JPH0451660B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic speed control device capable of keeping the rotational speed of a reciprocating engine constant and, in particular, reducing the amount of rotational fluctuation.

In generators using reciprocating engines, etc.
Depending on the application, high frequency accuracy may be required. In this case, it is necessary to keep the engine rotational speed constant with high precision, and it is also required to quickly stabilize the engine rotational speed to a constant rotational speed even in response to sudden load changes.

Traditionally, as an electronic speed control device, a large number of pulse signals are generated by the rotation of the engine crankshaft, the frequency of these pulse signals is converted into a voltage signal by an F/V converter, and this voltage signal is kept constant. An analog speed control device is known. In order to improve control accuracy and response speed during load fluctuations with this type of analog type, it is necessary to increase the number of pulse signals per revolution of the crankshaft. However, in engines with a small number of cylinders, such as single-cylinder engines,
The speed fluctuation within one rotation of the crankshaft is large. That is, the speed decreases during the compression stroke, and the speed increases during the explosion stroke. In order to improve the response speed when the load fluctuates as mentioned above, it is desirable to increase the amount of differential compensation, but as mentioned above, if the speed fluctuation within one revolution of the crankshaft is large, hunting will occur and the operation will become unstable. However, it has been difficult to effectively apply differential compensation. For this reason, speed control had to be performed at the expense of the response speed.

Furthermore, when a four-stroke single-cylinder engine is used, the entire stroke of suction, compression, explosion, and exhaust is performed in two revolutions of the crankshaft, so the amount of variation in rotational speed per revolution of the crankshaft becomes even larger. Therefore, it is more difficult to increase the amount of differential compensation, and a problem arises in that it is impossible to prevent deterioration of control accuracy and decrease in response speed.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide an electronic speed control device for an engine that is highly accurate, has good responsiveness during load fluctuations, and enables stable speed control. do.

According to the present invention, the purpose is to provide a speed detection circuit that calculates a speed signal for each rotation of the crankshaft from the time required for one rotation of the crankshaft, and a proportional calculation that calculates a proportional compensation amount based on the error with the target speed. and a differential calculation unit that obtains a differential value of the speed signal with respect to time and calculates a differential compensation amount, and performs control including a proportional operation and a differential operation to make the rotation speed match a target value, wherein the proportional The arithmetic unit has a register that stores the speed signal from one revolution before, and subtracts a set value corresponding to twice the target speed from the sum of the speed signal at a certain point in time and the speed signal from one revolution before to obtain an error. an error calculation section, and uses the error to obtain a proportional compensation amount, while the differential calculation section includes a register for storing the speed signal two revolutions ago, and a register that stores the speed signal at a certain point in time and the speed two revolutions ago. This is achieved by an electronic speed control device for an engine, characterized in that it includes a subtracter for determining a speed difference from a signal, and calculates the differential compensation amount based on the speed difference. The present invention will be explained in detail below based on the illustrated embodiments.

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a timing diagram. In FIG. 1, reference numeral 10 is a four-stroke single-cylinder engine, 12 is a carburetor, and 14 is a throttle valve, which is driven to open and close by an actuator 16 such as a servo motor. This throttle valve 1
The opening degree of No. 4 is constantly detected by an opening degree sensor 18 such as a potentiometer.

20 is a speed detection circuit, and this circuit 20 is
A count value n as a speed signal is determined from the time or period required for one rotation of the crankshaft of the engine 10, as described later. This circuit 20 includes a waveform shaping circuit 22, a timing signal generation control circuit 24,
It includes a counter 26 and a register 28. The waveform shaping circuit 22 uses a rotation signal A (FIG. 2) that changes by one cycle per crankshaft rotation, which is output by an alternator connected to the crankshaft of the engine 10, for example, to generate a signal for one crankshaft rotation. One pulse signal B is output. The timing control generation control circuit 24 generates a timing pulse at a predetermined timing based on the rising edge of the waveform of this pulse signal.
_T1 to _T6 , count pulse C, reset pulse R,
Outputs select signal SEL, etc. The count pulse C is always output at a fixed period shorter than the pulse signal B regardless of the rotation speed. The counter 26 returns to zero when the reset pulse R is input, and adds the count pulse C between the two reset pulses R. In other words, the time it takes for the crankshaft to rotate once is
It is determined by the count value n of the counter 26, and this count value n becomes a speed signal. In this case, the resolution is determined by the generation period of the count pulse C. The register 28 reads the count value n, which is the content of the counter 26, in synchronization with the rise of the waveform of the timing pulse _T1 , and stores this read count value n until the next timing pulse _T1 is generated. are doing.

