DE4038301A1 - Suppressing motor vehicle bodywork vibration by alternator excitation - pulse width modulating field current supplied by proportional controller comparing measured and desired accelerations - Google Patents

Abstract

The vibrational wave detected by an accelerometer (31a) is filtered (31b) with a passband of e.g. 5.5 Hz for comparison with a preset desired acceleration value. The difference gives rise to proportional control (40) of the field current of the alternator (10) by pulse-width modulation (40a). The field current varies approximately in phase with the vibration so that the alternator (10) generates electric power to absorb the mechanical energy. Loading (29) is regarded as an external disturbance of the driving system. ADVANTAGE - Vibration esp. under acceleration is suppressed effectively by absorption of energy in alternator.

Description

The present invention relates to a method as well as a device for suppressing vibratio nen the construction of a vehicle and in particular on a Method or device for suppressing Vibration of a vehicle when accelerating Vehicle.

In automotive engineering, it is a well-known technique, the rotary Torque change of a vehicle due to the machine work and the torque change through control tion of the output power of a generator, such as. B. the Alternator to suppress. One such technique is  for example in Japanese laid-open publications 58-1 85 937, 58-1 85 938 and 63-2 12 723.

One makes use of the fact that the machine load effective power to drive the alternator correspond according to the output power of the alternator (generated Energy) varies. If there is a torque change in the vehicle takes place, the output power of the alternator is like this controlled that they change according to the torque changes, absorbing the change in torque and the vibrations of the vehicle body due to the rotation torque change can be suppressed.

This known technique mainly suppresses the same permanent vibrations of the vehicle body as they go through the operation of the engine. Periodic rotation Torque changes occur synchronously with the intake stroke, ver seal cycle, explosion cycle and exhaust cycle of the engine, and the periodic change in torque is under presses by the output power of the alternator so ge is controlled that in its phase it runs counter to the perio is the torque change.

Vibrations of the vehicle body also include others than these constant, through the machine cycle cause vibrations such as B. Vibrations of the driving stuff caused by acceleration of the vehicle will. The constant vibrations are caused by the constant cycle of torque change in the vehicle construction creates, and known techniques suppress the Torque change by capturing it, especially the Increase in torque in the ignition stroke, and a torque opposite phase to that of the torque change in Generate drive. With this technique it is difficult possible, the starting vibrations of a vehicle body  enough to suppress.

The object of the invention is to provide a method and a to indicate the direction with which vibrations of the vehicle body, especially vibrations when accelerating driving stuff can be effectively suppressed by driving Witness motor coupled generator is controlled.

A vehicle has a main drive and a transmission system for transferring engine energy to the wheels of the Vehicle, as well as an auxiliary apparatus drive and one audible transmission system. The main drive as well as its Transmission system includes the engine to drive the vehicle stuff, and the auxiliary apparatus drive including the associated over Carrier system includes a gene associated with the engine rator, such as B. the alternator by this engine is driven. If the generator produces a lot of energy, it extracts this from the engine power, thereby reducing the torque is reduced to drive the vehicle.

In such a vehicle, the present Er The underlying problem is solved in that the Torque changes, for example, when driving vibrations stuff generated by accelerating the engine is detected, then by means of pulse width modulation with which it seized vibration wave a control signal for the field current of the generator is generated, and the field current through the Control signal is modulated. According to the key ratio of the field current through the pulse width modulation controlled the vibration wave so that the field current is close approximately in phase with the vibration wave and Torque change in the vehicle by generating energy Generator caused by the field current changed in this way is generated, absorbed.  

One aspect of the invention is characterized in that the vibration of the vehicle generated by acceleration of the vehicle Vehicle is detected that an acceleration value of the he caught vibration with a predetermined target acceleration supply value is compared to form a difference that a control signal for the field current of the generator Pulse width modulation of the oscillation wave is generated, by a control loop with at least one proportional control tion is used, and that the field current with the Steue tion signal is modulated to thereby a torque generate that to absorb the vibration in the generator leads.

Another aspect of the invention is characterized in that that the initial phase of a vibration cycle is one by the Acceleration of the vehicle caused vibrations of the Vehicle is detected that a vibration wave pattern of the Vehicle based on the detected vibration cycle partly in the initial phase it is predicted that a tax signal for the field current of the generator by pulse width modulation of the predicted vibration wave mus sters is generated, and that the field current through the control tion signal is changed so that it approximately in phase with the predicted vibration wave pattern is, which generates a torque that leads to Absorp tion of vibration in the generator leads.

