatively, the predetermined number is corrected to a value less by "1". As a result, even when noise is detected, it is possible to suppress a decrease in the calculation accuracy of the rotational speed.

(6) If the short interval exists at the end of the interval set and the sum of the short interval and its adjacent edge interval is equal to or greater than the addition threshold, the short interval among the short interval and the paired edge interval is determined to be included in the interval set. In this case, the spacing set is deficient in edge spacings corresponding to pairwise edge spacings. Therefore, the difference between the interval average value calculated last time and the short interval is added to the interval total value obtained by totaling the predetermined number of edge intervals, and the interval total value is corrected. Alternatively, the total interval value is corrected to a value obtained by subtracting the short interval from the total interval value, and the predetermined number is corrected to a value less by "1". As a result, even when noise is detected, it is possible to suppress a decrease in the calculation accuracy of the rotational speed.

(7) The number of noise inclusions detected in the interval set is limited to one or less. That is, no more than one noise can be filtered out in the interval set. As a result, it is possible to cope with changes in the rotation speed while suppressing erroneous recognition of the rotation speed.

(Second embodiment)
<1. Difference from First Embodiment>
Since the basic configuration of the second embodiment is the same as that of the first embodiment, description of common configurations will be omitted, and differences will be mainly described. Note that the same reference numerals as in the first embodiment indicate the same configurations, and refer to the preceding description.

The second embodiment differs from the first embodiment in the process of calculating the motor rotation speed. In the first embodiment described above, the rotation speed is calculated by correcting at least one of the interval total value and the predetermined number in the special calculation process. On the other hand, the second embodiment differs from the first embodiment in that the rotational speed calculated last time is calculated as the current rotational speed in the special calculation process.

<2. Processing>
Next, rotation speed calculation processing executed by the control circuit 31 in place of the rotation speed calculation processing of FIG. 5 in the second embodiment will be described with reference to the flowchart of FIG.

First, in S300, similarly to S200, it is determined whether or not the interval set contains noise. If noise contamination is not detected, in S310 and S320, similarly to S210 and S230, the rotational speed is calculated by normal calculation processing, and this processing ends.

On the other hand, if noise mixture is detected in S300, the process ends. As a result, the rotational speed calculated in the previous processing cycle becomes the rotational speed in the current processing cycle.
<3. Effect>
According to the second embodiment described above, in addition to the effects (1) to (2) and (4) of the first embodiment described above, the following effects can be obtained.

(8) Normally, the rotation speed of the motor 15 is often close to the rotation speed value calculated in the previous processing cycle. Therefore, when noise contamination is detected, the rotational speed calculated in the previous processing cycle is calculated as the current rotational speed. As a result, it is possible to suppress erroneous recognition of the rotational speed even when noise is detected.

(Other embodiments)
Although the embodiments for implementing the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented with various modifications.

(a) In the above embodiment, the lawn mower 1 is shown as an electric working machine, but the electric working machine is not limited to this. For example, the electric working machine may be a working machine such as a circular saw, a chain saw, a hedge trimmer, or the like, in which a working tool is driven by the rotational force of a motor.

(b) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or a function possessed by one component may be realized by a plurality of components. . Also, a plurality of functions possessed by a plurality of components may be realized by a single component, or a function realized by a plurality of components may be realized by a single component. Also, part of the configuration of the above embodiment may be omitted. Moreover, at least part of the configuration of the above embodiment may be added or replaced with respect to the configuration of the other above embodiment.

DESCRIPTION OF SYMBOLS 1... Grass cutter, 15... Motor, 22... Battery pack, 30... Controller, 31... Control circuit, 61... Hall sensor.

Claims (8)