30 is a differential calculation section, and this calculation section 30 is
Registers 32, 34, selector 36, subtracter 3
8, a multiplier 40 and a register 42. Registers 32 and 34 are timing pulses T ₂ and T ₃
Based on the register 2 of the speed detection circuit 20
The calculated values n stored in 8 are read alternately once each within one cycle of the crankshaft. In Figure 2, n
(0), n(1), . . . sequentially indicate the count value n of the counter 26 for each revolution of the crankshaft. The selector 36 selects the stored contents of either the registers 32 or 34 based on the select signal SEL and inputs the selected content to the subtracter 38. The select signal SEL goes H every crankshaft cycle.
The select signal SEL changes between the level and the L level. For example, when the select signal SEL is at the H level, the contents of the register 34 are input to the subtracter 38, and when it is at the L level, the contents of the register 32 are input to the subtracter 38. Subtractor 38
subtracts the output of selector 38 from the contents of register 28. For example, if the content of the register 28 is n(0) in a certain cycle, the selector 36 selects the register 32 that stores the calculated value n(0-2) two cycles before.
The content n(0-2) is sent to the subtracter 38. Therefore, the subtracter 38 at this time calculates the difference n(0)-n(0-2) between the two.
Output. This difference indicates the amount of variation in the rotational speed over a predetermined cycle period, that is, the differential value.
Multiplier 40 multiplies this difference by a coefficient K ₁ and inputs the result, D(0)=K ₁ ×[n(0)−n(0−2)], to register 42 . Register 42 reads and stores the output of multiplier 40 in synchronization with timing pulse _T4 . The contents of this register 42 are for the differential compensation amount D, and by changing the coefficient _K1 , the rate of differential operation in this control system can be changed.

In this way, the differential calculation unit 30 determines the differential compensation amount D based on the difference in the calculated value n between a certain cycle and the cycle two cycles before, that is, the difference in rotational speed.
If the engine is in the compression stroke at a certain point in time, the same compression stroke will occur two cycles before, and the engine will not be affected by variations in rotational speed due to the difference in the operating stroke. Therefore, control stability is increased and differential compensation can be effectively applied.

50 is an error calculation unit, which includes an adder 52 and a subtracter 54. The adder 52 is the differential calculation section 30
The count values of two consecutive cycles stored in the registers 32 and 34, for example, n(0-1) and n(0), are added, and the subtracter 54 adds this added value n(0-1).
+n(0) and a set value S corresponding to twice the control target speed, Y(0)=n(0-1)+n(0)-S, is calculated. By calculating the sum of the count values for two consecutive cycles in this manner, speed fluctuations between the compression stroke cycle and the exhaust stroke cycle, especially in a four-stroke engine, can be canceled out. That is, this added value n(0-1)n(0) corresponds to the average value of the rotational speeds for two cycles. Also, the difference Y(0)=n
(0-1)+n(0)-S corresponds to the error Y between the actual rotational speed and the target speed.

60 is a proportional calculation section, which includes a multiplier 62. This multiplier 62 multiplies the error n(0-1)+n(0)-S obtained by the error calculation unit 50 by a coefficient _K2 ,
P(0)=K ₂ {n(0-1)+n(0)-S} is calculated. This value P indicates the amount of proportional compensation, and by changing the coefficient _K2 , the proportion of proportional operation in this control system can be changed.

Reference numeral 70 denotes an integral calculation section, which includes an adder 72, a register 74, and a divider 76. The adder 72 adds the error Y, which is the output of the error calculation unit 50, and the contents stored in the register 74, and stores the sum in the register 7.
4 every cycle based on the timing pulse _T5 . The result register 74 stores the value _i=0 {n(i-1)+n(i)-S}, and this value corresponds to the integral value of the error Y. A divider 76 is used for this integral value.
is multiplied by a coefficient 1/ _K3 , and the output is I(0)={n(i-1)+n(i)-S}/ _K3 . This I(0) corresponds to the integral compensation amount, and by changing the coefficient _K3 , the contribution ratio of the integral operation in this control system can be changed.

The proportional compensation amount P and the differential compensation amount D obtained as described above are added by an adder 80, and the integral compensation amount I is further added to this sum P+D by an adder 82. These sums P+D+I are stored in register 84.
is stored in the register 86 every cycle based on the timing pulse _T6 .

Each of the above calculations is processed using digital signals. That is, the count value n of the counter 26 of the speed detecting section 20 is outputted, for example, in binary coded decimal notation, and all data transfers in subsequent calculations are performed by a bus having a plurality of bits.