Referring now to the drawings, single out management examples of the present invention explained. It demonstrate:

Fig. 1 is a wave diagram for explaining the present invention;

Fig. 2 is a block diagram of an embodiment of a device for suppressing the vibration of a vehicle according to the present invention;

Fig. 3 is a block diagram of the important parts of Fig. 2;

Fig. 4 is a diagram of a tion by a Proportionalsteue controlled oscillation;

Fig. 5 is a diagram of vibration waves in a before prediction control;

Fig. 6 is a block diagram of an actual circuit of an embodiment of the device for suppressing vibrations, which has a proportional control;

Fig. 7 is an explanatory diagram showing a noun Schwingungsphä the time of vehicle acceleration; and

Fig. 8 is a diagram explaining the vibration mechanism of a control system according to the prior art.

Referring to FIG. 7, a Schwingungsphäno of the vehicle is first explained men, the time is entered as the abscissa and the speed as ordinate. When a vehicle is started and accelerated, its speed pulsates. In the example of FIG. 7, the vehicle speed pulsates at a frequency of approximately 5.5 Hz.

Next, referring to Fig. 8, a mechanism in which vibrational phenomena occur will be explained.

The engine control 20 in Fig. 8 includes a throttle valve opening sensor 21 , an air flow sensor 22 and a speed sensor 23 , a controller 24 , a fuel supply system 25 and an ignition system 26th Based on the signals from the accelerator pedal-operated throttle opening sensor 21 , the air flow sensor 22 and the speed sensor 23 , the controller 24 controls the fuel supply system 25 and the ignition system 26 and outputs power to the drive system 28 .

The driving load 29 can always be seen as an external disturbance of the drive system 28 . Under the influence of inertia, for example that of the vehicle, machine power is temporarily stored in a drive shaft and released again. A sequence of several such processes leads to an oscillation phenomenon, such as, for example, that of lagging the speed or oscillating the speed around a setpoint. From this it can be seen that the vibration phenomenon differs from the continuous torque change due to the engine cycle, so that the vibrations are difficult to suppress by detecting the cyclic torque change, especially the increase during the ignition cycle, and then a torque whose Phase opposite to the torque change is generated in the alternator. And since the response speed of a commonly used fuel supply system 25 is also limited, vibration of the vehicle body is difficult to be suppressed by suppressing the vibration of the fuel supply system 25 .

According to the present invention, vibration of a vehicle body is detected when it occurs, so that an output signal from the acceleration sensor as shown in Fig. 1 (a) is produced. As further shown in FIGS. 1 (b) and 1 (c), the output signal of the acceleration detector, after which it has been filtered, is subjected to pulse width modulation using a reference triangular voltage, so that a pulse width modulated output signal is produced (PWM output), With this PWM output, the field current of the alternator is then modulated, so that the modulated field current has an at least approximately the same phase as the oscillation wave.

The principle of this field current control is explained in detail with reference to FIG. 1.

The output signal of an acceleration sensor set for vibration detection is shown in Fig. 1 (a) as a vibration wave.

After passing through an amplifier and a bandpass filter which passes a certain frequency range, for example around 5.5 Hz, a wave is generated as shown by the solid line in Fig. 1 (b).

The vibration wave shown in Fig. 1 (b) is compared with a triangular wave of constant frequency and converted into a pulse width modulated signal (digital signal) as shown in Fig. 1 (c). As shown in Figure 1 (b). And 1 (c) can be seen, the duty cycle is greater when the torque change (acceleration value) is larger. By using the pulse width modulated signal as a control signal for the field current of the alternator and in which the wave is temporally adapted to the vibration cycle of the vibration, the field current is obtained which is in phase or almost in phase with the vibration wave.

This control of the field current leads to an enlargement of the field current when the torque change is positive Direction when vibration occurs when accelerating of the vehicle occurs, causing the amount of generated Energy and that needed to drive the alternator Torque increases. This increasing torque is used for Cancellation of the vibration, it is absorbed by it.

If the torque change in the negative direction is greater the field current and thus for the light measure Required drive torque from, so that the rotation torque change is reduced.

In this way, the vehicle acceleration caused vehicle vibration are suppressed.