a motor;
a Hall sensor configured to detect a rotational position of a rotor of the motor;
an interval detection unit configured to detect an edge interval of the detection signal of the Hall sensor;
a speed calculation unit configured to calculate a rotation speed of the motor using the edge interval detected by the interval detection unit;
a threshold setting unit configured to set an interval threshold for determining whether the edge interval is normal;
a noise detection unit configured to detect noise contamination when the edge interval for calculating the current rotational speed is equal to or less than the interval threshold value set by the threshold value setting unit;
The speed calculation unit
when the noise detection unit detects the noise mixture, executing a special calculation process of the rotation speed that is different from the normal calculation process of the rotation speed ,
In the normal calculation process, calculating the rotation speed from an average interval value obtained by dividing a total interval value of an interval set, which is a predetermined number of the edge intervals continuously detected by the interval detection unit, by the predetermined number;
In the special calculation process, if the short interval, which is the edge interval equal to or less than the interval threshold, exists in the interval set other than at both ends; correcting the total interval value by adding the average interval value calculated last time to the total interval value when the added value obtained by adding the interval and the adjacent edge interval is less than the addition threshold;
electric work machine. a motor;
a Hall sensor configured to detect a rotational position of a rotor of the motor;
an interval detection unit configured to detect an edge interval of the detection signal of the Hall sensor;
a speed calculation unit configured to calculate a rotation speed of the motor using the edge interval detected by the interval detection unit;
a threshold setting unit configured to set an interval threshold for determining whether the edge interval is normal;
a noise detection unit configured to detect noise contamination when the edge interval for calculating the current rotational speed is equal to or less than the interval threshold value set by the threshold value setting unit;
The speed calculation unit
when the noise detection unit detects the noise mixture, executing a special calculation process of the rotation speed that is different from the normal calculation process of the rotation speed ,
In the normal calculation process, calculating the rotation speed from an average interval value obtained by dividing a total interval value of an interval set, which is a predetermined number of the edge intervals continuously detected by the interval detection unit, by the predetermined number;
In the special calculation process, a short interval that is the edge interval equal to or less than the interval threshold exists at an end in the interval set, and addition is performed by adding the short interval and the adjacent edge interval in the interval set. if the value is equal to or greater than the addition threshold, adding the difference between the previously calculated interval average value and the short interval to the interval total value to correct the interval total value;
electric work machine. a motor;
a Hall sensor configured to detect a rotational position of a rotor of the motor;
an interval detection unit configured to detect an edge interval of the detection signal of the Hall sensor;
a speed calculation unit configured to calculate a rotation speed of the motor using the edge interval detected by the interval detection unit;
a threshold setting unit configured to set an interval threshold for determining whether the edge interval is normal;
a noise detection unit configured to detect noise contamination when the edge interval for calculating the current rotational speed is equal to or less than the interval threshold value set by the threshold value setting unit;
The speed calculation unit
when the noise detection unit detects the noise mixture, executing a special calculation process of the rotation speed that is different from the normal calculation process of the rotation speed ,
In the normal calculation process, calculating the rotation speed from an average interval value obtained by dividing a total interval value of an interval set, which is a predetermined number of the edge intervals continuously detected by the interval detection unit, by the predetermined number;
In the special calculation process, if the short interval, which is the edge interval equal to or less than the interval threshold value, exists in the interval set other than at both ends; if the added value obtained by adding the short interval and the adjacent edge interval is less than the addition threshold, correcting the predetermined number to a value that is one less;
electric work machine. a motor;
a Hall sensor configured to detect a rotational position of a rotor of the motor;
an interval detection unit configured to detect an edge interval of the detection signal of the Hall sensor;
a speed calculation unit configured to calculate a rotation speed of the motor using the edge interval detected by the interval detection unit;
a threshold setting unit configured to set an interval threshold for determining whether the edge interval is normal;
a noise detection unit configured to detect noise contamination when the edge interval for calculating the current rotational speed is equal to or less than the interval threshold value set by the threshold value setting unit;
The speed calculation unit
when the noise detection unit detects the noise mixture, executing a special calculation process of the rotation speed that is different from the normal calculation process of the rotation speed ,
In the normal calculation process, calculating the rotation speed from an average interval value obtained by dividing a total interval value of an interval set, which is a predetermined number of the edge intervals continuously detected by the interval detection unit, by the predetermined number;
In the special calculation process, a short interval that is the edge interval equal to or less than the interval threshold exists at an end in the interval set, and addition is performed by adding the short interval and the adjacent edge interval in the interval set. If the value is equal to or greater than the addition threshold value, the short interval is subtracted from the interval total value to correct the interval total value, and the predetermined number is corrected to a value that is one less.
electric work machine. The noise detection unit limits the detected noise mixture to one or less in the edge interval used to calculate the rotational speed.
The electric working machine according to any one of claims 1 to 4 . a motor;
a Hall sensor configured to detect a rotational position of a rotor of the motor;
an interval detection unit configured to detect an edge interval of the detection signal of the Hall sensor;
a speed calculation unit configured to calculate a rotation speed of the motor using the edge interval detected by the interval detection unit;
a threshold setting unit configured to set an interval threshold for determining whether the edge interval is normal;
a noise detection unit configured to detect noise contamination when the edge interval for calculating the current rotational speed is equal to or less than the interval threshold value set by the threshold value setting unit;
When the noise detection unit detects the noise mixture, the speed calculation unit executes a special calculation process of the rotation speed that is different from the normal calculation process of the rotation speed ,
The noise detection unit limits the detected noise mixture to one or less in the edge interval used to calculate the rotational speed.
electric work machine. In the normal calculation process, the speed calculation unit divides a total interval value of an interval set, which is a predetermined number of the edge intervals continuously detected by the interval detection unit, by the predetermined number, and calculates the average interval value from the average interval value. calculate the rotation speed,
The electric working machine according to claim 6 . The threshold value setting unit sets the interval threshold value based on the interval average value used to calculate the previous rotation speed.
The electric working machine according to any one of claims 1 to 5 and 7 .

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