90 is a throttle control section, and a conversion ROM
(random access memory) 92, actuator control section 94, and actuator driver 96
, the actuator 16 , and a throttle opening sensor 18 . The content P+D+I of the register 86 is a binary signal indicating the control amount, and this binary signal is converted into a binary signal indicating the opening/closing amount of the throttle valve 14 in the conversion ROM 92.
The actuator control unit 94 uses this conversion ROM 92.
and the opening signal indicated by the throttle opening sensor 18, and outputs an opening/closing control signal. This opening/closing control signal is amplified by an actuator driver 96 consisting of an amplifier, and the actuator 16
By operating the throttle valve 14, the throttle valve 14 is opened and closed. As a result, the throttle valve 14 is controlled to open and close so as to match the opening degree corresponding to the control amount (P+D+I) stored in the register 86.

In this embodiment, as described above, using the count value n of the counter 26 added during one cycle of the crankshaft,
The differential compensation amount D is determined based on the difference between the count values n(0-1) and n(1) every other cycle. Also consecutive 2
The sum of the period counts, for example, n(0-1)+n(0),
A speed error Y is determined based on the difference from a set value S that determines the target speed, and based on this speed error Y, a proportional compensation amount P and an integral compensation amount I are determined. Using the sum P+D+I of these compensation amounts, the throttle control section 90 controls the opening degree of the throttle valve 14 to match the opening degree indicated by the sum P+D+I.

In addition, the differential calculation unit 30 calculates the differential compensation amount D from the difference between the count value n as the current speed signal and the count value n as the speed signal two revolutions ago. Even though the rotational fluctuation is large between the period including the explosion stroke and the period including the explosion stroke, it is no longer affected by the fluctuation.

Furthermore, in this embodiment, the difference between the actual rotational speed of the crankshaft and the target speed is determined based on the sum of the count value n as the speed signal for two cycles.
In particular, it is possible to cancel out the influence of rotational fluctuations in the 4th cycle, and more accurate speed control becomes possible.

As described above, this embodiment performs proportional+integral+differential operation (so-called PID operation), so speed control accuracy is significantly improved. However, the present invention is of course applicable to devices that perform proportional + differential operation (so-called PD operation), and at least differential compensation can be applied to speed control devices, and these devices are also included in the present invention. It is.

It goes without saying that the present invention can be applied directly to not only 4-stroke engines but also 2-stroke engines. In a two-stroke engine, when the throttle valve is fully closed or at a low opening, irregular combustion occurs due to deterioration of scavenging air, and rotational fluctuations often occur. If the present invention is applied to such a two-stroke engine, it is possible to suppress the occurrence of hunting caused by rotational fluctuations during low/no-load conditions, and the stability of speed control is significantly improved.

As described above, the present invention stores the speed signal of the crankshaft two revolutions ago, that is, two cycles ago, in a register, and calculates the differential compensation amount based on the difference between each speed signal at a certain point and two revolutions before. Therefore, the influence of rotational fluctuations of the crankshaft can be suppressed, and the amount of differential compensation can be increased without destabilizing the control.

Further, an error is obtained by subtracting a set value corresponding to twice the target speed from the sum of the speed signal one rotation before and the current speed signal, and the proportional compensation amount is obtained from this error. By using the sum of the speed signals for two consecutive revolutions in this way, even if there is a fluctuation in speed for each revolution, the influence of this speed fluctuation can be canceled out, and high accuracy using proportional compensation can be achieved. Control becomes possible. The response speed of the control for this purpose can be improved, and the speed control accuracy can be improved. In particular, when applied to a four-stroke single-cylinder engine, it is possible to completely cancel out the effects of speed fluctuations, making the effects of the present invention even more remarkable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a timing diagram. 10...Engine, 20...Speed detection circuit, 3
0... Differential operation section, 32, 34... Register, 3
8...Subtractor, 50...Error calculation unit, 60...Proportional calculation unit, P...Proportional correction amount, n...Count value as speed signal, D...Differential compensation amount.

Claims (1)

[Claims] 1. A speed detection circuit that calculates a speed signal for each rotation of the crankshaft from the time required for one rotation of the crankshaft, a proportional calculation unit that calculates a proportional compensation amount based on an error with the target speed, and a time of the speed signal. and a differential calculation section that calculates a differential compensation amount by determining a differential value for the rotation speed, and performs control including a proportional operation and a differential operation so that the rotation speed matches a target value, wherein the proportional calculation section calculates the differential value of the rotation speed one rotation before. a register for storing a signal; and an error calculation unit that subtracts a set value corresponding to twice the target speed from the sum of the speed signal at a certain point in time and the speed signal one rotation before, and obtains an error; While determining the proportional compensation amount using the error, the differential calculation section has a register that stores the speed signal two revolutions ago, and a subtraction operation that calculates the speed difference between the speed signal at a certain point in time and the speed signal two revolutions ago. What is claimed is: 1. An electronic speed control device for an engine, characterized in that the electronic speed control device for an engine is provided with a device for determining the differential compensation amount based on the speed difference.