According to one aspect of the present invention, the Control signal of the field current of the alternator on the Basis of the difference between a torque sands approximate value that was recorded during acceleration (detected acceleration value), and a target acceleration supply value controlled so that it is the output signal of a Re gelkreises is equal to the target value, at least one Proportional control is used.

When regulating the control signal for the field current the alternator by means of a proportional control is carried out increases with increasing size detected torque change value the pulse width (the Duty cycle) of the pulse width modulated signal. By doing thus the field current with the pulse width modulated signal  is controlled, the field current has a wave that is close approximately in phase with the vibration wave. How described above, is thus in the alternator generates a torque absorbing the vibration. If in the control loop a PID control consisting of the Sum of an integrating member (I), a differenzie renden member (D) and a proportional member (P), ver is used, the response speed to Schwin suppression can be done very quickly, what the Vibration suppression favorably influenced.

According to another aspect of the present invention when vibrations occur the acceleration in the Initial phase of a vibration cycle, for example the Vibration within the first quarter of a cycle in the Initial phase of vibration, detected and then a swing wave patterns are predicted. The acceleration The generated vibration phenomenon has the property that it due to the fact that it belongs to the drive system of the vehicle vibrating components always have the same pattern of vibrations of the vehicle body, so that it is possible to do the swing prediction patterns. Then using pulse width mo dulation the control signal for the field current of light machine generated so that the field current approximately phase is equal to the predicted vibration wave pattern, which creates a torque for absorption in the alternator the vibration is generated.

Referring next to the drawings, one Embodiment of the invention explained.

In FIG. 2, a control unit 24 receives various signals from a throttle valve opening sensor 21 , an air flow sensor 22 and a speed sensor 23 and controls a fuel supply system 25 and the ignition system 26 . The throttle valve sensor 21 outputs a throttle valve opening signal, the air flow sensor 22 is richly attached in the intake to measure an air flow amount of the air drawn into the engine, and the speed sensor 23 detects the revolutions per minute of the engine to a speed or revolution signal to spend. As mentioned above, these signals are input to the control unit 24 for controlling the fuel supply system 25 and the ignition system 26 . The fuel supply system 25 and the ignition system 26 control the running of the engine 27 by means of the signals from the control unit 24 . The engine 27 transmits its output to the drive system 28 of the vehicle to thereby drive it.

In this embodiment, an AC generator 10 (hereinafter referred to as an alternator), which is to be regarded as an auxiliary device, is used as an actuator of a control system for suppressing vehicle vibrations because it is well suited for suppressing vibrations occurring during acceleration. The system for vibration suppression includes a vibration detector 31 , which detects a torque change of the drive system 28 of the vehicle, such as is caused by vibrations, a controller 40 , which is based on the detected torque change value, such as the detected one Vibration value, the pulse width modulation of the field current of the alternator 10 performs, and an actuator 41 , which receives the pulse width modulated signals and controls the field current, resulting in a control of the output torque.

The controller 40 performs the pulse width modulation of the control signal for the field current on the basis of the detected vibration value, so that the field current of the alternator 10 is approximately in phase with the vibration wave. In practice, either a proportional control system (P) or a predictive controller is used for the controller 40 to perform the vibration suppression control.

In Fig. 3, an example is shown in which the pulse width modulation of the control signal for the field current using a proportional control is performed, the controller 40 performs the proportional control (P control). An acceleration detector 31 a and a bandpass filter 31 c are components of the vibration detector of the vehicle. When the vehicle is operating, the drive system is now subjected to a driving load 29 as an external disturbance, which can cause vibrations. If this is the case, the acceleration detector 31 will detect the vibration. The detected vibration wave runs through the bandpass filter 31 a, which only allows frequencies within a certain frequency range, for example around 5.5 Hz.

The detected acceleration value is compared with a preset target acceleration value in order to obtain the difference between them, and on the basis of which the controller 40 then carries out a proportional control of the field current of the alternator so that the detected acceleration value becomes equal to the target acceleration value; this results in control of the output power of the alternator. The controlled output power of the alternator absorbs the torque changes in the vehicle caused by the acceleration. In this proportional control, the signal for controlling the field current of the alternator is generated by pulse width modulation of the detected vibration wave.

The control for vibration absorption or suppression only works if the electrical load of the alternator is large is. Thus, in order to suppress vibration to generate the necessary torque, a sufficiently large one Electricity is available, and therefore a sufficiently large out current of the alternator can flow, a demented speaking electrical load may be provided.

Fig. 4 shows a decaying vibration when the proportional control in accordance with this embodiment intervenes. The proportional control can be carried out with comparatively little circuitry, but there is a response delay because the field winding 13 of the alternator has a large inductance, so that there is a ten long time until the oscillation subsides.

The response delay can be reduced by using a PID control circuit (proportional / integral / differenzie rend) is used, whereby gain and phase ent be corrected according to the control system.

The exact construction of the system for generating electrical energy with the proportional control shown in Fig. 3 will be described below with reference to Fig. 6 be.

In Fig. 6, a three-phase alternator 10 is Darge, which has an armature winding 11 , a three-phase full-wave rectifier 12 , a field winding 13 and an actuator 41 . The alternator 10 is electrically connected to the battery 14 and an electrical load 15 . The actuator 41 consists of a power transistor 42 for controlling the current flowing in the field winding 13 , a diode 43 for damping the changes in the current flowing through the power transistor 42 , an AND gate 44 , a comparator 45 , a reference voltage 46 and one Voltage dividers (resistors) 47 a, 47 b.

The actuator 41 is a control system for the generator for vibration suppression is added, which has a vibration detector 31 , a controller 40 and a pulse width modulator 40 a.

The vibration detector 31 consists of an acceleration detector 31 a and an amplifier 31 b. As an acceleration detector 31 a, for example, a component can be used to convert the pressure into electrical voltage by means of the piezo effect. The vibration caused by vehicle acceleration causes this pressure. The detected acceleration is directed both forward and backward and is caused by the vehicle acceleration.

The bandpass filter 31 can be c by a vibration component of about 5.5 Hz, the vibration wave from Fig. 1 to produce (b).

In the above construction, the alternator charges the battery 14 and supplies the electrical load with energy. If in the actuator 41, the voltage of the battery 14 is less than a reference voltage, the voltage at the tap of the voltage divider from the resistors 47 a, 47 b is less than the reference voltage 46 , so that the output of the comparator 45 assumes a high-level state. On the other hand, the signal output by the controller 40 via the pulse width modulator 40 a is usually high. When the signals from the comparator 45 and the controller 40 are high, the output of the AND gate 43 also goes high and the power transistor 42 becomes conductive, which increases the field current and thus also the energy generated.

If the energy generated increases, the output voltage of the armature winding 11 increases and the voltage of the bat terie 14 increases, so that the voltage at the tap of the voltage divider 47 a, 47 b is greater than the reference voltage 46 . As a result, the output of the comparator 45 becomes low and the output of the gate 44 likewise, where the power transistor 42 turns off and the field current decreases. When the field current becomes smaller, the output voltage of the armature winding 11 decreases as well as that of the battery 14 . The sequence of the above operations regulates the battery voltage so that it remains constant.

If the acceleration vibrations of the vehicle are large due to the vibrations occurring during acceleration, a vibration wave is output by the acceleration detector 31 a, the amplifier 31 b and the bandpass filter 31 c as a detected acceleration value. The wave shown in Fig. 1 (a) is the output wave of the acceleration detector 31 a, it changes into a wave shown by the solid line in Fig. 1 (b) after they pass through the amplifier 31 b and the bandpass filter 41 c Has. The bandpass filter 41 c includes a controller for automatic gain control (AGC) so that the vibration waves do not become excessively large.

Via the controller 40 , the wave shown in FIG. 1 (b) with a solid line is input into the pulse width modulator and compared with a triangular wave as shown in FIG. 1 (b), the output of the pulse width modulator 40 a being the in Fig. 1 (c) digital signal shown is generated. The pulse width of the digital signal becomes larger when the value of the detected acceleration (the change in torque) increases in the positive direction, whereby the duty cycle of the digital signal is controlled. The field current is controlled by the digital signal, that is by the pulse width modulated signal; if the digital signal is used as a control signal for the field current of the alternator, a field current results as shown in FIG. 1 (d), which is approximately in phase with the oscillation from FIG. 1 (a). If a negative acceleration component occurs, the output power of the alternator is reduced due to the field current being in phase with the oscillation wave, which also reduces the engine load, whereas if a positive acceleration component occurs, the output power of the alternator increases, which also increases the engine load, so that by the increase and decrease in the drive torque of the alternator, the vibrations of the vehicle are suppressed.

Vibration suppression using field current control is effective when the electrical load of the alternator is high. In order to obtain the waveform of the field current shown in Fig. 1 (d), it is necessary that the necessary field current is available immediately when the transistor 42 is controlled by the pulse width modulated signal. If the electrical load 15 at the output of the alternator is large, the output of the comparator 45 will be constantly high and the output of the pulse width modulator 40 a will be output to the base of the power transistor 42 , which means that the field current flowing in the field winding will flow Field winding is energized when the power transistor 42 is turned on, and on the other hand, energy is removed from the field winding when the power transistor 42 is switched off, so that no field current flows. A current wave as shown in Fig. 1 (d) is thus obtained.

As further shown in Fig. 1 (d), it is necessary that the field current is approximately in phase with the vibration wave and that a drive torque for the alternator is generated whose torque is in phase opposition to the vibration wave. For vibration suppression, it is very important that the field current and the vibration wave are in phase.

As a control to achieve vibration suppression it is possible to use a proportional control, a PID control and predictive control.

The prediction control used for vibration suppression of the alternator will now be explained in detail with reference to FIG. 5.

About the vibration caused by vehicle acceleration Predicting the wave of a vehicle becomes the first Quarter of a cycle of the vibration wave, i.e. the Be change in acceleration, detected. The vibration wave will as a sinusoid predicted what is dotted by a Line of vibration strength H and cycle time 4T Darge represents is. The output power of the alternator will be like this generates the predicted vibration to be canceled what the method of the method described above equal. The forecast control is based on the principle that the vibration phenomenon vehicle body vibrations he testifies to the natural frequency of a drive system of the Vehicle. The forecast control has a fast one Responsiveness of this control, so that this type of Vibration absorption works effectively.  

Through the above embodiment of the invention, the Vibration occurring during acceleration is sufficient chend suppressed, so that the driving comfort in Interior of the vehicle increased. According to the Alternator output current not directly controlled, but indirectly via a control of the field current, so that the nominal values of the power elements for control ver are equally small, which has the effect of reducing costs. Since also the use of powerful Schaltele can be avoided, the formation of rough be avoided by switching, so that does not affect the radio in the vehicle. It can thus by a small improvement in the control of one conventional alternator the alternator control to suppress vibration of a vehicle be performed.

Instead of a detector for vehicle acceleration can also be used as a vibration detector either for the change in the amount of acceleration of a signal according to the second derivative of the vehicle speed emits speed, an angular acceleration detector that one Output amount of change in engine speed, an Winkelbe acceleration change amount detector which ent a signal outputs the second derivative of the engine speed, an acceleration detector that is forward or backward directional acceleration of the vehicle detected, or a Circuit that the vehicle acceleration in forward and Reverse direction detected and the output signal after differentiated in time, using the signals of each detector can run over a filter circuit, of frequencies within a certain frequency range lets through. These signals can be used to control the Lichtma machine used to suppress vehicle vibrations will.  

Since the vehicle vibrations usually only then occur in vehicle acceleration when in the transmission the lowest gear is engaged, you can also imagine a circuit in which the gear position is detected and the control of vibration suppression only performed when the lowest gear is engaged sets is.

Claims (12)

1. A method for suppressing vibrations of a vehicle which has a motor for driving it and an alternator which is connected to and driven by the motor in order to generate electrical energy, characterized by the following steps:

• - detection of vehicle vibrations;
• - Performing a pulse width modulation with the vibration, whereby a pulse width modulated control signal is generated; and
• - Changes in the field current of the alternator with the pulse-width-modulated control signal, so that the field current is approximately in phase with the vibration, the alternator generating energy to absorb the vibration of the vehicle.

2. The method of claim 1, wherein the he seized vibration with a predetermined target value for Er generating a difference between the two is compared and wherein the pulse width modulation of the field current control signal of the alternator with a closed Re Gelkreis, which contains a proportional control, through leads. 3. A method for suppressing vibrations of a vehicle, which are caused by the acceleration of the vehicle, wherein the vehicle has an engine for driving it and an alternator, which is connected to and driven by the engine to generate electrical energy, characterized through the following steps:

• - Detection of the initial stage of a vibration cycle of the vibration caused by vehicle acceleration;
• - predicting a vibration pattern based on the detected initial stage of the vibration cycle of the vibration;
• - Implementation of the pulse width modulation by means of the predicted oscillation wave in order to generate a control signal; and
• - Change the field current of the generator with the pulse width modulated control signal, so that the field current is approximately in phase with the predicted vibration wave, the alternator generating energy to absorb the vehicle vibration.

4. The method of claim 3, wherein the catchy stage of the vibration cycle of vibration Acceleration value after a quarter of a cycle. 5. The method according to claim 4, wherein the loading acceleration value after a quarter of a cycle the Vi H value. 6. A method for suppressing a torque change taking place in a vehicle, the vehicle having a motor for driving it and an alternator which is connected to the motor so that it can be driven by it and generates electrical energy, the method includes the following steps:

• - Detection of a torque change in the vehicle;
• - Filtering the detected torque change, wherein vibration waves of a certain frequency of the torque change are allowed to pass;
• - Implementation of pulse width modulation using the vibration wave to generate a pulse width modulated control signal; and
• - Change the field current of the alternator with the pulse width modulated control signal, so that the field current is approximately in phase with the vibration wave, the alternator generating energy to absorb the vibration wave of the vehicle.

7. The method according to any one of claims 1 to 6, in which the field current of the alternator is only influenced when a low gear is engaged in the transmission. 8. Device for suppressing vibrations in vehicles which are provided with a motor ( 27 ) for driving them and a generator ( 10 ) connected to and driven by the motor ( 27 ) for generating electrical energy, characterized by:

• - Means ( 31 ) for detecting vehicle vibrations generated by the vehicle acceleration;
• - Means ( 40 , 40 a) for performing pulse width modulation of the detected vibration to generate a pulse width modulated control signal; and
• - Means ( 41 ) for changing the field current of the generator ( 10 ) with the pulse-width-modulated control signal, so that the field current is approximately approximately in phase with the vehicle vibration, the alternator ( 10 ) generating electrical energy for absorption of the vehicle vibration.

9. Device for vibration suppression in vehicles, which are provided with a main drive transmission system for transmitting engine power to the vehicle wheels and with an auxiliary drive for transmitting a portion of the engine power to an alternator ( 10 ), characterized by:

• - a sensor ( 31 ) for detecting vehicle vibrations caused by acceleration,
• - Means ( 40 ) for comparing an acceleration value of the detected vibration with a target acceleration value to form a differential wave therebetween, and for performing pulse width modulation with the differential wave by using a closed loop including proportional control, whereby pulse-width-modulated control signals are generated; and
• - Means ( 42 , 44 ) for entering the pulse width modulated signal and for controlling the field current of the alternator with the pulse width modulated signal to control the energy generation of the alternator ( 10 ), whereby the vibration of the vehicle is absorbed.

10. Device for vibration suppression in a vehicle, which is provided with a main drive system for transmitting engine power to the wheels and with an auxiliary drive system for transmitting a portion of the engine power to a generator ( 10 ), characterized by:

• - means ( 31 ) for detecting a part of a vibration of the vehicle caused by the vehicle acceleration;
• - means ( 40 ) for predicting a vibration wave pattern based on the detected part of the vibration and for performing pulse width modulation with the predicted vibration wave, thereby generating pulse width modulated control signals; and
• - Means ( 42 , 44 ) for entering the pulse width modulated control signal and for controlling the field current of the alternator ( 10 ), thereby controlling the generation of electrical energy and absorbing the vibration of the vehicle.

11. The device according to claim 9 or 10, wherein the vibration detection means ( 31 ) an acceleration detector ( 31 a) for detecting a change in the driving speed of the vehicle and a filter circuit ( 31 c) within the output of the acceleration detector ( 31 a) of a certain frequency range passes on. 12. The apparatus of claim 9 or 10, wherein the vibration detection means ( 31 ) comprises:

• - a first means ( 31 a) that either
  • a detector for the amount of change in the acceleration for outputting a value corresponding to the second derivative of the vehicle's driving speed, or
  • - An angular acceleration detector to output the change amount of the engine speed; or
  • - A detector for the amount of change in angular acceleration to output a value corresponding to the second derivative of the engine speed; or
  • an acceleration detector for detecting forward and backward acceleration; or
  • - is a combination of an acceleration detector for detecting forward and backward acceleration with a differentiating circuit for differentiating the output of the acceleration detector over time; and
• - A filter circuit ( 31 c) which allows an output of the first means ( 31 a) of a certain frequency range.